Aggregator

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0145 AM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHWEST INTO CENTRAL NEVADA... ...Synopsis... A southward-moving shortwave trough is forecast to approach the Oregon/Washington coasts on Thursday, before moving east on Friday. This will result in an intensified height gradient across the Great Basin and a deepening surface low over Oregon that will bring widespread dry/windy conditions to portions of Oregon, Nevada, and Idaho. ...Dry/Windy... Critical fire-weather conditions are forecast across southwestern and central Nevada, where single-digit relative humidity values and winds of 25-30 MPH will overlap with ERC values exceeding the 80th-98th annual percentiles. Uncertainty exists in the eastward extent of the Critical area due to recent wetting rainfall and a tight gradient in fuel receptiveness to wildfire spread, and some areal expansion may be needed in future updates. Elevated fire-weather conditions are expected on the periphery of the Critical highlight area, as well as portions of northwestern Nevada into southeastern Oregon. Southeastern Oregon and northwestern Nevada will have slightly higher boundary-layer relative humidity values of 10-15%, and slightly slower wind speeds of 20-25 MPH. However, fuels in the region are widely receptive to wildfire spread, and if surface winds trend higher, a subsequent upgrade to Critical may be needed in this area. ..Halbert/Squitieri.. 08/21/2024 ...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 0145 AM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHWEST INTO CENTRAL NEVADA... ...Synopsis... A southward-moving shortwave trough is forecast to approach the Oregon/Washington coasts on Thursday, before moving east on Friday. This will result in an intensified height gradient across the Great Basin and a deepening surface low over Oregon that will bring widespread dry/windy conditions to portions of Oregon, Nevada, and Idaho. ...Dry/Windy... Critical fire-weather conditions are forecast across southwestern and central Nevada, where single-digit relative humidity values and winds of 25-30 MPH will overlap with ERC values exceeding the 80th-98th annual percentiles. Uncertainty exists in the eastward extent of the Critical area due to recent wetting rainfall and a tight gradient in fuel receptiveness to wildfire spread, and some areal expansion may be needed in future updates. Elevated fire-weather conditions are expected on the periphery of the Critical highlight area, as well as portions of northwestern Nevada into southeastern Oregon. Southeastern Oregon and northwestern Nevada will have slightly higher boundary-layer relative humidity values of 10-15%, and slightly slower wind speeds of 20-25 MPH. However, fuels in the region are widely receptive to wildfire spread, and if surface winds trend higher, a subsequent upgrade to Critical may be needed in this area. ..Halbert/Squitieri.. 08/21/2024 ...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 0141 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...Synopsis... Broad mid-level southwesterly flow will overspread much of the Great Basin and portions of the Pacific Northwest in advance of a southward-moving shortwave trough approaching the Washington coast. This will result in pockets of elevated fire-weather conditions across Nevada, Idaho, and Wyoming, with an additional risk for isolated dry thunderstorms across eastern and central Wyoming. ...Dry/Windy... Deep boundary-layer mixing beneath 40-45kt mid-level flow will result in elevated to locally critical fire-weather conditions across portions of Nevada, eastern Idaho, and northern Wyoming. The best overlap of elevated fire-weather conditions with receptive fuels will be across northern Wyoming and central Nevada, where fuels guidance suggest ERCs are above the 90th annual percentile. Across eastern Idaho in the Snake River Plain, meteorological conditions are expected to exceed Elevated criteria, but recent wetting rainfall and current fuels guidance suggests a narrower corridor supporting wildfire spread. ...Dry Thunderstorms... Isolated dry thunderstorms are expected across central and eastern Wyoming, where ERC fuels are in the 90th-98th annual percentile range and thunderstorms are expected to develop in deeply mixed, dry boundary-layer profiles. Storm motion estimates of 30 kts and PWAT values < 0.8 in should limit wetting rainfall except for in the strongest cores, and some overlap with elevated fire-weather conditions could pose a risk for wildfire spread with any new ignitions. ..Halbert/Squitieri.. 08/21/2024 ...