Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0640 AM CST Thu Nov 20 2025 Valid 201300Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS INTO ARKANSAS... ...SUMMARY... Isolated strong to severe thunderstorms may occur today into this evening across the southern Plains into Arkansas. Large hail, damaging winds, and a tornado or two all appear possible. ...Southern Plains into Arkansas... A mid/upper-level trough extending from the Southwest into northern Mexico this morning will eject northeastward across parts of the southern Plains today. In response, a surface low will gradually deepen across the south-central High Plains and develop eastward through the period. A front extending across parts of OK/AR this morning will lift slowly northward as a warm front ahead of the surface low. Thunderstorms ongoing across parts of the southern Plains/ArkLaTex this morning are being aided by a modest low-level jet and ascent attendant to the approaching upper trough. Weak to locally moderate instability and effective shear of 40-50 kt may support a few strong to severe thunderstorms this morning from parts of eastern NM into west/central TX and OK, with a threat for mainly isolated hail and locally gusty winds. Convection and widespread cloud cover will likely persist through the day, resulting in generally modest diurnal heating and weakening mid-level lapse rates with time. While enhanced deep-layer shear will remain across the warm sector owing to persistent strong southwesterly mid-level flow, the potential for organized thunderstorms downstream or in the wake of ongoing morning convection remains uncertain. Still, depending on the extent of heating and related destabilization, most guidance continues to show some potential for isolated supercells and/or organized multicell clusters this afternoon/evening across portions of TX, with a threat of isolated severe hail and damaging winds. Modest enlargement of low-level hodographs with time could also support a tornado threat from parts of central/east TX into eastern OK/western AR along and south of the warm front, assuming surface-based supercells can be sustained. An isolated severe risk may persist into east TX and the ArkLaTex tonight. However, confidence in a corridor of greater severe risk remains too low to include higher severe probabilities at this time. Farther west, some high-resolution guidance continues to show the development of a modestly organized convective line across far eastern NM into west TX during the afternoon/evening, in closer proximity to the ejecting upper trough. This convection could pose a threat of strong gusts and perhaps some hail, but it remains uncertain as to whether sufficient instability will develop to support a severe threat. Have therefore maintained the Marginal Risk across this region with only minor changes. ..Gleason/Broyles.. 11/20/2025Read more