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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Thu Jul 11 2024 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN ARIZONA... ...SUMMARY... Severe thunderstorm gusts are possible over parts of southern Arizona from midafternoon into early evening. ...Synopsis... In mid/upper levels, the overall pattern will change little through the period, with mean ridging in the West, and troughing over the Great Lakes and vicinity. The persistent anticyclone will remain over the Great Basin, with some deamplification of ridging to its north leading to more-zonal flow across the northern tier of states from WA-ND. A weak shortwave trough -- apparent in moisture-channel imagery over parts of central/eastern MT -- should move slowly east-southeastward across the northern High Plains today amid difluent flow. Meanwhile and downstream, a pronounced shortwave trough now over parts of WI/IL/IA should eject northeastward over the Upper Great Lakes and weaken, while smaller/upstream perturbations help to maintain the mean trough. Both the low/middle-level remains of TC Beryl, and a closely associated shortwave trough of midlatitude origins, should shear northeastward across southern QC, the lower St. Lawrence Valley, and northern New England, weakening considerably. At the surface, 11Z analysis showed a low near the NH/QC border with slow-moving, weakening cold front across western New England, the coastal Mid-Atlantic/Carolinas, southern GA, and FL Panhandle, becoming quasistationary along the northwestern Gulf Coast. This front should continue weakening near or just east of its present position through the period, over the Northeast, and also weaken over the Gulf Coast and southern Atlantic Coast States. Enough low-level shear exists over parts of ME today to support a conditional supercell potential, but strength/coverage/longevity are in question due to weakness of both instability and lift. Elsewhere, a lee trough analyzed on that chart over eastern parts of MT/WY/CO should remain over the central/northern High Plains today, with some eastward drift possible. ...AZ... Widely scattered to scattered thunderstorms are expected to develop this afternoon, over the Mogollon Rim and smaller mountain ranges to the south. That will occur as strong insolation at those higher elevations preferentially removes MLCINH, in the presence of generally greater low-level moisture than previous days. Some strengthening of flow aloft is expected over this region, around the southeastern rim of the anticyclone. This will support convective motion off the Rim (and small mountain ranges to its south), then atop well-heated/deeply mixed boundary layers of the desert floor. Isolated strong-severe gusts are possible from the relatively early, more-discrete activity. With the lower-elevation boundary layers being very deep (surface to around 600 mb), but enough moisture maintained through mixing to keep surface-based buoyancy (MLCAPE in the 500-1000 J/kg range), expect some aggregation of outflows with additional development atop those -- especially over southeastern AZ. The net result should be both translation and developmental propagation of convection southwestward to and across the international border, with swaths of strong-severe gusts possible. ...Northern High Plains... Isolated to widely scattered, high-based thunderstorms are expected to form near the lee trough, where both relatively maximized convergence and strong surface heating should contribute to enough lift for convective initiation. The main concern up and down the corridor should be damaging to severe gusts, given the deeply mixed subcloud layer and ample downdraft-acceleration opportunity that will afford. Isolated severe hail also may occur, amidst enough deep-layer shear for some organized thunderstorms (effective-shear magnitudes of 30-40 kt). Lack of greater moisture and buoyancy will be a limiting factor for coverage and intensity of convection, which should diminish rapidly after dark. ..Edwards/Bentley.. 07/11/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Thu Jul 11 2024 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN ARIZONA... ...SUMMARY... Severe thunderstorm gusts are possible over parts of southern Arizona from midafternoon into early evening. ...Synopsis... In mid/upper levels, the overall pattern will change little through the period, with mean ridging in the West, and troughing over the Great Lakes and vicinity. The persistent anticyclone will remain over the Great Basin, with some deamplification of ridging to its north leading to more-zonal flow across the northern tier of states from WA-ND. A weak shortwave trough -- apparent in moisture-channel imagery over parts of central/eastern MT -- should move slowly east-southeastward across the northern High Plains today amid difluent flow. Meanwhile and downstream, a pronounced shortwave trough now over parts of WI/IL/IA should eject northeastward over the Upper Great Lakes and weaken, while smaller/upstream perturbations help to maintain the mean trough. Both the low/middle-level remains of TC Beryl, and a closely associated shortwave trough of midlatitude origins, should shear northeastward across southern QC, the lower St. Lawrence Valley, and northern New England, weakening considerably. At the surface, 11Z analysis showed a low near the NH/QC border with slow-moving, weakening cold front across western New England, the coastal Mid-Atlantic/Carolinas, southern GA, and FL Panhandle, becoming quasistationary along the northwestern Gulf Coast. This front should continue weakening near or just east of its present position through the period, over the Northeast, and also weaken over the Gulf Coast and southern Atlantic Coast States. Enough low-level shear exists over parts of ME today to support a conditional supercell potential, but strength/coverage/longevity are in question due to weakness of both instability and lift. Elsewhere, a lee trough analyzed on that chart over eastern parts of MT/WY/CO should remain over the central/northern High Plains today, with some eastward drift possible. ...AZ... Widely scattered to scattered thunderstorms are expected to develop this afternoon, over the Mogollon Rim and smaller mountain ranges to the south. That will occur as strong insolation at those higher elevations preferentially removes MLCINH, in the presence of generally greater low-level moisture than previous days. Some strengthening of flow aloft is expected over this region, around the southeastern rim of the anticyclone. This will support convective motion off the Rim (and small mountain ranges to its south), then atop well-heated/deeply mixed boundary layers of the desert floor. Isolated strong-severe gusts are possible from the relatively early, more-discrete activity. With the lower-elevation boundary layers being very deep (surface to around 600 mb), but enough moisture maintained through mixing to keep surface-based buoyancy (MLCAPE in the 500-1000 J/kg range), expect some aggregation of outflows with additional development atop those -- especially over southeastern AZ. The net result should be both translation and developmental propagation of convection southwestward to and across the international border, with swaths of strong-severe gusts possible. ...Northern High Plains... Isolated to widely scattered, high-based thunderstorms are expected to form near the lee trough, where both relatively maximized convergence and strong surface heating should contribute to enough lift for convective initiation. The main concern up and down the corridor should be damaging to severe gusts, given the deeply mixed subcloud layer and ample downdraft-acceleration opportunity that will afford. Isolated severe hail also may occur, amidst enough deep-layer shear for some organized thunderstorms (effective-shear magnitudes of 30-40 kt). Lack of greater moisture and buoyancy will be a limiting factor for coverage and intensity of convection, which should diminish rapidly after dark. ..Edwards/Bentley.. 