SPC 1630Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1123 AM CDT WED MAY 29 2013 VALID 291630Z - 301200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS WRN/CNTRL PARTS OF NEB/KS/OK...THE ERN OK/TX PNHDLS...AND NWRN TX... ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE GREAT PLAINS INTO UPPER MIDWEST... ...THERE IS A SLGT RISK OF SVR TSTMS OVER THE LOWER GREAT LAKES INTO NEW ENGLAND... ...SYNOPSIS... STRONG MID AND UPPER-LEVEL JET STREAKS FROM THE NERN PACIFIC INTO SRN ROCKIES WILL DEVELOP EWD/SEWD THROUGH THE BASE OF AND EVENTUALLY DOWNSTREAM FROM A NEGATIVELY TILTED LONG-WAVE TROUGH EXTENDING FROM THE PACIFIC NW INTO CNTRL/SRN PLAINS. MORNING WATER VAPOR IMAGERY SHOWS SEVERAL VORTICITY MAXIMA EMBEDDED WITHIN THIS LARGE-SCALE PATTERN...ONE OVER THE SRN HIGH PLAINS WHICH WILL SHIFT INTO LOWER ELEVATIONS OF THE CNTRL/SRN PLAINS TODAY...AND ANOTHER MORE COMPACT SYSTEM OVER THE CNTRL ROCKIES WHICH WILL EVOLVE INTO A CLOSED CIRCULATION WHILE ADVANCING NEWD INTO THE DAKOTAS AND NEB. AN MCV OVER CNTRL KS WILL MOVE NNEWD INTO THE MID-MO VALLEY AHEAD OF THESE TWO FORMER FEATURES. ELSEWHERE...A MIGRATORY SHORT-WAVE TROUGH OVER THE GREAT LAKES WILL TRANSLATE EWD THROUGH QUEBEC AND NEW ENGLAND TODAY INTO TONIGHT. IN THE LOW LEVELS...A LEE CYCLONE INITIALLY OVER THE CNTRL HIGH PLAINS WILL CALVE A LOW CENTER THAT WILL DEVELOP NWD THROUGH WRN NEB TODAY BEFORE OCCLUDING OVER NWRN SD TONIGHT. MEANWHILE...THE RESIDUAL LEE LOW WILL SLOWLY DEVELOP SEWD INTO NWRN OK BY 30/12Z. AN ASSOCIATED DRYLINE WILL MIX EWD ACROSS THE HIGH PLAINS TODAY BEFORE BEING OVERTAKEN BY A PACIFIC FRONT TONIGHT. OVER THE LOWER GREAT LAKES INTO NEW ENGLAND...A WARM FRONT WILL ADVANCE EWD ACROSS THE REGION. ...CNTRL/SRN PLAINS TODAY AND TONIGHT... A CLUSTER OF ELEVATED TSTMS HAVE DEVELOPED THIS MORNING ACROSS PARTS OF NEB/IA/KS AHEAD OF AN MCV LIFTING NEWD THROUGH CNTRL KS. THE 12Z TOP/OAX SOUNDINGS SHOWED THE PRESENCE OF AN ALREADY MODERATELY UNSTABLE ENVIRONMENT FOR PARCELS BASED AROUND 850 MB AND LARGE HAIL WILL BE POSSIBLE WITH THIS ACTIVITY AS IT PROGRESSES THROUGH THE MID-MO VALLEY TODAY. OTHERWISE...12Z REGIONAL SOUNDINGS INDICATE THE POTENTIAL FOR STRONG AIR MASS DESTABILIZATION TODAY OWING TO 8.0-9.0+ C/KM 700-500-MB LAPSE RATES ATOP A MOIST BOUNDARY LAYER WITH LOWEST-100-MB MEAN MIXING RATIOS OF GENERALLY 13.5-14.5 G/KG. THE ONGOING STORMS OVER THE CNTRL PLAINS/MID-MO VALLEY AND APPARENT EARLY EMERGENCE OF THE LOWER LATITUDE IMPULSE INTO THE SRN PLAINS CAST UNCERTAINTY ON SPECIFIC DETAILS REGARDING SURFACE-BASED STORM EVOLUTION TODAY. IT DOES