Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0307 PM CDT Mon Mar 27 2017 Valid 272000Z - 281200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF WESTERN AND CENTRAL KENTUCKY...WESTERN AND MIDDLE TENNESSEE...NORTHEAST MISSISSIPPI...AND NORTHERN ALABAMA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK AREA FROM THE OHIO VALLEY TO THE LOWER MISSISSIPPI VALLEY TO ALABAMA... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK AREA FROM THE OHIO VALLEY TO LOWER MISSISSIPPI VALLEY... ...SUMMARY... Scattered to numerous severe thunderstorms are expected across the Lower Mississippi and Ohio Valleys into the Tennessee Valley this afternoon and evening. Very large hail, damaging winds, and a couple tornadoes will be possible. ...KY/TN/MS/AL... Given the eastern progression of the midlevel shortwave trough and the western portions of the severe-weather probabilities have been trimmed eastward, while the Enhanced Risk for severe/damaging winds has been expanded eastward some across central KY, middle TN, and northern AL. ...Far southern IL, southeast MO and eastern AR... Given the eastward progression of the midlevel shortwave trough, the severe probabilities have been trimmed across parts of far southern IL and southeast MO, and shifted east across much of central and eastern AR and part of northwest MS, where the severe threat has diminished. The exception is across northeast AR, where moderate instability and sufficient bulk shear are maintaining a severe threat with storms developing along the cold front. ...Northeast LA to northeast AL and northwest GA... The severe probabilities have been expanded into more of northeast LA/southwest MS and northeast AL into northern GA for an increase severe weather threat than was forecast in the earlier outlook. ...Eastern KY into southwest WV... A leading midlevel shortwave trough appears to be moving across eastern KY and eastern AL into western GA. Forcing for ascent with this trough and destabilization into eastern KY to WV suggests the severe weather threat needed an eastward expansion. ..Peters.. 03/27/2017 .PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Mar 27 2017/ ...Lower Ohio/Mississippi River Valleys and Tennessee Valley... A low-amplitude shortwave trough over the southern MO late this morning will continue generally eastward and reach the middle OH River Valley by late tonight. A preceding belt of 40-50 kt west-southwesterly mid level winds will continue to overspread an increasingly moist, albeit modestly so, warm sector. Ahead of an eastward-moving cold front currently across the Ozarks and Ark-La-Tex, lower/some middle 60s F surface dewpoints will continue to become increasingly common across eastern AR, northern MS into western TN, northward into western KY. While warm-sector cloud cover has remained semi-prevalent thus far, some cloud breaks are noted in visible satellite imagery an additional thinning seems likely in concert especially with the eastward-spread mid/high-level dry slot as per water vapor satellite imagery. Linearly organized convection across far northeast AR/far southeast MO late this morning should continue to spread east-northeastward and increase in coverage/intensify into northwest TN and western/central KY as the downstream air mass continues to moisten and destabilize. This activity will pose a damaging wind and severe hail risk, although a tornado cannot be ruled out. Farther south, other initially more discrete storms should develop within the warm sector this afternoon across additional portions of TN, far eastern AR, northern MS and eventually northwest AL later this afternoon/evening. Here, supercell-favorable wind profiles and steep mid-level lapse rates as noted per 12Z observed soundings will support large hail potential. A few tornadoes also appear possible, particularly around mid/late afternoon into early evening across western/middle portions of TN and northern MS and northwest AL. In this corridor, a modest westerly component of the mid-level winds will coincide with modestly strong low-level shear/SRH.Read more
from SPC Forecast Products http://ift.tt/u32qoI
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