SWODY1
SPC AC 191245
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0745 AM CDT THU APR 19 2012
VALID 191300Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLNS NE INTO THE
LWR MO VLY...
...SYNOPSIS...
TREND TOWARD INCREASED AMPLIFICATION WILL BEGIN IN EARNEST THIS
PERIOD AS HEIGHT RISES ALONG THE W CST INDUCE DEEPENING/DECELERATION
OF DOWNSTREAM TROUGH NOW OVER THE RCKYS/HI PLNS. LEAD IMPULSE
WITHIN THE TROUGH...NOW OVER NW KS...SHOULD WEAKEN AS IT CONTINUES
ENE TO THE UPR MS VLY THIS EVE. MEANWHILE...A SERIES OF ILL-DEFINED
DISTURBANCES NOW OVER THE INTERMOUNTAIN REGION SHOULD MOVE SEWD.
ONE OF THESE FEATURES WILL REACH THE TX PANHANDLE THIS EVE...AND
CNTRL OK/NW TX EARLY FRI.
AT LWR LVLS...SFC LOW NOW OVER SW KS SHOULD MOVE NE ALONG STALLING
CNTRL PLNS COLD FRONT INTO NRN MO THIS EVE...AND TO NEAR CHICAGO
EARLY FRI...WITH LITTLE CHANGE IN INTENSITY. FARTHER S...APPROACH
OF UPSTREAM UPR IMPULSE AND DAYTIME HEATING LIKELY WILL MAINTAIN A
SEPARATE...NEARLY STNRY SFC LOW OVER NW TX/SW OK TODAY. THIS
LOW...AND DRY LINE/LEE TROUGH EXTENDING SSW FROM THE LOW...LIKELY
WILL BE OVERTAKEN ACCELERATING SFC COLD FRONT TNGT AND EARLY FRI.
...NW TX/MUCH OF OK INTO LWR MO VLY THIS AFTN THROUGH TNGT...
CURRENT SFC OBSERVATIONS AND GPS/SATELLITE-DERIVED PW DATA SUGGEST
THAT MOISTURE WILL REMAIN RELATIVELY LIMITED OVER THE SLIGHT RISK
AREA THROUGH MUCH OF THIS PERIOD...WITH SFC DEWPOINTS GENERALLY
REMAINING AOB 60F. THE MOST SUBSTANTIAL MOISTURE INCREASE SHOULD
OCCUR OVER SRN PORTIONS OF THE OUTLOOK...WHERE PERSISTENT LOW LVL
SSWLY FLOW AND EVAPOTRANSPIRATION MAY BOOST PW TO AROUND 1.25
INCHES.
WHILE MEAGER MOISTURE WILL LIMIT BUOYANCY...SWLY MID LVL FLOW ON ERN
SIDE OF AMPLIFYING UPR TROUGH WILL TRANSPORT EML/STEEP MID LVL LAPSE
RATE PLUME NEWD ATOP MOIST AXIS AHEAD OF COLD FRONT AND DRY LINE.
COUPLED WITH DAYTIME HEATING...EXPECT SBCAPE TO RANGE FROM AROUND
500 J/KG IN SRN IA/NRN MO TO AROUND 2000 J/KG IN SW OK/NW TX BY LATE
IN THE DAY. EML CAP LIKELY WILL DELAY STORM INITIATION. BUT
COMBINATION OF SFC HEATING...FRONTAL UPLIFT...AND INCREASING LARGE
SCALE ASCENT SHOULD SUPPORT TSTM DEVELOPMENT SWWD ALONG THE FRONT
FROM IA/NRN MO THROUGH ERN KS INTO NW OK BY LATE AFTN.
50 KT MID LVL FLOW WILL CONTRIBUTE TO WIND PROFILES EXHIBITING
MODERATE DEEP DIRECTIONAL SHEAR THAT SHOULD FOSTER BOTH SUSTAINED
MULTICELLS AND A FEW SUPERCELLS. FAIRLY STRONG LOW LVL LINEAR
FORCING AND SIZABLE TEMP-DEWPOINT SPREADS SUGGEST THAT THE STORMS
SHOULD EVOLVE INTO BROKEN LINE SEGMENTS...WITH THE MAIN SVR THREATS
BEING DMGG WIND AND HAIL THROUGH THIS EVE.
FARTHER S...OTHER STORMS LIKELY WILL FORM A BIT LATER IN THE DAY OR
THIS EVE NEAR COLD FRONT/DRY LINE INTERSECTION AND SFC LOW OVER NW
TX AND SW OK. DEEP SHEAR AND ASCENT WILL INCREASE OVER THE REGION
THIS EVE AS UPR IMPULSE APPROACHES FROM THE NW. SETUP MAY PROVE
FAVORABLE FOR A FEW DISCRETE SUPERCELLS WITH VERY LARGE HAIL AND
ISOLD DMGG WIND. IN ADDITION...A TORNADO OR TWO CANNOT
BE RULED OUT INTO THE EVE AS LLJ NOCTURNALLY STRENGTHENS AND
TEMP-DEWPOINT SPREADS DIMINISH. BUT RELATIVELY WEAK LOW LVL SHEAR
DURING THE EARLY STAGES OF STORM DEVELOPMENT...AND ONSET OF
NOCTURNAL COOLING...SHOULD LIMIT DURATION OF SUCH A THREAT.
WHILE ADDITIONAL STORMS LIKELY WILL FORM THROUGH EARLY FRI FROM THE
SRN PLNS NEWD INTO THE NRN OZARKS/MID MS VLY...THE SVR THREAT SHOULD
DIMINISH AS THE COLD FRONT UNDERCUTS THE CONVECTION AND BUOYANCY
LESSENS WITH BOUNDARY LAYER COOLING.
..CORFIDI/MOSIER.. 04/19/2012
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