Aggregator

MD 1800 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF CENTRAL AND NORTHERN MAINE
Mesoscale Discussion 1800 NWS Storm Prediction Center Norman OK 0120 PM CDT Mon Aug 19 2019 Areas affected...Portions of central and northern Maine Concerning...Severe potential...Watch unlikely Valid 191820Z - 192015Z Probability of Watch Issuance...20 percent SUMMARY...Widely scattered thunderstorms will move over the area this afternoon and pose a limited threat for damaging wind gusts and marginally severe hail. However, at this time the coverage of the threat is expected to remain low enough to preclude a Severe Thunderstorm Watch. DISCUSSION...A mid-level shortwave trough pivoting through the broadly cyclonic mid-upper-level flow, and an approaching pre-frontal trough, is supporting thunderstorm development over western Maine. Although the low-to-mid-level flow approaching the area is somewhat stronger than that farther south, persistent low-level clouds have limited heating over much of the area. Therefore the severe wind threat should be limited to localized pockets of stronger heating where evaporatively-driven downdrafts and surface outflow winds may be enhanced. Some transient updraft rotation in a few of the storms amidst the 0-3 (0-6) km shear of 25-30 (30-35) kt could support some small hail in the stronger updrafts, and some isolated hail approaching an inch in diameter, but this threat is expected to remain low enough, and isolated enough, to preclude a Watch. ..Coniglio/Thompson.. 08/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CAR...GYX... LAT...LON 44316879 44276918 44206967 44607021 45117036 46027014 47016949 47206889 47306833 47066791 46226781 45126818 44316879 Read more

No watches are valid as of Mon Aug 19 18:03:02 UTC 2019.

MD 1799 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF CENTRAL TO SOUTHERN NEW ENGLAND INTO FAR SOUTHEAST NEW YORK AND NORTHEAST NEW JERSEY
Mesoscale Discussion 1799 NWS Storm Prediction Center Norman OK 1238 PM CDT Mon Aug 19 2019 Areas affected...Portions of central to southern New England into far southeast New York and northeast New Jersey Concerning...Severe potential...Watch possible Valid 191738Z - 191845Z Probability of Watch Issuance...60 percent SUMMARY...Scattered thunderstorms will expand in coverage by early afternoon and pose a threat for some wind damage through mid-to-late afternoon. A Severe Thunderstorm Watch may be needed between 18-19z. DISCUSSION...Strong heating amidst upper 60s to lower 70s near-surface dewpoints ahead of a mid-level cloud shield is contributing to MLCAPE of 500-1000 J/kg over southwest Maine to 2000-2500 J/kg over central New Jersey. Broad low-level confluence associated with a pre-frontal trough, and the southern fringe of a mid-level shortwave trough traversing southern Quebec, will contribute to scattered thunderstorm development in this environment by early afternoon. Although low-to-deep-layer shear of 20-30 kt is rather marginal for long-lived storm organization, a broken line of multicells should be the dominant mode as suggested by morning convection-allowing guidance. The main threat will be isolated to widely scattered wind damage from sub-cloud evaporation-driven downdrafts supported by somewhat steep low-level lapse rates of 8-8.5 C/km. The coverage of thunderstorms capable of producing wind damage is expected to be modest but may be sufficient to require a Severe Thunderstorm Watch in the 18-19z time period. ..Coniglio/Thompson.. 08/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GYX...BOX...OKX...ALY...PHI... LAT...LON 43017221 43667164 44107123 44427085 44337037 44056989 43536991 42667009 41727105 40657227 40197329 40407488 40807496 41407440 42747253 43017221 Read more

000
ABPZ20 KNHC 191733
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Mon Aug 19 2019

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

Showers and thunderstorms associated with an area of low pressure
located a couple of hundred miles southeast of the southern coast
Mexico have become better organized during the past several hours.
Environmental conditions are conducive for further development,
and a tropical depression is likely to form during the next day or
two while the low moves west-northwestward at about 10 mph parallel
to the coast of Mexico. Moisture associated with this disturbance
could produce heavy rainfall and possible flash flooding across
portions of Guatemala and southeastern Mexico during the next couple
of days.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...90 percent.

A low pressure system located a little over 900 miles southwest of
the southern tip of the Baja California peninsula continues to
produce a large area of cloudiness and thunderstorms. Environmental
conditions are expected to become more conducive for development by
mid-week, and a tropical depression is likely to form during the
next few days while the system moves westward to west-northwestward
at about 10 mph.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...high...80 percent.

