Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Fri Mar 31 2017 Valid 311300Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY FROM EASTERN NORTH CAROLINA INTO SOUTHEASTERN VIRGINIA... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE NORTH CAROLINA AND VIRGINIA SLIGHT RISK AREA... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM WESTERN OKLAHOMA AND THE TEXAS PANHANDLE INTO SOUTHERN KANSAS... ...SUMMARY... A few severe thunderstorms with damaging winds, isolated large hail, and perhaps a tornado, are expected today across North Carolina and Virginia. Isolated, marginally severe hail will be possible tonight across parts of Kansas/western Oklahoma and the Texas/Oklahoma Panhandles. ...North Carolina/Virginia area through this afternoon... A midlevel trough over the OH Valley this morning will progress eastward to the Mid Atlantic coast tonight, as an associated surface cyclone and cold front likewise cross NC/VA during the afternoon. An initial band of convection across eastern NC this morning will pose a marginal risk for damaging winds or a tornado in conjunction with a moistening boundary layer (mid 60s dewpoints) and an increase in low-level shear. In the wake of this morning convection, some surface heating is expected in advance of the surface cold front. Destabilization in a corridor ahead of the front will contribute to thunderstorm development along and east of the boundary by early afternoon, and the storms will cross eastern NC and VA during the afternoon/evening. Sufficient buoyancy (MLCAPE 500-1000 J/kg) and deep-layer vertical shear (effective bulk wind differences in excess of 40 kt) will support a risk of supercells/organized line segments capable of producing damaging gusts and marginally severe hail. An isolated tornado or two cannot be ruled out with the more discrete storms given a moist boundary layer and effective SRH near 200 m2/s2. ...Texas Panhandle to southwest Kansas tonight... Initial low-level moisture return will occur today across TX in response to cyclogenesis across the southern High Plains (downstream from a closed low passing south of the Four Corners). 12z soundings along the TX coast suggest the moist layer will be shallow and susceptible to vertical mixing today. A gradual increase in moisture by tonight should be sufficient for thunderstorm development to the north of a slow-moving front in a low-level warm-advection regime from the TX Panhandle into western OK and southwestern KS. The NAM appears to be too aggressive with the moisture return and resultant buoyancy tonight, while the RAP/GFS forecasts of 1000-1500 J/kg MUCAPE look more reasonable. The combination of modest buoyancy rooted in the 850-700 mb layer, midlevel lapse rates at or above 8 C/km and effective bulk shear in excess of 40 kt could support some storm organization and a risk for isolated marginally severe hail. ..Thompson.. 03/31/2017Read more
from SPC Forecast Products http://ift.tt/rATNzD
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