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 0141 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...Synopsis... Broad mid-level southwesterly flow will overspread much of the Great Basin and portions of the Pacific Northwest in advance of a southward-moving shortwave trough approaching the Washington coast. This will result in pockets of elevated fire-weather conditions across Nevada, Idaho, and Wyoming, with an additional risk for isolated dry thunderstorms across eastern and central Wyoming. ...Dry/Windy... Deep boundary-layer mixing beneath 40-45kt mid-level flow will result in elevated to locally critical fire-weather conditions across portions of Nevada, eastern Idaho, and northern Wyoming. The best overlap of elevated fire-weather conditions with receptive fuels will be across northern Wyoming and central Nevada, where fuels guidance suggest ERCs are above the 90th annual percentile. Across eastern Idaho in the Snake River Plain, meteorological conditions are expected to exceed Elevated criteria, but recent wetting rainfall and current fuels guidance suggests a narrower corridor supporting wildfire spread. ...Dry Thunderstorms... Isolated dry thunderstorms are expected across central and eastern Wyoming, where ERC fuels are in the 90th-98th annual percentile range and thunderstorms are expected to develop in deeply mixed, dry boundary-layer profiles. Storm motion estimates of 30 kts and PWAT values < 0.8 in should limit wetting rainfall except for in the strongest cores, and some overlap with elevated fire-weather conditions could pose a risk for wildfire spread with any new ignitions. ..Halbert/Squitieri.. 08/21/2024 ...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 0141 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...Synopsis... Broad mid-level southwesterly flow will overspread much of the Great Basin and portions of the Pacific Northwest in advance of a southward-moving shortwave trough approaching the Washington coast. This will result in pockets of elevated fire-weather conditions across Nevada, Idaho, and Wyoming, with an additional risk for isolated dry thunderstorms across eastern and central Wyoming. ...Dry/Windy... Deep boundary-layer mixing beneath 40-45kt mid-level flow will result in elevated to locally critical fire-weather conditions across portions of Nevada, eastern Idaho, and northern Wyoming. The best overlap of elevated fire-weather conditions with receptive fuels will be across northern Wyoming and central Nevada, where fuels guidance suggest ERCs are above the 90th annual percentile. Across eastern Idaho in the Snake River Plain, meteorological conditions are expected to exceed Elevated criteria, but recent wetting rainfall and current fuels guidance suggests a narrower corridor supporting wildfire spread. ...Dry Thunderstorms... Isolated dry thunderstorms are expected across central and eastern Wyoming, where ERC fuels are in the 90th-98th annual percentile range and thunderstorms are expected to develop in deeply mixed, dry boundary-layer profiles. Storm motion estimates of 30 kts and PWAT values < 0.8 in should limit wetting rainfall except for in the strongest cores, and some overlap with elevated fire-weather conditions could pose a risk for wildfire spread with any new ignitions. ..Halbert/Squitieri.. 08/21/2024 ...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 0141 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...Synopsis... Broad mid-level southwesterly flow will overspread much of the Great Basin and portions of the Pacific Northwest in advance of a southward-moving shortwave trough approaching the Washington coast. This will result in pockets of elevated fire-weather conditions across Nevada, Idaho, and Wyoming, with an additional risk for isolated dry thunderstorms across eastern and central Wyoming. ...Dry/Windy... Deep boundary-layer mixing beneath 40-45kt mid-level flow will result in elevated to locally critical fire-weather conditions across portions of Nevada, eastern Idaho, and northern Wyoming. The best overlap of elevated fire-weather conditions with receptive fuels will be across northern Wyoming and central Nevada, where fuels guidance suggest ERCs are above the 90th annual percentile. Across eastern Idaho in the Snake River Plain, meteorological conditions are expected to exceed Elevated criteria, but recent wetting rainfall and current fuels guidance suggests a narrower corridor supporting wildfire spread. ...Dry Thunderstorms... Isolated dry thunderstorms are expected across central and eastern Wyoming, where ERC fuels are in the 90th-98th annual percentile range and thunderstorms are expected to develop in deeply mixed, dry boundary-layer profiles. Storm motion estimates of 30 kts and PWAT values < 0.8 in should limit wetting rainfall except for in the strongest cores, and some overlap with elevated fire-weather conditions could pose a risk for wildfire spread with any new ignitions. ..Halbert/Squitieri.. 