SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0645 AM CST Sat Jan 30 2021 Valid 301300Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FROM NORTHEAST OK AND SOUTHEAST KS INTO SOUTHWEST MO AND NORTHWEST AR... ...SUMMARY... Isolated severe thunderstorms will be possible this afternoon and early evening from northeast Oklahoma into southwest Missouri, including parts of southeast Kansas and northwest Arkansas. ...OK/KS/MO/AR this afternoon... A well-defined midlevel trough over the TX Panhandle this morning will continue east-northeastward over OK/KS today and MO/AR this evening, before slowing over the lower OH Valley tonight as the larger-scale pattern begins to amplify upstream (pronounced height rises over Intermountain West). An associated surface cyclone will likewise develop eastward along the KS/OK border today, reaching southwest MO this evening and southern IL late tonight. Low-level moisture return within the warm sector of the cyclone has been muted by ongoing air mass modification over the Gulf of Mexico in the wake of a prior frontal intrusion. However, midlevel moistening and lapse rates have been sufficient to support clusters of elevated thunderstorms (rooted near 700 mb) this morning in the zone of ascent preceding the midlevel trough. The swath of elevated thunderstorms will likely persist into the day across OK/KS and overspread MO/AR this afternoon. In the wake of the elevated convection, a zone of surface heating along a dryline will overlap a narrow corridor of boundary-layer dewpoints of 50-55 F from southeast KS across northeast OK, from roughly midday into the afternoon. Destabilization in this narrow corridor could be sufficient for surface-based convection to develop near and immediately south of the surface cyclone. Steep low-midlevel lapse rates and 500 mb temperatures of -20 C and colder should allow MLCAPE of 250-500 J/kg, with a brief window of opportunity for low-topped supercells within the left-exit region of the midlevel jet. Isolated damaging gusts and large hail, as well as an isolated tornado, will be possible this afternoon with peak buoyancy, before diminishing rapidly this evening with eastward extent and the onset of nocturnal cooling. ..Thompson/Broyles.. 01/30/2021
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