Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1155 PM CDT Thu Jul 02 2020 Valid 031200Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF EASTERN MONTANA AND THE WESTERN DAKOTAS... ...SUMMARY... Severe thunderstorms capable of mainly large hail and severe gusts are possible late this afternoon and into tonight over eastern Montana and parts of the western Dakotas. ...Synopsis... A large-scale mid-level trough will maintain a positive tilt over the Pacific Northwest/British Columbia during the period while a belt of moderate southwesterly 500-mb flow is located over the Northern Rockies and northern High Plains. A mid-level ridge will remain over the central U.S. while a weak disturbance moves southeast across the lower Great Lakes during the day. ...Northern Rockies into the western Dakotas... Neutral mid-level heights are forecast across this region during the day with strong heating and orographic ascent contributing to weakening convective inhibition by mid afternoon. An appreciably moist boundary layer, maintained by low-level easterlies, will probably become moderately unstable by mid-late afternoon from southeast MT to the western Dakotas. Isolated thunderstorms are forecast as far south as the Black Hills/northeast WY where a few severe thunderstorms are possible during the late afternoon/evening. Farther west, storm development over the higher terrain in southwest MT/ID will gradually spread northeast during the late afternoon/evening. An accompanying risk for isolated severe gusts/large hail is possible. Additional storm development over eastern MT into the western Dakotas is possible during the latter part of the evening into the overnight with the severe activity concentrating with this regime. ...CO High Plains southeastward into OK... A residual outflow boundary from Thursday overnight activity will likely become positioned across parts of OK/southern KS during the day. Although no appreciable feature focusing large-scale ascent is forecast, strong heating and a very moist boundary layer across central/eastern OK will contribute to very strong destabilization by early-mid afternoon. Isolated storms are possible with isolated severe gusts the primary risk with the stronger downdrafts. Farther north and west, isolated to scattered thunderstorms are forecast by mid afternoon near I-25 with increasing storm coverage expected by early evening over parts of east-central CO and a separate area near Raton Mesa. Strongly veering flow with height may yield 25 kt effective shear, sufficient for organized multicells. Isolated large hail and severe gusts are possible over the High Plains. This activity will likely diminish during the evening. ...NY/PA/NJ... A series of weak mid-level disturbances are forecast to rotate through the base of a larger-scale trough situated farther east over the western Atlantic. Model guidance shows an impulse moving southeast from southern Ontario into the NY/PA vicinity during peak heating. A reservoir of 60s F dewpoints and heating will favor moderate destabilization by early-mid afternoon. It appears greater convective coverage may occur near the Delaware River Valley during the afternoon. Isolated downbursts yielding gusts 50-60 mph gusts may result in wind damage with the stronger multicells. Storms will likely weaken below severe thresholds by early evening as temperatures gradually cool. ..Smith/Moore.. 07/03/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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