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Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1300Z Outlook
 Forecast Discussion

000 ACUS01 KWNS 201255 SWODY1 SPC AC 201253 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0753 AM CDT Sun May 20 2018 Valid 201300Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER MISSOURI VALLEY AND OHIO VALLEY AS WELL AS PARTS OF TEXAS... ...SUMMARY... Strong to severe storms are possible across portions of the lower Missouri and Ohio Valley today. Additional strong storms are possible across portions of central and southwest Texas. ...Lower Missouri Valley to Lower Ohio Valley... Multiple eastward-moving clusters of strong thunderstorms are ongoing early this morning across Missouri into southern Illinois. Storm-scale cold pools aside, this activity appears to be aided by a weak impulse/MCV across Oklahoma into southeast Kansas and low-level jet-enhanced isentropic ascent. These storms are generally moving into an air mass that has been overturned or at least muddled and influenced by convection yesterday afternoon and evening. Thus, any early-day severe risk should remain very localized, with convective outflows and cloud debris otherwise complicating forecast details later today amidst a late spring-like flow pattern. Although subtle/weak surface wave development may occur into Missouri through the day along the remnant synoptic frontal zone, prevalent outflow (across much of southwest Missouri early this morning) should effectively limit the northward extent of the severe risk while likely muting the magnitude of the region's overall severe potential. While forecast-detail confidence is not particularly high, and various model forecasts are likely overly aggressive with air mass recovery/destabilization, the best potential for strong to severe thunderstorm development this afternoon into evening should be across southern/south-central Missouri into southern Illinois as outflow presumably modifies and some northward-return of moist/unstable air across Arkansas occurs. As a belt of modestly enhanced mid-level winds (30-40 kt at 500 mb) overspreads the region today, some potential for damaging winds and sporadic severe hail may exist especially later this afternoon into evening pending sufficient destabilization. ...Texas... An outflow-augmented cold front continues to surge southward across southwest Texas and at a somewhat slower southeastward pace across central Texas. While deep-layer shear will be very weak across central/east-central Texas, convective outflows could focus some stronger pulse-type updrafts later today, but any severe potential is current expected to remain very marginal/localized across south-central/east-central Texas. Farther west, moist upslope low-level flow will increase across far west Texas into southeast New Mexico today. The influence of upslope trajectories and heating over the high terrain will aid storm development this afternoon particularly over the Transpecos. Increasing moisture, moderate buoyancy, and upwards of 35-40 kt effective shear should support a few isolated supercells capable of large hail. ..Guyer/Goss.. 05/20/2018 $$