####018004275#### ACUS01 KWNS 301958 SWODY1 SPC AC 301956 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Tue Apr 30 2024 Valid 302000Z - 011200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN WESTERN/CENTRAL IA TO NORTHEAST KS... ...SUMMARY... The greatest threat for severe weather (large hail, severe gusts, and a few tornadoes) is from western and central Iowa to northeastern Kansas. ...20Z Update... Main concerns with this outlook are the extent/amplitude of tornado probabilities over the IA vicinity and MRGL versus SLGT risk across the southern Great Plains. Scattered thunderstorms have developed across the Mid-MO Valley after midday soundings from OAX/TOP sampled a mean mixing ratio near 10 g/kg, within the plume of around 60 F surface dew points. Primary uncertainty is the degree of tornado potential as these storms spread into parts of southwest to south-central IA vicinity. A couple long-track supercells might evolve given the favorable low to deep-layer wind profile. But the relatively modest boundary-layer moisture, with potential for appreciable cold pools as convection consolidates, lowers confidence in sustaining a greater tornado threat. The northern extent of severe potential will continue to be modulated by weaker instability amid downstream convection currently from central IA to eastern SD. Non-HRRR guidance is fairly insistent on isolated to scattered thunderstorms along the dryline, south of its triple-point intersection with the surface cold front pushing southeast from southwest to central KS. Across western portions of TX and OK, the environment will be supportive of isolated large hail and localized severe winds through about dusk. Have opted to bring the SLGT to the agitated CU field near CSM in western OK and leave MRGL in effect farther south. ..Grams.. 04/30/2024 .PREV DISCUSSION... /ISSUED 1129 AM CDT Tue Apr 30 2024/ ...Eastern NE/Western IA/Northwest MO/Northeast KS... Water vapor loops show a fast-moving shortwave trough and associated mid/upper level speed max moving across the central Rockies into the Plains. Ahead of this trough, southerly low-level winds are transporting moisture northward with dewpoints in the 60s now as far north as southeast NE. Continued daytime heating and moisture advection will lead to a narrow corridor of moderate CAPE over eastern NE by mid-afternoon. A consensus of morning model guidance indicated that thunderstorms will form in this regime, with other intense storms developing southward along the surface cold front into northeast KS by late afternoon. Forecast soundings show shear profiles favorable for supercell structures capable of very large hail and a few tornadoes. After dark, these storms are expected to congeal into one or more bowing structures that will track eastward into central IA/northern MO with a greater risk of damaging wind gusts along with hail and perhaps tornadoes. ...Eastern KS/Western OK/Northwest TX... The surface dryline will extend southward from northeast KS into northwest OK and northwest TX. Isolated intense storms are expected from roughly Wichita northward, with decreasing confidence from there southward. Weak large scale forcing, rising mid level heights, and generally warming temperatures at 700mb suggest any storms that form along the dryline will be widely scattered. However, large CAPE values, steep mid level lapse rates, and sufficient vertical shear will support supercell structures capable of all severe hazards in any storm that can form/sustain. Will maintain the ongoing SLGT/MRGL areas at this time, but will reevaluate at 20z. ...NY/PA... Strong daytime heating is occurring over areas from central NY into central PA, where dewpoints are in the upper 50s. Forecast soundings suggest afternoon MLCAPE values of 500-1000 J/kg, leading to scattered afternoon thunderstorms. Low-level winds are relatively weak/veered, but sufficient winds aloft and steep low-level lapse rates could contribute to a risk of gusty/damaging wind gusts and hail in the strongest cells this afternoon. $$