$$
Forecaster Roberts

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TUESDAY ACROSS PARTS OF SOUTHEASTERN IOWA AND NORTHWEST MISSOURI...MUCH OF CENTRAL ILLINOIS AND CENTRAL/SOUTHERN INDIANA... ...SUMMARY... An organized cluster of thunderstorms may develop and overspread portions of the middle Mississippi and lower Ohio Valleys Tuesday, accompanied by the risk for severe wind and hail. ...Synopsis... The stronger westerlies will remain confined to areas near/north of the Canadian/U.S. border, but may undergo amplification during this period, as a significant short wave trough pivots inland across the British Columbia coast. Downstream, positively tilted mid/upper ridging is forecast to build across the Canadian prairies into Nunavut and western Hudson Bay, while another significant short wave trough digs southeastward across Manitoba and northwest Ontario, toward the upper Great Lakes region. To the south, a broad plume of very warm elevated mixed-layer air is already beginning to emerge from the Intermountain West/Mexican Plateau/Rockies region. The northeastern periphery of this air mass appears to likely to continue advecting across the middle Missouri Valley region, toward the Upper Midwest, through daybreak Tuesday. As this overspreads seasonably moist boundary layer air, it is expected to contribute to the maintenance of moderate to strong potential instability across a broad area of the interior United States. By early Tuesday, it appears that this will be focused ahead of a stalling initial front extending across southern portions of the Great Lakes region into middle Missouri Valley, and ahead of another surface cold front advancing into the northern Plains and Upper Midwest. This instability is expected to provide support for scattered vigorous thunderstorm activity, as far east as the upper Ohio Valley and northern Mid Atlantic region, Tuesday into Tuesday night. Some of these storms will pose a risk for severe wind and hail, particularly across portions of the middle Mississippi into lower Ohio Valleys. ...Middle Mississippi/Ohio Valleys... A considerable signal remains evident within the latest model output suggesting the potential for the evolution of a large, organized convective system during this period. It appears that forcing for ascent associated with a low amplitude impulse migrating around the northern periphery of the subtropical ridging, near/south of the stronger westerlies, will provide support for the initiation of this activity, perhaps as early as late tonight across southern Iowa. Aided by inflow of moderate to large CAPE, particularly as the boundary layer begins to warm with insolation, there appears potential for considerable intensification Tuesday morning into afternoon, across southeast Iowa and adjacent northwestern Missouri through central Illinois. Aided by deep-layer shear associated with a 30-50 kt mid-level jet streak, and steep mid-level lapse rates, the environment may become supportive of large to very large hail and damaging surface gusts, associated with both downbursts and a strengthening convectively generated surface cold pool. Some uncertainty exists concerning the subsequent track of the convective system, and highest severe probabilities, but this seems most likely to become focused near the northeastern periphery of mid-level ridging, centered (around 700 mb) across southern Missouri. Based on this, activity may gradually turn south-southeastward into/through the lower Ohio Valley by Tuesday evening, although eastward development toward portions of the Upper Ohio Valley may not be out of the question. ...Central Plains into Mid Missouri Valley... More uncertainty exits concerning coverage and location of convective development, particularly with regard to mid/upper support for activity. However, a zone of stronger differential surface heating may provide the general focus for strong/severe storm development across central/southern Nebraska and northeast Kansas late Tuesday afternoon and evening. ...Upper Midwest... Models suggest that an area of mid/upper forcing for ascent, developing ahead of the primary digging short wave trough, may provide support for thunderstorm development during the peak heating across parts of east central Minnesota into northern Wisconsin and adjacent portions of upper Michigan, where the environment may become at least marginally conducive to isolated supercells posing a risk for severe hail and wind. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 30% - Enhanced Hail: 30% SIG - Enhanced ..Kerr.. 08/19/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TUESDAY ACROSS PARTS OF SOUTHEASTERN IOWA AND NORTHWEST MISSOURI...MUCH OF CENTRAL ILLINOIS AND CENTRAL/SOUTHERN INDIANA... ...SUMMARY... An organized cluster of thunderstorms may develop and overspread portions of the middle Mississippi and lower Ohio Valleys Tuesday, accompanied by the risk for severe wind and hail. ...Synopsis... The stronger westerlies will remain confined to areas near/north of the Canadian/U.S. border, but may undergo amplification during this period, as a significant short wave trough pivots inland across the British Columbia coast. Downstream, positively tilted mid/upper ridging is forecast to build across the Canadian prairies into Nunavut and western Hudson Bay, while another significant short wave trough digs southeastward across Manitoba and northwest Ontario, toward the upper Great Lakes region. To the south, a broad plume of very warm elevated mixed-layer air is already beginning to emerge from the Intermountain West/Mexican Plateau/Rockies region. The northeastern periphery of this air mass appears to likely to continue advecting across the middle Missouri Valley region, toward the Upper Midwest, through daybreak Tuesday. As this overspreads seasonably moist boundary layer air, it is expected to contribute to the maintenance of moderate to strong potential instability across a broad area of the interior United States. By early Tuesday, it appears that this will be focused ahead of a stalling initial front extending across southern portions of the Great Lakes region into middle Missouri Valley, and ahead of another surface cold front advancing into the northern Plains and Upper Midwest. This instability is expected to provide support for scattered vigorous thunderstorm activity, as far east as the upper Ohio Valley and northern Mid Atlantic region, Tuesday into Tuesday night. Some of these storms will pose a risk for severe wind and hail, particularly across portions of the middle Mississippi into lower Ohio Valleys. ...Middle Mississippi/Ohio Valleys... A considerable signal remains evident within the latest model output suggesting the potential for the evolution of a large, organized convective system during this period. It appears that forcing for ascent associated with a low amplitude impulse migrating around the northern periphery of the subtropical ridging, near/south of the stronger westerlies, will provide support for the initiation of this activity, perhaps as early as late tonight across southern Iowa. Aided by inflow of moderate to large CAPE, particularly as the boundary layer begins to warm with insolation, there appears potential for considerable intensification Tuesday morning into afternoon, across southeast Iowa and adjacent northwestern Missouri through central Illinois. Aided by deep-layer shear associated with a 30-50 kt mid-level jet streak, and steep mid-level lapse rates, the environment may become supportive of large to very large hail and damaging surface gusts, associated with both downbursts and a strengthening convectively generated surface cold pool. Some uncertainty exists concerning the subsequent track of the convective system, and highest severe probabilities, but this seems most likely to become focused near the northeastern periphery of mid-level ridging, centered (around 700 mb) across southern Missouri. Based on this, activity may gradually turn south-southeastward into/through the lower Ohio Valley by Tuesday evening, although eastward development toward portions of the Upper Ohio Valley may not be out of the question. ...Central Plains into Mid Missouri Valley... More uncertainty exits concerning coverage and location of convective development, particularly with regard to mid/upper support for activity. However, a zone of stronger differential surface heating may provide the general focus for strong/severe storm development across central/southern Nebraska and northeast Kansas late Tuesday afternoon and evening. ...Upper Midwest... Models suggest that an area of mid/upper forcing for ascent, developing ahead of the primary digging short wave trough, may provide support for thunderstorm development during the peak heating across parts of east central Minnesota into northern Wisconsin and adjacent portions of upper Michigan, where the environment may become at least marginally conducive to isolated supercells posing a risk for severe hail and wind. