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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Fri Sep 06 2024 Valid 061300Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF OHIO TO THE OHIO VALLEY... ...SUMMARY... Strong to locally severe storms are possible this afternoon from Lake Erie across much of Ohio to the Ohio Valley. ...Synopsis... A highly amplified mid/upper-level pattern will persist across the CONUS, but with some weakening of the western mean ridge and intensification of troughing over the Great Lakes/Ohio Valley regions. The latter will occur in relation to a synoptic-scale trough with several accompanying vorticity maxima and broad cyclonic flow -- apparent in moisture-channel imagery over much of northern ON and the Lake Superior vicinity. Phasing of accompanying shortwaves/ vorticity lobes will contribute to both amplification and wavelength shortening through the period. A closed 500-mb low should develop around 00Z near the eastern end of Upper MI, with trough near an MKG-ORD-MVN line. By 12Z, a fully developed cyclone should cover much of ON from the southern end of James Bay to Lake Erie, with 500-mb trough extending southwestward near a CVG-BNA line. Associated cyclonic flow at that time will cover most of the CONUS over and east of the mid/upper Mississippi Valley. At the surface, a cold front related to the ON trough was drawn at 11Z near a DTW-FDY-IND-ICT line. This front should proceed eastward/southeastward across the Ohio Valley, Lower Great Lakes and into the central/northern Appalachians through the period, ahead of the mid/upper trough. By 00Z, the front should extend from Lake Ontario across western parts of NY/PA to southeastern OH, northern middle to western TN, and AR, becoming diffuse amidst northeast flow on both sides over OK. Northeasterlies over the southern Plains south of the cold front will be largely in isallobaric response to a deepening surface frontal-wave low over the northwestern Gulf, initially drawn about 100 nm south of GLS, and forecast to drift erratically eastward through tonight. Strong/organized convection related to the Gulf cyclone is expected to remain over water through the period. ...OH, Ohio Valley... Damaging to isolated, marginally severe gusts, as well as marginal hail, will be possible with thunderstorms moving eastward across the outlook area today. A broken line of convection -- including widely scattered non-severe thunderstorms -- is apparent this morning from northwestern OH to western MO approximately along the low-level cold front. This activity, or succeeding/newer development after a short time gap later this morning -- should become better organized between Lake Erie and the Ohio Valley around midday as the foregoing boundary layer (and prospective inflow) destabilizes. This will occur in response to a combination of warm advection and diurnal heating/ mixing, whose mixing-related moisture-reduction effects will be counterbalanced to some extent by moist advection. Activity should move into a narrow corridor of 50s to mid 60s F surface dewpoints, combining with diurnal heating to support patchy, highly variable MLCAPE in the 500-1500 J/kg range. Substantial westerly component to prefrontal near-surface flow will limit both convergence and vertical shear, though weak MLCINH will permit frontal development/maintenance of thunderstorms, regardless. Around 30-35 kt effective-shear magnitudes will support mainly multicells, though some intermittent/transient supercell character will be possible for longer-lived, discrete cells. Activity should weaken this evening as it moves eastward out of the most favorable moisture, and into a nocturnally cooling/stabilizing boundary layer. ..Edwards/Kerr.. 09/06/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Fri Sep 06 2024 Valid 061300Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF OHIO TO THE OHIO VALLEY... ...SUMMARY... Strong to locally severe storms are possible this afternoon from Lake Erie across much of Ohio to the Ohio Valley. ...Synopsis... A highly amplified mid/upper-level pattern will persist across the CONUS, but with some weakening of the western mean ridge and intensification of troughing over the Great Lakes/Ohio Valley regions. The latter will occur in relation to a synoptic-scale trough with several accompanying vorticity maxima and broad cyclonic flow -- apparent in moisture-channel imagery over much of northern ON and the Lake Superior vicinity. Phasing of accompanying shortwaves/ vorticity lobes will contribute to both amplification and wavelength shortening through the period. A closed 500-mb low should develop around 00Z near the eastern end of Upper MI, with trough near an MKG-ORD-MVN line. By 12Z, a fully developed cyclone should cover much of ON from the southern end of James Bay to Lake Erie, with 500-mb trough extending southwestward near a CVG-BNA line. Associated cyclonic flow at that time will cover most of the CONUS over and east of the mid/upper Mississippi Valley. At the surface, a cold front related to the ON trough was drawn at 11Z near a DTW-FDY-IND-ICT line. This front should proceed eastward/southeastward across the Ohio Valley, Lower Great Lakes and into the central/northern Appalachians through the period, ahead of the mid/upper trough. By 00Z, the front should extend from Lake Ontario across western parts of NY/PA to southeastern OH, northern middle to western TN, and AR, becoming diffuse amidst northeast flow on both sides over OK. Northeasterlies over the southern Plains south of the cold front will be largely in isallobaric response to a deepening surface frontal-wave low over the northwestern Gulf, initially drawn about 100 nm south of GLS, and forecast to drift erratically eastward through tonight. Strong/organized convection related to the Gulf cyclone is expected to remain over water through the period. ...OH, Ohio Valley... Damaging to isolated, marginally severe gusts, as well as marginal hail, will be possible with thunderstorms moving eastward across the outlook area today. A broken line of convection -- including widely scattered non-severe thunderstorms -- is apparent this morning from northwestern OH to western MO approximately along the low-level cold front. This activity, or succeeding/newer development after a short time gap later this morning -- should become better organized between Lake Erie and the Ohio Valley around midday as the foregoing boundary layer (and prospective inflow) destabilizes. This will occur in response to a combination of warm advection and diurnal heating/ mixing, whose mixing-related moisture-reduction effects will be counterbalanced to some extent by moist advection. Activity should move into a narrow corridor of 50s to mid 60s F surface dewpoints, combining with diurnal heating to support patchy, highly variable MLCAPE in the 500-1500 J/kg range. Substantial westerly component to prefrontal near-surface flow will limit both convergence and vertical shear, though weak MLCINH will permit frontal development/maintenance of thunderstorms, regardless. Around 30-35 kt effective-shear magnitudes will support mainly multicells, though some intermittent/transient supercell character will be possible for longer-lived, discrete cells. Activity should weaken this evening as it moves eastward out of the most favorable moisture, and into a nocturnally cooling/stabilizing boundary layer. ..Edwards/Kerr.. 09/06/2024 Read more

