SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0640 AM CST Mon Mar 01 2021 Valid 011300Z - 021200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible today from portions of Texas across the Southeast. ...Synopsis/Discussion, TX-Southeast... In mid/upper levels, a split-flow pattern will prevail over the central CONUS. Confluence of northern and southern streams will occur over the Southeast, downstream from a compact cyclone now located over southern NM. This cyclone will move slowly east- northeastward to OK and north TX by the end of the period. Meanwhile, a northern-stream synoptic trough -- evident in moisture-channel imagery from Hudson Bay across northern ON and parts of the upper Great Lakes -- will shift east-southeastward through the period. By 00Z, a closed 500-mb low should form over southwestern QC, with trough southwestward over the central/southern Appalachians. The mid/upper cyclone should cross ME overnight. The associated surface cold front was analyzed at 11Z across central VA, western NC, extreme western SC, to near an ATL-MEI line, then across north-central LA and between LRD-COT. This front will proceed eastward off the Atlantic Coast down to northern FL by 00Z, across northeastern Gulf shelf waters to near the Mississippi River mouth, through a weak low over the Gulf southeast of PSX, to northeastern MX. By 12Z the front should be moving slowly southward over central FL, then extending westward as a quasistationary to northward-drifting warm front across the northern Gulf to the low, by then located southeast of GLS and south of the western LA coastline. Isolated to widely scattered thunderstorms are possible in the elevated warm-advection regime north of the front this morning, across portions of TX/LA, with thunder potential isolated elsewhere in the outlook through this evening. ...Carolinas/GA... A shallow band of non-lightning-producing convection -- now evident near the front over portions of northern GA and western SC, broken into west-central NC -- may fill through the remainder of the morning across portions of SC/NC, along or ahead of the front, before moving offshore by early afternoon. Some of this activity may offer strong downdraft gusts as it moves into diurnally increasing boundary-layer lapse rates. 60-70-kt winds are expected at the top of the buoyant layer, with some potential for momentum transfer to the surface. Weak midlevel lapse rates include a pronounced layer of relatively warm/stable air variably positioned between 600-800 mb sampled at (among others) 12Z RAOBs from FFC, CHS and MHX, persisting in forecast soundings. This will keep buoyancy shallow over most areas (with 150-400 J/kg MUCAPE below the midlevel cap), and thunder potential quite limited. At this time, lightning probability is nonzero but appears too isolated, brief and conditional for addition/expansion of the general thunder outlook now located to the south. ..Edwards/Jewell.. 03/01/2021
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