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 30% - Enhanced Hail: 30% SIG - Enhanced ..Kerr.. 08/19/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TUESDAY ACROSS PARTS OF SOUTHEASTERN IOWA AND NORTHWEST MISSOURI...MUCH OF CENTRAL ILLINOIS AND CENTRAL/SOUTHERN INDIANA... ...SUMMARY... An organized cluster of thunderstorms may develop and overspread portions of the middle Mississippi and lower Ohio Valleys Tuesday, accompanied by the risk for severe wind and hail. ...Synopsis... The stronger westerlies will remain confined to areas near/north of the Canadian/U.S. border, but may undergo amplification during this period, as a significant short wave trough pivots inland across the British Columbia coast. Downstream, positively tilted mid/upper ridging is forecast to build across the Canadian prairies into Nunavut and western Hudson Bay, while another significant short wave trough digs southeastward across Manitoba and northwest Ontario, toward the upper Great Lakes region. To the south, a broad plume of very warm elevated mixed-layer air is already beginning to emerge from the Intermountain West/Mexican Plateau/Rockies region. The northeastern periphery of this air mass appears to likely to continue advecting across the middle Missouri Valley region, toward the Upper Midwest, through daybreak Tuesday. As this overspreads seasonably moist boundary layer air, it is expected to contribute to the maintenance of moderate to strong potential instability across a broad area of the interior United States. By early Tuesday, it appears that this will be focused ahead of a stalling initial front extending across southern portions of the Great Lakes region into middle Missouri Valley, and ahead of another surface cold front advancing into the northern Plains and Upper Midwest. This instability is expected to provide support for scattered vigorous thunderstorm activity, as far east as the upper Ohio Valley and northern Mid Atlantic region, Tuesday into Tuesday night. Some of these storms will pose a risk for severe wind and hail, particularly across portions of the middle Mississippi into lower Ohio Valleys. ...Middle Mississippi/Ohio Valleys... A considerable signal remains evident within the latest model output suggesting the potential for the evolution of a large, organized convective system during this period. It appears that forcing for ascent associated with a low amplitude impulse migrating around the northern periphery of the subtropical ridging, near/south of the stronger westerlies, will provide support for the initiation of this activity, perhaps as early as late tonight across southern Iowa. Aided by inflow of moderate to large CAPE, particularly as the boundary layer begins to warm with insolation, there appears potential for considerable intensification Tuesday morning into afternoon, across southeast Iowa and adjacent northwestern Missouri through central Illinois. Aided by deep-layer shear associated with a 30-50 kt mid-level jet streak, and steep mid-level lapse rates, the environment may become supportive of large to very large hail and damaging surface gusts, associated with both downbursts and a strengthening convectively generated surface cold pool. Some uncertainty exists concerning the subsequent track of the convective system, and highest severe probabilities, but this seems most likely to become focused near the northeastern periphery of mid-level ridging, centered (around 700 mb) across southern Missouri. Based on this, activity may gradually turn south-southeastward into/through the lower Ohio Valley by Tuesday evening, although eastward development toward portions of the Upper Ohio Valley may not be out of the question. ...Central Plains into Mid Missouri Valley... More uncertainty exits concerning coverage and location of convective development, particularly with regard to mid/upper support for activity. However, a zone of stronger differential surface heating may provide the general focus for strong/severe storm development across central/southern Nebraska and northeast Kansas late Tuesday afternoon and evening. ...Upper Midwest... Models suggest that an area of mid/upper forcing for ascent, developing ahead of the primary digging short wave trough, may provide support for thunderstorm development during the peak heating across parts of east central Minnesota into northern Wisconsin and adjacent portions of upper Michigan, where the environment may become at least marginally conducive to isolated supercells posing a risk for severe hail and wind. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 30% - Enhanced Hail: 30% SIG - Enhanced ..Kerr.. 08/19/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TUESDAY ACROSS PARTS OF SOUTHEASTERN IOWA AND NORTHWEST MISSOURI...MUCH OF CENTRAL ILLINOIS AND CENTRAL/SOUTHERN INDIANA... ...SUMMARY... An organized cluster of thunderstorms may develop and overspread portions of the middle Mississippi and lower Ohio Valleys Tuesday, accompanied by the risk for severe wind and hail. ...Synopsis... The stronger westerlies will remain confined to areas near/north of the Canadian/U.S. border, but may undergo amplification during this period, as a significant short wave trough pivots inland across the British Columbia coast. Downstream, positively tilted mid/upper ridging is forecast to build across the Canadian prairies into Nunavut and western Hudson Bay, while another significant short wave trough digs southeastward across Manitoba and northwest Ontario, toward the upper Great Lakes region. To the south, a broad plume of very warm elevated mixed-layer air is already beginning to emerge from the Intermountain West/Mexican Plateau/Rockies region. The northeastern periphery of this air mass appears to likely to continue advecting across the middle Missouri Valley region, toward the Upper Midwest, through daybreak Tuesday. As this overspreads seasonably moist boundary layer air, it is expected to contribute to the maintenance of moderate to strong potential instability across a broad area of the interior United States. By early Tuesday, it appears that this will be focused ahead of a stalling initial front extending across southern portions of the Great Lakes region into middle Missouri Valley, and ahead of another surface cold front advancing into the northern Plains and Upper Midwest. This instability is expected to provide support for scattered vigorous thunderstorm activity, as far east as the upper Ohio Valley and northern Mid Atlantic region, Tuesday into Tuesday night. Some of these storms will pose a risk for severe wind and hail, particularly across portions of the middle Mississippi into lower Ohio Valleys. ...Middle Mississippi/Ohio Valleys... A considerable signal remains evident within the latest model output suggesting the