08/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Thunderstorms with hail and a few marginally severe gusts will be possible on Thursday across parts of the central and northern Plains. ...Central and Northern Plains... An upper-level ridge over the central Plains and upper Mississippi Valley is forecast to move eastward on Thursday, as a shortwave trough moves through the northern Plains. In association with the trough, elevated morning thunderstorms appear likely in parts of North Dakota. As the convective cluster moves eastward into Minnesota, an axis of moderate instability is expected to develop in its wake across central and eastern North Dakota. The instability axis should be located from the Dakotas south-southwestward into western Nebraska and far western Kansas. During the day, isolated severe thunderstorm development will be possible along and near the instability axis. Most locations near the instability axis have 0-6 km shear forecast in the 25 to 35 knot range. This combined with steep low to mid-level lapse rates will support a marginal severe threat during the late afternoon. Hail and a few severe gusts will be possible. During the evening, the focus is expected to shift southward into far eastern Colorado and western Kansas, as the low-level jet ramps up. A small cluster of thunderstorms with severe potential is expected to develop and move across the central High Plains during the early to mid evening. Model solutions differ on the exact location of this cluster, and have widely varying instability distributions suggesting uncertainty is substantial. For this reason, Marginal seems to be appropriate category at this time. ..Broyles.. 08/21/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Thunderstorms with hail and a few marginally severe gusts will be possible on Thursday across parts of the central and northern Plains. ...Central and Northern Plains... An upper-level ridge over the central Plains and upper Mississippi Valley is forecast to move eastward on Thursday, as a shortwave trough moves through the northern Plains. In association with the trough, elevated morning thunderstorms appear likely in parts of North Dakota. As the convective cluster moves eastward into Minnesota, an axis of moderate instability is expected to develop in its wake across central and eastern North Dakota. The instability axis should be located from the Dakotas south-southwestward into western Nebraska and far western Kansas. During the day, isolated severe thunderstorm development will be possible along and near the instability axis. Most locations near the instability axis have 0-6 km shear forecast in the 25 to 35 knot range. This combined with steep low to mid-level lapse rates will support a marginal severe threat during the late afternoon. Hail and a few severe gusts will be possible. During the evening, the focus is expected to shift southward into far eastern Colorado and western Kansas, as the low-level jet ramps up. A small cluster of thunderstorms with severe potential is expected to develop and move across the central High Plains during the early to mid evening. Model solutions differ on the exact location of this cluster, and have widely varying instability distributions suggesting uncertainty is substantial. For this reason, Marginal seems to be appropriate category at this time. ..Broyles.. 08/21/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Thunderstorms with hail and a few marginally severe gusts will be possible on Thursday across parts of the central and northern Plains. ...Central and Northern Plains... An upper-level ridge over the central Plains and upper Mississippi Valley is forecast to move eastward on Thursday, as a shortwave trough moves through the northern Plains. In association with the trough, elevated morning thunderstorms appear likely in parts of North Dakota. As the convective cluster moves eastward into Minnesota, an axis of moderate instability is expected to develop in its wake across central and eastern North Dakota. The instability axis should be located from the Dakotas south-southwestward into western Nebraska and far western Kansas. During the day, isolated severe thunderstorm development will be possible along and near the instability axis. Most locations near the instability axis have 0-6 km shear forecast in the 25 to 35 knot range. This combined with steep low to mid-level lapse rates will support a marginal severe threat during the late afternoon. Hail and a few severe gusts will be possible. During the evening, the focus is expected to shift southward into far eastern Colorado and western Kansas, as the low-level jet ramps up. A small cluster of thunderstorms with severe potential is expected to develop and move across the central High Plains during the early to mid evening. Model solutions differ on the exact location of this cluster, and have widely varying instability distributions suggesting uncertainty is substantial. For this reason, Marginal seems to be appropriate category at this time. ..Broyles.. 