SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1109 AM CST Mon Nov 16 2020

Valid 171200Z - 181200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms are possible to the west of the Washington and
Oregon Cascades Tuesday afternoon and evening.  Otherwise, the risk
for thunderstorms appears negligible across much of the U.S.

...Synopsis...
Much of the U.S. will remain under the influence of an amplified
branch of westerlies emanating from the mid-latitude Pacific through
this period.  While lead large-scale mid/upper troughing continues
to gradually shift east of the Atlantic Seaboard, large-scale
ridging appears likely to prevail and expand eastward across the
remainder of the interior U.S., ahead of large-scale troughing
across the eastern Pacific into the Pacific Coast states.

One short wave perturbation emanating from the western troughing may
progress toward the crest of the downstream ridging and contribute
to significant cyclogenesis to the lee of the Canadian Rockies late
Tuesday through Tuesday night.  Deepening surface troughing appears
likely as far south as the Texas and Oklahoma Panhandle region. 
However, the southwestern flank of cold surface ridging shifting
across and east of the lower Great Plains and Mississippi Valley
will remain prominent across the northwestern Gulf of Mexico and
Gulf Coast region.  The will preclude substantive Gulf
boundary-layer recovery and southerly inland return flow in the wake
of the recent cold intrusion.

...South Florida...
The boundary layer may remain seasonably moist across southeastern
portions of the peninsula and Florida Keys through much of the day
Tuesday, possibly contributing to weak to moderate CAPE with daytime
heating.  However, a remnant mid-level cyclonic shear axis
progressing across the region may be in the process of weakening. 
Coupled with inhibition associated with relatively warm mid-level
temperatures, probabilities for thunderstorms appear generally low
and mostly confined to areas offshore of southeastern coastal areas/
southeast of the Keys.

...Pacific Northwest...
The extent to which thermodynamic profiles will become conducive to
charge separation remain unclear, with the mid-level cold core of
the larger-scale troughing remaining mostly offshore through this
period.  However, models do indicate a swath of mid-level cooling
(including 500 mb temps of -24 to -26 C) across coastal areas into
the southern Washington/northern Oregon Cascades late Tuesday
afternoon and evening, coincident with a belt of modest
southwesterly onshore/upslope low-level flow.  This seems to offer
the best potential for scattered thunderstorm activity, and could
become focused around the Greater Portland OR area.

..Kerr.. 11/16/2020

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