SPC AC 221248
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 AM CDT TUE MAR 22 2011
VALID 221300Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
ERN KS/NEB INTO IA...MO...AND NRN IL...
...ERN NEB/KS INTO IA...MO AND NRN IL THIS AFTERNOON INTO TONIGHT...
A MIDLEVEL SHORTWAVE TROUGH OVER NM/CO THIS MORNING WILL EJECT NEWD
OVER KS/NEB TODAY AND REACH NRN MO/IA THIS EVENING...AS A LARGER
SCALE MIDLEVEL LOW DEVELOPS EWD FROM THE NRN HIGH PLAINS TO MN/IA BY
THE END OF THE PERIOD. AN ASSOCIATED SURFACE CYCLONE IN CENTRAL NEB
WILL DEVELOP EWD ALONG A BAROCLINIC ZONE THAT EXTENDS EWD INTO
IA...WITHIN THE LEFT EXIT REGION OF A 90-130 KT MID-UPPER JET MAX.
THIS KINEMATIC ENVIRONMENT WILL CONTRIBUTE TO FOCUSED ASCENT NEAR
AND IMMEDIATELY E OF THE SURFACE LOW THIS AFTERNOON/EVENING...AND
VERTICAL SHEAR PROFILES FAVORABLE FOR SUPERCELLS IN THE WARM SECTOR
OF THE CYCLONE.
THE PRIMARY LIMITING FACTOR FOR A MORE WIDESPREAD/SIGNIFICANT SEVERE
STORM EPISODE WILL BE THE MODEST BOUNDARY LAYER MOISTURE IN THE WARM
SECTOR. LARGE SCALE SUBSIDENCE OVER THE GULF BASIN AND PERSISTENT
TRAJECTORIES FROM WITHIN THE RIDGE HAVE INHIBITED APPRECIABLE WARM
SECTOR MOISTENING OVER THE PAST SEVERAL DAYS...AND ALLOWED BOUNDARY
LAYER MOISTURE QUALITY TO BE REDUCED EACH AFTERNOON VIA MIXING
INLAND FROM THE COAST. THUS...DEWPOINTS ARE UNLIKELY TO INCREASE
FROM THE MID-UPPER 50S ALREADY PRESENT. DESPITE THE MODEST
MOISTURE...AFTERNOON TEMPERATURES WELL INTO THE 70S/LOW 80S ALONG
THE DRYLINE...AND STEEP MIDLEVEL LAPSE RATES ALONG AND N OF THE JET
CORE...WILL CONTRIBUTE TO MLCAPE VALUES APPROACHING 1500 J/KG NEAR
AND IMMEDIATELY SE OF THE TRIPLE POINT /WITH WEAKER INSTABILITY
FARTHER TO THE S/.
PRESENT INDICATIONS ARE THAT THUNDERSTORMS WILL DEVELOP AROUND 21Z
NEAR THE TRIPLE POINT INVOF THE KS/NEB BORDER AS THE CAP
WEAKENS...WITH CONVECTION EXPECTED TO INCREASE IN COVERAGE AND
SPREAD EWD/NEWD INTO IA DURING THE EVENING. OTHER MORE ISOLATED
STORMS MAY ALSO FORM FARTHER S ALONG THE DRYLINE INTO ERN KS AND
EXTREME NE OK. THE MODERATE INSTABILITY AND STRONG DEEP-LAYER
VERTICAL SHEAR WILL FAVOR SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL
AND A FEW DAMAGING GUSTS. A FEW TORNADOES WILL ALSO BE POSSIBLE
GIVEN THE RELATIVELY STRONG LOW-LEVEL SHEAR /EFFECTIVE SRH IN EXCESS
OF 250 M2 PER S2/ AND SUFFICIENT BOUNDARY LAYER MOISTURE E OF THE
SURFACE CYCLONE THIS EVENING. THE WINDOW OF OPPORTUNITY FOR SEVERE
STORMS WILL BE WIDER ALONG THE PATH OF THE CYCLONE ACROSS IA INTO
THE EARLY OVERNIGHT HOURS...WHILE ANY DRYLINE STORMS FARTHER S
SHOULD WEAKEN JUST AFTER SUNSET AS CONVECTIVE INHIBITION INCREASES.
..THOMPSON/GRAMS.. 03/22/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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