Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Apr 25 2023 16:26:23 ACUS01 KWNS 251626 SWODY1 SPC AC 251624 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1124 AM CDT Tue Apr 25 2023 Valid 251630Z - 261200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF TEXAS AND SOUTHWESTERN OKLAHOMA... ....SUMMARY... Severe thunderstorms are possible mainly late this afternoon into tonight over parts of the southern Plains, with a risk for large to very large hail, damaging winds, and perhaps a couple of tornadoes. ....Southern Plains... An upper trough/low centered over the Great Basin and central Rockies this morning will advance south-southeastward towards the Four Corners by this evening, and will eventually reach the southern High Plains late tonight. A subtle, southern-stream perturbation over northern Mexico will move eastward across west/central TX through the day. At the surface, weak cyclogenesis should occur across eastern NM this afternoon/evening. Low-level moisture, characterized by generally low 50s to low 60s surface dewpoints, will continue streaming northward today along/south of a warm front and east of a dryline. Convective potential and evolution across the warm sector this afternoon through tonight remains unclear owing to weak/nebulous large-scale ascent. Still, the best signal for thunderstorm initiation appears to be across the higher terrain of southeastern CO and northeastern NM this afternoon with weak low-level upslope flow occurring and ascent from the approaching upper trough. This activity should spread generally southeastward across the OK/TX Panhandles and eventually northwest TX. Although low-level moisture will remain rather limited, the presence of steep mid-level lapse rates and 30-40 kt of deep-layer shear should prove sufficient for thunderstorm organization, including the potential for multiple supercells posing a threat for mainly large hail. Confidence in greater coverage of intense convection has increased enough to expand the Slight Risk farther northwest into parts of the TX Panhandle. These thunderstorms should continue east-southeastward towards northwest TX and southwestern OK this evening/tonight. The activity in OK will probably tend to become elevated to the north of the warm front, but it may still pose some threat for hail. Gusty winds will be possible with any clusters that can persist with eastward extent tonight from northwest into central TX. The prospect for convective initiation along the dryline this afternoon from northwest to central TX still appears rather conditional, as a pronounced cap noted on 12Z soundings from MAF and DRT will be slow to erode and potentially difficult to breach. Widespread low-level cloud cover noted on morning visible satellite imagery east of the dryline will need to mix out to some extent to generate sufficient diurnal heating to support parcels being lifted near/to their LFCs. A somewhat better chance for surface-based convective development may be across northwest into western north TX, where some cloud breaks and filtered daytime heating have already been observed. If thunderstorms can form and be sustained across this region, they will likely be supercells and pose a threat for large to very large hail initially given the presence of moderate instability, steep mid-level lapse rates, and sufficient effective bulk shear. As a southerly low-level jet modestly strengthens this evening, there may also be a narrow, 2-4 hour window (from roughly 22-02Z) for a couple of tornadoes with any supercell that can remain surface based. The possibility of open warm sector development this afternoon also remains apparent over portions of coastal/southeast TX. If this activity forms, it would likely be tied to weak low-level warm advection and daytime heating on the southern fringe of persistent cloud cover. Any thunderstorms that can persist in this regime may pose a threat for large hail and damaging winds. Based on signals in 12Z guidance on where this convection may develop, have expanded the Slight Risk a little southeastward towards the middle TX Coast. ....Florida... Generally zonal flow aloft will persist over the FL Peninsula today. With robust diurnal heating expected, scattered thunderstorms should once again develop along both the Atlantic and Gulf Coast sea breezes this afternoon, and to the south of a remnant front draped across the north/central FL Peninsula. While low-level winds will remain weak, strengthening west-southwesterly flow at mid/upper levels should support around 30-35 kt of deep-layer shear. This should be sufficient for some updraft organization, including the potential for a mix of multicells and perhaps marginal supercell structures. With seasonably cool mid-level temperatures present, some of these thunderstorms could pose an isolated threat for severe hail and damaging wind gusts this afternoon and early evening. ...Gleason/Wendt.. 04/25/2023 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. 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