SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1130 PM CDT Fri Oct 30 2020

Valid 311200Z - 011200Z


Aside from parts of the southern Florida Peninsula, the risk for
thunderstorms appears negligible across much of the U.S. today
through tonight.

Amplification within the westerlies is underway across the
mid-latitude Pacific into western North America, and this appears
likely to translate eastward, across the Rockies toward the Atlantic
Seaboard, later today through tonight.  This includes a building
large-scale ridge near the Pacific coast, which may build further
while also expanding eastward across the Rockies by late tonight.

To the east of the ridging, an intensifying short wave trough is
forecast to sharply dig southeastward out of Alberta and
Saskatchewan, through the northern U.S. Great Plains and much of the
Mississippi Valley by 12Z Sunday.  This will be accompanied by
another cold front.  However, in the wake of recent cold intrusions
to the lee of the Rockies, including cold surface ridging still
present across much of the eastern U.S. through much of the
northwestern Gulf of Mexico, models indicate that pre-frontal
moistening will be quite modest to weak.  With colder mid-level air
also lagging to the northwest of the surface front, this will result
in negligible destabilization and risk for thunderstorms.

A narrow plume of deep-layered moisture/seasonably high precipitable
water is forecast to linger along a weakening remnant frontal zone
across the southern Florida Peninsula.  This regime likely will
include upper 60s to lower 70s surface dew points, which probably
will contribute to boundary-layer CAPE in excess of 1000 J/kg with
daytime heating.  Perhaps aided by weak large-scale forcing for
ascent, to the south of a remnant mid-level cyclonic shear axis,
this is expected to support a few thunderstorms today.  Generally
weak lapse rates and weak deep-layer mean flow/shear, among other
factors, suggest the potential for severe weather is negligible.

..Kerr/Dean.. 10/31/2020

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