SPC AC 251702
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1102 AM CST Sat Dec 25 2021
Valid 261200Z - 271200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
A couple of thunderstorms are possible along the Pacific Northwest
Coastline, portions of the Inter-Mountain West, and eastern Missouri
into Indiana Sunday into Sunday night.
...Synopsis...
Broad cyclonic upper flow will prevail across the western two thirds
of the CONUS tomorrow/Sunday, with embedded mid-level impulses
pivoting around the cyclonic flow aloft. A surface low will develop
during the day across the Pacific Northwest as another surface low
occludes while ejecting into the Upper MS Valley Sunday night.
As a mid-level impulse impinges on the Pacific Northwest Coastline,
-15 to -20C 700 mb temperatures aloft will overspread a moist marine
low-level airmass, generating enough buoyancy in the -10 to -20C
layer to support charge separation in stronger updrafts. Adequate
deep-layer ascent should promote isolated thunderstorm potential
throughout the day. Another mid-level impulse will traverse the
Interior West, with cold temperatures aloft and deep-layer ascent
supporting a couple of thunderstorms during the afternoon. Later in
the evening, the mid-level impulse will de-amplify while propagating
northeast towards the Upper MS Valley in tandem with the surface
low. A capped, marginally unstable low-level airmass will advect
northward to the mid MS/OH Valley tomorrow night, with a couple of
elevated thunderstorms possible in a warm-air advection regime atop
the MLCINH layer.
..Squitieri.. 12/25/2021
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