SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0136 PM CST Thu Feb 11 2021

Valid 112000Z - 121200Z


Appreciable risk for severe weather is unlikely across the U.S.

...Southeast Louisiana into Georgia...
A batch of thunderstorms extends from southeast LA into southwest AL
as of 20Z, with periodic bowing structures noted earlier across
southern MS. These storms are currently near the MLCAPE axis with
500-750 J/kg, and may be already peaking in intensity. Large-scale
ascent is forecast to decrease later today, with storms also
encountering weaker instability. Until then, a few strong wind gusts
cannot be ruled out.

..Jewell.. 02/11/2021

.PREV DISCUSSION... /ISSUED 1030 AM CST Thu Feb 11 2021/

Broad/low-amplitude cyclonic flow aloft within the polar stream will
persist through the period, south of a strong/cold upper low
residing over the Canadian Prairie.  Meanwhile in the southern
stream, weak perturbations will move eastward across Texas and the
southeastern states, ahead of a larger short-wave trough moving
into/across Mexico.

At the surface, cold air continues to spread southward out of
Canada, affecting a large portion of the country east of the
Rockies.  A baroclinic zone separating the polar air from the
lingering/higher theta-e southern U.S. airmass is currently
stretched from the Carolinas southwestward to the western Gulf of
Mexico.  This front will sag slowly southeastward with time, as cold
air advances.

Moderate mid-level flow is observed atop the higher theta-e airmass
across portions of the Southeast.  However, abundant cloud cover
will continue to retard any appreciable heating, keeping the
boundary layer slightly stable in most areas and limiting available
CAPE to generally only a few hundred J/kg at best.  

The modest instability, combined with relatively weak flow in the
lower troposphere, suggests that despite locally gusty winds, storms
should remain sub-severe.  As such, the MRGL risk over portions of
northern Georgia and into South Carolina is being removed at this
time.  Farther to the southwest, into eastern Louisiana and
southeastern Mississippi, a small area of greater low-level moisture
is indicated southeast of the surface cold front -- supporting
mixed-layer CAPE in the 500 to 1000 J/kg range.  However, with
modest shear, and storms expected to shift through this small zone
of slightly more favorable thermodynamics over the next couple of
hours, risk for any more than a briefly stronger updraft appears
unlikely, and thus will not introduce MRGL risk across this area.

Elsewhere, severe storms are not expected across the CONUS.

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