SWODY1
SPC AC 170557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1157 PM CST MON JAN 16 2012
VALID 171200Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF MS/AL...
...SYNOPSIS...
A PROGRESSIVE/BROADLY CYCLONIC LONGWAVE UPPER FLOW PATTERN WILL
PREVAIL OVER THE CONUS THROUGH TONIGHT. WITHIN THIS REGIME...A
STRONG UPPER JET/LOW-AMPLITUDE TROUGH WILL TRANSITION
EAST-NORTHEASTWARD FROM THE CENTRAL ROCKIES TO THE NORTH-CENTRAL
PLAINS AND EVENTUALLY UPPER MIDWEST/GREAT LAKES REGION TONIGHT. AS
THIS OCCURS...APPRECIABLE SURFACE CYCLOGENESIS WILL STEADILY OCCUR
FROM THE MIDWEST NORTHEASTWARD TO THE LOWER GREAT LAKES/SOUTHERN
ONTARIO...WHILE A COLD FRONT ADVANCES EAST-SOUTHEASTWARD ACROSS THE
OH VALLEY/LOWER MS VALLEY TODAY AND REACHES THE APPALACHIANS LATE
TONIGHT.
...LOWER MS VALLEY/TN VALLEY TO SOUTHEAST STATES...
WITH THE LARGE SCALE SCENARIO AS PREVIOUSLY DESCRIBED...AMPLE CLOUDS
AND SHOWERS WITH SOME EMBEDDED TSTMS SHOULD ACCOMPANY MUCH OF THE
FRONTAL ZONE AS IT MOVES SOUTHEASTWARD ACROSS THE REGION TODAY. A
VERY STRONG /BUT WANING AND VEERING WITH TIME/ SOUTHWESTERLY LOW
LEVEL JET WILL HELP ESTABLISH A PRE-COLD FRONTAL CORRIDOR OF LOWER
60S F SURFACE DEWPOINTS ACROSS THE LOWER MS VALLEY EARLY IN THE
PERIOD. UPPER 50S F SURFACE DEWPOINTS SHOULD EXTEND INTO THE TN
VALLEY.
WHILE THE PREVALENCE OF LOW CLOUD COVER WILL HINDER MORE APPRECIABLE
DESTABILIZATION...CLOUD BREAKS/POCKETS OF SOMEWHAT STRONGER
LOW-LEVEL HEATING COULD OCCUR AHEAD OF THE COLD FRONT THIS AFTERNOON
ACROSS PORTIONS OF LA/MS INTO AL. WHILE BUOYANCY WILL NONETHELESS BE
MODEST...MLCAPE TO 500-1000 J/KG MAY PROVE SUFFICIENT FOR SUSTAINED
UPDRAFTS WITH A CORRESPONDING STRONG/SEVERE TSTM THREAT BY THIS
AFTERNOON ALONG/IMMEDIATELY AHEAD OF THE ADVANCING FRONT.
WHILE THE BRUNT OF LARGE SCALE FORCING FOR ASCENT/MASS CONVERGENCE
WILL TEND TO FOCUS/SHIFT AWAY FROM THE REGION WITH TIME...A SEVERE
CONCERN SEEMS LIKELY TO EXIST /AT LEAST AN ISOLATED BASIS/ GIVEN
WEAK INHIBITION AND VERY STRONG LOW-MID TROPOSPHERIC SOUTHWESTERLY
FLOW. LONG HODOGRAPHS/NEARLY UNIDIRECTIONAL SHEAR WILL FAVOR
SPLITTING/GENERALLY FAST EAST-NORTHEASTWARD MOVING STORMS PENDING
SUFFICIENT DESTABILIZATION. GIVEN THIS...SOME SEMI-DISCRETE
SUPERCELLS AND MORE PREVALENT MULTICELLS /WITH SMALL BOWING
SEGMENTS/ MAY YIELD DAMAGING WINDS AND SOME SEVERE HAIL...PRIMARILY
FROM EARLY AFTERNOON THROUGH SUNSET. A TORNADO MAY BE POSSIBLE AS
WELL GIVEN AMPLE SPEED SHEAR/LOW LEVEL SRH.
...TN VALLEY TO OH VALLEY...
WITH NORTHWARD EXTENT ACROSS THE REGION...THE PRE-COLD FRONTAL
AIRMASS WILL HAVE LIMITED MOISTURE CONTENT WITH
HEATING/DESTABILIZATION OTHERWISE LIMITED BY THE PREVALENCE OF CLOUD
COVER/SHOWERS TODAY. THIS LOW-TOPPED CONVECTION WILL TEND TO BE
ROOTED JUST ABOVE A SHALLOW/MARGINALLY MOIST BOUNDARY LAYER.
STILL...A STRONG CONVECTIVE WIND GUST OR TWO COULD OCCUR AS FAR
NORTH AS THE OH VALLEY TODAY GIVEN THE MAGNITUDE OF SOUTHWESTERLY
FLOW WITHIN THE LOWER HALF OF THE TROPOSPHERE.
..GUYER/DEAN.. 01/17/2012
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