potential for the evolution of a large, organized convective system during this period. It appears that forcing for ascent associated with a low amplitude impulse migrating around the northern periphery of the subtropical ridging, near/south of the stronger westerlies, will provide support for the initiation of this activity, perhaps as early as late tonight across southern Iowa. Aided by inflow of moderate to large CAPE, particularly as the boundary layer begins to warm with insolation, there appears potential for considerable intensification Tuesday morning into afternoon, across southeast Iowa and adjacent northwestern Missouri through central Illinois. Aided by deep-layer shear associated with a 30-50 kt mid-level jet streak, and steep mid-level lapse rates, the environment may become supportive of large to very large hail and damaging surface gusts, associated with both downbursts and a strengthening convectively generated surface cold pool. Some uncertainty exists concerning the subsequent track of the convective system, and highest severe probabilities, but this seems most likely to become focused near the northeastern periphery of mid-level ridging, centered (around 700 mb) across southern Missouri. Based on this, activity may gradually turn south-southeastward into/through the lower Ohio Valley by Tuesday evening, although eastward development toward portions of the Upper Ohio Valley may not be out of the question. ...Central Plains into Mid Missouri Valley... More uncertainty exits concerning coverage and location of convective development, particularly with regard to mid/upper support for activity. However, a zone of stronger differential surface heating may provide the general focus for strong/severe storm development across central/southern Nebraska and northeast Kansas late Tuesday afternoon and evening. ...Upper Midwest... Models suggest that an area of mid/upper forcing for ascent, developing ahead of the primary digging short wave trough, may provide support for thunderstorm development during the peak heating across parts of east central Minnesota into northern Wisconsin and adjacent portions of upper Michigan, where the environment may become at least marginally conducive to isolated supercells posing a risk for severe hail and wind. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 30% - Enhanced Hail: 30% SIG - Enhanced ..Kerr.. 08/19/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Mon Aug 19 2019 Valid 191700Z - 201200Z Expanded the elevated southwestward through Utah and into far northwest Arizona and southern Nevada. While conditions will not be much different from climatology, they are expected to be similar in Utah and Northwest Arizona as they will be in Wyoming. Therefore, an expansion of the elevated was warranted. In addition, added an elevated area for portions of eastern Idaho where it appears winds will be around 15 to 20 mph with RH around 12 to 18 percent this afternoon. ..Bentley.. 08/19/2019 .PREV DISCUSSION... /ISSUED 0131 AM CDT Mon Aug 19 2019/ ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Mon Aug 19 2019 Valid 191700Z - 201200Z Expanded the elevated southwestward through Utah and into far northwest Arizona and southern Nevada. While conditions will not be much different from climatology, they are expected to be similar in Utah and Northwest Arizona as they will be in Wyoming. Therefore, an expansion of the elevated was warranted. In addition, added an elevated area for portions of eastern Idaho where it appears winds will be around 15 to 20 mph with RH around 12 to 18 percent this afternoon. ..Bentley.. 08/19/2019 .PREV DISCUSSION... /ISSUED 0131 AM CDT Mon Aug 19 2019/ ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Mon Aug 19 2019 Valid 191700Z - 201200Z Expanded the elevated southwestward through Utah and into far northwest Arizona and southern Nevada. While conditions will not be much different from climatology, they are expected to be similar in Utah and Northwest Arizona as they will be in Wyoming. Therefore, an expansion of the elevated was warranted. In addition, added an elevated area for portions of eastern Idaho where it appears winds will be around 15 to 20 mph with RH around 12 to 18 percent this afternoon. ..Bentley.. 08/19/2019 .PREV DISCUSSION... /ISSUED 0131 AM CDT Mon Aug 19 2019/ ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Mon Aug 19 2019 Valid 191700Z - 201200Z Expanded the elevated southwestward through Utah and into far northwest Arizona and southern Nevada. While conditions will not be much different from climatology, they are expected to be similar in Utah and Northwest Arizona as they will be in Wyoming. Therefore, an expansion of the elevated was warranted. In addition, added an elevated area for portions of eastern Idaho where it appears winds will be around 15 to 20 mph with RH around 12 to 18 percent this afternoon. ..Bentley.. 08/19/2019 .PREV DISCUSSION... /ISSUED 0131 AM CDT Mon Aug 19 2019/ ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Mon Aug 19 2019 Valid 191630Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE TONIGHT ACROSS PARTS OF IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FROM NJ INTO SOUTHEAST NEW ENGLAND... ...SUMMARY... A few damaging gusts will be possible from the Mid-Atlantic into New England this afternoon, while large hail and damaging gusts are expected late tonight across Iowa. ...IA late tonight... Low-level warm advection and moistening will focus across IA overnight, on the nose of a 30-35 kt southwesterly low-level jet. The richer moisture observed this morning at TOP and LBF will spread northeastward beneath a warm elevated mixed layer which will act to cap the boundary layer through the day. After 06z, ascent and moistening with the warm advection should be sufficient for elevated thunderstorm development across IA, and storms will subsequently spread southeastward and likely evolve into an MCS. Large hail will be the initial threat with elevated supercells. As storms coalesce into an MCS, there will be increasing potential for damaging surface winds to reach the ground, given large buoyancy (MUCAPE at or above 3000 J/kg), steep midlevel lapse rates, and DCAPE at or above 1000 J/kg. ...New England to the Mid-Atlantic this afternoon/evening... A midlevel shortwave trough will move eastward over PA/NY and New England this afternoon/evening, with an accompanying surface cold front. East of a band of thicker clouds near the front, surface heating and boundary-layer dewpoints ranging from the upper 60s in southern NH to the mid 70s in NJ will contribute to afternoon MLCAPE ranging from 1500 J/kg north to 3000 J/kg south. Midlevel west-southwesterly flow of 25-30 kt and the moderate to strong buoyancy will favor primarily multicell clusters capable of producing occasional wind damage with 45-60 mph outflow gusts. More persistent clouds across Maine will slow surface heating/destabilization, though deep-layer vertical shear will be a little stronger with northward extent compared to southern New England. Farther south, a weak lee trough will persist through the afternoon across the Piedmont, with a warm/moist air mass to its east. Strong surface heating will boost MLCAPE into the 2000-3000 J/kg range east of the surface trough, where DCAPE near 1000 J/kg will favor isolated strong/damaging winds with multicell storms in a weak vertical shear environment. ...Northern Plains through tonight... Low-level moisture is returning northward from the central Plains to the Dakotas, east of a diffuse lee trough. Surface heating/mixing could be sufficient for isolated high-based storms across western ND this evening, but overall storm coverage is expected to remain sparse in response to weak forcing for ascent and a lingering cap. Storm development will be more probable tonight near the international border along a cold front as an embedded speed max moves across southern SK/MB. This convection should be elevated, posing a threat for isolated large hail and a few strong gusts could reach the ground. ...Central High Plains this afternoon/evening... Deep mixing with strong surface heating could support isolated, high-based thunderstorm development this afternoon along the surface lee trough in the vicinity of the KS/CO border. Inverted-v profiles will favor gusty outflow winds with any sustained storms or small clusters for a few hours late this afternoon/evening. ..Thompson/Coniglio.. 