SPC Feb 19, 2018 2000 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 19 Feb 14:51

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0148 PM CST Mon Feb 19 2018 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON THROUGH TONIGHT ACROSS PARTS OF THE SOUTHERN PLAINS... ...SUMMARY... A few strong to severe thunderstorms are possible over a portion of the Southern Plains, mainly late this afternoon into tonight. ...Discussion... The previously issued outlook forecast reasoning appears on track. Only a slight adjustment southward of the northern bound of the 2% tornado probabilities were made near I-40 in OK. ..Smith.. 02/19/2018 .PREV DISCUSSION... /ISSUED 1029 AM CST Mon Feb 19 2018/ ...Southern Plains to the MS Valley through tonight... An amplified large-scale pattern with a western trough and eastern ridge is now established and should persist for the next several days. An expansive warm sector is in place from the mid MS Valley and southern Plains to the Gulf Coast, with boundary-layer dewpoints ranging from near 60 F north to the upper 60s along the coast. This moist warm sector is supportive of clusters of slightly elevated convection in multiple clusters, primarily focused along the low-level jet corridor where warm advection is maximized from OK to MO. Conditionally unstable midlevel lapse rates (around 7 C/km) and the low-level warm/moist advection will continue to support elevated thunderstorms through the period, though clouds will tend to limit surface heating from eastern/northern OK northeastward along a slow-moving front. Some cloud breaks are more probable this afternoon from western OK into northwest TX, where surface heating will boost MLCAPE values into the 1000-1500 J/kg range with only weak convective inhibition. However, forcing for ascent will also be weak at best along the dryline south of the triple point near I-40 along the OK/TX border, and storm initiation is somewhat in question. If isolated storms do form this afternoon/evening, buoyancy and vertical shear will be sufficient for supercells capable of producing large hail and perhaps an isolated tornado. The odds for storm development should increase later this evening through tonight from southwest/central TX into central OK, as an embedded shortwave trough (now over Baja) ejects northeastward and interacts with the unstable warm sector. Embedded supercells and/or short bowing segments will be possible, with an associated threat for isolated large hail/damaging winds, as well as an isolated tornado. Will maintain the low severe probabilities in this update, but there will still be some potential for an upgrade in later outlook updates across parts of TX/OK. Read more



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