SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Wed Sep 29 2021 Valid 292000Z - 301200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF CENTRAL AND NORTH TEXAS... ...SUMMARY... Isolated severe thunderstorms are possible this afternoon or early evening across parts of central and north Texas. Minimal changes to the general thunder area in central/south Texas behind earlier convection. The forecast remains unchanged elsewhere. ..Wendt/Smith.. 09/29/2021 .PREV DISCUSSION... /ISSUED 1110 AM CDT Wed Sep 29 2021/ ...Central/southern Plains through tonight... Within a southern stream, a weak lead shortwave trough will eject generally northward across the central/northern Plains today, as an upstream trough moves slowly eastward toward the Four Corners. In the wake of a northern stream midlevel trough, surface pressure rises over the northern Rockies/High Plains will drive a cold front southeastward into NE/northwestern KS by tonight. Heating/mixing and modest low-level moisture (dewpoints mainly in the mid-upper 50s) will support thunderstorm development along the cold front this afternoon in west central NE, with development southward along the front into western KS this evening. Some gusty outflow winds will be possible with steep low-level lapse rates, but weak vertical shear and the tendency for the front to slowly undercut convection suggest the severe threat is quite low. Storms will likely be maintained overnight as low-level moisture gradually increases and a weak southerly low-level jet focuses ascent along the front. A somewhat diffuse lee trough/dryline will persist from a lee cyclone in southeast CO south-southeastward across the TX Panhandle into west central TX. Forcing for ascent will be weak along the dryline in the wake of the ejecting midlevel trough, and low-level moisture return has been somewhat disrupted by widespread overnight convection across south central/southeast TX. However, destabilization along the west edge of the remnant cold pool, and weak lift along the dryline with a trailing vorticity lobe, could support the development of a few thunderstorms this afternoon across northwest TX. Though vertical shear and midlevel lapse rates will be rather modest, isolated strong outflow gusts and marginally severe hail may occur with steep low-level lapse rates and MLCAPE near 2000 J/kg. Read more LIVE: spc.noaa.gov
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