SPC Feb 28, 2018 2000 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 28 Feb 2018

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0148 PM CST Wed Feb 28 2018 Valid 282000Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NORTH TX EAST ACROSS SOUTHERN AR... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF CENTRAL TX EAST INTO THE LOWER MS VALLEY... ...SUMMARY... Thunderstorms capable of large hail and damaging winds may affect a corridor from central and north-central Texas to parts of the Mid-South this afternoon and tonight. ...20Z Update... The Marginal Risk across central MO has been removed, as lingering cloud cover and generally cool/stable conditions in advance of a cold front will not be favorable for strong/severe storm development. Thunderstorms will continue to develop across portions of central/north TX this afternoon and evening as height falls/large-scale forcing for ascent impinges on the dryline/pre-frontal trough over west TX. Latest visible imagery shows deepening cumulus/isolated convective cells developing between Throckmorton and Sweetwater in the vicinity of this feature and, with MLCAPE of 1000-1250 J/kg and strong effective shear in place, organized storms including supercell structures will be possible. As storms increase in coverage and spread east, a continued severe risk will exist towards the Arklatex tonight. The large hail risk will be greatest with initial/more discrete development. The overall tornado risk will be tempered by weak low-level shear. ..Bunting.. 02/28/2018 .PREV DISCUSSION... /ISSUED 1007 AM CST Wed Feb 28 2018/ ...TX to LA/MS this afternoon/evening... The ongoing forecast remains on track, with only minor changes made in this update. Strong low-level warm advection and lift will continue to promote scattered showers and thunderstorms this afternoon from northeast TX into parts of southeast OK/southern AR/northern LA. Extensive cloud cover is limiting daytime heating and destabilization, and will likely preclude a more organized severe risk. Nevertheless, forecast soundings show sufficient CAPE and strong deep-layer shear, favorable for a few rotating cells capable of locally damaging winds or hail. Storms may track as far east as northern MS after dark with a continued risk of gusty winds. ...Central/northeast TX this evening... By late afternoon, a surface dryline is expected to become established over west-central TX. This area will see at least broken sunshine, helping to destabilize the area and weaken the cap. Most 12z model solutions suggest isolated discrete storms forming along the dryline by early evening. Forecast soundings suggest moderate CAPE and favorable effective shear, promoting supercell structures capable of large hail. These storms should track east-northeastward across north-central and northeast TX during the evening with a continued severe threat. Low-level shear is expected to be relatively weak, limiting the tornado threat. ...MO... 12z model guidance is backing off the potential for thunderstorm activity over MO later today. This may be due to widespread clouds, limiting heating and destabilization. Will maintain the ongoing Marginal risk area for now, but confidence is decreasing. This area may require a downgrade at 20z. Read more



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