SPC Oct 23, 2018 1300 UTC Day 1 Convective Outlook

1 hour 2 minutes ago
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 AM CDT Tue Oct 23 2018 Valid 231300Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FOR SOUTHEASTERN AZ AND VICINITY... ...SUMMARY... A few storms could produce marginally severe hail and strong wind gusts across southeastern Arizona and vicinity this afternoon/evening. ...Southeastern AZ and vicinity from 20-01z... A southern-stream shortwave trough over northern Baja this morning will move generally eastward to near El Paso by the end of the period. Ascent preceding the midlevel trough will contribute to clouds and some early/elevated thunderstorm development this morning across eastern AZ, with storms expected to spread into western NM by late morning and through the afternoon. West of this early convection, there should be a narrow corridor of surface heating, roughly coincident with the arrival of the midlevel thermal trough over southeastern AZ this afternoon. The cool midlevel temperatures and surface heating will promote MLCAPE of 1000-1500 J/kg, and deep-layer vertical shear will initially favor supercells. However, vertical shear will tend to weaken this afternoon from west to east across southern AZ near the midlevel trough. Thus, the primary convective modes should be marginal supercells and/or multicell clusters capable of producing isolated large hail/damaging winds from about 20-01z. ...NY to southern New England through this evening... A surface cyclone will move eastward from NY to the southeast New England coast by this evening, in advance of an amplifying midlevel trough now over the lower Great Lakes. Cold midlevel temperatures and residual low-level moisture will contribute to weak buoyancy rooted at the surface this afternoon, when isolated/low-topped thunderstorms will be possible within a broader area of precipitation/shallow convection. The buoyancy will be a little deeper/larger to the north of the jet core, where flow within the buoyant layer will be rather modest. There will be sufficient vertical shear for weak rotation in the strongest updrafts across southeast New England this evening, but the severe weather threat still appears too low to warrant introducing a categorical area. ..Thompson/Jewell.. 10/23/2018 Read more

SPC Oct 23, 2018 Day 4-8 Severe Weather Outlook

5 hours 26 minutes ago
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0322 AM CDT Tue Oct 23 2018 Valid 261200Z - 311200Z ...DISCUSSION... A mid/upper trough will amplify across the Mississippi Valley on D4/Friday. Broad forcing for ascent along its southeastern flank is forecast to support a surface cyclone advancing from near the Florida Panhandle east/northeastward to near/just offshore the Carolina coast. To the south/east of this cyclone, the warm sector will support at least modest levels of surface-based buoyancy. In conjunction with strengthening low/mid-level wind fields, this destabilization may foster some potential for a few strong/severe storms during the day. However, subsidence/drying aloft in the wake of a prior impulse and veered deep-layer flow may keep most convection relatively shallow, while deeper cells remain sparse due to weak low-level convergence. Therefore, while some (most likely marginal) damaging wind threat could evolve on D4/Friday, uncertainty with this potential is too great for highlights. Thereafter, the potential for severe weather appears low across the country through the remainder of the extended period, as an eastern US trough prevents significant poleward moisture return. Read more

SPC Oct 23, 2018 Day 4-8 Severe Weather Outlook

5 hours 26 minutes ago
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0322 AM CDT Tue Oct 23 2018 Valid 261200Z - 311200Z ...DISCUSSION... A mid/upper trough will amplify across the Mississippi Valley on D4/Friday. Broad forcing for ascent along its southeastern flank is forecast to support a surface cyclone advancing from near the Florida Panhandle east/northeastward to near/just offshore the Carolina coast. To the south/east of this cyclone, the warm sector will support at least modest levels of surface-based buoyancy. In conjunction with strengthening low/mid-level wind fields, this destabilization may foster some potential for a few strong/severe storms during the day. However, subsidence/drying aloft in the wake of a prior impulse and veered deep-layer flow may keep most convection relatively shallow, while deeper cells remain sparse due to weak low-level convergence. Therefore, while some (most likely marginal) damaging wind threat could evolve on D4/Friday, uncertainty with this potential is too great for highlights. Thereafter, the potential for severe weather appears low across the country through the remainder of the extended period, as an eastern US trough prevents significant poleward moisture return. Read more

