SPC AC 201729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT SUN MAR 20 2011
VALID 211200Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE MID MO
VALLEY INTO CENTRAL IA MONDAY NIGHT...
...SYNOPSIS...
MODELS CONTINUE TO SHOW A COUPLE OF SIGNIFICANT SHORTWAVE
TROUGHS...ATTENDANT TO THE EVOLVING ERN PACIFIC/WRN U.S. TROUGH...
ADVANCING INLAND ON DAY 2 ACROSS THE GREAT BASIN/SWRN STATES. THE
LEAD TROUGH SHOULD REACH THE NRN HIGH PLAINS BY 12Z TUESDAY...WHILE
THE SECOND TROUGH PROGRESSES INTO THE FOUR CORNERS/SRN ROCKIES
REGION BY THE SAME TIME PERIOD. DESPITE MODEL AGREEMENT...STRONGER
HEIGHT FALLS/FORCING FOR ASCENT SHOULD NOT REACH THE CENTRAL PLAINS
UNTIL WELL AFTER DARK MONDAY NIGHT.
MEANWHILE...MODELS MAINTAIN PREVIOUS FORECAST FOR THE NERN EXTENT OF
THE U.S. RIDGE TO BE SUPPRESSED ACROSS THE MID-UPPER OH VALLEY AND
CENTRAL/NRN APPALACHIANS. THIS WILL BE DUE PRIMARILY TO THE EWD
PROGRESSION OF THE SHORTWAVE TROUGH MOVING THROUGH THE UPPER
MIDWEST/GREAT LAKES ON SUNDAY.
...CENTRAL PLAINS/MID MO VALLEY ...
GIVEN THE FOLLOWING FACTORS 1/ THE LATER ARRIVAL OF STRONGER HEIGHT
FALLS INTO THE CENTRAL PLAINS WITH THE LEAD WRN U.S. SHORTWAVE
TROUGH THAN PREVIOUS INDICATED BY MODELS...2/ A STRONG EML/CAP
ALREADY EVIDENT WITH 12Z SUNDAY PLAINS SOUNDINGS...3/ INCREASING
MIDLEVEL TEMPERATURES ACROSS THE CENTRAL PLAINS ENHANCING THE CAP ON
MONDAY...THE SLIGHT RISK HAS BEEN REDUCED IN SIZE TO ACCOUNT FOR
MAINLY THE THREAT FOR STRONG TO SEVERE ELEVATED STORMS. THIS
SCENARIO IS FURTHER REINFORCED BY THE LACK OF BOTH OPERATIONAL
DETERMINISTIC MODELS AND MOST OF THE SREF MEMBERS INDICATING A LACK
OF WARM SECTOR CONVECTIVE DEVELOPMENT MONDAY AFTERNOON. THE
EXCEPTION MAY BE ALONG THE SRN EXTENT OF THE DRY LINE ACROSS SW/W
TX...WHERE LOW LEVEL CONVERGENCE WILL BE GREATER SUPPORTING A
DIURNAL AND...AT LEAST INITIALLY...HIGH BASED TSTMS WITH LOCALLY
STRONGER WIND GUSTS AND PERHAPS SOME HAIL.
MEANWHILE...MODELS CONTINUE TO DIFFER IN THE NWD RETURN OF THE WARM
FRONT WITH THE WRF-NAM BEING THE SLOWEST AND THUS REACHING THE
KS/NEB BORDER BY PEAK HEATING. HOWEVER...EVEN THE LATEST 12Z
GFS/00Z ECMWF...WHICH BRING THIS BOUNDARY INTO SRN NEB INDICATED
THAT CONVECTIVE PRECIPITATION WILL NOT INITIATE UNTIL AFTER
22/00Z...AND PRIMARILY N OF THE WARM FRONT WITHIN INCREASING WAA
REGIME ALONG NOSE OF STRENGTHENING PLAINS LLJ. STORMS SHOULD
BACKBUILD FROM IA/ERN NEB INTO CENTRAL PART OF NEB LATE MONDAY NIGHT
AS STRONGER FORCING FOR ASCENT REACHES THIS REGION. STEEP MIDLEVEL
LAPSE RATES...ELEVATED MUCAPE TO 1000 J/KG AND EFFECTIVE BULK SHEAR
30-50 KT SUGGEST LARGE HAIL WILL BE THE PRIMARY THREAT.
...PARTS OF THE OHIO VALLEY INTO THE CNTRL APPALACHIANS...
MODELS CONTINUE TO SUGGEST THAT AN AREA OF ENHANCED FORCING WILL
SPREAD FROM PORTIONS OF SOUTHERN INDIANA/OHIO AND NORTHERN KENTUCKY
INTO THE CENTRAL APPALACHIANS DURING THE PEAK HEATING HOURS MONDAY.
AHEAD OF THE SOUTHWARD ADVANCING FRONT...WEAK BOUNDARY LAYER
DESTABILIZATION IN THE PRESENCE OF 30-40+ KT WESTERLY DEEP LAYER
MEAN FLOW COULD CONTRIBUTE TO STORM DEVELOPMENT CAPABLE OF PRODUCING
AT LEAST A FEW POTENTIALLY DAMAGING WIND GUSTS.
..PETERS.. 03/20/2011
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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