SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0302 PM CDT FRI MAY 31 2013 VALID 312000Z - 011200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM CNTRL OK INTO SWRN MO... ...THERE IS A SLGT RISK OF SVR TSTMS FROM FAR NRN TX INTO NERN MN AND WI... ...OK...SERN KS INTO SWRN MO... STORMS ARE BEGINNING TO FORM OVER SERN KS ALONG THE COLD FRONT...AS WELL AS ALONG THE OUTFLOW BOUNDARY INTO W CNTRL MO. 18Z SGF SOUNDING SHOWED A LOADED GUN PROFILE WITH STEEP MIDLEVEL LAPSE RATES AND A VERY DEEP MOIST BOUNDARY LAYER AND A SUPERCELL TORNADO HODOGRAPH. WITH LIFTED INDICIES OF -10 TO -12...A COUPLE STRONG TORNADOES WILL BE POSSIBLE IN ADDITION TO VERY LARGE HAIL. FARTHER S INTO OK...THE 18Z OUN SOUNDING SHOWED A PRONOUNCED CAPPING INVERSION...WITH A VERY MOIST AND DEEPENING BOUNDARY LAYER WITH PRECIPITABLE WATER AROUND 1.50 INCHES. OK MESONET OBSERVATIONS CONTINUE TO SHOW DEWPOINTS HOLDING IN THE LOWER 70S F WITH EXTREME INSTABILITY IN PLACE. HIGHER BASED CU HAVE RECENTLY FORMED OVER NW TX AND SWRN OK WHERE TEMPERATURES WERE NEARING 100 F...AND THE GREATEST PRESSURE FALLS ARE CENTERED IN THIS REGION AS WELL. MODELS ALSO CONTINUE TO SHOW CYCLOGENESIS THROUGH THE EVENING...WITH WINDS OVER CNTRL OK BECOMING MORE BACKED WITH TIME. THIS WILL HAVE THE EFFECT OF ENLARGING HODOGRAPHS AND SRH VALUES. THIS WILL ALSO LIKELY PULL THE STATIONARY BOUNDARY...NOW FROM N CNTRL INTO WRN OK...SWD TO NEAR I-40. CELLS THAT FORM OVER SWRN OR W CNTRL OK WILL MOVE E WITH A VERY HIGH THREAT OF GIANT HAIL AND A FEW STRONG TO VIOLENT TORNADOES. ONE CAVEAT IS INITIAL LCL HEIGHTS IN THE HOTTER AIR...AND POTENTIAL OUTFLOW MAGNITUDE. HOWEVER...THE EXTREMELY FAVORABLE SUPERCELL ENVIRONMENT IS EXPECTED TO KEEP STORMS MAINLY CELLULAR...HELPING TO COUNTERACT ANY NEGATIVE OUTFLOW EFFECTS. LATER IN THE EVENING...A SEVERE MCS AND/OR ADDITIONAL SUPERCELLS ARE STILL LIKELY ACROSS MUCH OF NRN AND NERN OK INTO SWRN MO...WITH DAMAGING WINDS AND A FEW TORNADOES. ...ERN MN...WI...ERN IA... EXPANDED THE SLIGHT RISK FARTHER W INTO MN AS STORMS CONTINUE TO FORM W OF THE MS RIVER WHERE DESTABILIZATION CONTINUES AND WITH COOLING ALOFT OVERSPREADING THE WARM SECTOR. COOL TEMPERATURES ALOFT AND SUFFICIENT DEEP LAYER SHEAR WILL FAVOR SEVERE HAIL. STORMS SHOULD PERSIST WITH A SWD EXTENSION LIKELY INTO IA BY LATE AFTERNOON/EARLY EVENING. ..JEWELL.. 