Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Wed Jul 15 2020 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHEAST OH INTO WESTERN PA/NY... ...SUMMARY... Strong to severe storms are possible on Thursday from the Ozarks into the Ohio Valley and western New York. Additional strong storms are possible over the central High Plains. ...Ozarks/Ohio Valley into western PA/NY... A broad upper trough will be centered over the Upper Midwest Thursday morning. A shortwave impulse embedded in the broader-scale trough will eject northeast from the lower Ohio Valley to western PA/NY through 00z, while the main upper trough pivots eastward across the upper Great Lakes during the day, to the lower Great Lakes by Friday morning. This will result in a band of enhanced southwesterly flow from the lower Ohio Valley to western PA/NY. At the surface, low pressure near southern Lake MI early Thursday will develop east/northeast toward Lake Erie by Thursday night. A trailing cold front will push east/southeast across much of the Midwest, stretching from west-central NY southwestward to the MO Bootheel and then westward near the OK/KS border by Friday morning. A seasonally moist airmass will reside ahead of the front, with mid-to-upper 60s F dewpoints in place. Moderate to strong instability is expected by mid-afternoon and scattered thunderstorms are expected to develop ahead of the surface low and cold front. Guidance varies in the strength of vertical shear and this will have some impact on how well organized convection becomes. However, given expected instability and forcing aloft as well as at the surface in relation to the cold front, at least isolated clusters of strong to severe storms appear possible. High PW values and steepening low level lapse rates will favor a threat mainly for locally damaging wind gusts. However, backed southeasterly low level winds ahead of the surface front should augment low level shear, and mean mixing ratio values near 15-17 g/kg, could support a tornado or two. A low level jet is forecast to increase during the evening, and this could lead to some upscale development into eastward propagating line segments, but instability will wane with eastward extent as inhibition increases with the loss of daytime heating. Guidance varies on timing and how widespread additional thunderstorm develop will occur over the Ozarks, where the cold front will not be a well-defined as further northeast. However, a very unstable and moist air mass will reside over this region as well. Additionally, an MCV may shift eastward into the region from convection expected across parts of the central/southern Plains in the Day 1 period. This should result in at least isolated storms by evening, mainly posing a locally damaging wind gusts threat. ...Central High Plains... Moist upslope flow will transport low 60s dewpoints westward across the region. Strong heating and steep midlevel lapse rates will aid in moderate to strong destabilization, and a weak shortwave impulse ejecting across the central/southern Rockies will support isolated to scattered thunderstorm development. High-based supercells are possible, posing a threat for locally strong gusts. While deep layer flow will be rather weak, west/northwesterlies atop southeasterly low level winds will result in effective shear near 35 kt amid very steep lapse rates, and isolated large hail also will be possible. ..Leitman.. 07/15/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_0600.html
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