08/21/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Thunderstorms with hail and a few marginally severe gusts will be possible on Thursday across parts of the central and northern Plains. ...Central and Northern Plains... An upper-level ridge over the central Plains and upper Mississippi Valley is forecast to move eastward on Thursday, as a shortwave trough moves through the northern Plains. In association with the trough, elevated morning thunderstorms appear likely in parts of North Dakota. As the convective cluster moves eastward into Minnesota, an axis of moderate instability is expected to develop in its wake across central and eastern North Dakota. The instability axis should be located from the Dakotas south-southwestward into western Nebraska and far western Kansas. During the day, isolated severe thunderstorm development will be possible along and near the instability axis. Most locations near the instability axis have 0-6 km shear forecast in the 25 to 35 knot range. This combined with steep low to mid-level lapse rates will support a marginal severe threat during the late afternoon. Hail and a few severe gusts will be possible. During the evening, the focus is expected to shift southward into far eastern Colorado and western Kansas, as the low-level jet ramps up. A small cluster of thunderstorms with severe potential is expected to develop and move across the central High Plains during the early to mid evening. Model solutions differ on the exact location of this cluster, and have widely varying instability distributions suggesting uncertainty is substantial. For this reason, Marginal seems to be appropriate category at this time. ..Broyles.. 08/21/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN MONTANA AND WESTERN NORTH DAKOTA.... ...SUMMARY... Scattered thunderstorms, some with severe hail and damaging gusts, are expected to develop today over parts of far eastern Montana and western North Dakota. ...Synopsis... A mid-level shortwave trough over north-central California early this morning will move across the Great Basin and emerge across eastern Montana this afternoon. This shortwave trough will be the focus for a severe weather threat this afternoon/evening across eastern Montana and western North Dakota. Farther east, a mid-level trough centered over the Plains will start to break down during the day today. As this occurs, surface troughing is forecast to develop from the northern Plains to the central High Plains. Scattered strong to potentially severe storms are expected along the extent of this surface trough from western South Dakota to eastern Colorado. ...Eastern Montana and western North Dakota... Significant heating is forecast across eastern Montana this afternoon with temperatures forecast to warm into the mid to upper 90s (depending on the degree of mixing). This will result in moderate instability and a mostly uncapped atmosphere by mid to late afternoon. DCVA ahead of the approaching mid-level trough will result in sufficient deep-layer ascent for thunderstorm development by mid to late afternoon. These storms will likely be supercellular in nature as mid-level flow strengthens to near 50 knots while the associated mid-level jet streak overspreads the region. The long-straight hodograph may also support some splitting storms. Large hail (up to golf ball size) and severe wind gusts of 60 to 80 mph will be the primary threats associated with this activity. ...Western South Dakota to eastern Colorado... Scattered thunderstorm activity is expected within a broad surface trough from western South Dakota to eastern Colorado where moderate to strong instability will be in place by mid-afternoon. Mid-level flow will be mostly weak across this region (15 to 20 knots) which will limit the overall shear magnitude. However, moderate southeasterly flow ahead of this surface trough, coupled with the westerly mid-level flow may result in adequate shear for storm organization and perhaps a few slow-moving supercells. The deeply mixed boundary layer across this zone will support a threat for severe wind gusts with isolated hail as a lesser threat (predominantly associated with any more robust supercell development which may occur). A few regions within the marginal risk may have a greater threat (southwest South Dakota/northern Nebraska and northeast Colorado), but it is not clear at this time whether coverage/intensity will be sufficient for a slight risk. ...Southeast Arizona... A surge of monsoon moisture across southern Arizona will result in moderate (1500-2000 J/kg MLCAPE) instability and scattered to widespread thunderstorm development this afternoon. Storm organization will likely be somewhat weak given the weak shear (~15 knots). However, the moderate instability in a deeply mixed boundary layer will support an isolated severe-wind threat. In addition, the widespread nature of the convection will likely result in numerous outflow boundary collisions which may locally enhance updraft intensity and support a few stronger cells. ..Bentley.. 