08/19/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Mon Aug 19 2019 Valid 191630Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE TONIGHT ACROSS PARTS OF IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FROM NJ INTO SOUTHEAST NEW ENGLAND... ...SUMMARY... A few damaging gusts will be possible from the Mid-Atlantic into New England this afternoon, while large hail and damaging gusts are expected late tonight across Iowa. ...IA late tonight... Low-level warm advection and moistening will focus across IA overnight, on the nose of a 30-35 kt southwesterly low-level jet. The richer moisture observed this morning at TOP and LBF will spread northeastward beneath a warm elevated mixed layer which will act to cap the boundary layer through the day. After 06z, ascent and moistening with the warm advection should be sufficient for elevated thunderstorm development across IA, and storms will subsequently spread southeastward and likely evolve into an MCS. Large hail will be the initial threat with elevated supercells. As storms coalesce into an MCS, there will be increasing potential for damaging surface winds to reach the ground, given large buoyancy (MUCAPE at or above 3000 J/kg), steep midlevel lapse rates, and DCAPE at or above 1000 J/kg. ...New England to the Mid-Atlantic this afternoon/evening... A midlevel shortwave trough will move eastward over PA/NY and New England this afternoon/evening, with an accompanying surface cold front. East of a band of thicker clouds near the front, surface heating and boundary-layer dewpoints ranging from the upper 60s in southern NH to the mid 70s in NJ will contribute to afternoon MLCAPE ranging from 1500 J/kg north to 3000 J/kg south. Midlevel west-southwesterly flow of 25-30 kt and the moderate to strong buoyancy will favor primarily multicell clusters capable of producing occasional wind damage with 45-60 mph outflow gusts. More persistent clouds across Maine will slow surface heating/destabilization, though deep-layer vertical shear will be a little stronger with northward extent compared to southern New England. Farther south, a weak lee trough will persist through the afternoon across the Piedmont, with a warm/moist air mass to its east. Strong surface heating will boost MLCAPE into the 2000-3000 J/kg range east of the surface trough, where DCAPE near 1000 J/kg will favor isolated strong/damaging winds with multicell storms in a weak vertical shear environment. ...Northern Plains through tonight... Low-level moisture is returning northward from the central Plains to the Dakotas, east of a diffuse lee trough. Surface heating/mixing could be sufficient for isolated high-based storms across western ND this evening, but overall storm coverage is expected to remain sparse in response to weak forcing for ascent and a lingering cap. Storm development will be more probable tonight near the international border along a cold front as an embedded speed max moves across southern SK/MB. This convection should be elevated, posing a threat for isolated large hail and a few strong gusts could reach the ground. ...Central High Plains this afternoon/evening... Deep mixing with strong surface heating could support isolated, high-based thunderstorm development this afternoon along the surface lee trough in the vicinity of the KS/CO border. Inverted-v profiles will favor gusty outflow winds with any sustained storms or small clusters for a few hours late this afternoon/evening. ..Thompson/Coniglio.. 08/19/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Mon Aug 19 2019 Valid 191630Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE TONIGHT ACROSS PARTS OF IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FROM NJ INTO SOUTHEAST NEW ENGLAND... ...SUMMARY... A few damaging gusts will be possible from the Mid-Atlantic into New England this afternoon, while large hail and damaging gusts are expected late tonight across Iowa. ...IA late tonight... Low-level warm advection and moistening will focus across IA overnight, on the nose of a 30-35 kt southwesterly low-level jet. The richer moisture observed this morning at TOP and LBF will spread northeastward beneath a warm elevated mixed layer which will act to cap the boundary layer through the day. After 06z, ascent and moistening with the warm advection should be sufficient for elevated thunderstorm development across IA, and storms will subsequently spread southeastward and likely evolve into an MCS. Large hail will be the initial threat with elevated supercells. As storms coalesce into an MCS, there will be increasing potential for damaging surface winds to reach the ground, given large buoyancy (MUCAPE at or above 3000 J/kg), steep midlevel lapse rates, and DCAPE at or above 1000 J/kg. ...New England to the Mid-Atlantic this afternoon/evening... A midlevel shortwave trough will move eastward over PA/NY and New England this afternoon/evening, with an accompanying surface cold front. East of a band of thicker clouds near the front, surface heating and boundary-layer dewpoints ranging from the upper 60s in southern NH to the mid 70s in NJ will contribute to afternoon MLCAPE ranging from 1500 J/kg north to 3000 J/kg south. Midlevel west-southwesterly flow of 25-30 kt and the moderate to strong buoyancy will favor primarily multicell clusters capable of producing occasional wind damage with 45-60 mph outflow gusts. More persistent clouds across Maine will slow surface heating/destabilization, though deep-layer vertical shear will be a little stronger with northward extent compared to southern New England. Farther south, a weak lee trough will persist through the afternoon across the Piedmont, with a warm/moist air mass to its east. Strong surface heating will boost MLCAPE into the 2000-3000 J/kg range east of the surface trough, where DCAPE near 1000 J/kg will favor isolated strong/damaging winds with multicell storms in a weak vertical shear environment. ...Northern Plains through tonight... Low-level moisture is returning northward from the central Plains to the Dakotas, east of a diffuse lee trough. Surface heating/mixing could be sufficient for isolated high-based storms across western ND this evening, but overall storm coverage is expected to remain sparse in response to weak forcing for ascent and a lingering cap. Storm development will be more probable tonight near the international border along a cold front as an embedded speed max moves across southern SK/MB. This convection should be elevated, posing a threat for isolated large hail and a few strong gusts could reach the ground. ...Central High Plains this afternoon/evening... Deep mixing with strong surface heating could support isolated, high-based thunderstorm development this afternoon along the surface lee trough in the vicinity of the KS/CO border. Inverted-v profiles will favor gusty outflow winds with any sustained storms or small clusters for a few hours late this afternoon/evening. ..Thompson/Coniglio.. 