SPC Oct 23, 2018 Day 4-8 Severe Weather Outlook

5 hours 26 minutes ago
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0322 AM CDT Tue Oct 23 2018 Valid 261200Z - 311200Z ...DISCUSSION... A mid/upper trough will amplify across the Mississippi Valley on D4/Friday. Broad forcing for ascent along its southeastern flank is forecast to support a surface cyclone advancing from near the Florida Panhandle east/northeastward to near/just offshore the Carolina coast. To the south/east of this cyclone, the warm sector will support at least modest levels of surface-based buoyancy. In conjunction with strengthening low/mid-level wind fields, this destabilization may foster some potential for a few strong/severe storms during the day. However, subsidence/drying aloft in the wake of a prior impulse and veered deep-layer flow may keep most convection relatively shallow, while deeper cells remain sparse due to weak low-level convergence. Therefore, while some (most likely marginal) damaging wind threat could evolve on D4/Friday, uncertainty with this potential is too great for highlights. Thereafter, the potential for severe weather appears low across the country through the remainder of the extended period, as an eastern US trough prevents significant poleward moisture return. Read more

SPC Oct 23, 2018 Day 4-8 Severe Weather Outlook

5 hours 26 minutes ago
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0322 AM CDT Tue Oct 23 2018 Valid 261200Z - 311200Z ...DISCUSSION... A mid/upper trough will amplify across the Mississippi Valley on D4/Friday. Broad forcing for ascent along its southeastern flank is forecast to support a surface cyclone advancing from near the Florida Panhandle east/northeastward to near/just offshore the Carolina coast. To the south/east of this cyclone, the warm sector will support at least modest levels of surface-based buoyancy. In conjunction with strengthening low/mid-level wind fields, this destabilization may foster some potential for a few strong/severe storms during the day. However, subsidence/drying aloft in the wake of a prior impulse and veered deep-layer flow may keep most convection relatively shallow, while deeper cells remain sparse due to weak low-level convergence. Therefore, while some (most likely marginal) damaging wind threat could evolve on D4/Friday, uncertainty with this potential is too great for highlights. Thereafter, the potential for severe weather appears low across the country through the remainder of the extended period, as an eastern US trough prevents significant poleward moisture return. Read more

SPC Oct 23, 2018 0730 UTC Day 3 Severe Thunderstorm Outlook

6 hours 38 minutes ago
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0211 AM CDT Tue Oct 23 2018 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms are expected along the central/eastern Gulf Coast on Thursday, but severe weather is not expected. ...Discussion... Weakly cyclonic flow aloft will overspread areas from the central Gulf Coast eastward on Thursday. A weak/low-amplitude impulse will initially cross the region during the day, and an initial surge of warm-air advection may yield enough elevated buoyancy for a few thunderstorms from southeastern Louisiana to the western Florida Panhandle. Behind this initial impulse, a secondary, more amplified shortwave trough will approach the southeastern US Thursday night. Strengthening southwesterly 850mb flow and isentropic ascent may yield isolated thunderstorms farther east across the Florida Peninsula and portions of southern Georgia. Through the period, expansive precipitation across inland areas and a lack of stronger large-scale ascent near the coast should preclude significant poleward return of surface theta-e, limiting surface-based destabilization. In turn, severe weather is not forecast, despite strengthening wind fields. ..Picca.. 10/23/2018 Read more