08/21/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN MONTANA AND WESTERN NORTH DAKOTA.... ...SUMMARY... Scattered thunderstorms, some with severe hail and damaging gusts, are expected to develop today over parts of far eastern Montana and western North Dakota. ...Synopsis... A mid-level shortwave trough over north-central California early this morning will move across the Great Basin and emerge across eastern Montana this afternoon. This shortwave trough will be the focus for a severe weather threat this afternoon/evening across eastern Montana and western North Dakota. Farther east, a mid-level trough centered over the Plains will start to break down during the day today. As this occurs, surface troughing is forecast to develop from the northern Plains to the central High Plains. Scattered strong to potentially severe storms are expected along the extent of this surface trough from western South Dakota to eastern Colorado. ...Eastern Montana and western North Dakota... Significant heating is forecast across eastern Montana this afternoon with temperatures forecast to warm into the mid to upper 90s (depending on the degree of mixing). This will result in moderate instability and a mostly uncapped atmosphere by mid to late afternoon. DCVA ahead of the approaching mid-level trough will result in sufficient deep-layer ascent for thunderstorm development by mid to late afternoon. These storms will likely be supercellular in nature as mid-level flow strengthens to near 50 knots while the associated mid-level jet streak overspreads the region. The long-straight hodograph may also support some splitting storms. Large hail (up to golf ball size) and severe wind gusts of 60 to 80 mph will be the primary threats associated with this activity. ...Western South Dakota to eastern Colorado... Scattered thunderstorm activity is expected within a broad surface trough from western South Dakota to eastern Colorado where moderate to strong instability will be in place by mid-afternoon. Mid-level flow will be mostly weak across this region (15 to 20 knots) which will limit the overall shear magnitude. However, moderate southeasterly flow ahead of this surface trough, coupled with the westerly mid-level flow may result in adequate shear for storm organization and perhaps a few slow-moving supercells. The deeply mixed boundary layer across this zone will support a threat for severe wind gusts with isolated hail as a lesser threat (predominantly associated with any more robust supercell development which may occur). A few regions within the marginal risk may have a greater threat (southwest South Dakota/northern Nebraska and northeast Colorado), but it is not clear at this time whether coverage/intensity will be sufficient for a slight risk. ...Southeast Arizona... A surge of monsoon moisture across southern Arizona will result in moderate (1500-2000 J/kg MLCAPE) instability and scattered to widespread thunderstorm development this afternoon. Storm organization will likely be somewhat weak given the weak shear (~15 knots). However, the moderate instability in a deeply mixed boundary layer will support an isolated severe-wind threat. In addition, the widespread nature of the convection will likely result in numerous outflow boundary collisions which may locally enhance updraft intensity and support a few stronger cells. ..Bentley.. 08/21/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN MONTANA AND WESTERN NORTH DAKOTA.... ...SUMMARY... Scattered thunderstorms, some with severe hail and damaging gusts, are expected to develop today over parts of far eastern Montana and western North Dakota. ...Synopsis... A mid-level shortwave trough over north-central California early this morning will move across the Great Basin and emerge across eastern Montana this afternoon. This shortwave trough will be the focus for a severe weather threat this afternoon/evening across eastern Montana and western North Dakota. Farther east, a mid-level trough centered over the Plains will start to break down during the day today. As this occurs, surface troughing is forecast to develop from the northern Plains to the central High Plains. Scattered strong to potentially severe storms are expected along the extent of this surface trough from western South Dakota to eastern Colorado. ...Eastern Montana and western North Dakota... Significant heating is forecast across eastern Montana this afternoon with temperatures forecast to warm into the mid to upper 90s (depending on the degree of mixing). This will result in moderate instability and a mostly uncapped atmosphere by mid to late afternoon. DCVA ahead of the approaching mid-level trough will result in sufficient deep-layer ascent for thunderstorm development by mid to late afternoon. These storms will likely be supercellular in nature as mid-level flow strengthens to near 50 knots while the associated mid-level jet streak overspreads the region. The long-straight hodograph may also support some splitting storms. Large hail (up to golf ball size) and severe wind gusts of 60 to 80 mph will be the primary threats associated with this activity. ...Western South Dakota to eastern Colorado... Scattered thunderstorm