Outlook (Main)
Storm Prediction Center
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SPC - No watches are valid as of Fri Apr 16 08:36:02 UTC 2021
No watches are valid as of Fri Apr 16 08:36:02 UTC 2021. -
SPC MD 392
MD 0392 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHERN LOUISIANA
Mesoscale Discussion 0392 NWS Storm Prediction Center Norman OK 0330 AM CDT Fri Apr 16 2021 Areas affected...Southern Louisiana Concerning...Severe potential...Watch unlikely Valid 160830Z - 161100Z Probability of Watch Issuance...20 percent SUMMARY...An isolated large hail and strong wind gusts potential will exist early this morning across parts of southern Louisiana. The threat is expected to remain localized and weather watch issuance appears unlikely. DISCUSSION...Over the last few hours, a small cluster of strong thunderstorms has developed in the Sabine River Valley. This cluster is being supported by large-scale ascent ahead of a shortwave trough currently moving through the southern Plains. A short line segment at the western end of the cluster appears to to be an organized supercell but elevated in nature. This storm will continue to move eastward along a gradient of instability, with the RAP analyzing MUCAPE in the 500 to 1000 J/kg range. This combined with about 70 kt of westerly flow in the mid-levels will support an isolated severe threat over the next few hours. Large hail and strong wind gusts will be possible. Storm coverage is expected to remain relatively isolated. For this reason, weather watch issuance is not expected. ..Broyles/Grams.. 04/16/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LIX...LCH... LAT...LON 31089330 31049361 30879385 30719395 30539401 30239390 30159374 30019327 29889279 29799209 29799163 29989143 30229136 30479139 30709166 30969231 31069294 31089330Read more -
SPC Apr 16, 2021 0600 UTC Day 1 Convective Outlook
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Fri Apr 16 2021 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TEXAS ALONG THE GULF COAST TO NORTHERN FLORIDA AND IN PORTIONS SOUTH TEXAS.... ...SUMMARY... Isolated strong to severe storms capable of hail and gusty winds are possible across parts of eastern Texas along the Gulf Coast and into north Florida today. An isolated strong to severe storm capable of large hail may be possible along the Rio Grande in the South Texas late in the period. ...Synopsis... A mid-level shortwave trough will slowly move through the central Plains today with an moderately strong mid-level jet overspreading much of Texas into the Gulf States. At the surface, a cold front is forecast to be in the Texas Panhandle at 12Z Friday and quickly accelerate southward across the entire state of Texas to near Brownsville by 12Z Saturday. ...Eastern Texas into Louisiana and southwest Mississippi... Ongoing convection is expected across much of Texas and southern Oklahoma at the beginning of the period as a result of increasing isentropic ascent resulting from the strengthening low-level jet. These morning storms are expected to move southeastward along the instability gradient into east Texas and Louisiana during the afternoon. Some additional development is possible in a warm air advection regime across south and central Louisiana this afternoon/evening. However, there is still some uncertainty regarding the strength of the low-level jet and therefore, the coverage of storms. Regardless of coverage, storms in the area will likely be elevated with some supercell structures possible given very strong 70+ kts of effective shear. These better organized supercell structures will likely pose the primary threat for large hail, however the limited instability will likely preclude more than an isolated threat. Farther west across Texas, some surface based instability is expected to develop ahead of the cold front. This instability combined with lift from the surface front may be sufficient for a few storms during the afternoon/early evening. However, most of the forcing is expected to be across Louisiana and Arkansas by late afternoon with height rises expected across central and south Texas after 21Z. In addition, the rapid southward movement of the cold front will likely limit parcel residence time and may also be a negative factor for deep convection along the front. Any storms which can develop would pose an isolated large hail and damaging wind threat. ...South Texas near the Rio Grande... Forecast soundings show much of this region capped through the evening hours, but height falls from an approaching shortwave after 06Z will increase the chances for storms late in the period. Storms will have a greater probability across the border in Mexico with the assistance of upslope flow behind the front. Forecast soundings show elevated instability for several hours post-frontal which would support a brief supercell or two late in the period with large hail as the primary threat. ...Southern Alabama and north Florida... A weak mid-level shortwave trough over Louisiana early this morning will move east-southeastward through the morning hours. As this impulse approaches a stalled surface front across north-central Florida during the morning hours, convection is expected to develop and strengthen. Temperatures are expected to warm into the mid 70s with dewpoints in the mid to upper 60s south of this warm front yielding around 1000 to 1500 J/kg MLCAPE. Strong mid-level flow in excess of 50 knots will provide ample effective shear (45+ kts) or storm organization and the potential for supercell structures. Large hail and damaging winds will be the primary threat with this activity. A strengthening low-level jet is expected to persist across the northern Gulf Friday night with a large reservoir of 1000+ J/kg MUCAPE available to feed mostly elevated storm activity along the coast. Strong shear may help maintain storm longevity within these clusters with occasional strong to isolated severe storms. The unstable upstream airmass will likely maintain this marginal severe threat through 12Z Saturday into the northern Florida Peninsula. ..Bentley/Dial.. 04/16/2021