07/11/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Thu Jul 11 2024 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN ARIZONA... ...SUMMARY... Severe thunderstorm gusts are possible over parts of southern Arizona from midafternoon into early evening. ...Synopsis... In mid/upper levels, the overall pattern will change little through the period, with mean ridging in the West, and troughing over the Great Lakes and vicinity. The persistent anticyclone will remain over the Great Basin, with some deamplification of ridging to its north leading to more-zonal flow across the northern tier of states from WA-ND. A weak shortwave trough -- apparent in moisture-channel imagery over parts of central/eastern MT -- should move slowly east-southeastward across the northern High Plains today amid difluent flow. Meanwhile and downstream, a pronounced shortwave trough now over parts of WI/IL/IA should eject northeastward over the Upper Great Lakes and weaken, while smaller/upstream perturbations help to maintain the mean trough. Both the low/middle-level remains of TC Beryl, and a closely associated shortwave trough of midlatitude origins, should shear northeastward across southern QC, the lower St. Lawrence Valley, and northern New England, weakening considerably. At the surface, 11Z analysis showed a low near the NH/QC border with slow-moving, weakening cold front across western New England, the coastal Mid-Atlantic/Carolinas, southern GA, and FL Panhandle, becoming quasistationary along the northwestern Gulf Coast. This front should continue weakening near or just east of its present position through the period, over the Northeast, and also weaken over the Gulf Coast and southern Atlantic Coast States. Enough low-level shear exists over parts of ME today to support a conditional supercell potential, but strength/coverage/longevity are in question due to weakness of both instability and lift. Elsewhere, a lee trough analyzed on that chart over eastern parts of MT/WY/CO should remain over the central/northern High Plains today, with some eastward drift possible. ...AZ... Widely scattered to scattered thunderstorms are expected to develop this afternoon, over the Mogollon Rim and smaller mountain ranges to the south. That will occur as strong insolation at those higher elevations preferentially removes MLCINH, in the presence of generally greater low-level moisture than previous days. Some strengthening of flow aloft is expected over this region, around the southeastern rim of the anticyclone. This will support convective motion off the Rim (and small mountain ranges to its south), then atop well-heated/deeply mixed boundary layers of the desert floor. Isolated strong-severe gusts are possible from the relatively early, more-discrete activity. With the lower-elevation boundary layers being very deep (surface to around 600 mb), but enough moisture maintained through mixing to keep surface-based buoyancy (MLCAPE in the 500-1000 J/kg range), expect some aggregation of outflows with additional development atop those -- especially over southeastern AZ. The net result should be both translation and developmental propagation of convection southwestward to and across the international border, with swaths of strong-severe gusts possible. ...Northern High Plains... Isolated to widely scattered, high-based thunderstorms are expected to form near the lee trough, where both relatively maximized convergence and strong surface heating should contribute to enough lift for convective initiation. The main concern up and down the corridor should be damaging to severe gusts, given the deeply mixed subcloud layer and ample downdraft-acceleration opportunity that will afford. Isolated severe hail also may occur, amidst enough deep-layer shear for some organized thunderstorms (effective-shear magnitudes of 30-40 kt). Lack of greater moisture and buoyancy will be a limiting factor for coverage and intensity of convection, which should diminish rapidly after dark. ..Edwards/Bentley.. 07/11/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Thu Jul 11 2024 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN ARIZONA... ...SUMMARY... Severe thunderstorm gusts are possible over parts of southern Arizona from midafternoon into early evening. ...Synopsis... In mid/upper levels, the overall pattern will change little through the period, with mean ridging in the West, and troughing over the Great Lakes and vicinity. The persistent anticyclone will remain over the Great Basin, with some deamplification of ridging to its north leading to more-zonal flow across the northern tier of states from WA-ND. A weak shortwave trough -- apparent in moisture-channel imagery over parts of central/eastern MT -- should move slowly east-southeastward across the northern High Plains today amid difluent flow. Meanwhile and downstream, a pronounced shortwave trough now over parts of WI/IL/IA should eject northeastward over the Upper Great Lakes and weaken, while smaller/upstream perturbations help to maintain the mean trough. Both the low/middle-level remains of TC Beryl, and a closely associated shortwave trough of midlatitude origins, should shear northeastward across southern QC, the lower St. Lawrence Valley, and northern New England, weakening considerably. At the surface, 11Z analysis showed a low near the NH/QC border with slow-moving, weakening cold front across western New England, the coastal Mid-Atlantic/Carolinas, southern GA, and FL Panhandle, becoming quasistationary along the northwestern Gulf Coast. This front should continue weakening near or just east of its present position through the period, over the Northeast, and also weaken over the Gulf Coast and southern Atlantic Coast States. Enough low-level shear exists over parts of ME today to support a conditional supercell potential, but strength/coverage/longevity are in question due to weakness of both instability and lift. Elsewhere, a lee trough analyzed on that chart over eastern parts of MT/WY/CO should remain over the central/northern High Plains today, with some eastward drift possible. ...AZ... Widely scattered to scattered thunderstorms are expected to develop this afternoon, over the Mogollon Rim and smaller mountain ranges to the south. That will occur as strong insolation at those higher elevations preferentially removes MLCINH, in the presence of generally greater low-level moisture than previous days. Some strengthening of flow aloft is expected over this region, around the southeastern rim of the anticyclone. This will support convective motion off the Rim (and small mountain ranges to its south), then atop well-heated/deeply mixed boundary layers of the desert floor. Isolated strong-severe gusts are possible from the relatively early, more-discrete activity. With the lower-elevation boundary layers being very deep (surface to around 600 mb), but enough moisture maintained through mixing to keep surface-based buoyancy (MLCAPE in the 500-1000 J/kg range), expect some aggregation of outflows with additional development atop those -- especially over southeastern AZ. The net result should be both translation and developmental propagation of convection southwestward to and across the international border, with swaths of strong-severe gusts possible. ...Northern High Plains... Isolated to widely scattered, high-based thunderstorms are expected to form near the lee trough, where both relatively maximized convergence and strong surface heating should contribute to enough lift for convective initiation. The main concern up and down the corridor should be damaging to severe gusts, given the deeply mixed subcloud layer and ample downdraft-acceleration opportunity that will afford. Isolated severe hail also may occur, amidst enough deep-layer shear for some organized thunderstorms (effective-shear magnitudes of 30-40 kt). Lack of greater moisture and buoyancy will be a limiting factor for coverage and intensity of convection, which should diminish rapidly after dark. ..Edwards/Bentley.. 