000
ABPZ20 KNHC 061153
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Fri Sep 6 2024

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

Offshore of Southwestern Mexico:
An area of low pressure is forecast to form in the early to middle
parts of next week off the coast of southern or southwestern Mexico.
Environmental conditions could support gradual development of this
system thereafter while it moves generally west-northwestward,
roughly parallel to the coast of southwestern Mexico.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...30 percent.

$$
Forecaster Bucci

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough is forecast to move through the Ohio and Tennessee Valleys on Sunday, as a front remains located over the central and eastern Gulf Coast states. Thunderstorms will be possible on Sunday near and to the south of the front. Thunderstorms will also be possible within southwest mid-level flow to the west of a ridge in the western U.S. Isolated thunderstorms may also occur in north-northwesterly mid-level flow over parts of the Great Lakes. No severe threat is expected across the U.S. on Sunday or Sunday night. ..Broyles.. 09/06/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough is forecast to move through the Ohio and Tennessee Valleys on Sunday, as a front remains located over the central and eastern Gulf Coast states. Thunderstorms will be possible on Sunday near and to the south of the front. Thunderstorms will also be possible within southwest mid-level flow to the west of a ridge in the western U.S. Isolated thunderstorms may also occur in north-northwesterly mid-level flow over parts of the Great Lakes. No severe threat is expected across the U.S. on Sunday or Sunday night. ..Broyles.. 09/06/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough is forecast to move through the Ohio and Tennessee Valleys on Sunday, as a front remains located over the central and eastern Gulf Coast states. Thunderstorms will be possible on Sunday near and to the south of the front. Thunderstorms will also be possible within southwest mid-level flow to the west of a ridge in the western U.S. Isolated thunderstorms may also occur in north-northwesterly mid-level flow over parts of the Great Lakes. No severe threat is expected across the U.S. on Sunday or Sunday night. ..Broyles.. 09/06/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough is forecast to move through the Ohio and Tennessee Valleys on Sunday, as a front remains located over the central and eastern Gulf Coast states. Thunderstorms will be possible on Sunday near and to the south of the front. Thunderstorms will also be possible within southwest mid-level flow to the west of a ridge in the western U.S. Isolated thunderstorms may also occur in north-northwesterly mid-level flow over parts of the Great Lakes. No severe threat is expected across the U.S. on Sunday or Sunday night. ..Broyles.. 09/06/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough is forecast to move through the Ohio and Tennessee Valleys on Sunday, as a front remains located over the central and eastern Gulf Coast states. Thunderstorms will be possible on Sunday near and to the south of the front. Thunderstorms will also be possible within southwest mid-level flow to the west of a ridge in the western U.S. Isolated thunderstorms may also occur in north-northwesterly mid-level flow over parts of the Great Lakes. No severe threat is expected across the U.S. on Sunday or Sunday night. ..Broyles.. 09/06/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0153 AM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...Synopsis... As the weak Pacific trough continues inland, additional mid-level moisture will advect onshore over portions of the northern Sierra and Cascades through the weekend. The upper ridge will continue to slowly weaken, allowing for isolated thunderstorms over the Northwest. Thunderstorms are likely across portions of the Cascades in OR and southern WA, across the Sierra, and into portions of southern CA. Hot and well-mixed boundary-layer profiles will likely support low precipitation efficiency, especially with storm motions greater than 20 kt. Confidence in dry thunderstorm coverage is greatest across portions of the central Cascades, though drier storms will also be possible, albeit less certain, across the northern Sierra and parts of southern CA. Given the risk for lightning atop dry fuels, an IsoDryT area has been added where storm coverage and confidence in lightning atop dry fuels is highest. In addition to the risk for lightning, increasingly strong southwesterly flow aloft is expected to support gusty downslope winds over parts of northern CA and northwest NV. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values below 20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ..Lyons.. 09/06/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0153 AM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...Synopsis... As the weak Pacific trough continues inland, additional mid-level moisture will advect onshore over portions of the northern Sierra and Cascades through the weekend. The upper ridge will continue to slowly weaken, allowing for isolated thunderstorms over the Northwest. Thunderstorms are likely across portions of the Cascades in OR and southern WA, across the Sierra, and into portions of southern CA. Hot and well-mixed boundary-layer profiles will likely support low precipitation efficiency, especially with storm motions greater than 20 kt. Confidence in dry thunderstorm coverage is greatest across portions of the central Cascades, though drier storms will also be possible, albeit less certain, across the northern Sierra and parts of southern CA. Given the risk for lightning atop dry fuels, an IsoDryT area has been added where storm coverage and confidence in lightning atop dry fuels is highest. In addition to the risk for lightning, increasingly strong southwesterly flow aloft is expected to support gusty downslope winds over parts of northern CA and northwest NV. