DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT SAT MAY 28 2016 VALID 281200Z - 291200Z ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE WRN UPPER GREAT LAKES/UPPER MS VALLEY SWWD TO THE RIO GRANDE VALLEY... ...SUMMARY... ISOLATED SEVERE STORMS WILL BE POSSIBLE FROM TEXAS TO THE UPPER MISSISSIPPI VALLEY...MAINLY ON SATURDAY AFTERNOON AND EVENING. ...SYNOPSIS... SHORT-WAVE MID-LEVEL TROUGHING OVER THE CENTRAL PLAINS IS FORECAST MAINTAIN NEGATIVE TILT AS IT SHIFTS NNEWD ACROSS THE MID MO VALLEY THROUGH THE DAY...AND INTO THE UPPER MS VALLEY BY THE END OF THE PERIOD. MEANWHILE IN THE W...FAST WLY FLOW IS FORECAST ACROSS THE PAC NW S OF A BRITISH COLUMBIA VORTEX...WHILE FARTHER S A WEAK TROUGH LINGERS OVER THE CA/NV VICINITY THROUGH 29/12Z. AT THE SURFACE...A RATHER WEAK/NONDESCRIPT PATTERN IS ANTICIPATED IN GENERAL. WEAK/DISORGANIZED LOW PRESSURE IS FORECAST TO SHIFT NNEWD ACROSS THE UPPER MIDWEST THROUGH THE DAY...REACHING THE LK SUPERIOR VICINITY OVERNIGHT. THIS LOW -- AND A ZONE OF BROAD LOW-LEVEL WARM ADVECTION AHEAD OF IT -- SHOULD SUPPORT AREAS OF SCATTERED TO ISOLATED SHOWERS AND STORMS IN A ZONE STRETCHING FROM THE RIO GRANDE TO THE WRN UPPER GREAT LAKES. FINALLY...TROPICAL DEPRESSION NUMBER TWO IS FORECAST TO GRADUALLY INTENSIFY TO TROPICAL STORM STRENGTH...AND APPROACH THE SERN U.S. COAST TOWARD THE END OF THE PERIOD. FOR ADDITIONAL TROPICAL FORECAST INFORMATION...PLEASE REFER TO THE LATEST ADVISORIES FROM THE NATIONAL HURRICANE CENTER. ...UPPER MS VALLEY/WRN UPPER GREAT LAKES SWWD TO THE RIO GRANDE VALLEY OF TX... SHOWERS AND A FEW THUNDERSTORMS -- ONGOING EARLY IN THE PERIOD INVOF THE UPPER TROUGH SHIFTING NNEWD ACROSS THE MID MO VALLEY -- SHOULD EXPAND IN COVERAGE/INTENSITY DURING THE AFTERNOON FROM PARTS OF WI/MN SWD INTO MO...AS MODEST AFTERNOON DESTABILIZATION OCCURS. THE MOST WIDESPREAD CONVECTION SHOULD FOCUS ACROSS ERN SD/ERN NEB/SRN MN/WI/IA...SPIRALING AROUND THE CENTER OF UPPER CIRCULATION. MORE ISOLATED STORMS MAY DEVELOP SSWWD ACROSS MO -- AND POSSIBLY EVEN INTO PARTS OF ERN OK/WRN AR -- IN THE AFOREMENTIONED WARM ADVECTION ZONE. WITH SOMEWHAT ENHANCED -- THOUGH LARGELY UNIDIRECTIONAL -- FLOW ALOFT...A COUPLE OF THE STRONGER STORMS MAY BECOME CAPABLE OF PRODUCING MARGINAL HAIL AND LOCALLY DAMAGING WIND GUSTS. AN ISOLATED/BRIEF TORNADO OR TWO MAY ALSO OCCUR IN THE IA VICINITY NEAR THE UPPER CIRCULATION CENTER. MEANWHILE FARTHER S INTO TX...RISING HEIGHTS ALOFT IN THE WAKE OF THE TROUGH DEPARTING NNEWD ACROSS THE UPPER MIDWEST SUGGEST WEAK BROAD-SCALE SUBSIDENCE. FURTHER...WITH NWWD ADVECTION OF LOW-LEVEL MOISTURE INTO W TX PROGGED WITH TIME THUS HINDERING ANY ADVANCE OF A DRYLINE...LACK OF LOW-LEVEL FOCUS FOR UVV IS INDICATED. HAVING SAID THAT...STEEP LAPSE RATES ALOFT RESIDING ABOVE A CAPPED BOUNDARY LAYER WILL CONTRIBUTE TO SUBSTANTIAL AFTERNOON CAPE DEVELOPMENT IN CONJUNCTION WITH DIURNAL HEATING/MIXING. MODELS -- TO VARYING DEGREES -- FORECAST ISOLATED TO SCATTERED AFTERNOON STORM INITIATION RANGING AREALLY FROM THE HIGHER TERRAIN OF NERN MEXICO /AIDED BY HEATING AND WEAK UPSLOPE FLOW/ TO PARTS OF CENTRAL TX /PRESUMABLY DUE TO VERY WEAK LOW-LEVEL WARM ADVECTION/. WITH THE LOW-LEVEL SELY FLOW EXPECTED ACROSS CENTRAL AND SRN TX VEERING TO MODEST/WLY AT MID LEVELS...SHEAR SUPPORTIVE OF MID-LEVEL UPDRAFT ROTATION IS EVIDENT...PARTICULARLY CONSIDERING THE THERMODYNAMIC ENVIRONMENT. THUS...LARGE HAIL AND LOCALLY DAMAGING WINDS WOULD BE LIKELY WITH ANY STORM WHICH DOES DEVELOP. HOWEVER...QUESTIONS REGARDING THE NUMBER OF STORMS WHICH WILL ACTUALLY DEVELOP -- GIVEN THE GENERALLY UNSUPPORTIVE BACKGROUND SYNOPTIC ENVIRONMENT -- PRECLUDES AN UPGRADE TO SLIGHT RISK ATTM. ..GOSS/MOSIER.. 05/28/2016Read more
from SPC Forecast Products http://ift.tt/s7Jkvo
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