07/11/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Thu Jul 11 2024 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN ARIZONA... ...SUMMARY... Severe thunderstorm gusts are possible over parts of southern Arizona from midafternoon into early evening. ...Synopsis... In mid/upper levels, the overall pattern will change little through the period, with mean ridging in the West, and troughing over the Great Lakes and vicinity. The persistent anticyclone will remain over the Great Basin, with some deamplification of ridging to its north leading to more-zonal flow across the northern tier of states from WA-ND. A weak shortwave trough -- apparent in moisture-channel imagery over parts of central/eastern MT -- should move slowly east-southeastward across the northern High Plains today amid difluent flow. Meanwhile and downstream, a pronounced shortwave trough now over parts of WI/IL/IA should eject northeastward over the Upper Great Lakes and weaken, while smaller/upstream perturbations help to maintain the mean trough. Both the low/middle-level remains of TC Beryl, and a closely associated shortwave trough of midlatitude origins, should shear northeastward across southern QC, the lower St. Lawrence Valley, and northern New England, weakening considerably. At the surface, 11Z analysis showed a low near the NH/QC border with slow-moving, weakening cold front across western New England, the coastal Mid-Atlantic/Carolinas, southern GA, and FL Panhandle, becoming quasistationary along the northwestern Gulf Coast. This front should continue weakening near or just east of its present position through the period, over the Northeast, and also weaken over the Gulf Coast and southern Atlantic Coast States. Enough low-level shear exists over parts of ME today to support a conditional supercell potential, but strength/coverage/longevity are in question due to weakness of both instability and lift. Elsewhere, a lee trough analyzed on that chart over eastern parts of MT/WY/CO should remain over the central/northern High Plains today, with some eastward drift possible. ...AZ... Widely scattered to scattered thunderstorms are expected to develop this afternoon, over the Mogollon Rim and smaller mountain ranges to the south. That will occur as strong insolation at those higher elevations preferentially removes MLCINH, in the presence of generally greater low-level moisture than previous days. Some strengthening of flow aloft is expected over this region, around the southeastern rim of the anticyclone. This will support convective motion off the Rim (and small mountain ranges to its south), then atop well-heated/deeply mixed boundary layers of the desert floor. Isolated strong-severe gusts are possible from the relatively early, more-discrete activity. With the lower-elevation boundary layers being very deep (surface to around 600 mb), but enough moisture maintained through mixing to keep surface-based buoyancy (MLCAPE in the 500-1000 J/kg range), expect some aggregation of outflows with additional development atop those -- especially over southeastern AZ. The net result should be both translation and developmental propagation of convection southwestward to and across the international border, with swaths of strong-severe gusts possible. ...Northern High Plains... Isolated to widely scattered, high-based thunderstorms are expected to form near the lee trough, where both relatively maximized convergence and strong surface heating should contribute to enough lift for convective initiation. The main concern up and down the corridor should be damaging to severe gusts, given the deeply mixed subcloud layer and ample downdraft-acceleration opportunity that will afford. Isolated severe hail also may occur, amidst enough deep-layer shear for some organized thunderstorms (effective-shear magnitudes of 30-40 kt). Lack of greater moisture and buoyancy will be a limiting factor for coverage and intensity of convection, which should diminish rapidly after dark. ..Edwards/Bentley.. 07/11/2024 Read more

000
ABPZ20 KNHC 111128
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Thu Jul 11 2024

For the eastern North Pacific...east of 140 degrees west longitude:

Central East Pacific:
A tropical wave located near Central America is forecast to move
westward at 10 to 15 mph across the tropical East Pacific during
the next week. Conditions could become favorable for some slow
development of the wave next week as it approaches the central
portion of the basin.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.

$$
Forecaster D. Zelinsky

000
ABNT20 KNHC 111116
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Thu Jul 11 2024

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Active Systems:
The Weather Prediction Center has issued its final advisory on
Post-Tropical Cyclone Beryl, located over southeastern Canada.

Off the Southeastern U.S. Coast:
A broad area of low pressure located a few hundred miles off the
southeastern U.S. coast continues to produce disorganized showers
and thunderstorms. Environmental conditions do not appear favorable
for much additional development of this system over the next day or
two before it moves inland over the southeastern U.S. by this
weekend. Regardless of development, heavy rainfall will be possible
for portions of the Carolina coast late this week into the weekend.
For more information about the potential for heavy rainfall, see
products issued by the Weather Prediction Center and your local
National Weather Service office.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...low...10 percent.

$$
Forecaster Papin

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Thu Jul 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... An upper-level ridge will remain in place over much of the western and central CONUS through at least early next week. Multiple mid-level impulses are expected to traverse the anticyclonic flow over the northern CONUS through at least Days 4-5 (Sunday-Monday). These impulses may be accompanied by multiple rounds of strong to severe thunderstorms given continued low-level WAA/moisture advection along the eastern periphery of a regenerating EML. By days 6-7 (Tuesday-Wednesday), a mid-level trough will amplify over the Great Lakes, with a surface cold front expected to sweep southward across the northern Plains into the Northeast, promoting showers and thunderstorms (perhaps strong to severe), but also clearing out the low-level moisture, EML, and associated buoyancy in the process. ...Days 4-5 (Sunday-Monday)... Medium-range guidance consensus shows a mid-level impulse approaching the Great Lakes region from the northern Plains on Sunday (albeit later than earlier model runs). While both the latest ECMWF and GFS agree on the mid-level impulse overspreading the nose of the WAA (and associated 3000-4000 J/kg MUCAPE) over the Upper MS Valley on Sunday, the later arrival of the mid-level impulse past peak afternoon heating results in a complex forecast. The GFS depicts potential convection over the northern Great Lakes by late afternoon/early evening while the ECMWF develops precipitation over central/southern MN that rapidly progress to the WI/IL border. While it is unclear which scenario will unfold, both regimes involve organized convection traversing an axis of strong to extreme instability amid adequate deep-layer shear to support a severe threat. This includes the possibility of a severe-wind producing MCS, warranting a broad 15 percent area. Substantial modifications may be needed to this highlight in later outlooks as mesoscale details and associated placement of key baroclinic boundaries becomes evident. The latest ECMWF and GFS depicts a more pronounced mid-level trough traversing the Upper MS Valley by afternoon peak heating on Day 5 (Monday). Continued low-level moisture advection from the south, beneath a regenerating plume of steep mid-level lapse rates from the west, will support another day of strong to extreme instability overspreading the Upper Midwest. This time, stronger deep-layer shear with the better-timed mid-level impulse will coincide with the instability axis, fostering an environment favorable for severe storms. Given impacts from Day 4 (Sunday) convection, it is unclear how and where mesoscale low-level boundaries will become established over the Midwest, and these will be key to supporting a severe threat (including the possibility of severe wind-producing bow-echo MCSs). 