Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0218 PM CST Wed Mar 01 2017 Valid 012000Z - 021200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EXTENDING FROM PORTIONS OF EAST-CENTRAL MISSISSIPPI...NORTHERN ALABAMA...NORTHERN GEORGIA...AND FAR EASTERN TENNESSEE TO COASTAL AREAS OF THE MID-ATLANTIC STATES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK FROM THE CENTRAL GULF COAST STATES TO SOUTHERN NEW ENGLAND... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EXTENDING FROM THE CENTRAL GULF COAST STATES TO THE UPPER OHIO VALLEY AND SOUTHERN NEW ENGLAND... ...SUMMARY... Severe thunderstorms with damaging winds are expected from portions of the Southeast to the Mid Atlantic region and parts of southern New England. Damaging winds will be likely, and the risk for tornadoes will exist particularly from parts of east-central Mississippi to portions of north Georgia and vicinity. ...Southern New England to the Mid-Atlantic States... Severe weather threat remains valid for southern New England toward DelMarVA as the environment destabilizes poleward, with surface dew points in the 60s now spreading north across NJ. The western parts of Mid-Atlantic severe probabilities have been trimmed from the convective outlook, as the air mass has stabilized in the wake of the storms now reaching parts of the East Coast States. A marginal risk remains for isolated strong to possibly severe storms across the upper OH Valley into western PA as discussed in the previous outlook. Residual moisture located across southern VA in vicinity of the trailing portion of a convective outflow boundary extending southwest from southeast VA to far northwest NC may depict the northern extent of a severe-weather threat as strong to severe storms spread east from the southern Appalachians. The downstream air mass across the Carolinas will continue to destabilize with strong deep-layer and low-level shear supporting all severe hazards into this evening. ...Carolinas/Southeast States to lower MS Valley... Strong to severe storms will continue to develop along and ahead of the cold front as it advances through this region of the U.S. during the remainder of the afternoon and through the evening and early overnight. Previous forecast reasoning remains valid, while the western portions of this outlook have been trimmed with the passage of the ongoing band of storms extending from LA to middle and eastern TN as the environment stabilizes in the wake of this activity. ..Peters.. 03/01/2017 .PREV DISCUSSION... /ISSUED 1028 AM CST Wed Mar 01 2017/ ...Portions of the Southeast to the Mid-Atlantic region and southern New England... An extensive belt of strong mid/high-level flow across the Southern and Eastern States will maintain strong deep shear over a moist and diurnally destabilizing warm sector across the area. A squall line from Middle TN toward the central Appalachians will likely spread across the adjacent Piedmont during the next several hours. Re-intensification of this activity is expected, owing to the presence of adequate moisture return (upper 50s to lower 60s dewpoints) amidst surface heating and relatively steep midlevel lapse rates. Swaths of damaging wind gusts will be likely as this activity spreads toward the coastal plain through the evening. A couple of tornadoes will be possible. Severe-wind probabilities have been increased eastward across the Piedmont area. More separated updrafts/discrete convection are evolving across parts of the lower MS Valley, at the southern end of a zone of stronger deep ascent. As this activity spreads eastward toward parts of the southern Appalachians and vicinity, it will intercept a relatively more moist boundary layer supporting stronger instability further aided by steep midlevel lapse rates (around 8.5 C/km in the 700-500-mb layer per the 12Z Jackson sounding). With 250-350 m2/s2 of effective SRH associated with modestly curved though long hodographs, tornado probabilities have been increased in this area. With northward extent across the East (i.e., toward southern New England and vicinity), weaker instability will exist owing to more widespread cloud coverage amidst an antecedent cooler/drier boundary layer. However, strong vertical shear profiles will support a conditional severe risk. Modest destabilization may take place around the upper Ohio Valley and eastern Great Lakes area amidst recycled moisture ahead of the primary cold front, perhaps supporting a band of strongly forced convection spreading eastward from the late afternoon through the evening. Locally damaging wind gusts may accompany this activity.Read more
from SPC Forecast Products http://ift.tt/u32qoI
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