APPEAR THAT THE PRIMARY FOCUS FOR TSTM DEVELOPMENT WILL BE THE DRYLINE BY EARLY TO MID AFTERNOON FROM SWRN NEB SWD THROUGH FAR SWRN KS INTO THE CNTRL OR ERN TX PNDHL. THE COMBINATION OF MODERATE TO STRONG INSTABILITY AND MODERATELY STRONG DEEP-LAYER SHEAR WILL SUPPORT SUPERCELLS AS THE INITIAL STORM MODE. LARGE HAIL AND TORNADOES WILL BE THE PRIMARY HAZARDS WITHIN THE FIRST FEW HOURS OF INITIATION. WHILE A FEW STRONG TORNADOES APPEAR POSSIBLE...THE TENDENCY FOR VEER-BACK SIGNATURES IN FORECAST HODOGRAPHS MAY RESULT IN AN EVENTUAL TRANSITION TO MIXED STORM MODES /I.E. SUPERCELLS EMBEDDED IN LINE SEGMENTS/ WHICH IS SUGGESTED BY SOME RECENT CONVECTION-ALLOWING MODEL GUIDANCE. THERE IS ALSO SOME SUGGESTION BY LATEST MODEL GUIDANCE THAT A SECOND BAND OF TSTMS DEVELOPS THIS AFTERNOON E OF THE DRYLINE FROM CNTRL KS SWD INTO N-CNTRL TX. UNCERTAINTY IN THIS SCENARIO REMAINS HIGH...BUT SHOULD IT UNFOLD...ENVIRONMENTAL CONDITIONS WILL BE SUPPORTIVE OF EMBEDDED SUPERCELL STRUCTURES WITH A RISK FOR A FEW TORNADOES...LARGE HAIL...AND DAMAGING WINDS. UPSCALE GROWTH OF STORMS INTO ONE OR MULTIPLE MCS/S IS ANTICIPATED TONIGHT WITH A HAIL/DAMAGING WIND THREAT SPREADING EWD ACROSS LOWER ELEVATIONS OF THE GREAT PLAINS. ...NRN PLAINS INTO THE UPPER MIDWEST TODAY INTO TONIGHT... EPISODES OF ELEVATED TSTMS /CAPABLE OF SEVERE HAIL/ WILL BE POSSIBLE TODAY ACROSS PARTS OF ERN SD AND MN IN CONJUNCTION WITH A COUPLE OF MCV/S LIFTING NNEWD. FARTHER W...SURFACE-BASED TSTM DEVELOPMENT IS ANTICIPATED THIS AFTERNOON ALONG A LEE/INVERTED TROUGH OVER THE NRN HIGH PLAINS...ALONG AND AHEAD OF THE SURFACE LOW DEVELOPING NWD. SOME STORM ORGANIZATION IS POSSIBLE GIVEN AT LEAST MODEST AMOUNTS OF INSTABILITY AND VERTICAL SHEAR WITH HAIL AND DAMAGING WINDS POSSIBLE. ...LOWER GREAT LAKES INTO NEW ENGLAND THIS AFTERNOON AND EVENING... DECREASING CLOUDS COUPLED WITH INCREASING BOUNDARY LAYER MOISTURE IN THE WAKE WARM FRONTAL PASSAGE WILL CONTRIBUTE TO RAPID AIR MASS DESTABILIZATION TODAY ACROSS THE REGION. FORCING FOR ASCENT ATTENDANT TO THE SHORT-WAVE TROUGH MENTIONED IN THE SYNOPSIS WILL FOSTER WIDELY SCATTERED TSTMS BY AFTERNOON FROM SWRN ONTARIO TO THE LEE OF THE LOWER GREAT LAKES. THIS ACTIVITY WILL RAPIDLY SPREAD EWD THROUGH THE HUDSON VALLEY LATER THIS AFTERNOON WITHIN A STRONG...WLY WIND FIELD. A MIXTURE OF SUPERCELLS AND BOWING STRUCTURES APPEAR POSSIBLE WITH A RISK FOR DAMAGING WINDS...LARGE HAIL...AND PERHAPS A COUPLE OF TORNADOES. ..MEAD/MOSIER.. 05/29/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1630.html
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