15 percent highlights have been added over the general area where both the GFS and ECMWF agree on precipitation occurring with overlapping favorable vertical wind shear and strong/extreme instability. Like Sunday though, the highlights provided for Monday will likely need substantial modification based on later-known placement of important mesoscale meteorological features. ...Days 6-7 (Tuesday-Wednesday)... ECMWF and GFS are in general agreement in thunderstorms initiating along and ahead of a surface cold front, anywhere from the northern Plains to the Northeast states in the Days 6-7 (Tuesday-Wednesday) time frame. These storms would traverse a buoyancy axis, possibly becoming strong or even severe in the process. However, great uncertainty exists on precisely where and when the greatest severe threat would materialize, since there is more disagreement among medium-range guidance members compared to earlier days. Furthermore, details on severe placement and timing still hinge on the evolution of earlier thunderstorm events (i.e. where baroclinic boundaries are left behind). When taking into account both model disagreements and uncertainties of preceding convective influences, severe probabilities have been withheld this outlook. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Thu Jul 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... An upper-level ridge will remain in place over much of the western and central CONUS through at least early next week. Multiple mid-level impulses are expected to traverse the anticyclonic flow over the northern CONUS through at least Days 4-5 (Sunday-Monday). These impulses may be accompanied by multiple rounds of strong to severe thunderstorms given continued low-level WAA/moisture advection along the eastern periphery of a regenerating EML. By days 6-7 (Tuesday-Wednesday), a mid-level trough will amplify over the Great Lakes, with a surface cold front expected to sweep southward across the northern Plains into the Northeast, promoting showers and thunderstorms (perhaps strong to severe), but also clearing out the low-level moisture, EML, and associated buoyancy in the process. ...Days 4-5 (Sunday-Monday)... Medium-range guidance consensus shows a mid-level impulse approaching the Great Lakes region from the northern Plains on Sunday (albeit later than earlier model runs). While both the latest ECMWF and GFS agree on the mid-level impulse overspreading the nose of the WAA (and associated 3000-4000 J/kg MUCAPE) over the Upper MS Valley on Sunday, the later arrival of the mid-level impulse past peak afternoon heating results in a complex forecast. The GFS depicts potential convection over the northern Great Lakes by late afternoon/early evening while the ECMWF develops precipitation over central/southern MN that rapidly progress to the WI/IL border. While it is unclear which scenario will unfold, both regimes involve organized convection traversing an axis of strong to extreme instability amid adequate deep-layer shear to support a severe threat. This includes the possibility of a severe-wind producing MCS, warranting a broad 15 percent area. Substantial modifications may be needed to this highlight in later outlooks as mesoscale details and associated placement of key baroclinic boundaries becomes evident. The latest ECMWF and GFS depicts a more pronounced mid-level trough traversing the Upper MS Valley by afternoon peak heating on Day 5 (Monday). Continued low-level moisture advection from the south, beneath a regenerating plume of steep mid-level lapse rates from the west, will support another day of strong to extreme instability overspreading the Upper Midwest. This time, stronger deep-layer shear with the better-timed mid-level impulse will coincide with the instability axis, fostering an environment favorable for severe storms. Given impacts from Day 4 (Sunday) convection, it is unclear how and where mesoscale low-level boundaries will become established over the Midwest, and these will be key to supporting a severe threat (including the possibility of severe wind-producing bow-echo MCSs). 15 percent highlights have been added over the general area where both the GFS and ECMWF agree on precipitation occurring with overlapping favorable vertical wind shear and strong/extreme instability. Like Sunday though, the highlights provided for Monday will likely need substantial modification based on later-known placement of important mesoscale meteorological features. ...Days 6-7 (Tuesday-Wednesday)... ECMWF and GFS are in general agreement in thunderstorms initiating along and ahead of a surface cold front, anywhere from the northern Plains to the Northeast states in the Days 6-7 (Tuesday-Wednesday) time frame. These storms would traverse a buoyancy axis, possibly becoming strong or even severe in the process. However, great uncertainty exists on precisely where and when the greatest severe threat would materialize, since there is more disagreement among medium-range guidance members compared to earlier days. Furthermore, details on severe placement and timing still hinge on the evolution of earlier thunderstorm events (i.e. where baroclinic boundaries are left behind). When taking into account both model disagreements and uncertainties of preceding convective influences, severe probabilities have been withheld this outlook. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Thu Jul 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... An upper-level ridge will remain in place over much of the western and central CONUS through at least early next week. Multiple mid-level impulses are expected to traverse the anticyclonic flow over the northern CONUS through at least Days 4-5 (Sunday-Monday). These impulses may be accompanied by multiple rounds of strong to severe thunderstorms given continued low-level WAA/moisture advection along the eastern periphery of a regenerating EML. By days 6-7 (Tuesday-Wednesday), a mid-level trough will amplify over the Great Lakes, with a surface cold front expected to sweep southward across the northern Plains into the Northeast, promoting showers and thunderstorms (perhaps strong to severe), but also clearing out the low-level moisture, EML, and associated buoyancy in the process. ...Days 4-5 (Sunday-Monday)... Medium-range guidance consensus shows a mid-level impulse approaching the Great Lakes region from the northern Plains on Sunday (albeit later than earlier model runs). While both the latest ECMWF and GFS agree on the mid-level impulse overspreading the nose of the WAA (and associated 3000-4000 J/kg MUCAPE) over the Upper MS Valley on Sunday, the later arrival of the mid-level impulse past peak afternoon heating results in a complex forecast. The GFS depicts potential convection over the northern Great Lakes by late afternoon/early evening while the ECMWF develops precipitation over central/southern MN that rapidly progress to the WI/IL border. While it is unclear which scenario will unfold, both regimes involve organized convection traversing an axis of strong to extreme instability amid adequate deep-layer shear to support a severe threat. This includes the possibility of a severe-wind producing MCS, warranting a broad 15 percent area. Substantial modifications may be needed to this highlight in later outlooks as mesoscale details and associated placement of key baroclinic boundaries becomes evident. The latest ECMWF and GFS depicts a more pronounced mid-level trough traversing the Upper MS Valley by afternoon peak heating on Day 5 (Monday). Continued low-level moisture advection from the south, beneath a regenerating plume of steep mid-level lapse rates from the west, will support another day of strong to extreme instability overspreading the Upper Midwest. This time, stronger deep-layer shear with the better-timed mid-level impulse will coincide with the instability axis, fostering an environment favorable for severe storms. Given impacts from Day 4 (Sunday) convection, it is unclear how and where mesoscale low-level boundaries will become established over the Midwest, and these will be key to supporting a severe threat (including the possibility of severe wind-producing bow-echo MCSs). 