SPC AC 151224 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0624 AM CST Sun Dec 15 2024 Valid 151300Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated hail near severe limits is possible tonight from portions of north Texas to the Ozarks. ...Synopsis... In mid/upper levels, a low-amplitude longwave pattern will remain in place over the CONUS, with progressive shortwave to synoptic troughs traversing the prevailing westerlies. The leading trough -- currently anchored by a closed low near the northern IL/IN border -- should devolve to an open wave and move to the northern Mid-Atlantic region by 12Z tomorrow. Meanwhile, a series of shortwaves and vorticity lobes -- occupying broadly cyclonic flow over much of the western CONUS -- will consolidate/phase somewhat through the period while shifting eastward. By 00Z, a loosely organized synoptic trough will extend from the Dakotas across the central High Plains to AZ. Overnight, a closed 500-mb low should develop over southern MB, with the trough extending across central NE/KS to southern NM and northwestern MX by 12Z. At the surface, 11Z analysis showed a decaying cold to stationary front from eastern IL across southern AR, north-central and west- central TX. This boundary will move slowly northward through the day and continue to weaken. Meanwhile, cold frontogenesis is forecast today ahead of the mid/upper trough, and over parts of the central/northern Plains. This Plains front should reach western parts of MN/IA, northeastern to south-central KS, and the TX Panhandle by 00Z. By 12Z, the cold front should reach central/ southern IL, the Ozarks, eastern/southern OK, and the TX South Plains region. ...North TX to the Lower OH Valley... Episodic, isolated to scattered thunderstorms are expected throughout the period, embedded in a plume of low-level warm/moist advection and moisture transport extending from central/east TX to the lower Ohio Valley. Through the day, this activity will occur in weak midlevel lapse rates and modest deep shear, with most or all of it elevated over a relatively stable, near-surface layer, and accordingly minimal severe potential. Meanwhile, surface dewpoints in the 60s F will spread northward into and across much of the outlook area, as the older boundary becomes diffuse ahead of the Plains cold front. Concurrent with height falls aloft and increasing deep shear, the warm conveyor and accompanying isentropic ascent to LFC should intensify this evening amid mass response to the consolidation/ approach of the mid/upper trough, and related 45-55-kt LLJ. Greatest thunderstorm coverage in the plume is expected after about 03Z from near the Red River Valley to the Ozarks, spreading into the lower Ohio Valley from around 09Z onward. During phases when convection is still relatively discrete, and around the southern part of denser/later convective coverage, the most vigorous cells may produce severe hail. Forecast soundings show a nearly saturated, near-neutral stability profile in the boundary layer over north TX to eastern OK, and perhaps into some of northwestern AR, depending on outflow timing/intensity. This renders profiles that may be effectively surface-based, with MLCAPE in the 1000-1500 J/kg rage and slightly greater MUCAPE, but still often containing weak, near-surface static stability. At this time, severe-gust/tornado potential appears too conditional and low to draw even marginal categorical probabilities for those hazards, and the previous outlook area still appears to capture the consensus of most probable, favorably positioned convection in the plume as well. ..Edwards/Goss.. 12/15/2024 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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2024-12-15 12:28:27