SPC Oct 23, 2018 0730 UTC Day 3 Severe Thunderstorm Outlook

6 hours 38 minutes ago
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0211 AM CDT Tue Oct 23 2018 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms are expected along the central/eastern Gulf Coast on Thursday, but severe weather is not expected. ...Discussion... Weakly cyclonic flow aloft will overspread areas from the central Gulf Coast eastward on Thursday. A weak/low-amplitude impulse will initially cross the region during the day, and an initial surge of warm-air advection may yield enough elevated buoyancy for a few thunderstorms from southeastern Louisiana to the western Florida Panhandle. Behind this initial impulse, a secondary, more amplified shortwave trough will approach the southeastern US Thursday night. Strengthening southwesterly 850mb flow and isentropic ascent may yield isolated thunderstorms farther east across the Florida Peninsula and portions of southern Georgia. Through the period, expansive precipitation across inland areas and a lack of stronger large-scale ascent near the coast should preclude significant poleward return of surface theta-e, limiting surface-based destabilization. In turn, severe weather is not forecast, despite strengthening wind fields. ..Picca.. 10/23/2018 Read more

SPC Oct 23, 2018 0730 UTC Day 3 Severe Thunderstorm Outlook

6 hours 38 minutes ago
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0211 AM CDT Tue Oct 23 2018 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms are expected along the central/eastern Gulf Coast on Thursday, but severe weather is not expected. ...Discussion... Weakly cyclonic flow aloft will overspread areas from the central Gulf Coast eastward on Thursday. A weak/low-amplitude impulse will initially cross the region during the day, and an initial surge of warm-air advection may yield enough elevated buoyancy for a few thunderstorms from southeastern Louisiana to the western Florida Panhandle. Behind this initial impulse, a secondary, more amplified shortwave trough will approach the southeastern US Thursday night. Strengthening southwesterly 850mb flow and isentropic ascent may yield isolated thunderstorms farther east across the Florida Peninsula and portions of southern Georgia. Through the period, expansive precipitation across inland areas and a lack of stronger large-scale ascent near the coast should preclude significant poleward return of surface theta-e, limiting surface-based destabilization. In turn, severe weather is not forecast, despite strengthening wind fields. ..Picca.. 10/23/2018 Read more

SPC Day 2 Fire Weather Outlook

7 hours 4 minutes ago
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0144 AM CDT Tue Oct 23 2018 Valid 241200Z - 251200Z ...NO CRITICAL AREAS... ...Synopsis... An upper-level jet max will begin to nose into the Pacific Northwest on Wednesday as ridging starts to build along the West Coast. By the end of the Day 2 period (i.e., Thursday morning), northwesterly flow aloft is forecast to overspread the Great Basin. In response at the surface, high pressure will begin to develop over the Intermountain West, leading to the onset of offshore low-level flow across southern California. While afternoon surface conditions over inland portions of southern California will be dry (RH values around 15%), confidence is too low in the development of strong offshore flow to highlight elevated fire weather conditions at this time. ..Jirak.. 10/23/2018 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook

7 hours 4 minutes ago
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0144 AM CDT Tue Oct 23 2018 Valid 241200Z - 251200Z ...NO CRITICAL AREAS... ...Synopsis... An upper-level jet max will begin to nose into the Pacific Northwest on Wednesday as ridging starts to build along the West Coast. By the end of the Day 2 period (i.e., Thursday morning), northwesterly flow aloft is forecast to overspread the Great Basin. In response at the surface, high pressure will begin to develop over the Intermountain West, leading to the onset of offshore low-level flow across southern California. While afternoon surface conditions over inland portions of southern California will be dry (RH values around 15%), confidence is too low in the development of strong offshore flow to highlight elevated fire weather conditions at this time. ..Jirak.. 10/23/2018 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook

7 hours 6 minutes ago
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0142 AM CDT Tue Oct 23 2018 Valid 231200Z - 241200Z ...NO CRITICAL AREAS... ...Synopsis... An upper-level shortwave trough will approach the Pacific Northwest coast during the day and lift northeastward overnight into British Columbia. While enhanced midlevel and low-level flow will accompany this trough, locations with a dry boundary layer (i.e., afternoon surface RH values falling below 20%) across central/southern Oregon, northeastern California, and northwestern Nevada will only experience a modest increase in low-level flow. Given the relatively weak surface pressure gradient across the area, sustained winds will likely remain below 15 mph, limiting the overall fire weather concerns. ..Jirak.. 10/23/2018 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook

7 hours 6 minutes ago
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0142 AM CDT Tue Oct 23 2018 Valid 231200Z - 241200Z ...NO CRITICAL AREAS... ...Synopsis... An upper-level shortwave trough will approach the Pacific Northwest coast during the day and lift northeastward overnight into British Columbia. While enhanced midlevel and low-level flow will accompany this trough, locations with a dry boundary layer (i.e., afternoon surface RH values falling below 20%) across central/southern Oregon, northeastern California, and northwestern Nevada will only experience a modest increase in low-level flow. Given the relatively weak surface pressure gradient across the area, sustained winds will likely remain below 15 mph, limiting the overall fire weather concerns. ..Jirak.. 10/23/2018 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Oct 23, 2018 0600 UTC Day 2 Convective Outlook

8 hours 18 minutes ago
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1224 AM CDT Tue Oct 23 2018 Valid 241200Z - 251200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Only isolated thunderstorms are expected on Wednesday across the western/central Gulf Coast, and severe weather is not forecast. ...Discussion... Downstream of a broad trough ejecting east/northeast across the southern Plains on Wednesday, a warm-advection regime will establish from eastern Texas to the lower Mississippi Valley. This pattern should support widespread rainfall across much of the region, but very limited buoyancy will likely preclude thunderstorms in most locations. The only exception is expected to exist along the middle/upper Texas and Louisiana coasts, where sufficient inland destabilization should favor isolated thunderstorm activity. A lack of more substantive buoyancy, combined with the unorganized nature of the ejecting trough, is expected to preclude severe weather, though. Elsewhere, a couple of lightning strikes may occur over western Colorado, but the eastward departure of the primary trough should limit cooling aloft, likely keeping any lightning too isolated for a general thunder area. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Picca.. 10/23/2018 Read more

SPC Oct 23, 2018 0600 UTC Day 1 Convective Outlook

8 hours 19 minutes ago
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1228 AM CDT Tue Oct 23 2018 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN ARIZONA AND FAR WESTERN NEW MEXICO... ...SUMMARY... Scattered thunderstorms may produce marginally severe hail and gusty winds over parts of eastern Arizona and western New Mexico this afternoon and early evening. ...Synopsis... A weak southern-stream mid-level wave - initially positioned over Baja California - will traverse portions of the Southwest today and reach the Four Corners region tonight. Downstream of this wave, a powerful mid-level trough will amplify southeastward into the northeastern CONUS. Ridging will persist across the central U.S. between the two disturbances. At the surface, a trough will remain positioned across the Lower Colorado River Valley and vicinity and move very little through the forecast period. Meanwhile, a low near southeastern Ontario will migrate through New York state, then reorganize and deepen late near coastal areas of southern New England. An anticyclone will build southeastward across much of the central and southern U.S. in the wake of the coastal low. ...Arizona and western New Mexico... Scattered precipitation should be ongoing at the beginning of the forecast period over New Mexico due to lift associated with the upstream wave. West of the precipitation shield, models indicate surface warming beneath modestly steep mid-level lapse rates (around 7.5-8C/km) resulting in weak to moderate instability. Storms should redevelop in central Arizona during the afternoon and grow upscale into loosely organized clusters while migrating northeastward, with an attendant threat for isolated hail/wind given the favorable thermodynamic profiles. ...New York into southern New England... Cold temperatures aloft associated with the approaching mid-level trough will contribute to enough destabilization for afternoon convection producing a few lightning strikes. Though instability profiles will be weak, steep lapse rates and convection may result in enough downward transfer of higher-momentum air for a low-end threat of isolated wind gusts - especially in portions of southern New England beneath a belt of stronger mid/upper flow. Flow should be weaker in New York state, however. The severe-wind threat currently appears to be too low/unfocused for any probabilities, although an upgrade to Marginal may be needed in later outlooks if a corridor of locally gusty thunderstorm winds can materialize. ..Cook/Jirak.. 10/23/2018 Read more