15 percent highlights have been added over the general area where both the GFS and ECMWF agree on precipitation occurring with overlapping favorable vertical wind shear and strong/extreme instability. Like Sunday though, the highlights provided for Monday will likely need substantial modification based on later-known placement of important mesoscale meteorological features. ...Days 6-7 (Tuesday-Wednesday)... ECMWF and GFS are in general agreement in thunderstorms initiating along and ahead of a surface cold front, anywhere from the northern Plains to the Northeast states in the Days 6-7 (Tuesday-Wednesday) time frame. These storms would traverse a buoyancy axis, possibly becoming strong or even severe in the process. However, great uncertainty exists on precisely where and when the greatest severe threat would materialize, since there is more disagreement among medium-range guidance members compared to earlier days. Furthermore, details on severe placement and timing still hinge on the evolution of earlier thunderstorm events (i.e. where baroclinic boundaries are left behind). When taking into account both model disagreements and uncertainties of preceding convective influences, severe probabilities have been withheld this outlook. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Thu Jul 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... An upper-level ridge will remain in place over much of the western and central CONUS through at least early next week. Multiple mid-level impulses are expected to traverse the anticyclonic flow over the northern CONUS through at least Days 4-5 (Sunday-Monday). These impulses may be accompanied by multiple rounds of strong to severe thunderstorms given continued low-level WAA/moisture advection along the eastern periphery of a regenerating EML. By days 6-7 (Tuesday-Wednesday), a mid-level trough will amplify over the Great Lakes, with a surface cold front expected to sweep southward across the northern Plains into the Northeast, promoting showers and thunderstorms (perhaps strong to severe), but also clearing out the low-level moisture, EML, and associated buoyancy in the process. ...Days 4-5 (Sunday-Monday)... Medium-range guidance consensus shows a mid-level impulse approaching the Great Lakes region from the northern Plains on Sunday (albeit later than earlier model runs). While both the latest ECMWF and GFS agree on the mid-level impulse overspreading the nose of the WAA (and associated 3000-4000 J/kg MUCAPE) over the Upper MS Valley on Sunday, the later arrival of the mid-level impulse past peak afternoon heating results in a complex forecast. The GFS depicts potential convection over the northern Great Lakes by late afternoon/early evening while the ECMWF develops precipitation over central/southern MN that rapidly progress to the WI/IL border. While it is unclear which scenario will unfold, both regimes involve organized convection traversing an axis of strong to extreme instability amid adequate deep-layer shear to support a severe threat. This includes the possibility of a severe-wind producing MCS, warranting a broad 15 percent area. Substantial modifications may be needed to this highlight in later outlooks as mesoscale details and associated placement of key baroclinic boundaries becomes evident. The latest ECMWF and GFS depicts a more pronounced mid-level trough traversing the Upper MS Valley by afternoon peak heating on Day 5 (Monday). Continued low-level moisture advection from the south, beneath a regenerating plume of steep mid-level lapse rates from the west, will support another day of strong to extreme instability overspreading the Upper Midwest. This time, stronger deep-layer shear with the better-timed mid-level impulse will coincide with the instability axis, fostering an environment favorable for severe storms. Given impacts from Day 4 (Sunday) convection, it is unclear how and where mesoscale low-level boundaries will become established over the Midwest, and these will be key to supporting a severe threat (including the possibility of severe wind-producing bow-echo MCSs). 15 percent highlights have been added over the general area where both the GFS and ECMWF agree on precipitation occurring with overlapping favorable vertical wind shear and strong/extreme instability. Like Sunday though, the highlights provided for Monday will likely need substantial modification based on later-known placement of important mesoscale meteorological features. ...Days 6-7 (Tuesday-Wednesday)... ECMWF and GFS are in general agreement in thunderstorms initiating along and ahead of a surface cold front, anywhere from the northern Plains to the Northeast states in the Days 6-7 (Tuesday-Wednesday) time frame. These storms would traverse a buoyancy axis, possibly becoming strong or even severe in the process. However, great uncertainty exists on precisely where and when the greatest severe threat would materialize, since there is more disagreement among medium-range guidance members compared to earlier days. Furthermore, details on severe placement and timing still hinge on the evolution of earlier thunderstorm events (i.e. where baroclinic boundaries are left behind). When taking into account both model disagreements and uncertainties of preceding convective influences, severe probabilities have been withheld this outlook. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Thu Jul 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... An upper-level ridge will remain in place over much of the western and central CONUS through at least early next week. Multiple mid-level impulses are expected to traverse the anticyclonic flow over the northern CONUS through at least Days 4-5 (Sunday-Monday). These impulses may be accompanied by multiple rounds of strong to severe thunderstorms given continued low-level WAA/moisture advection along the eastern periphery of a regenerating EML. By days 6-7 (Tuesday-Wednesday), a mid-level trough will amplify over the Great Lakes, with a surface cold front expected to sweep southward across the northern Plains into the Northeast, promoting showers and thunderstorms (perhaps strong to severe), but also clearing out the low-level moisture, EML, and associated buoyancy in the process. ...Days 4-5 (Sunday-Monday)... Medium-range guidance consensus shows a mid-level impulse approaching the Great Lakes region from the northern Plains on Sunday (albeit later than earlier model runs). While both the latest ECMWF and GFS agree on the mid-level impulse overspreading the nose of the WAA (and associated 3000-4000 J/kg MUCAPE) over the Upper MS Valley on Sunday, the later arrival of the mid-level impulse past peak afternoon heating results in a complex forecast. The GFS depicts potential convection over the northern Great Lakes by late afternoon/early evening while the ECMWF develops precipitation over central/southern MN that rapidly progress to the WI/IL border. While it is unclear which scenario will unfold, both