08/19/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Mon Aug 19 2019 Valid 191630Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE TONIGHT ACROSS PARTS OF IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FROM NJ INTO SOUTHEAST NEW ENGLAND... ...SUMMARY... A few damaging gusts will be possible from the Mid-Atlantic into New England this afternoon, while large hail and damaging gusts are expected late tonight across Iowa. ...IA late tonight... Low-level warm advection and moistening will focus across IA overnight, on the nose of a 30-35 kt southwesterly low-level jet. The richer moisture observed this morning at TOP and LBF will spread northeastward beneath a warm elevated mixed layer which will act to cap the boundary layer through the day. After 06z, ascent and moistening with the warm advection should be sufficient for elevated thunderstorm development across IA, and storms will subsequently spread southeastward and likely evolve into an MCS. Large hail will be the initial threat with elevated supercells. As storms coalesce into an MCS, there will be increasing potential for damaging surface winds to reach the ground, given large buoyancy (MUCAPE at or above 3000 J/kg), steep midlevel lapse rates, and DCAPE at or above 1000 J/kg. ...New England to the Mid-Atlantic this afternoon/evening... A midlevel shortwave trough will move eastward over PA/NY and New England this afternoon/evening, with an accompanying surface cold front. East of a band of thicker clouds near the front, surface heating and boundary-layer dewpoints ranging from the upper 60s in southern NH to the mid 70s in NJ will contribute to afternoon MLCAPE ranging from 1500 J/kg north to 3000 J/kg south. Midlevel west-southwesterly flow of 25-30 kt and the moderate to strong buoyancy will favor primarily multicell clusters capable of producing occasional wind damage with 45-60 mph outflow gusts. More persistent clouds across Maine will slow surface heating/destabilization, though deep-layer vertical shear will be a little stronger with northward extent compared to southern New England. Farther south, a weak lee trough will persist through the afternoon across the Piedmont, with a warm/moist air mass to its east. Strong surface heating will boost MLCAPE into the 2000-3000 J/kg range east of the surface trough, where DCAPE near 1000 J/kg will favor isolated strong/damaging winds with multicell storms in a weak vertical shear environment. ...Northern Plains through tonight... Low-level moisture is returning northward from the central Plains to the Dakotas, east of a diffuse lee trough. Surface heating/mixing could be sufficient for isolated high-based storms across western ND this evening, but overall storm coverage is expected to remain sparse in response to weak forcing for ascent and a lingering cap. Storm development will be more probable tonight near the international border along a cold front as an embedded speed max moves across southern SK/MB. This convection should be elevated, posing a threat for isolated large hail and a few strong gusts could reach the ground. ...Central High Plains this afternoon/evening... Deep mixing with strong surface heating could support isolated, high-based thunderstorm development this afternoon along the surface lee trough in the vicinity of the KS/CO border. Inverted-v profiles will favor gusty outflow winds with any sustained storms or small clusters for a few hours late this afternoon/evening. ..Thompson/Coniglio.. 08/19/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Mon Aug 19 2019 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF IOWA TONIGHT... ...SUMMARY... The severe-thunderstorm threat appears most concentrated tonight over parts of Iowa, in the form of wind and hail. ...Synopsis... The broader mid/upper-level pattern over the CONUS is expected to amplify somewhat through tomorrow morning, as ridging builds from the southern High Plains across the central/northern Rockies. A synoptic cyclone over northern MB is progged to elongate zonally and redevelop eastward across southern Hudson Bay to northern QC through the period. As that occurs, general height rises are expected across most of the Great Lakes region. A related, positively tilted shortwave trough is located from western NY southwestward across the Tennessee Valley region. The southern portion of this trough, from KY southward, will move eastward and weaken considerably. The northern part will eject northeastward across the remainder of PA, NY and New England through about 00Z. A weak shortwave trough -- initially apparent in moisture-channel imagery over WY -- is forecast to move eastward across much of southern SD and northern NE through 00Z, then turn southeastward over IA overnight. At the surface, the 11Z analysis showed a cold front from southwestern QC across southern ON to southern/central Lower MI, becoming wavy and quasistationary southwestward across southeastern IA, northwestern MO, and central/western KS. The central Plains segment of this front is forecast to move northward and reorient from northwest to southeast through the period. By 12Z the resulting warm front should extend from east-central/northeastern WY across northern NE and western/southern IA. A dryline should mix eastward across the High Plains today, reaching the NE Panhandle, extreme eastern CO/western KS and northeastern NM. ...Northern Plains to IA... Isolated to widely scattered thunderstorms are expected to form over the northern Plains part of the outlook area this afternoon into evening, offering the potential for isolated severe gusts/hail. A more-robust severe threat is becoming apparent overnight across portions of IA in association with potential formation of severe thunderstorms with large hail as the main early-stage threat, evolving toward damaging wind as activity aggregates upscale. A forward-propagational MCS is possible into parts of central/southern IA late overnight. Return flow on either side of the warm-frontal zone will foster increasing low-level theta-e throughout the day and into tonight, with 60s surface dew points becoming common, and values near 70 F possible on an isolated basis. Large-scale support will be weak, especially with heights building over and west of the area, but weak MLCINH and strong surface heating should foster the development of at least a few thunderstorms in an environment of steep low/middle- level lapse rates and well-mixed subcloud layers. Increasing moisture with southward/southeastward extent and backing of low- level flow near and on the north side of the warm front will augment deep shear in support of some supercell potential with any sustained convection. MLCAPE 3000-4500 J/kg is possible. Lack of stronger large-scale support, and concerns over convective coverage, preclude more than a marginal risk for most of the region at this time. However, concerns (and prognostic consensus) for overnight MCS action are increasing across portions of IA in the zone of strong low-level warm advection and moisture transport, near the nose of a 40-50-kt southwesterly LLJ. Steep midlevel lapse rates and increasing low-level moisture will yield MUCAPE increasing to the 2500-3500 J/kg range with decreasing MUCINH. While forecast soundings depict parcels rooted in the low levels, but above the surface, the presence of dry air in the subcloud layer suggests the potential for strong-severe downdrafts to reach the surface -- especially with support from any cold-pool forcing and rear-inflow- jet processes that can organize on the storm scale. Effective-shear magnitudes in the 35-50-kt range also indicate the potential for supercells, especially in the early hours of convective organization before too much clustering occurs, and an attendant severe-hail threat. ...New England... Widely scattered thunderstorms are expected to form as early as midday over portions of central/northern NY and during the afternoon elsewhere, in a loosely north-northeast/south-southwest-oriented broken band. Damaging gusts, including isolated gusts to severe limits, are possible region-wide. A marginal hail threat exists mainly over ME, and a tornado cannot be ruled out. Activity should develop behind and between areas of antecedent cloud cover, near a surface trough, where diabatic