SPC 1630Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1130 AM CDT MON MAY 20 2013 VALID 201630Z - 211200Z ...THERE IS A MDT RISK OF SVR TSTMS FOR ERN/CNTRL OK...N-CNTRL TX...NWRN AR...SRN MO...FAR SERN KS... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY/CNTRL GREAT LAKES TO THE SRN PLAINS... ...SRN PLAINS TO OZARK PLATEAU... OVERALL FORECAST SCENARIO REMAINS SIMILAR TO EARLIER OUTLOOKS WITH ONLY MINOR OVERALL CHANGES TO INDIVIDUAL HAZARD PROBABILITIES. MID-LEVEL SPEED MAX /65 KT AT 500 MB IN THE 12Z ABQ RAOB/ ATTENDANT TO THE SHORTWAVE IMPULSE OVER THE LEE OF THE SRN ROCKIES WILL OVERSPREAD MOST OF OK TO THE LOWER MO VALLEY BY EARLY EVENING. TRAILING PORTION OF COLD FRONT HAS BECOME SLOW-MOVING FROM SERN KS TO SWRN OK...INTERSECTING A DRYLINE THAT WILL BECOME WELL ESTABLISHED S/SWWD ACROSS THE TX BIG COUNTRY TO THE ERN EDWARDS PLATEAU BY LATE AFTERNOON. SCATTERED TSTMS WILL INITIATE ALONG THESE BOUNDARIES BY MID-AFTERNOON. MORNING CONVECTION-ALLOWING MODEL GUIDANCE ARE INSISTENT THAT THIS ACTIVITY WILL RAPIDLY GROW UPSCALE INTO NUMEROUS LINE SEGMENTS...SURGING EWD THIS EVENING WITHIN A STRONGLY UNSTABLE ENVIRONMENT. INITIAL TSTMS WILL BECOME SUPERCELLUAR QUICKLY WITH VERY LARGE HAIL LIKELY AS HODOGRAPHS/INSTABILITY WILL BE QUITE FAVORABLE...ALONG WITH A FEW TORNADOES. THE GREATEST RISK FOR A COUPLE OF STRONG TORNADOES SHOULD EXIST FROM S-CNTRL INTO E-CNTRL OK. BUT WITH PREDOMINANT SWLY COMPONENT TO LOW-LEVEL FLOW AND MODERATE 0-1 KM SHEAR...OVERALL TORNADO INTENSITY/LONGEVITY MAY BE TEMPERED...ESPECIALLY WITH CONVECTION EXPECTED TO GROW UPSCALE SO QUICKLY. NEVERTHELESS...THIS GROWTH SHOULD YIELD BOWING LINEAR SEGMENTS CAPABLE OF SWATHS OF WIDESPREAD DAMAGING WINDS...LARGE HAIL AND A FEW TORNADOES. ...MID/UPPER-MS VALLEY TO CNTRL GREAT LAKES... PRIMARY CHANGE HAS BEEN TO EXPAND DAMAGING WIND PROBABILITIES E/NEWD FOR THIS AFTERNOON AND EVENING. IN THE WAKE OF CONVECTION YESTERDAY...LOW-LEVEL MOISTURE PLUME HAS BECOME CONFINED FROM LOWER MI S/SSWD TO THE CONFLUENCE OF THE MS/OH RIVERS. BUT PLENTIFUL HEATING IS OCCURRING TO THE N OF THIS PLUME WILL YIELD A RECOVERING AIR MASS DOWNSTREAM OF A TSTM CLUSTER APPROACHING CNTRL MO. THIS ACTIVITY SHOULD GROW UPSCALE ALONG THE EDGE OF THE INSTABILITY AXIS...WITH ADDITIONAL LINEAR SEGMENTS EMANATING E/NEWD FROM THE OZARK PLATEAU LATER TODAY. SWATHS OF DAMAGING WINDS...LARGE HAIL AND A COUPLE OF TORNADOES WILL BE POSSIBLE. FARTHER N/NW...SCATTERED TSTMS ARE EXPECTED TO FORM OVER LOWER MI AND IN PARTS OF THE UPPER MIDWEST IN ASSOCIATION WITH AN UPPER-LEVEL LOW CENTERED OVER ERN SD. BUOYANCY WILL BE STRONGEST OVER LOWER MI WITHIN THE LOW-LEVEL MOISTURE PLUME CHARACTERIZED BY MIDDLE TO UPPER 60S SURFACE DEW POINTS. IN THE UPPER MIDWEST...POCKETS OF ROBUST SURFACE HEATING WILL SUPPORT AT LEAST MODEST INSTABILITY AND WITH STRONG UNIDIRECTIONAL WIND PROFILES...SETUP COULD A FEW ORGANIZED TSTM CLUSTERS. A MIX OF ISOLATED SEVERE HAIL/WIND SHOULD BE THE PRIMARY THREATS. ..GRAMS/ROGERS.. 05/20/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1630.html
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