05/31/2013 .PREV DISCUSSION... /ISSUED 1156 AM CDT FRI MAY 31 2013/ CORRECTED FOR TYPOS ...REGIONAL SEVERE WEATHER OUTBREAK POSSIBLE TODAY OVER PARTS OF CENTRAL/EASTERN OK...SOUTHEAST KS...AND SOUTHWEST MO. VERY LARGE HAIL...WIDESPREAD DAMAGING WINDS...AND A FEW STRONG/VIOLENT TORNADOES ARE POSSIBLE... ...OK/KS/MO... ANOTHER VERY VOLATILE ENVIRONMENT IS IN PLACE ACROSS PARTS OF THE SOUTHERN PLAINS AND MID MS VALLEY TODAY. WIDESPREAD VERY STEEP MID LEVEL LAPSE RATES AND DEWPOINTS IN THE UPPER 60S/LOWER 70S ARE RESULTING IN THE POTENTIAL FOR AFTERNOON MLCAPE VALUES OVER 4000 J/KG. THIS AIR MASS IS CURRENTLY CAPPED...AND THE CAP SHOULD RESTRAIN DEEP CONVECTION THROUGH MUCH OF THE DAY ALLOWING STRONG HEATING. BY MID/LATE AFTERNOON...A SHORTWAVE TROUGH INDICATED IN WATER VAPOR IMAGERY OVER THE TX PANHANDLE...ALONG WITH A SECOND AND STRONGER TROUGH OVER CO...WILL APPROACH THE REGION. THIS WILL RAPIDLY WEAKEN THE CAP AND ALLOW EXPLOSIVE THUNDERSTORM DEVELOPMENT ALONG THE DRYLINE OVER WEST-CENTRAL OK...AND ALONG THE COLD FRONT EXTENDING FROM CENTRAL OK INTO SOUTHWEST MO. DEEP LAYER EFFECTIVE SHEAR VALUES ARE FAVORABLE FOR SUPERCELL STORMS CAPABLE OF VERY LARGE HAIL...DAMAGING WINDS...AND TORNADOES. SHEAR VECTORS PERPENDICULAR TO THE N-S DRYLINE OVER CENTRAL OK WILL FAVOR DISCRETE STORM STRUCTURES. ALL 12Z MODEL GUIDANCE INDICATES RAPID INTENSIFICATION OF THE LOW LEVEL JET OVER CENTRAL OK BY EVENING AS THE UPPER TROUGH APPROACHES. GIVEN THESE PARAMETERS...IT APPEARS THE THREAT OF A FEW STRONG/VIOLENT TORNADOES ARE IN PLACE. HAVE INCREASED SEVERE PROBABILITIES OVER THIS REGION...AND PORTIONS OF CENTRAL/EASTERN OK WILL BE CONSIDERED FOR AN UPGRADE TO HIGH RISK AT 20Z IF SHORTER-TERM MESOSCALE MODELS MAINTAIN THIS SCENARIO. DURING THE EVENING...NUMEROUS THUNDERSTORMS ARE EXPECTED TO CONGEAL INTO A FAST-MOVING MCS THAT TRACKS NORTHEASTWARD ACROSS NORTHEAST OK INTO SOUTHWEST MO. HIGH CAPE VALUES AND AN INCREASING LOW LEVEL JET WILL PROMOTE THE POTENTIAL FOR WIDESPREAD WIND DAMAGE...ALONG WITH LARGE HAIL AND ISOLATED TORNADOES. ...IA/MN/WI... AN UPPER LOW IS PRESENT THIS MORNING OVER WESTERN SD...WITH MULTIPLE SHORTWAVE TROUGHS ROTATING NORTHWARD ACROSS IA/MN. STRONG DAYTIME HEATING IS OCCURRING AHEAD OF THE SHORTWAVE TROUGHS OVER PARTS OF MN/WI/IA WHERE MODERATE AFTERNOON CAPE IS EXPECTED. SCATTERED THUNDERSTORMS ARE EXPECTED TO FORM BY MID AFTERNOON OVER MN/IA AND TRACK NORTHEASTWARD. A FEW OF THESE STORMS COULD BE SUPERCELLULAR WITH A RISK OF HAIL/DAMAGING WINDS OR AN ISOLATED TORNADO. ...IL/IND... AN ONGOING CLUSTER OF THUNDERSTORMS IN THE STL AREA MAY RE-INTENSIFY THIS AFTERNOON AS IT TRACKS INTO AN INCREASINGLY MOIST/UNSTABLE AIR MASS OVER IL/IND. IF THIS OCCURS...LOCALLY DAMAGING WINDS AND HAIL WILL BE POSSIBLE.
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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