surface heating can destabilize the boundary layer favorably and remove MLCINH. Weak large-scale ascent also should spread across the area very near the ejecting mid/upper-level shortwave trough. These factors, along with moisture represented by surface dew points generally in the mid/upper 60s F, should support the development of preconvective afternoon MLCAPE in the 1000-1500 J/kg range. Mid/upper-level winds will strengthen with northward extent across the outlook area, and with time through afternoon over northern New England, as the aforementioned cyclonic processes over Canada tighten the height gradient aloft. Though low-level hodograph size will be modest, effective-shear magnitudes of 30-40 kt may favor organized multicells, small bows, and transient/marginal supercellular characteristics especially in ME. ...Central High Plains... Isolated to widely scattered thunderstorms should develop this afternoon near the dryline and move eastward to northeastward. Very strong heating/mixing of the boundary layer is forecast, which will yield nearly dry-adiabatic lapse rates from surface to near 500 mb. Modified model soundings yield around 500-1000 J/kg MLCAPE in those areas east of the dryline/lee trough where CINH is minimized. CAPE increases with eastward extent into more robust moisture, but so will capping. Lack of more robust low/middle-level winds will limit vertical shear, but the well-mixed subcloud layer will support isolated severe downburst potential with any sustained convection. ..Edwards/Marsh.. 08/19/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 AM CDT Mon Aug 19 2019 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF IOWA TONIGHT... ...SUMMARY... The severe-thunderstorm threat appears most concentrated tonight over parts of Iowa, in the form of wind and hail. ...Synopsis... The broader mid/upper-level pattern over the CONUS is expected to amplify somewhat through tomorrow morning, as ridging builds from the southern High Plains across the central/northern Rockies. A synoptic cyclone over northern MB is progged to elongate zonally and redevelop eastward across southern Hudson Bay to northern QC through the period. As that occurs, general height rises are expected across most of the Great Lakes region. A related, positively tilted shortwave trough is located from western NY southwestward across the Tennessee Valley region. The southern portion of this trough, from KY southward, will move eastward and weaken considerably. The northern part will eject northeastward across the remainder of PA, NY and New England through about 00Z. A weak shortwave trough -- initially apparent in moisture-channel imagery over WY -- is forecast to move eastward across much of southern SD and northern NE through 00Z, then turn southeastward over IA overnight. At the surface, the 11Z analysis showed a cold front from southwestern QC across southern ON to southern/central Lower MI, becoming wavy and quasistationary southwestward across southeastern IA, northwestern MO, and central/western KS. The central Plains segment of this front is forecast to move northward and reorient from northwest to southeast through the period. By 12Z the resulting warm front should extend from east-central/northeastern WY across northern NE and western/southern IA. A dryline should mix eastward across the High Plains today, reaching the NE Panhandle, extreme eastern CO/western KS and northeastern NM. ...Northern Plains to IA... Isolated to widely scattered thunderstorms are expected to form over the northern Plains part of the outlook area this afternoon into evening, offering the potential for isolated severe gusts/hail. A more-robust severe threat is becoming apparent overnight across portions of IA in association with potential formation of severe thunderstorms with large hail as the main early-stage threat, evolving toward damaging wind as activity aggregates upscale. A forward-propagational MCS is possible into parts of central/southern IA late overnight. Return flow on either side of the warm-frontal zone will foster increasing low-level theta-e throughout the day and into tonight, with 60s surface dew points becoming common, and values near 70 F possible on an isolated basis. Large-scale support will be weak, especially with heights building over and west of the area, but weak MLCINH and strong surface heating should foster the development of at least a few thunderstorms in an environment of steep low/middle- level lapse rates and well-mixed subcloud layers. Increasing moisture with southward/southeastward extent and backing of low- level flow near and on the north side of the warm front will augment deep shear in support of some supercell potential with any sustained convection. MLCAPE 3000-4500 J/kg is possible. Lack of stronger large-scale support, and concerns over convective coverage, preclude more than a marginal risk for most of the region at this time. However, concerns (and prognostic consensus) for overnight MCS action are increasing across portions of IA in the zone of strong low-level warm advection and moisture transport, near the nose of a 40-50-kt southwesterly LLJ. Steep midlevel lapse rates and increasing low-level moisture will yield MUCAPE increasing to the 2500-3500 J/kg range with decreasing MUCINH. While forecast soundings depict parcels rooted in the low levels, but above the surface, the presence of dry air in the subcloud layer suggests the potential for strong-severe downdrafts to reach the surface -- especially with support from any cold-pool forcing and rear-inflow- jet processes that can organize on the storm scale. Effective-shear magnitudes in the 35-50-kt range also indicate the potential for supercells, especially in the early hours of convective organization before too much clustering occurs, and an attendant severe-hail threat. ...New England... Widely scattered thunderstorms are expected to form as early as midday over portions of central/northern NY and during the afternoon elsewhere, in a loosely north-northeast/south-southwest-oriented broken band. Damaging gusts, including isolated gusts to severe limits, are possible region-wide. A marginal hail threat exists mainly over ME, and a tornado cannot be ruled out. Activity should develop behind and between areas of antecedent cloud cover, near a surface trough, where diabatic surface heating can destabilize the boundary layer favorably and remove MLCINH. Weak large-scale ascent also should spread across the area very near the ejecting mid/upper-level shortwave trough. These factors, along with moisture represented by surface dew points generally in the mid/upper 60s F, should support the development of preconvective afternoon MLCAPE in the 1000-1500 J/kg range. Mid/upper-level winds will strengthen with northward extent across the outlook area, and with time through afternoon over northern New England, as the aforementioned cyclonic processes over Canada tighten the height gradient aloft. Though low-level hodograph size will be modest, effective-shear magnitudes of 30-40 kt may favor organized multicells, small bows, and transient/marginal supercellular characteristics especially in ME. ...Central High Plains... Isolated to widely scattered thunderstorms should develop this afternoon near the dryline and move eastward to northeastward. Very strong heating/mixing of the boundary layer is forecast, which will yield nearly dry-adiabatic lapse rates from surface to near 500 mb. Modified model soundings yield around 500-1000 J/kg MLCAPE in those areas east of the dryline/lee trough where CINH is minimized. CAPE increases with eastward extent into more robust moisture, but so will capping. Lack of more robust low/middle-level winds will limit vertical shear, but the well-mixed subcloud layer will support isolated severe downburst potential with any sustained convection. ..Edwards/Marsh.. 08/19/2019 Read more