SPC MD 1591

17 hours 13 minutes ago
MD 1591 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHEAST ARIZONA
Mesoscale Discussion 1591 NWS Storm Prediction Center Norman OK 0337 PM CDT Mon Oct 22 2018 Areas affected...northeast Arizona Concerning...Severe potential...Watch unlikely Valid 222037Z - 222230Z Probability of Watch Issuance...5 percent SUMMARY...Isolated storms may become capable of producing hail and gusty winds this afternoon into early evening. Threat is expected to remain too marginal for a WW. DISCUSSION...As of mid afternoon storms are developing over a portion of the Rim of north central AZ fostered by deeper forcing for ascent accompanying a northeast-advancing shortwave trough. Diabatic heating is destabilizing the boundary layer, but limited low-level moisture with dewpoints in the 40s F is resulting in MLCAPE near or below 500 J/kg. A corridor of modest winds aloft within base of the upper trough is spreading through this region with 30-35 kt effective bulk shear supportive of both multicells and some marginal supercell structures. This environment will promote some potential for a few instances of hail and gusty winds through early evening, but overall threat should remain limited due primarily to the marginal thermodynamic environment. ..Dial.. 10/22/2018 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGZ... LAT...LON 34521071 35081151 36001170 36851013 36750951 36120928 35200987 34521071 Read more

SPC Oct 22, 2018 2000 UTC Day 1 Convective Outlook

18 hours 3 minutes ago
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Mon Oct 22 2018 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN/NORTHERN ARIZONA...EXTREME SOUTHEASTERN UTAH...AND FAR WESTERN NEW MEXICO... ...SUMMARY... Isolated large hail will remain possible through the early evening across eastern/northern Arizona, extreme southeastern Utah and far western New Mexico. ...20Z Update... No changes have been made to the Marginal risk area across parts of the Southwest. Greater coverage of thunderstorms is still expected across northern AZ into the Four Corners region this afternoon, which will remain in closer proximity to forcing associated with an upper trough over southern NV/UT and northwestern AZ. Generally isolated thunderstorms driven mainly by terrain-induced circulations will be possible with southward extent in southeastern AZ and far western NM. Around 35 kt of effective bulk shear noted in recent mesoanalysis should support some updraft organization/rotation, and isolated instances of large hail remain the primary risk. ..Gleason.. 10/22/2018 .PREV DISCUSSION... /ISSUED 1110 AM CDT Mon Oct 22 2018/ ...Eastern Arizona, southeast Utah and western New Mexico... Corridor of greatest instability will evolve this afternoon across southeast AZ along low-level moist axis where surface dewpoints are currently in the 50s F. Diabatic heating will support up to 1500 J/kg MLCAPE in southeast AZ with much weaker instability (MLCAPE near 500 J/kg) farther north and east where low-level moisture is more limited. Widely scattered showers and thunderstorms persist this morning from northern through southeast AZ. This activity will develop northeast in association with ascent attending a vorticity maximum rotating through base of an upper trough. Unlike yesterday, timing of the vorticity maximum is not ideal, and the deeper ascent will gradually shift north of the zone of greater CAPE located across southeast AZ. Nevertheless, at least weak instability will evolve as the surface layer destabilizes within a more favorable zone of ascent from northern AZ into southeast UT and northwest NM, supporting potential for storm intensification where wind profiles (30-35 kt effective bulk shear) will be supportive of marginal supercell structures. Much weaker ascent or subsidence is expected farther south across southern AZ which should contribute to a more sparse coverage of storms capable of hail. Read more
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