Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 12 2020 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE CENTRAL PLAINS INTO THE EASTERN DAKOTAS AND WESTERN MN... ...SUMMARY... Severe storms are possible across portions of the central Plains into the eastern Dakotas, western Minnesota and Iowa on Monday afternoon into Monday night. Additional isolated strong storms are possible from the eastern Carolinas into Southern New England Monday afternoon. ...Synopsis... A strong upper trough will develop eastward from the northern Rockies to the northern Plains on Monday. This will result in substantial height falls from the central Rockies and central Plains northward across the northern Plains and into the Upper Midwest. This will result in a band of strong west/southwest flow spreading across the region. At the surface, low pressure over the central Dakotas during the morning will develop east/northeast toward southeast Manitoba and Ontario with a trailing cold front advancing east/southeast across the northern/central Plains during the afternoon into early Tuesday morning. Thunderstorms are expected to develop along the front during the afternoon across the eastern Dakotas. Additional storms are expected further southwest during the evening as convection moves off the higher terrain of CO/northeast NM. Further east, an upper trough will be oriented from the lower Great Lakes to the southeastern U.S. A shortwave trough embedded within the northern portion of the trough near Lake Huron will pivot eastward across the Northeast. A surface low and trailing front will shift east across the mid-Atlantic and southern New England through the afternoon, and scattered strong storms are possible. ...Eastern Dakotas into western MN/IA... Most guidance shows strong moisture return will occur ahead of the surface front on strong southerly low level flow. Surface dewpoints as high as the mid/upper 60s are forecast with strong heating occurring ahead of the boundary across the eastern Dakotas into western MN. This will result in a corridor of moderate to strong MLCAPE amid strong effective shear and steep midlevel lapse rates. With increasing upper forcing and lower level frontal forcing, capping should erode and initially discrete cells are possible. Backed low level winds ahead of the surface boundary, and 0-3 km shear near 35 kt will result in enlarged, curved hodographs, suggesting a few tornadoes will be possible should convection remain discrete. However, LCLs will be on the high side and mean mixing ratio values near 14 g/kg suggest this may temper the tornado threat somewhat. Large to very large hail also will be possible with any more discrete convection. A low level jet is expected to increase during the evening, and upscale development into a bowing line segment/QLCS is possible as convection spread eastward across MN and parts of IA into the nighttime hours. ...Central/Southern High Plains into the Central Plains... Further south, a surface trough will extend southward through the High Plains of CO/NM with a weak lee cyclone developing near the intersection of this surface trough and the cold front associated with the northern Plains surface low. Southeasterly low level winds along the boundary will transport low to mid 60s dewpoints as far east as parts of western KS into central NE, with values quickly falling into the mid 40s to mid 50s across eastern CO southward into northwest NM and the OK/TX Panhandle. Falling heights with the approaching of the trough and strong heating amid steep midlevel lapse rates will support thunderstorm development over the mountains during the afternoon. As this convection spreads eastward, adequate effective shear should maintain organized cells through a corridor of weak to moderate MLCAPE. A deeply-mixed boundary layer will aid in strong downdrafts and isolated severe gusts are possible. Convection could become better organized along the surface boundary across NE later in the evening as the low level jet increases and storms encounter a more unstable air mass, with some guidance suggesting a second MCS south of the northern plains MCS could move eastward across parts of the central Plains overnight. ...Eastern Carolinas to the Mid-Atlantic and southern New England... A belt of moderate midlevel southwesterly flow will overspread portions of Atlantic coast from the eastern Carolinas into New England as one shortwave impulse ejects eastward offshore during the afternoon, and another pivots eastward from the Great Lakes during the evening. A surface low will track northeast across New England with a front extending southward through the Mid-Atlantic, and a surface trough extending southward through the Piedmont vicinity. A seasonally warm/moist air mass will be in place, with weak to moderate instability occurring by late morning. Scattered strong storms are possible with locally damaging winds through the afternoon. ..Leitman.. 07/12/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_0600.html
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