SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0744 AM CDT Sat Oct 24 2020

Valid 241300Z - 251200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast across the contiguous U.S.
today or tonight.

...Synopsis/Discussion...
The mid/upper level feature broadly cyclonic flow covering roughly
the northern half of the CONUS.  Amplification of the western part
of the pattern will occur through the period, related to a nearly
zonal trough now evident in moisture-channel imagery from southern
MB to southern BC.  That portion of this trough over the Canadian
Rockies will split off southeastward and strengthen as several
vorticity maxima phase, while the eastern part over SK/MB pivots
eastward and deforms ahead of a strong shortwave approaching from
Nunavut.  By 12Z tomorrow, the net result should be a deepening
synoptic trough from eastern MT to northern NV and northeastern CA,
which will dig southeastward and deepen further on day 2. 

In the southern stream, a lower-amplitude (but still well-defined)
shortwave trough and embedded MCV -- initially over portions of MS
and southeastern LA -- will shift eastward across the Deep South
through the period.  Large-scale forcing associated with this
feature, above a moist and minimally capped, diurnally destabilized
boundary layer, may foster a relative max in general thunderstorm
potential over parts of the central/eastern Gulf Coastal Plain
today.  

Deep-convective potential will be loosely bounded from northeast to
southwest along and shortly behind a cold front -- analyzed at 11Z
from southeastern QC across southern PA, eastern TN, western AL, and
the northwestern Gulf.  By 12Z, this front should move to a position
across the Carolinas and northern GA, through a frontal wave in AL,
to the central Gulf.  The Gulf part of the front will weaken
substantially as frontogenesis occurs from northeastern NM across
northwest/east-central TX, with late-period cyclogenesis over the TX
Panhandle.

..Edwards/Mosier.. 10/24/2020

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