regimes involve organized convection traversing an axis of strong to extreme instability amid adequate deep-layer shear to support a severe threat. This includes the possibility of a severe-wind producing MCS, warranting a broad 15 percent area. Substantial modifications may be needed to this highlight in later outlooks as mesoscale details and associated placement of key baroclinic boundaries becomes evident. The latest ECMWF and GFS depicts a more pronounced mid-level trough traversing the Upper MS Valley by afternoon peak heating on Day 5 (Monday). Continued low-level moisture advection from the south, beneath a regenerating plume of steep mid-level lapse rates from the west, will support another day of strong to extreme instability overspreading the Upper Midwest. This time, stronger deep-layer shear with the better-timed mid-level impulse will coincide with the instability axis, fostering an environment favorable for severe storms. Given impacts from Day 4 (Sunday) convection, it is unclear how and where mesoscale low-level boundaries will become established over the Midwest, and these will be key to supporting a severe threat (including the possibility of severe wind-producing bow-echo MCSs). 15 percent highlights have been added over the general area where both the GFS and ECMWF agree on precipitation occurring with overlapping favorable vertical wind shear and strong/extreme instability. Like Sunday though, the highlights provided for Monday will likely need substantial modification based on later-known placement of important mesoscale meteorological features. ...Days 6-7 (Tuesday-Wednesday)... ECMWF and GFS are in general agreement in thunderstorms initiating along and ahead of a surface cold front, anywhere from the northern Plains to the Northeast states in the Days 6-7 (Tuesday-Wednesday) time frame. These storms would traverse a buoyancy axis, possibly becoming strong or even severe in the process. However, great uncertainty exists on precisely where and when the greatest severe threat would materialize, since there is more disagreement among medium-range guidance members compared to earlier days. Furthermore, details on severe placement and timing still hinge on the evolution of earlier thunderstorm events (i.e. where baroclinic boundaries are left behind). When taking into account both model disagreements and uncertainties of preceding convective influences, severe probabilities have been withheld this outlook. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Thu Jul 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... An upper-level ridge will remain in place over much of the western and central CONUS through at least early next week. Multiple mid-level impulses are expected to traverse the anticyclonic flow over the northern CONUS through at least Days 4-5 (Sunday-Monday). These impulses may be accompanied by multiple rounds of strong to severe thunderstorms given continued low-level WAA/moisture advection along the eastern periphery of a regenerating EML. By days 6-7 (Tuesday-Wednesday), a mid-level trough will amplify over the Great Lakes, with a surface cold front expected to sweep southward across the northern Plains into the Northeast, promoting showers and thunderstorms (perhaps strong to severe), but also clearing out the low-level moisture, EML, and associated buoyancy in the process. ...Days 4-5 (Sunday-Monday)... Medium-range guidance consensus shows a mid-level impulse approaching the Great Lakes region from the northern Plains on Sunday (albeit later than earlier model runs). While both the latest ECMWF and GFS agree on the mid-level impulse overspreading the nose of the WAA (and associated 3000-4000 J/kg MUCAPE) over the Upper MS Valley on Sunday, the later arrival of the mid-level impulse past peak afternoon heating results in a complex forecast. The GFS depicts potential convection over the northern Great Lakes by late afternoon/early evening while the ECMWF develops precipitation over central/southern MN that rapidly progress to the WI/IL border. While it is unclear which scenario will unfold, both regimes involve organized convection traversing an axis of strong to extreme instability amid adequate deep-layer shear to support a severe threat. This includes the possibility of a severe-wind producing MCS, warranting a broad 15 percent area. Substantial modifications may be needed to this highlight in later outlooks as mesoscale details and associated placement of key baroclinic boundaries becomes evident. The latest ECMWF and GFS depicts a more pronounced mid-level trough traversing the Upper MS Valley by afternoon peak heating on Day 5 (Monday). Continued low-level moisture advection from the south, beneath a regenerating plume of steep mid-level lapse rates from the west, will support another day of strong to extreme instability overspreading the Upper Midwest. This time, stronger deep-layer shear with the better-timed mid-level impulse will coincide with the instability axis, fostering an environment favorable for severe storms. Given impacts from Day 4 (Sunday) convection, it is unclear how and where mesoscale low-level boundaries will become established over the Midwest, and these will be key to supporting a severe threat (including the possibility of severe wind-producing bow-echo MCSs). 15 percent highlights have been added over the general area where both the GFS and ECMWF agree on precipitation occurring with overlapping favorable vertical wind shear and strong/extreme instability. Like Sunday though, the highlights provided for Monday will likely need substantial modification based on later-known placement of important mesoscale meteorological features. ...Days 6-7 (Tuesday-Wednesday)... ECMWF and GFS are in general agreement in thunderstorms initiating along and ahead of a surface cold front, anywhere from the northern Plains to the Northeast states in the Days 6-7 (Tuesday-Wednesday) time frame. These storms would traverse a buoyancy axis, possibly becoming strong or even severe in the process. However, great uncertainty exists on precisely where and when the greatest severe threat would materialize, since there is more disagreement among medium-range guidance members compared to earlier days. Furthermore, details on severe placement and timing still hinge on the evolution of earlier thunderstorm events (i.e. where baroclinic boundaries are left behind). When taking into account both model disagreements and uncertainties of preceding convective influences, severe probabilities have been withheld this outlook. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 AM CDT Thu Jul 11 2024 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Multiple clusters of strong to severe thunderstorms are possible across portions of the Northern Plains into the Upper Mississippi Valley on Saturday. ...Synopsis... A mid-level anticylone, centered over the central Rockies, will promote upper ridging from the Interior West to the MS Valley on Saturday. The first in a series of pronounced mid-level impulses is poised to pivot around the anticyclone and rapidly traverse the northern Plains and Upper MS Valley through the period. Rich low-level moisture, aided by widespread WAA beneath an EML, will precede the arrival of the mid-level impulse, resulting in strong to extreme buoyancy becoming established over the northern Plains and Upper MS Valley. The capping inversion associated with the EML makes it difficult to pinpoint precisely where and when the greatest severe threat will be. Nonetheless, at least a few clusters of strong to severe storms should evolve across the north-central CONUS on Saturday. ...Northern Plains into the Upper MS Valley... Surface lee troughing over the Plains will continue to foster low-level WAA, ushering in mid to upper 70s F surface dewpoints beneath an eastward-advecting plume of 7-8 C/km mid-level lapse rates from the EML. This thermodynamic regime will support 