activity is expected within a broad surface trough from western South Dakota to eastern Colorado where moderate to strong instability will be in place by mid-afternoon. Mid-level flow will be mostly weak across this region (15 to 20 knots) which will limit the overall shear magnitude. However, moderate southeasterly flow ahead of this surface trough, coupled with the westerly mid-level flow may result in adequate shear for storm organization and perhaps a few slow-moving supercells. The deeply mixed boundary layer across this zone will support a threat for severe wind gusts with isolated hail as a lesser threat (predominantly associated with any more robust supercell development which may occur). A few regions within the marginal risk may have a greater threat (southwest South Dakota/northern Nebraska and northeast Colorado), but it is not clear at this time whether coverage/intensity will be sufficient for a slight risk. ...Southeast Arizona... A surge of monsoon moisture across southern Arizona will result in moderate (1500-2000 J/kg MLCAPE) instability and scattered to widespread thunderstorm development this afternoon. Storm organization will likely be somewhat weak given the weak shear (~15 knots). However, the moderate instability in a deeply mixed boundary layer will support an isolated severe-wind threat. In addition, the widespread nature of the convection will likely result in numerous outflow boundary collisions which may locally enhance updraft intensity and support a few stronger cells. ..Bentley.. 08/21/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Aug 21 2024 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN MONTANA AND WESTERN NORTH DAKOTA.... ...SUMMARY... Scattered thunderstorms, some with severe hail and damaging gusts, are expected to develop today over parts of far eastern Montana and western North Dakota. ...Synopsis... A mid-level shortwave trough over north-central California early this morning will move across the Great Basin and emerge across eastern Montana this afternoon. This shortwave trough will be the focus for a severe weather threat this afternoon/evening across eastern Montana and western North Dakota. Farther east, a mid-level trough centered over the Plains will start to break down during the day today. As this occurs, surface troughing is forecast to develop from the northern Plains to the central High Plains. Scattered strong to potentially severe storms are expected along the extent of this surface trough from western South Dakota to eastern Colorado. ...Eastern Montana and western North Dakota... Significant heating is forecast across eastern Montana this afternoon with temperatures forecast to warm into the mid to upper 90s (depending on the degree of mixing). This will result in moderate instability and a mostly uncapped atmosphere by mid to late afternoon. DCVA ahead of the approaching mid-level trough will result in sufficient deep-layer ascent for thunderstorm development by mid to late afternoon. These storms will likely be supercellular in nature as mid-level flow strengthens to near 50 knots while the associated mid-level jet streak overspreads the region. The long-straight hodograph may also support some splitting storms. Large hail (up to golf ball size) and severe wind gusts of 60 to 80 mph will be the primary threats associated with this activity. ...Western South Dakota to eastern Colorado... Scattered thunderstorm activity is expected within a broad surface trough from western South Dakota to eastern Colorado where moderate to strong instability will be in place by mid-afternoon. Mid-level flow will be mostly weak across this region (15 to 20 knots) which will limit the overall shear magnitude. However, moderate southeasterly flow ahead of this surface trough, coupled with the westerly mid-level flow may result in adequate shear for storm organization and perhaps a few slow-moving supercells. The deeply mixed boundary layer across this zone will support a threat for severe wind gusts with isolated hail as a lesser threat (predominantly associated with any more robust supercell development which may occur). A few regions within the marginal risk may have a greater threat (southwest South Dakota/northern Nebraska and northeast Colorado), but it is not clear at this time whether coverage/intensity will be sufficient for a slight risk. ...Southeast Arizona... A surge of monsoon moisture across southern Arizona will result in moderate (1500-2000 J/kg MLCAPE) instability and scattered to widespread thunderstorm development this afternoon. Storm organization will likely be somewhat weak given the weak shear (~15 knots). However, the moderate instability in a deeply mixed boundary layer will support an isolated severe-wind threat. In addition, the widespread nature of the convection will likely result in numerous outflow boundary collisions which may locally enhance updraft intensity and support a few stronger cells. ..Bentley.. 08/21/2024 Read more