000
ABPZ20 KNHC 191149
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Mon Aug 19 2019

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

An elongated area of low pressure located a couple of hundred miles
southeast of the Gulf of Tehuantepec is producing disorganized
showers and thunderstorms. Environmental conditions are
forecast to become conducive for development during the next
couple of days, and a tropical depression is likely to form by
mid-week while the low moves west-northwestward at about
10 mph parallel to the coast of Mexico. Moisture associated with
this disturbance could produce heavy rainfall and possible flash
flooding across portions of Guatemala and southeastern Mexico during
the next couple of days.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...high...90 percent.

A well-defined low pressure system located more 900 miles southwest
of the southern tip of the Baja California peninsula continues to
produce a large area of cloudiness and thunderstorms. Environmental
conditions are expected to gradually become more conducive for
development, and a tropical depression is likely to form during the
next few days while the system moves westward to west-northwestward
at about 10 mph.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...high...70 percent.

$$
Forecaster Roberts

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0333 AM CDT Mon Aug 19 2019 Valid 221200Z - 271200Z ...DISCUSSION... On Thursday/D4, a vertically stacked low will develop over southern Quebec with strong southwest winds aloft overspreading the northeastern states. A cold front will rapidly move across New England and will trail southward toward the Delmarva, though models differ in timing. MUCAPE on the order of 1000 J/kg is expected over northern areas ahead of the front, with greater values approaching 2000 J/kg into NJ and eastern VA where dewpoints will be in the 70s F. Shear will be less over southern areas, but still sufficient to support at least a marginal wind and hail threat. Long hodographs will favor cells or fast-moving line segments over northern areas, but there is more model discrepancy regarding speed of the cold front. If the more progressive model solutions are correct, there may be little opportunity for severe storms north of Long Island. As such, will defer possible upgrades to later outlooks. To the west, a lesser shortwave trough will move across the northern Rockies and Plains during the Thursday/D4 to Friday/D5 period, though models vary greatly with the strength of this feature. Regardless, southeast surface winds may result in enough moisture advection into the northern Plains for at least a marginal severe risk along an attendant cold front. For the Saturday/D6 to Monday/D8 period, a relatively strong upper jet is forecast to nose into the northern Rockies and Plains, then eventually into the upper MS Valley. Increasing shear and lift will likely interact with increasing low-level moisture and instability over the Dakotas, MN, NE and IA. Predictability is low for this time frame, but probabilities could be added in future outlooks. Read more