3000-5000 J/kg of MUCAPE from the Dakotas eastward to the MS River. However, accompanying this strong to locally extreme instability is an appreciable amount of MLCINH, which is typical for EML plumes pivoting around a synoptic scale anticyclone. The aforementioned approaching mid-level impulse cresting the upper ridge is expected to reach the MT/ND border by around 00Z and reach the MS River by 12Z. The point where the mid-level impulse overspreads the rich low-level moisture, along with the east-northeastern terminus of the low-level WAA regime, appear to be the most likely regions for convective initiation. Peak afternoon heating, along with low-level convergence at the WAA terminus, may support the initiation of multicellular clusters over parts of eastern IA into IL sometime during the mid-afternoon to early evening time frame. Given modest vertical wind shear, cold-pool mergers could support upscale growth into one or more MCSs that will approach Lake Michigan, accompanied by at least isolated severe wind or hail. Around sunset, additional storms may develop across northern and eastern MN into western WI, perhaps driven by isentropic lift. Since these storms will traverse the periphery of greater instability amid modest vertical wind shear, it is unclear how severe these storms will become, though at least isolated severe hail and/or wind is plausible. Finally, thunderstorms may initiate as far west as the MT/ND border or even adjacent parts of Canada by early evening. This severe threat is the most conditional of all scenarios. Should capping be overcome, the storms will initiate west of an elongated axis of strong to extreme instability, amid at least 30 kts of effective bulk shear. The storms will be initially displaced west of the richer low-level moisture, hence they would be high-based in nature, accompanied by primarily a severe gust threat. Though less likely, if these storms can congeal into an organized MCS, the MCS could become longer-lived and pose a threat for a more focused corridor of severe gusts. ..Squitieri.. 07/11/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 AM CDT Thu Jul 11 2024 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Multiple clusters of strong to severe thunderstorms are possible across portions of the Northern Plains into the Upper Mississippi Valley on Saturday. ...Synopsis... A mid-level anticylone, centered over the central Rockies, will promote upper ridging from the Interior West to the MS Valley on Saturday. The first in a series of pronounced mid-level impulses is poised to pivot around the anticyclone and rapidly traverse the northern Plains and Upper MS Valley through the period. Rich low-level moisture, aided by widespread WAA beneath an EML, will precede the arrival of the mid-level impulse, resulting in strong to extreme buoyancy becoming established over the northern Plains and Upper MS Valley. The capping inversion associated with the EML makes it difficult to pinpoint precisely where and when the greatest severe threat will be. Nonetheless, at least a few clusters of strong to severe storms should evolve across the north-central CONUS on Saturday. ...Northern Plains into the Upper MS Valley... Surface lee troughing over the Plains will continue to foster low-level WAA, ushering in mid to upper 70s F surface dewpoints beneath an eastward-advecting plume of 7-8 C/km mid-level lapse rates from the EML. This thermodynamic regime will support 3000-5000 J/kg of MUCAPE from the Dakotas eastward to the MS River. However, accompanying this strong to locally extreme instability is an appreciable amount of MLCINH, which is typical for EML plumes pivoting around a synoptic scale anticyclone. The aforementioned approaching mid-level impulse cresting the upper ridge is expected to reach the MT/ND border by around 00Z and reach the MS River by 12Z. The point where the mid-level impulse overspreads the rich low-level moisture, along with the east-northeastern terminus of the low-level WAA regime, appear to be the most likely regions for convective initiation. Peak afternoon heating, along with low-level convergence at the WAA terminus, may support the initiation of multicellular clusters over parts of eastern IA into IL sometime during the mid-afternoon to early evening time frame. Given modest vertical wind shear, cold-pool mergers could support upscale growth into one or more MCSs that will approach Lake Michigan, accompanied by at least isolated severe wind or hail. Around sunset, additional storms may develop across northern and eastern MN into western WI, perhaps driven by isentropic lift. Since these storms will traverse the periphery of greater instability amid modest vertical wind shear, it is unclear how severe these storms will become, though at least isolated severe hail and/or wind is plausible. Finally, thunderstorms may initiate as far west as the MT/ND border or even adjacent parts of Canada by early evening. This severe threat is the most conditional of all scenarios. Should capping be overcome, the storms will initiate west of an elongated axis of strong to extreme instability, amid at least 30 kts of effective bulk shear. The storms will be initially displaced west of the richer low-level moisture, hence they would be high-based in nature, accompanied by primarily a severe gust threat. Though less likely, if these storms can congeal into an organized MCS, the MCS could become longer-lived and pose a threat for a more focused corridor of severe gusts. ..Squitieri.. 07/11/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 AM CDT Thu Jul 11 2024 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Multiple clusters of strong to severe thunderstorms are possible across portions of the Northern Plains into the Upper Mississippi Valley on Saturday. ...Synopsis... A mid-level anticylone, centered over the central Rockies, will promote upper ridging from the Interior West to the MS Valley on Saturday. The first in a series of pronounced mid-level impulses is poised to pivot around the anticyclone and rapidly traverse the northern Plains and Upper MS Valley through the period. Rich low-level moisture, aided by widespread WAA beneath an EML, will precede the arrival of the mid-level impulse, resulting in strong to extreme buoyancy becoming established over the northern Plains and Upper MS Valley. The capping inversion associated with the EML makes it difficult to pinpoint precisely where and when the greatest severe threat will be. Nonetheless, at least a few clusters of strong to severe storms should evolve across the north-central CONUS on Saturday. ...Northern Plains into the Upper MS Valley... Surface lee troughing over the Plains will continue to foster low-level WAA, ushering in mid to upper 70s F surface dewpoints beneath an eastward-advecting plume of 7-8 C/km mid-level lapse rates from the EML. This thermodynamic regime will support 3000-5000 J/kg of MUCAPE from the Dakotas eastward to the MS River. However, accompanying this strong to locally extreme instability is an appreciable amount of MLCINH, which is typical for EML plumes pivoting around a synoptic scale anticyclone. The aforementioned approaching mid-level impulse cresting the upper ridge is expected to reach the MT/ND border by around 00Z and reach the MS River by 12Z. The point where the mid-level impulse overspreads the rich low-level moisture, along with the east-northeastern terminus of the low-level WAA regime, appear to be the most likely regions for convective initiation. Peak afternoon heating, along with low-level convergence at the WAA terminus, may support the initiation of multicellular clusters over parts of eastern IA into IL sometime during the mid-afternoon to early evening time frame. Given modest vertical wind shear, cold-pool mergers could support upscale growth into one or more MCSs that will approach Lake Michigan, accompanied by at least isolated severe wind or hail. Around sunset, additional storms may develop across northern and eastern MN into western WI, perhaps driven by isentropic lift. Since these storms will traverse the periphery of greater instability amid modest vertical wind shear, it is unclear how severe these storms will become, though at least isolated severe hail and/or wind is plausible. Finally, thunderstorms may initiate as far west as the MT/ND border or even adjacent parts of Canada by early evening. This severe threat is the most conditional of all scenarios. Should capping be overcome, the storms will initiate west of an elongated axis of strong to extreme instability, amid at least 30 kts of effective bulk shear. The storms will be initially displaced west of the richer low-level moisture, hence they would be high-based in nature, accompanied by primarily a severe gust threat. Though less likely, if these storms can congeal into an organized MCS, the MCS could become longer-lived and pose a threat for a more focused corridor of severe gusts. ..Squitieri.. 