MIL-OSI USA: SPC Jun 12, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook

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Source: US National Oceanic and Atmospheric Administration

SPC AC 120706

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0206 AM CDT Sat Jun 12 2021

Valid 141200Z – 151200Z

…NO SEVERE THUNDERSTORM AREAS FORECAST…

…SUMMARY…
Severe thunderstorm chances appear low across the USA on Monday, but
isolated strong storms may occur over parts of the High Plains,
Pacific Northwest, and Mid Atlantic.

…Synopsis and Discussion…
An upper high will remain centered over the Four Corners area with
upper ridge extending north into Canada. A shortwave trough will
become better amplified as it moves from the upper Great Lakes
toward the OH Valley, and as a deep upper low travels south across
Quebec. To the west of the upper ridge, an upper trough will amplify
further over the Pacific, reaching the WA/OR/CA Coasts by 12Z
Tuesday.

At the surface, a relatively cool air mass will drive south from the
upper MS Valley and Great Lakes across the OH and TN Valleys with a
cold front roughly from VA into northern GA at 00Z. South of this
front, ample moisture to support daytime storms scattered from the
Mid Atlantic to the Gulf coast. A better combination of strong
westerly winds aloft and instability may overlap across WV/VA/NC,
but models vary greatly regarding QPF. Therefore, will defer any
probabilities to later outlooks when predictability is greater.

To the west a ribbon of instability will remain across the central
and northern High Plains, with 50s to lower 60s F dewpoints, but
beneath the upper ridge. While a few severe storms cannot be ruled
out, predictability is too low to show a focused threat area.

Farther west, stronger shear will exist over the Pacific Northwest
and into western MT, but there may not be much instability where the
stronger large-scale lift is. While general thunderstorms will be
possible, will defer possible severe probabilities to later
outlooks.

..Jewell.. 06/12/2021

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