SWODY2
SPC AC 181730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED APR 18 2012
VALID 191200Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM S-CNTRL IA TO SWRN OK...
...SYNOPSIS...
A PROGRESSIVE/ZONAL UPPER-LEVEL PATTERN OVER THE NRN TIER WILL
AMPLIFY ON THU AS A BROAD TROUGH FORMS ACROSS THE GREAT PLAINS WITH
A SERIES OF EMBEDDED IMPULSES/SPEED MAXIMA. AS MID-LEVEL HEIGHTS
LOWER ACROSS THE CNTRL/SRN PLAINS...WEAK CYCLOGENESIS WILL OCCUR
ALONG A S/SEWD MOVING COLD FRONT. AT 20/00Z...A SURFACE LOW SHOULD
BE CENTERED INVOF THE IA/MO BORDER WITH THE COLD FRONT EXTENDING
SWWD AND INTERSECTING ANOTHER LOW AND DRYLINE INVOF NWRN TX.
...MID-MO VALLEY TO THE SRN PLAINS...
ALTHOUGH LOW-LEVEL TRAJECTORIES WILL NOT BE PARTICULARLY FAVORABLE
FOR A BROAD INFLUX OF RICH WRN GULF MOISTURE IN THE WAKE OF A
DEPARTING SHORT WAVE TROUGH IN THE SOUTHEAST...A CORRIDOR OF MIDDLE
50S TO LOWER 60S SURFACE DEW POINTS WILL LIKELY SPREAD NWD AHEAD OF
THE ADVANCING COLD FRONT. WITH STEEP MID-LEVEL LAPSE
RATES...MODERATE INSTABILITY WILL DEVELOP WITH MLCAPE GENERALLY
RANGING FROM 1000-2000 J/KG AT PEAK HEATING.
MODEL GUIDANCE IS HIGHLY CONSISTENT THAT AFTERNOON THUNDERSTORMS
APPEAR MOST LIKELY TO INITIATE INVOF THE MO/IA SURFACE CYCLONE AND
THEN DEVELOP SWWD INTO EARLY EVENING AS INHIBITION WEAKENS. STRONG
MID-LEVEL W/SWLYS WILL PROMOTE UPDRAFT ROTATION AND IN CONJUNCTION
WITH THE STEEP MID-LEVEL LAPSE RATES...RESULT IN A RISK FOR LARGE
HAIL. WITH STRONG FORCING WITHIN THE FRONTAL ZONE...AND LOW-LEVEL
FLOW WEAKENING/VEERING IN MUCH OF THE WARM SECTOR...THE POTENTIAL
FOR NUMEROUS STORM-SCALE INTERACTIONS MAY LIMIT THE LONGEVITY OF
SUPERCELL STRUCTURES AND INTENSITY OF HAIL GROWTH. A BRIEF TORNADO
OR TWO COULD DEVELOP AROUND SUNSET JUST NE OF THE COLD FRONT/DRYLINE
INTERSECTION IN SWRN OK WHERE LOW-LEVEL FLOW SHOULD REMAIN BACKED
PRIOR TO A NOCTURNAL INCREASE IN MLCIN. WITH THE NOCTURNAL LLJ
FORECAST TO STRENGTHEN ACROSS NWRN/N-CNTRL TX...AN MCS COULD BECOME
SUSTAINED IN OK TO THE OZARK PLATEAU THU NIGHT. BUT GIVEN THE
RELATIVELY NARROW CORRIDOR OF MODERATE INSTABILITY...SEVERE
POTENTIAL SHOULD WANE WITH TIME AND ERN EXTENT OVERNIGHT.
..GRAMS.. 04/18/2012
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