Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Jul 08 2020 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER MIDWEST AND ACROSS THE CENTRAL PLAINS... ...SUMMARY... Severe thunderstorms are possible across portions of the Upper Midwest and Central Plains on Thursday. ...Synopsis... A shortwave trough is forecast to be centered over southern Manitoba early Thursday. This shortwave is expected to continue eastward into western Ontario while another shortwave trough moves quickly through the Pacific Northwest and northern Rockies. Upper ridging centered over the Southwest is expected to build northward and eastward throughout the day. A belt of stronger flow aloft will exist throughout the northern periphery of this upper ridge, from northern CA eastward through the northern and central Plains. Much of the central and eastern CONUS will be characterized by warm, moist, and unstable conditions. However, these conditions will be displaced south and east of the stronger synoptic systems. Consequently, the severe-weather risk will be largely tied to the strength and evolution of antecedent thunderstorms and/or their outflow boundaries. Even with the forecast uncertainties inherent with this type of pattern, enough consensus exists within the guidance (including the available convective-allowing guidance) to include 15% wind/hail probabilities over portions of the central Plains as well as over the Upper MS Valley. ...Upper MS Valley... Convectively induced vorticity maximum will likely emanate from overnight storms across SD. Scattered to widespread thunderstorm development is anticipated ahead of this vorticity maximum as it moves eastward into the warm, moist, and unstable conditions over the region Thursday afternoon. Vertical shear across the region is generally expected to be weak. However, some localized enhancement is possible near the vorticity maximum, aiding the potential for a few stronger storms capable of damaging wind gusts and/or isolated hail. Cell interactions/mergers could also create updrafts strong enough to damaging wind gusts and/or isolated hail. ...Central/Southern Plains... Severe-weather threat across the central/southern Plains is expected to come as a result of two separate linear convective systems. The first system is forecast to be ongoing early Thursday morning, likely over southeast KS or eastern OK. Some severe threat will exist will this system, but it is generally expected to be past the mature phase. New storm development is possible along the outflow from this system during the afternoon, a few of which could be severe. Forecasting where the outflow will be located is difficult, evidenced by the broad 5% probabilities from the Ozark Plateau into central OK. Increased probabilities will likely be needed whenever the location of this outflow becomes more clear. Second linear convective system is forecast to develop out of the late day thunderstorms that initiate over the central High Plains. The overall pattern is favorable for these initially discrete storms to grow upscale and proceed downstream across southern NE and western/central KS. Hail is the primary threat with the initial discrete storms with damaging wind gusts more likely once the storms grow upscale. ...Carolinas into the Mid-Atlantic... A surface low is forecast to be just off the Carolina coast early Thursday morning. This low is then expected to move northeastward throughout the day. The speed of this movement is uncertain, with guidance currently showing a wide spread in where the low will be located by 00Z Friday. A more westerly track would potentially bring the enhanced southeasterly flow surrounding the system onshore, resulting in a low-probability severe risk. Given the uncertainty of the overall forecast evolution, no probabilities will be included with this outlook. However, probabilities may be needed in later outlooks if a more westerly track of the low appears probable. ..Mosier.. 07/08/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_0600.html
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