SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0137 PM CST Sat Jan 30 2021 Valid 302000Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST OK INTO SOUTHEAST KS...SOUTHWEST MO AND NORTHWEST AR THROUGH EARLY EVENING... ...SUMMARY... Isolated severe thunderstorms remain possible through early evening from northeast Oklahoma into southwest Missouri, as well as parts of southeast Kansas and northwest Arkansas. ...20z Update - OK/KS/MO/AR... The Marginal risk and 10% General Thunderstorm areas have been trimmed on the western and southern edges. This adjustments have been made based on the current position of the surface low and associated cold front and warm front. Additionally, very dry midlevel air, noted in water vapor imagery, and as sample by 12z regional RAOBs is precluding development of deep convection southward along the cold front/dryline. The best chance for strong to isolated severe storms will remain near the triple point where low level convergence is maximized. Strong ascent will also remain focused north/northeast of the surface low, associated with the eastward-ejecting shortwave trough. As such, a narrow corridor will exist close to the track of the surface low the next few hours from far northeast OK/southeast KS into far southwest MO/northwest AR. The severe threat should quickly diminish after sunset. For more details, reference MCD 44. ..Leitman.. 01/30/2021 .PREV DISCUSSION... /ISSUED 1022 AM CST Sat Jan 30 2021/ ...OK/KS/MO/AR this afternoon... Only minor adjustments have been made to previous forecast with main limiting factor being expected very weak buoyancy. A well-defined midlevel shortwave trough moving through western OK as of late this morning will continue east-northeastward over OK/KS today and MO/AR this evening. The associated surface cyclone will likewise develop eastward along the KS/OK border, reaching southwest MO this evening. Low-level moisture return within the cyclone warm sector remains limited 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. Ongoing elevated thunderstorms will likely persist from eastern OK, southeast KS, and western AR into early afternoon and southwest MO through mid 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 midday into the afternoon. Destabilization in this narrow corridor might become 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 may support 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 hail, as well as an isolated tornado, remain possible this afternoon with peak buoyancy, before diminishing rapidly this evening with eastward extent and the onset of nocturnal cooling. Given lingering concerns regarding destabilization potential, will maintain MRGL category for this outlook and continue to monitor for a possible SLGT risk in the upcoming 20Z update.
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