959 ACUS01 KWNS 191232 SWODY1 SPC AC 191230 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0730 AM CDT Fri Sep 19 2025 Valid 191300Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS... ...SUMMARY... Isolated severe thunderstorms may impact parts of southwestern Nebraska into western and central Kansas late this afternoon and evening, accompanied by some risk for severe hail and wind. ...Synopsis... A weak upper trough/low will move eastward today from the northern Plains to the Upper Midwest. An embedded mid-level shortwave trough and speed maximum over eastern WY/western SD this morning will rotate southeastward across parts of the central Plains this afternoon and evening. Weak upper ridging will be maintained over portions of the Southwest/Four Corners into the northern Great Basin, with multiple low-amplitude perturbations forecast to spread east-northeastward across these regions. At the surface, a weak low over the eastern Dakotas should gradually fill through the day, while a front stalls along/near the KS/NE border to the east of modest lee cyclogenesis over the central High Plains. ...Central Plains... It appears that increasing large-scale ascent associated with the embedded shortwave trough and modestly enhanced west-northwesterly jet may be sufficient to encourage isolated thunderstorms to develop by late afternoon/early evening across parts of southwest NE into western KS. This region should have a modestly moist low-level airmass in place, with enough daytime heating forecast to support around 1000-1500 J/kg of MLCAPE. Even though mid-level lapse rates are not expected to become overly steep, strong deep-layer shear should aid in convective updraft organization. There is still considerable uncertainty with overall thunderstorm coverage this afternoon/evening across the central Plains. Any thunderstorms that can form and be sustained could produce isolated severe hail and/or gusts as they spread southeastward across western/central KS through the evening. ...Upper Midwest... Modest west-southwesterly mid-level winds will be present today over parts of the Upper Midwest on the eastern side of the upper-level trough/low. Lapse rates aloft are forecast to remain rather poor, which should limit the development of any more than weak instability this afternoon. While scattered to numerous thunderstorms are expected to develop later today, the overall thermodynamic/kinematic environment appears too marginal to include low severe probabilities. ...Southwest... Showers and thunderstorms are ongoing this morning across parts of central/eastern AZ into western NM and far west TX. This activity is related to weak ascent aloft associated with minor perturbations rotating through/around a weak upper ridge over the Southwest. Some guidance shows potential for additional robust thunderstorm development by late afternoon/early evening, likely aided by orographic lift and other weak mid-level disturbances. Substantial uncertainty exists regarding the intensity of these thunderstorms later today owing to ongoing clouds/precipitation, lack of a notable EML, and limited forecast instability/low-level lapse rates. Have therefore not included any severe wind probabilities at this time. ..Gleason/Grams.. 09/19/2025 $$