SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0247 PM CDT Sun Jul 09 2023 Valid 092000Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE MID ATLANTIC... ...SUMMARY... The primary risk for damaging wind gusts remains across the Mid-Atlantic region this afternoon. Isolated severe gusts or marginal hail remain possible over much of the Southeast. ...Central Gulf Coast States... Remnant outflow from an earlier MCS continues to push east across AR and into western TN/northern MS. This system has not shown any signs of strengthening, despite the moist/unstable air mass downstream. Numerous showers and storms have already formed across LA, MS, and southern AL, and the large number of storms may tend to overturn the air mass quickly. Isolated strong gusts or marginal hail will remain possible mid modest effective shear around 30 kt. ...Mid Atlantic... Strong to severe storms currently extend from the Philadelphia area southward into eastern NC ahead of a cold front. These will continue to pose a wind damage threat as they consume the unstable air mass, then move offshore. ..Jewell.. 07/09/2023 .PREV DISCUSSION... /ISSUED 1132 AM CDT Sun Jul 09 2023/ ...Mid Atlantic Region... Recent satellite imagery shows a shortwave trough moving through the central Appalachians. This shortwave is expected to continue east-northeastward throughout the day, interacting with the very moist air mass across the Mid-Atlantic region. Mesoanalysis estimates that MLCAPE is already around 1500 J/kg from eastern PA into NJ and the Delmarva Peninsula vicinity. Shear is relatively modest across northern portions of the region, with effective bulk shear around 30 to 35 kt. As a result, a predominantly multicellular storm mode is anticipated, with updraft duration likely limited by the lack of strong shear and storm interactions. Even so, some water-loaded downdrafts appear likely, particularly from now until the early afternoon. Farther south (across VA and into the Carolinas), a cluster of storms developed along a pre-frontal trough this morning across western NC. Vertical shear over this area (particularly NC) is a bit stronger and more westerly than areas farther north. This vertical shear will combine with ample low-level moisture and moderate buoyancy to support the persistence of this line as it moves eastward this morning through the afternoon. Robust updrafts are possible within this line, with the potential to produce damaging gusts. Severe Thunderstorm Watch #466 was recently issued to address this threat. ...Arklatex into Gulf Coast states... Updrafts along the leading edge of the ongoing convective complex have weakened for now. By early afternoon, thunderstorms are expected to re-intensify along a cold front sagging across AR/TN. This activity will spread southeastward across much of northern MS/AL and northwest GA through the evening hours with a risk of locally damaging wind gusts and hail. Additionally, multiple clusters of storms are may form this afternoon ahead of the remnant aforementioned MCS over parts of southern MS/AL into the FL panhandle. This will be in a region of hot/humid boundary-layer air and beneath 25-35 knot westerly mid-level winds. The strongest storms will pose a risk of locally damaging wind gusts. ...Upper Midwest... Isolated thunderstorms are still possible later this afternoon into this evening as a subtle shortwave trough moves through the southern periphery of the cyclone centered over northern Manitoba. A modestly buoyant airmass is anticipated across the region, which will support isolated to widely scattered thunderstorms ahead of the shortwave. Steep low-level lapse rates and high cloud bases may support a few damaging gusts with any of the more robust storms.
