Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1226 AM CDT Thu Jul 16 2020 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OHIO INTO WESTERN NEW YORK STATE AND ACROSS WESTERN NEBRASKA... ...SUMMARY... Strong to severe storms will be possible Thursday from the Ozarks into the Ohio Valley and western Pennsylvania/New York. Additional isolated strong to severe storms may occur across parts of the central Plains and parts of Minnesota. ...Synopsis... A broad mid-level anticyclone will remain nearly stationary from Texas into the Carolinas today, On the periphery of this anticyclone, weak shortwave troughs will migrate from west to east across the central Plains and from east to west along the central Gulf Coast. Farther north, a progressive upper air pattern will dominate, with a shortwave trough traversing the eastern Great Lakes in the morning and a longer-wave trough extending from western portions of Hudson Bay to Minnesota through the day. At the surface, a weak trough will accompany the mid-level shortwave trough across the eastern Great Lakes and portions of Ohio/Pennsylvania through the day. This trough will extend southwestward through the Ozarks and into southern Kansas, where it will remain nearly stationary during peak heating hours. Another weak trough will migrate eastward across northern and central Minnesota during the day and act as an effective dryline/cold front. Another trough will remain nearly stationary in the lee of the Rockies. ...Ohio/Pennsylvania into western New York... Showers and a few thunderstorms may be ongoing initially along the surface trough over southern Michigan/western Ohio as lift/ascent associated with both the trough and aforementioned mid-level shortwave traverse the region. Through the day, convection will gradually intensify in response to surface heating, with 80s F surface temperatures and 70s F dewpoints resulting in around 1000-1500 J/kg MUCAPE. Shear profiles actually support supercellular storms - and 300-400 m2/s2 SRH values in the 0-3km layer support low-level mesocyclogenesis especially within persistent, discrete cells. A couple of tornadoes are possible in addition to damaging wind gusts and isolated hail - though limiting factors include weakening ascent aloft with the departing shortwave trough and poor mid-level lapse rates. Any severe threat should spread into western New York state in the early evening before weakening after dark. ...Eastern Colorado into much of Nebraska... As surface heating commences, destabilization and steep tropospheric lapse rates will result in convection developing initially along higher terrain of central Colorado and migrating eastward through the Colorado Plains and Nebraska. Storms may also focus along a weak surface boundary across northwestern/north-central Nebraska during the afternoon. Models peak in convective coverage in the 00-03Z timeframe across western Nebraska, where steep mid-level lapse rates and modest westerly mid-level flow will promote a few clusters/linear segments capable of damaging winds and large hail. One or two forward-propagating linear segments may persist overnight from western Kansas into central Nebraska. ...Minnesota... The eastward-moving surface trough and lift associated with the approaching mid-level wave will result in a few thunderstorms developing from northern into central Minnesota during the afternoon through early evening. Thermodynamic profiles are most impressive closer to the International Border area and along the surface trough, where mid-level cooling will promote 1500-2000 J/kg MLCAPE in the afternoon. Shear profiles in the region support organization and perhaps updraft rotation in a few cells, with west-southwesterly flow veering to northwesterly and strengthening with height. This should promote a risk of hail and damaging wind gusts, although an isolated tornado cannot be completely ruled out. Concerns regarding convective coverage preclude any introduction of Slight Risk and associated probabilities at this time, though portions of northern Minnesota may need an upgrade in later outlooks. ...South-central Kansas into northern Arkansas... Surface heating along the nearly stationary surface boundary across the area will foster at least isolated surface-based convection during the afternoon amidst an environment characterized by strong buoyancy (high dewpoints beneath steep mid-level lapse rates). Shear profiles are only marginally supportive of convective organization, though CAMs indicate some potential for small linear segments to develop and forward-propagate during the afternoon. The presence of a weak shortwave over central Kansas may also encourage afternoon convective development. Large hail and damaging wind gusts are possible with any convection that can materialize. ...Western Tennessee into Kentucky... Mid-level lapse rates are less in magnitude compared to areas farther west. However, surface convergence along a synoptic boundary draped across the region and any remnant surface boundaries from prior-day convection will likely result in isolated to scattered thunderstorm development within a weakly sheared environment. 2000-3000 J/kg MLCAPE and minimal inhibition suggests that loosely organized convection is possible, with isolated downbursts and hail being the primary threats. ..Cook.. 07/16/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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