722
ABPZ20 KNHC 210520
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 PM PDT Tue Aug 20 2024

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

The National Hurricane Center is issuing advisories on Tropical
Storm Gilma, located several hundred miles west-southwest of the
southern tip of the Baja California peninsula.

Well East-Southeast of the Hawaiian Islands (EP90/EP91):
Showers and thunderstorms associated with a well-defined area of
low pressure located well east-southeast of the Hawaiian Islands
are gradually becoming better organized, and only a slight increase
in organization could result in the formation of a tropical
depression or tropical storm while it moves generally westward at
10 to 15 mph. The weaker disturbance located just to its southwest
is expected to dissipate or merge with this system during the next
several hours. This system is expected to strengthen as it moves
across the central Pacific basin late this week and move near the
Hawaiian Islands late this weekend or early next week.

While it is too early to determine the exact location and magnitude
of potential impacts, interests in Hawaii should closely monitor
this disturbance. Information on this system's development can also
be found in the Tropical Weather Outlook for the Central Pacific
basin. For marine forecasts, including gale warnings, see High Seas
Forecasts issued by the National Weather Service.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 7 days...high...90 percent.

Eastern and Central Portion of the East Pacific:
Disorganized showers and thunderstorms centered several hundred
miles southwest of the coast of southwestern Mexico are associated
with a trough of low pressure. Environmental conditions are
forecast to become more conducive for development in a day or two,
and a tropical depression could form late this week or over the
weekend while the system moves west-northwestward over open waters,
well offshore of Mexico.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 7 days...medium...60 percent.

&&
High Seas Forecasts issued by the National Weather Service
can be found under AWIPS header NFDHSFEPI, WMO header FZPN02
KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php

The Tropical Weather Outlook for the Central Pacific basin can be
found under AWIPS header HFOTWOCP and WMO header ACPN50 PHFO and on
the web at hurricanes.gov

$$
Forecaster Hagen/Pasch

5-Day Uncertainty Track last updated Wed, 21 Aug 2024 02:36:38 GMT


Wind Speed Probabilities last updated Wed, 21 Aug 2024 03:23:39 GMT

Issued at 800 PM PDT Tue Aug 20 2024 000 WTPZ42 KNHC 210234 TCDEP2 Tropical Storm Gilma Discussion Number 11 NWS National Hurricane Center Miami FL EP072024 800 PM PDT Tue Aug 20 2024 Gilma is holding steady this evening. The low-level circulation is still hidden beneath a modest Central Dense Overcast (CDO). Recent satellite microwave imagery showed the deep convection is limited to the southern half of the storm, with a band extending to the southwest of the center. The initial intensity is held at 60 kt in deference to the earlier ASCAT data, slightly above the subjective Dvorak estimates of 55 kt from TAFB and SAB. A ridge centered over the southwestern U.S. is steering the storm at an estimated 275/9 kt. A westward to west-northwestward motion should continue for the next day or so. By Thursday, a slight turn poleward and decrease of forward speed is expected as a deep-layer trough moving in from the west erodes the ridge. Once again, the track model guidance has shifted southward this cycle. The latest NHC track forecast has been nudged to the south and lies between the previous track forecast and the simple consensus aid TVCE. Gilma seems to be holding its own against the moderate northeasterly wind shear. Global models suggest the upper-level winds should gradually become more favorable over the next day or so, allowing Gilma to reach hurricane status overnight or Wednesday morning. The storm should have the necessary ingredients to steadily strengthen through Thursday, and the forecast peak remains at 90 kt. By the end of the week and into the weekend, Gilma should encounter cooling sea surface temperatures, increasing shear, and dry mid-level humidities causing it to gradually weaken. The latest official forecast is largely an update of the previous prediction. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 16.1N 121.5W 60 KT 70 MPH 12H 21/1200Z 16.2N 122.6W 65 KT 75 MPH 24H 22/0000Z 16.6N 123.9W 70 KT 80 MPH 36H 22/1200Z 17.0N 125.0W 80 KT 90 MPH 48H 23/0000Z 17.4N 126.1W 85 KT 100 MPH 60H 23/1200Z 17.8N 127.3W 90 KT 105 MPH 72H 24/0000Z 18.2N 128.6W 85 KT 100 MPH 96H 25/0000Z 18.8N 131.6W 70 KT 80 MPH 120H 26/0000Z 19.6N 135.4W 55 KT 65 MPH $$ Forecaster Bucci

