SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1105 PM CST Wed Dec 02 2020

Valid 031200Z - 041200Z


The risk for severe thunderstorms appears negligible across the U.S.
today through tonight.

Much of North America will remain under the influence of amplified,
branching flow, downstream of a strong zonal jet across the western
and central mid-latitude Pacific.  Within this regime, positively
tilted large-scale ridging appears likely to remain prominent across
western portions of the U.S. and Canada.  Downstream, models
indicate that large-scale positively tilted troughing will continue
to evolve across eastern Canada into the Upper Midwest, Great Lakes
and Northeast.  

In lower-latitudes, increasingly deformed mid/upper troughing will
be a prominent influence across parts of the Southwest and northern
Mexican Plateau east-northeastward into the middle/lower Mississippi
Valley.  While an embedded mid-level low evolves south of the
international border, across parts of Sonora and Chihuahua, another
elongating embedded cyclonic circulation is forecast to continue
slowly shifting eastward across the south central Great Plains into
the Ozark Plateau.

Generally dry and/or cold and stable conditions prevail across much
of the U.S.  Aside from some continued low-level moistening off a
still recovering northwestern Gulf of Mexico boundary layer, little
change is expected through this period.

The moisture return will be focused along low-level troughing
associated with the southern Great Plains perturbation, across the
Louisiana coast into the Mid South.  However, it appears likely to
remain mostly elevated above at least a shallow residual
near-surface stable layer, and, at least initially, beneath
subsident and relatively warm mid/upper levels to the southeast of a
weakening cyclonic mid-level jet strSevere thunderstorms are not
forecast across the contiguous United States on Thursday.eak.

...Lower Mississippi Valley...
Inland of coastal areas, model forecast soundings indicate
thermodynamic profiles probably best characterized as only
marginally conducive to convection capable of producing lightning
today through tonight. Probabilities for thunderstorms appear
generally low, but perhaps highest in a corridor from northeastern
Louisiana into western and middle Tennessee late this afternoon into
tonight.  Occasional, scattered thunderstorm activity may become
focused just to the cool side of the slowly eastward advancing cold
front, perhaps aided by the onset of at least some cooling aloft.

Otherwise, a cluster of thunderstorms now evolving across the
northwestern Gulf of Mexico may persist into today, tending to
develop eastward and southeastward, well south of the Louisiana
coast.  It appears that this activity may have a negative impact on
convective potential near north central/northeastern Gulf coastal
areas through much of the period.  However, destabilization near a
possible developing frontal wave might support increasing
thunderstorm development near/east of Plaquemines Parish Louisiana
into the vicinity of the western Florida Panhandle coastal waters by
daybreak Friday.

..Kerr.. 12/03/2020

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