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SPC Apr 16, 2021 0600 UTC Day 2 Convective Outlook
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Fri Apr 16 2021 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL GULF COAST INTO SOUTHERN GEORGIA...AND DEEP SOUTH TEXAS... ...SUMMARY... Isolated strong to severe storms appear possible Saturday across parts of the central Gulf Coast into southern Georgia. A few instances of large hail may also occur Saturday morning across deep south Texas. ...Synopsis... A 60-80 kt mid-level westerly jet is forecast to be present over much of the Southeast Saturday. A low-amplitude shortwave trough will advance eastward from the mid MS Valley to the Mid-Atlantic through the day. A 30-40 kt west-southwesterly low-level jet should be focused over the vicinity of northern FL and southern GA through at least Saturday afternoon. At the surface, a cold front will move off the TX/LA Gulf Coast, while a weak low develops northeastward from coastal LA/MS/AL to northern FL and southern GA along a warm front. This front is not expected to make much northward progress through the day across southern GA. ...Southeast... Convection will likely be ongoing Saturday morning across the central Gulf Coast with support from a low-level jet. Limited convergence along the warm front and mid-level flow largely parallel to this boundary creates a fair amount of uncertainty regarding how much convection will develop through the day. Most guidance suggests that overall storm coverage may remain quite isolated, before possibly increasing some by late Saturday afternoon. Regardless, any storms that can form along/south of the warm front from coastal AL across the FL Panhandle and into southern GA may pose an isolated severe threat. Deep-layer shear appears strong enough to support supercells, but low-level shear may gradually decrease through the afternoon as the low-level jet veers to westerly and shifts towards the Atlantic Coast. Occasional strong to damaging winds appear possible with any surface-based convection, and a brief tornado may also occur near the warm front. Mid-level lapse rates should be relatively modest across this region, but isolated instances of large hail could also occur Saturday afternoon/evening across the warm sector as instability becomes maximized. ...Deep South Texas... A cold front will quickly progress southward across deep south TX Saturday morning. Low-level upslope flow over the mountains of adjacent northern Mexico may encourage a couple of elevated supercells to form and cross into this region around the beginning of the Day 2 period. Even though boundary-layer instability will quickly decrease behind the front, enough low-level moisture and modestly steepened mid-level lapse rates should still support around 1000-1500 J/kg of MUCAPE. This instability coupled with strong shear aloft may foster isolated large hail with any supercell that can persist for a few hours. Storms should weaken by mid morning as the elevated instability diminishes. ..Gleason.. 04/16/2021
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SPC Apr 16, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0220 AM CDT Fri Apr 16 2021 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms appear unlikely across the contiguous United States on Sunday. ...Synopsis and Discussion... A belt of strong mid-level westerly flow should be maintained across much of the lower MS Valley and Southeast on Sunday. At the surface, high pressure should dominate much of the CONUS. A cold front should stall and become nearly stationary across the northern FL Peninsula by Sunday afternoon. With low/mid-level flow largely parallel to the front, convergence is forecast to remain very weak. Accordingly, convective development along this boundary appears quite uncertain on Sunday. Even if storms form across the northern FL Peninsula, they will probably remain elevated. At this point, the potential for organized severe storms along/south of the front across the FL Peninsula appears unlikely given poor low-level convergence and nebulous large-scale ascent. Elsewhere, isolated thunderstorms appear possible through the day across parts of the mid MS Valley in association with a shortwave trough, and over portions of the southern Rockies and vicinity as large-scale ascent with a separate upper trough/low overspreads this region. Very limited instability is expected to preclude a severe threat for both areas. ..Gleason.. 04/16/2021
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