SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0106 AM CDT THU MAY 24 2012 VALID 241200Z - 251200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN KS/CNTRL AND NRN MO NWD ACROSS IA...SERN MN AND MUCH OF WI... ...SYNOPSIS... LATE NIGHT WATER VAPOR SATL LOOP AND SHORT TERM GUIDANCE DEPICT A VIGOROUS MID/UPPER LEVEL DISTURBANCE OVER NV/UT ROUNDING THE BASE OF A LARGER SCALE UPPER TROUGH ENCOMPASSING MUCH OF THE WRN U.S. THIS SHORT WAVE TROUGH AND ITS ASSOCIATED 75-90KT JET STREAK WILL EMERGE ACROSS THE CNTRL PLAINS LATER THIS MORNING BEFORE PIVOTING ACROSS THE MID MISSOURI RIVER VALLEY AND THEN EJECTING NEWD TOWARD THE ARROWHEAD OF MN BY LATE EVENING. IN RESPONSE TO STRENGTHENING DEEP-LAYER ASCENT ALONG AN ALREADY WELL ESTABLISHED FRONTAL ZONE DRAPED SW-NE ACROSS THE GREAT PLAINS...SURFACE CYCLOGENESIS IS FORECAST FROM KS TO IA THROUGH THE MORNING. RESULTING LOW PRESSURE CENTER IS FORECAST TO TRACK RAPIDLY NEWD ALONG THE SHARP FRONTAL ZONE...FROM SERN MN INTO NWRN WI THROUGH LATE AFTERNOON...WHILE DEEPENING RAPIDLY. COLD FRONT TRAILING FROM THE LOW CENTER WILL SPREAD EAST FROM IA TO NRN IL AND SOUTH INTO MO THROUGH TONIGHT BUT ITS ADVANCE AND INTENSITY SHOULD GRADUALLY DIMINISH OVER THE PLAINS AS THE PRIMARY UPPER TROUGH MOVES NORTH INTO CANADA AND STRONGER LARGE SCALE SUPPORT FOR LIFT ALONG THE FRONT WANES. BROAD BUT WEAKENING MID/UPPER LEVEL TROUGHING WILL PERSIST ALONG THE ERN SEABOARD THIS PERIOD WITH A BAND OF MORE MODEST MID LEVEL FLOW CONSTRAINED TO THE IMMEDIATE EAST COAST AND OVER PORTIONS OF THE MID ATLANTIC. PERSISTENT SWATH OF SLY FLOW OFF THE GULF STREAM AND CARIBBEAN SEA WILL MAINTAIN A VERY MOIST MARITIME TROPICAL AIRMASS OVER THE SOUTHEAST AND MID ATLANTIC. ...UPPER MS RIVER VALLEY... AS HAS BEEN THE CASE WITH SOME OF THE MORE RECENT SEVERE STORM EPISODES...LIMITED LOW LEVEL MOISTURE AND STRONG CAPPING WILL AGAIN PLAY A ROLE IN THE EVOLUTION OF SEVERE WEATHER POTENTIAL FROM IA AND IL NORTH ACROSS ERN WI AND MUCH OF WI TODAY. DESPITE THESE LIMITATIONS...THERE IS CONSIDERABLE AGREEMENT AMONGST THE LATEST GUIDANCE THAT SUBSTANTIAL SHEAR AND FORCING WILL ACCOMPANY THE DEVELOPING LOW PRESSURE SYSTEM FROM IA NNEWD ACROSS WRN WI LATER THIS AFTERNOON. GREATEST CONCENTRATION OF TSTMS WILL LIKELY BE ALONG THE COOLER SIDE OF THE SURFACE BOUNDARY...AT LEAST INITIALLY...WHERE PARCELS WILL BE FORCED TO ACHIEVE AN LFC ELEVATED ABOVE A STABLE SURFACE LAYER. EVEN IN THIS REGIME...SOME HAIL AND EVENING OCCASIONAL STRONGER WIND GUSTS MAY OCCUR WITH CELLS OR LINE SEGMENTS RACING NEWD AT 40-50KT. WARM SECTOR TO THE EAST OF THE SURFACE LOW IS LIKELY TO REMAIN CAPPED GIVEN PLUME OF VERY WARM AIR AT MID LEVELS STREAMING NEWD AHEAD OF THE EJECTING UPPER TROUGH. HOWEVER...OVERNIGHT RAIN AND CONTINUED SLY FLOW SHOULD ALLOW SURFACE DEWPOINTS TO CLIMB INTO THE LOW 60S F AS FAR WRN WI. MLCAPE COINCIDENT WITH THE DEEPENING SURFACE LOW MAY REACH INTO THE 500-1000 J PER KG RANGE AND...GIVEN MAGNITUDE OF FORCED ASCENT ACCOMPANYING THE INTENSIFYING LOW PRESSURE /DEEPENING AROUND 1MB/HR BETWEEN 18 AND 21Z PER LATEST PROGS/...EXPECT POTENTIALLY DANGEROUS AND FAST-MOVING STORMS TO DEVELOP. THE WINDOW OF OPPORTUNITY FOR THIS DEVELOPMENT WILL BE RATHER SMALL...FROM ABOUT 19-23Z AND OVER A RELATIVELY CONFINED REGION FROM EXTREME ERN MN INTO WRN/NWRN WI. FORECAST CONDITIONS IN THIS TIME AND AREA APPEAR SUPPORTIVE OF A COUPLE OF POSSIBLY STRONG TORNADOES AND/OR FAST-MOVING LINE SEGMENTS CAPABLE OF DAMAGING WINDS. SHEAR AND INSTABILITY VALUES NEAR THE LOW SUPPORT THE CURRENT CORRIDOR OF HIGH TORNADO PROBABILITIES AND AN UPGRADE TO GREATER PROBABILITIES/CONFIDENCE IS POSSIBLE WITH THE LIGHT OF DAY AND A CLOSE INSPECTION OF OVERNIGHT STORM-SCALE GUIDANCE. ADDITIONAL SURFACE-BASED STORM DEVELOPMENT IN THE FORM OF LINES OR BOWS MAY OCCUR THROUGH THE LATE AFTERNOON ALONG THE ADVANCING COLD FRONT. MAGNITUDE OF MID LEVEL FLOW DIRECTED INTO THE DEVELOPING CONVECTION SUGGESTS THAT THESE STORMS MAY POSE A THREAT OF DAMAGING WINDS AS THEY MOVE EAST FROM NERN IA INTO SRN WI AND PORTIONS OF NRN IL. ...MO... MORE ISOLATED TO SCATTERED STORM DEVELOPMENT COULD OCCUR AHEAD OF THE FRONT SPREADING INTO MO FROM LATE AFTERNOON INTO THE EVENING. LARGER SCALE SUPPORT WILL BE WANING ALONG THE FRONT IN THIS AREA. HOWEVER...ANY STORMS THAT CAN DEVELOP WILL DO SO IN A SUFFICIENTLY SHEARED ENVIRONMENT WHERE WARM/HOT BOUNDARY LAYER WILL CONTRIBUTE DAMAGING WIND POTENTIAL...AND PERHAPS SOME HAIL. ..CARBIN/MOSIER.. 05/24/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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