SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0640 AM CST Mon Mar 01 2021

Valid 011300Z - 021200Z


Thunderstorms will be possible today from portions of Texas across
the Southeast.

...Synopsis/Discussion, TX-Southeast...
In mid/upper levels, a split-flow pattern will prevail over the
central CONUS.  Confluence of northern and southern streams will
occur over the Southeast, downstream from a compact cyclone now
located over southern NM.  This cyclone will move slowly east-
northeastward to OK and north TX by the end of the period. 
Meanwhile, a northern-stream synoptic trough -- evident in
moisture-channel imagery from Hudson Bay across northern ON and
parts of the upper Great Lakes -- will shift east-southeastward
through the period.  By 00Z, a closed 500-mb low should form over
southwestern QC, with trough southwestward over the central/southern
Appalachians.  The mid/upper cyclone should cross ME overnight.

The associated surface cold front was analyzed at 11Z across central
VA, western NC, extreme western SC, to near an ATL-MEI line, then
across north-central LA and between LRD-COT.  This front will
proceed eastward off the Atlantic Coast down to northern FL by 00Z,
across northeastern Gulf shelf waters to near the Mississippi River
mouth, through a weak low over the Gulf southeast of PSX, to
northeastern MX.  By 12Z the front should be moving slowly southward
over central FL, then extending westward as a quasistationary to
northward-drifting warm front across the northern Gulf to the low,
by then located southeast of GLS and south of the western LA
coastline.  Isolated to widely scattered thunderstorms are possible
in the elevated warm-advection regime north of the front this
morning, across portions of TX/LA, with thunder potential isolated
elsewhere in the outlook through this evening.

A shallow band of non-lightning-producing convection -- now evident
near the front over portions of northern GA and western SC, broken
into west-central NC -- may fill through the remainder of the
morning across portions of SC/NC, along or ahead of the front,
before moving offshore by early afternoon.  Some of this activity
may offer strong downdraft gusts as it moves into diurnally
increasing boundary-layer lapse rates.  60-70-kt winds are expected
at the top of the buoyant layer, with some potential for momentum
transfer to the surface.  Weak midlevel lapse rates include a
pronounced layer of relatively warm/stable air variably positioned
between 600-800 mb sampled at (among others) 12Z RAOBs from FFC, CHS
and MHX, persisting in forecast soundings.  This will keep buoyancy
shallow over most areas (with 150-400 J/kg MUCAPE below the midlevel
cap), and thunder potential quite limited.  At this time, lightning
probability is nonzero but appears too isolated, brief and
conditional for addition/expansion of the general thunder outlook
now located to the south.

..Edwards/Jewell.. 03/01/2021

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