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values below 20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ..Lyons.. 09/06/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0153 AM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...Synopsis... As the weak Pacific trough continues inland, additional mid-level moisture will advect onshore over portions of the northern Sierra and Cascades through the weekend. The upper ridge will continue to slowly weaken, allowing for isolated thunderstorms over the Northwest. Thunderstorms are likely across portions of the Cascades in OR and southern WA, across the Sierra, and into portions of southern CA. Hot and well-mixed boundary-layer profiles will likely support low precipitation efficiency, especially with storm motions greater than 20 kt. Confidence in dry thunderstorm coverage is greatest across portions of the central Cascades, though drier storms will also be possible, albeit less certain, across the northern Sierra and parts of southern CA. Given the risk for lightning atop dry fuels, an IsoDryT area has been added where storm coverage and confidence in lightning atop dry fuels is highest. In addition to the risk for lightning, increasingly strong southwesterly flow aloft is expected to support gusty downslope winds over parts of northern CA and northwest NV. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values below 20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ..Lyons.. 09/06/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0153 AM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...Synopsis... As the weak Pacific trough continues inland, additional mid-level moisture will advect onshore over portions of the northern Sierra and Cascades through the weekend. The upper ridge will continue to slowly weaken, allowing for isolated thunderstorms over the Northwest. Thunderstorms are likely across portions of the Cascades in OR and southern WA, across the Sierra, and into portions of southern CA. Hot and well-mixed boundary-layer profiles will likely support low precipitation efficiency, especially with storm motions greater than 20 kt. Confidence in dry thunderstorm coverage is greatest across portions of the central Cascades, though drier storms will also be possible, albeit less certain, across the northern Sierra and parts of southern CA. Given the risk for lightning atop dry fuels, an IsoDryT area has been added where storm coverage and confidence in lightning atop dry fuels is highest. In addition to the risk for lightning, increasingly strong southwesterly flow aloft is expected to support gusty downslope winds over parts of northern CA and northwest NV. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values below 20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ..Lyons.. 09/06/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0153 AM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...Synopsis... As the weak Pacific trough continues inland, additional mid-level moisture will advect onshore over portions of the northern Sierra and Cascades through the weekend. The upper ridge will continue to slowly weaken, allowing for isolated thunderstorms over the Northwest. Thunderstorms are likely across portions of the Cascades in OR and southern WA, across the Sierra, and into portions of southern CA. Hot and well-mixed boundary-layer profiles will likely support low precipitation efficiency, especially with storm motions greater than 20 kt. Confidence in dry thunderstorm coverage is greatest across portions of the central Cascades, though drier storms will also be possible, albeit less certain, across the northern Sierra and parts of southern CA. Given the risk for lightning atop dry fuels, an IsoDryT area has been added where storm coverage and confidence in lightning atop dry fuels is highest. In addition to the risk for lightning, increasingly strong southwesterly flow aloft is expected to support gusty downslope winds over parts of northern CA and northwest NV. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values below 20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ..Lyons.. 09/06/2024 ...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 0151 AM CDT Fri Sep 06 2024 Valid 061200Z - 071200Z ...Synopsis... Mid-level ridging centered over the Great Basin is forecast to slowly decay today as a weak upper trough approaches the Pacific Coast. Ahead of the weak trough, a modest influx of mid-level moisture and ascent will overspread the northern Sierra and southern Cascades. Adequate buoyancy will develop with daytime heating supporting isolated thunderstorms through the evening hours. Beneath the advancing mid-level moisture, dry boundary-layer profiles and storm motions of 20-25 kt will favor low to very low rainfall efficiency with these storms. With thunderstorms expected atop areas of receptive fuels, dry lightning appears probable. Additionally, strengthening southwesterly mid-level flow should enhance downslope winds and low relative humidity across northern CA into northwest NV. Areas of brief elevated fire weather conditions are possible, though the duration and coverage should remain limited. ..Lyons.. 09/06/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more