07/11/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 AM CDT Thu Jul 11 2024 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Multiple clusters of strong to severe thunderstorms are possible across portions of the Northern Plains into the Upper Mississippi Valley on Saturday. ...Synopsis... A mid-level anticylone, centered over the central Rockies, will promote upper ridging from the Interior West to the MS Valley on Saturday. The first in a series of pronounced mid-level impulses is poised to pivot around the anticyclone and rapidly traverse the northern Plains and Upper MS Valley through the period. Rich low-level moisture, aided by widespread WAA beneath an EML, will precede the arrival of the mid-level impulse, resulting in strong to extreme buoyancy becoming established over the northern Plains and Upper MS Valley. The capping inversion associated with the EML makes it difficult to pinpoint precisely where and when the greatest severe threat will be. Nonetheless, at least a few clusters of strong to severe storms should evolve across the north-central CONUS on Saturday. ...Northern Plains into the Upper MS Valley... Surface lee troughing over the Plains will continue to foster low-level WAA, ushering in mid to upper 70s F surface dewpoints beneath an eastward-advecting plume of 7-8 C/km mid-level lapse rates from the EML. This thermodynamic regime will support 3000-5000 J/kg of MUCAPE from the Dakotas eastward to the MS River. However, accompanying this strong to locally extreme instability is an appreciable amount of MLCINH, which is typical for EML plumes pivoting around a synoptic scale anticyclone. The aforementioned approaching mid-level impulse cresting the upper ridge is expected to reach the MT/ND border by around 00Z and reach the MS River by 12Z. The point where the mid-level impulse overspreads the rich low-level moisture, along with the east-northeastern terminus of the low-level WAA regime, appear to be the most likely regions for convective initiation. Peak afternoon heating, along with low-level convergence at the WAA terminus, may support the initiation of multicellular clusters over parts of eastern IA into IL sometime during the mid-afternoon to early evening time frame. Given modest vertical wind shear, cold-pool mergers could support upscale growth into one or more MCSs that will approach Lake Michigan, accompanied by at least isolated severe wind or hail. Around sunset, additional storms may develop across northern and eastern MN into western WI, perhaps driven by isentropic lift. Since these storms will traverse the periphery of greater instability amid modest vertical wind shear, it is unclear how severe these storms will become, though at least isolated severe hail and/or wind is plausible. Finally, thunderstorms may initiate as far west as the MT/ND border or even adjacent parts of Canada by early evening. This severe threat is the most conditional of all scenarios. Should capping be overcome, the storms will initiate west of an elongated axis of strong to extreme instability, amid at least 30 kts of effective bulk shear. The storms will be initially displaced west of the richer low-level moisture, hence they would be high-based in nature, accompanied by primarily a severe gust threat. Though less likely, if these storms can congeal into an organized MCS, the MCS could become longer-lived and pose a threat for a more focused corridor of severe gusts. ..Squitieri.. 07/11/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 AM CDT Thu Jul 11 2024 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Multiple clusters of strong to severe thunderstorms are possible across portions of the Northern Plains into the Upper Mississippi Valley on Saturday. ...Synopsis... A mid-level anticylone, centered over the central Rockies, will promote upper ridging from the Interior West to the MS Valley on Saturday. The first in a series of pronounced mid-level impulses is poised to pivot around the anticyclone and rapidly traverse the northern Plains and Upper MS Valley through the period. Rich low-level moisture, aided by widespread WAA beneath an EML, will precede the arrival of the mid-level impulse, resulting in strong to extreme buoyancy becoming established over the northern Plains and Upper MS Valley. The capping inversion associated with the EML makes it difficult to pinpoint precisely where and when the greatest severe threat will be. Nonetheless, at least a few clusters of strong to severe storms should evolve across the north-central CONUS on Saturday. ...Northern Plains into the Upper MS Valley... Surface lee troughing over the Plains will continue to foster low-level WAA, ushering in mid to upper 70s F surface dewpoints beneath an eastward-advecting plume of 7-8 C/km mid-level lapse rates from the EML. This thermodynamic regime will support 3000-5000 J/kg of MUCAPE from the Dakotas eastward to the MS River. However, accompanying this strong to locally extreme instability is an appreciable amount of MLCINH, which is typical for EML plumes pivoting around a synoptic scale anticyclone. The aforementioned approaching mid-level impulse cresting the upper ridge is expected to reach the MT/ND border by around 00Z and reach the MS River by 12Z. The point where the mid-level impulse overspreads the rich low-level moisture, along with the east-northeastern terminus of the low-level WAA regime, appear to be the most likely regions for convective initiation. Peak afternoon heating, along with low-level convergence at the WAA terminus, may support the initiation of multicellular clusters over parts of eastern IA into IL sometime during the mid-afternoon to early evening time frame. Given modest vertical wind shear, cold-pool mergers could support upscale growth into one or more MCSs that will approach Lake Michigan, accompanied by at least isolated severe wind or hail. Around sunset, additional storms may develop across northern and eastern MN into western WI, perhaps driven by isentropic lift. Since these storms will traverse the periphery of greater instability amid modest vertical wind shear, it is unclear how severe these storms will become, though at least isolated severe hail and/or wind is plausible. Finally, thunderstorms may initiate as far west as the MT/ND border or even adjacent parts of Canada by early evening. This severe threat is the most conditional of all scenarios. Should capping be overcome, the storms will initiate west of an elongated axis of strong to extreme instability, amid at least 30 kts of effective bulk shear. The storms will be initially displaced west of the richer low-level moisture, hence they would be high-based in nature, accompanied by primarily a severe gust threat. Though less likely, if these storms can congeal into an organized MCS, the MCS could become longer-lived and pose a threat for a more focused corridor of severe gusts. ..Squitieri.. 07/11/2024 Read more