Issued at 800 PM PDT Tue Aug 20 2024 926 WTPZ32 KNHC 210234 TCPEP2 BULLETIN Tropical Storm Gilma Advisory Number 11 NWS National Hurricane Center Miami FL EP072024 800 PM PDT Tue Aug 20 2024 ...GILMA EXPECTED TO BECOME A HURRICANE OVERNIGHT OR TOMORROW MORNING... SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION ---------------------------------------------- LOCATION...16.1N 121.5W ABOUT 890 MI...1430 KM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H PRESENT MOVEMENT...W OR 275 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...992 MB...29.30 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 800 PM PDT (0300 UTC), the center of Tropical Storm Gilma was located near latitude 16.1 North, longitude 121.5 West. Gilma is moving toward the west near 10 mph (17 km/h). A slightly slower westward to west-northwestward motion is expected during the next few days. Maximum sustained winds remain near 70 mph (110 km/h) with higher gusts. Additional strengthening is forecast during the next couple of days, and Gilma could become a hurricane overnight or tomorrow morning. Tropical-storm-force winds extend outward up to 140 miles (220 km) from the center. The estimated minimum central pressure is 992 mb (29.30 inches). HAZARDS AFFECTING LAND ---------------------- None NEXT ADVISORY ------------- Next complete advisory at 200 AM PDT. $$ Forecaster Bucci

...GILMA EXPECTED TO BECOME A HURRICANE OVERNIGHT OR TOMORROW MORNING... As of 8:00 PM PDT Tue Aug 20 the center of Gilma was located near 16.1, -121.5 with movement W at 10 mph. The minimum central pressure was 992 mb with maximum sustained winds of about 70 mph.

Issued at 0300 UTC WED AUG 21 2024 858 FOPZ12 KNHC 210234 PWSEP2 TROPICAL STORM GILMA WIND SPEED PROBABILITIES NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP072024 0300 UTC WED AUG 21 2024 AT 0300Z THE CENTER OF TROPICAL STORM GILMA WAS LOCATED NEAR LATITUDE 16.1 NORTH...LONGITUDE 121.5 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 60 KTS...70 MPH...110 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) PACIFIC DAYLIGHT TIME (PDT)...SUBTRACT 7 HOURS FROM Z TIME HAWAIIAN STANDARD TIME (HST)...SUBTRACT 10 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 00Z WED AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 00Z WED 12Z WED 00Z THU 12Z THU 00Z FRI 00Z SAT 00Z SUN PERIODS TO TO TO TO TO TO TO 12Z WED 00Z THU 12Z THU 00Z FRI 00Z SAT 00Z SUN 00Z MON FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT 15N 120W 34 2 2( 4) 1( 5) 1( 6) X( 6) X( 6) X( 6) 20N 120W 34 1 1( 2) 1( 3) X( 3) X( 3) X( 3) X( 3) 15N 125W 34 3 26(29) 14(43) 3(46) 3(49) X(49) X(49) 15N 125W 50 X 1( 1) 2( 3) 1( 4) X( 4) X( 4) X( 4) 20N 125W 34 1 2( 3) 8(11) 11(22) 7(29) 1(30) X(30) 20N 125W 50 X X( X) 1( 1) 1( 2) 2( 4) X( 4) X( 4) 15N 130W 34 X X( X) 1( 1) 2( 3) 9(12) 5(17) X(17) 20N 130W 34 X X( X) 1( 1) 3( 4) 33(37) 27(64) 1(65) 20N 130W 50 X X( X) X( X) X( X) 8( 8) 17(25) 1(26) 20N 130W 64 X X( X) X( X) X( X) 3( 3) 9(12) X(12) 15N 135W 34 X X( X) X( X) X( X) X( X) 2( 2) 3( 5) 20N 135W 34 X X( X) X( X) X( X) X( X) 11(11) 29(40) 20N 135W 50 X X( X) X( X) X( X) X( X) 2( 2) 10(12) 20N 135W 64 X X( X) X( X) X( X) X( X) 1( 1) 3( 4) 25N 135W 34 X X( X) X( X) X( X) X( X) 1( 1) 2( 3) 20N 140W 34 X X( X) X( X) X( X) X( X) X( X) 4( 4) $$ FORECASTER BUCCI