SPC AC 271717
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1217 PM CDT MON JUN 27 2011
VALID 281200Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE LOWER MS VALLEY AND TN
VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CENTRAL HIGH PLAINS...
...SYNOPSIS...
MODEL GUIDANCE INDICATES UPPER FLOW PATTERN WILL AMPLIFY TOMORROW AS
THE UPPER LOW CURRENTLY DROPPING SWD OFF THE PACIFIC NW COAST TURNS
SEWD TOWARD THE NRN/CENTRAL CA COAST. THIS WILL RESULT IN THE
DOWNSTREAM RIDGE BUILDING OVER THE ROCKIES AND PLAINS...WHILE THE
UPPER LOW NOW NEARING THE UPPER MS VALLEY PROGRESSES EWD TOWARD THE
ST LAWRENCE VALLEY.
AT THE SURFACE...A LOW IS FORECAST TO MOVE FROM NRN LAKE HURON AT
THE BEGINNING OF THE PERIOD NEWD TOWARD WRN QUEBEC...WITH TRAILING A
COLD FRONT MOVING EWD/SEWD REACHING THE APPALACHIANS TO THE MID
SOUTH BY LATE AFTERNOON...AND CONTINUING EWD/SEWD DURING THE NIGHT.
THE WRN PART OF THE FRONT WILL BEGIN TO LIFT NWD OVER THE SRN HIGH
PLAINS TOMORROW AFTERNOON REACHING THE CENTRAL HIGH PLAINS DURING
THE OVERNIGHT HOURS.
...LOWER MS VALLEY AND TN VALLEY...
SCATTERED CONVECTION CONTINUING FROM LATE IN THE DAY 1 PERIOD MAY
PERSIST DURING THE EARLY PART OF DAY 2 FROM AR INTO THE TN
VALLEY...BUT THIS ACTIVITY IS EXPECTED TO DIMINISH DURING THE
MORNING. THIS WILL ALLOW SOME AREAS TO UNDERGO ENHANCED DIABATIC
HEATING INTO THE AFTERNOON...AND WHEN COUPLED WITH PRE-EXISTING
SURFACE DEW POINTS OF 70-75F...WILL RESULT IN CONSIDERABLE
INSTABILITY WITH MLCAPE OF 2000-3000 J/KG. THUNDERSTORMS ARE
EXPECTED TO REDEVELOP DURING THE AFTERNOON ALONG THE COLD FRONT
AND/OR EFFECTIVE OUTFLOW BOUNDARIES GENERATED BY EARLIER CONVECTION
IN THE WARM SECTOR. NWLY MID-LEVEL FLOW IS EXPECTED TO INCREASE TO
25-35 KT AS THE UPSTREAM UPPER RIDGE AMPLIFIES...CONTRIBUTING TO
SUFFICIENT DEEP LAYER SHEAR /30-35 KT IN THE LOWEST 6 KM/ TO ENHANCE
STORM ORGANIZATION AND INTENSITY. A FEW ORGANIZED MULTICELL
CLUSTERS AND LINEAR SEGMENTS MAY DEVELOP DURING THE AFTERNOON AND
EVENING WITH POTENTIAL TO PRODUCE LOCALLY DAMAGING WINDS AND
OCCASIONAL HAIL AS THE ACTIVITY PROGRESSES SEWD.
...CENTRAL HIGH PLAINS...
LOW LEVEL MOISTURE WITH SURFACE DEW POINTS OF 50-60F IS FORECAST TO
GRADUALLY INCREASE NWD INTO THE REGION AS MODEST SSELY FLOW DEVELOPS
NORTH OF THE RETREATING FRONTAL BOUNDARY. STEEP LOW-MID LEVEL LAPSE
RATES AND RESULTANT MLCAPE OF 1500-2500 J/KG COUPLED WITH WIND
PROFILES THAT VEER STRONGLY WITH HEIGHT WILL PROVIDE A POTENTIALLY
FAVORABLE ENVIRONMENT FOR STRONG/SEVERE STORM DEVELOPMENT. PRIMARY
LIMITING FACTOR IS THE LACK OF DYNAMIC FORCING FOR LARGE SCALE
ASCENT WITHIN THE UPPER RIDGE WHICH SUGGESTS THAT WIDESPREAD
CONVECTION IS UNLIKELY. HOWEVER...MODEL GUIDANCE CONTINUES TO
INDICATE ISOLATED/WIDELY SCATTERED STORMS FORMING DURING THE LATE
AFTERNOON/EVENING HOURS OVER NERN/EAST CENTRAL CO...WITH STORMS THEN
MOVING EWD INTO KS DURING THE OVERNIGHT HOURS AS THE LOW LEVEL JET
STRENGTHENS AFTER DARK. STRONGER STORMS WILL HAVE POTENTIAL TO
PRODUCE LARGE HAIL AND STRONG WIND GUSTS GIVEN STEEP LAPSE RATE AND
DEEP PBL ENVIRONMENT...BEFORE ACTIVITY BECOMES PRIMARILY ELEVATED
AFTER 03-06Z AS IT MOVES EWD ACROSS PARTS OF KS.
...MID ATLANTIC STATES INTO THE CAROLINAS...
MODELS INDICATE MORNING STORMS WILL SPREAD EWD AHEAD OF THE COLD
FRONT /ESPECIALLY OVER THE MID ATLANTIC REGION/ WITH WIDESPREAD
AREAS OF CLOUD COVER/PRECIPITATION IMPACTING THE DEGREE OF
SUBSEQUENT DESTABILIZATION PERHAPS INTO THE AFTERNOON.
HOWEVER...THERE WILL LIKELY BE REGIONS OF ENHANCED HEATING THAT DO
OCCUR WITH MLCAPE OF 1500-2500 J/KG DEVELOPING WHICH WILL BE
SUPPORTIVE OF STRONGER STORMS ALONG/AHEAD OF THE COLD FRONT.
ALTHOUGH THE STRENGTH OF FLOW ALOFT/VERTICAL SHEAR IS EXPECTED TO BE
MARGINAL WITH 0-6 KM SHEAR GENERALLY LESS THAN 20-25 KT...THE THREAT
FOR ISOLATED SEVERE STORMS WILL EXIST.
...NRN INTERMOUNTAIN REGION...
UPPER FLOW IS FORECAST TO BACK AND INCREASE IN SPEED TOMORROW AS THE
UPPER LOW MOVES SEWD TOWARD THE NRN/CENTRAL CA COAST. THIS WILL
RESULT IN THE DEVELOPMENT OF WIND PROFILES SUPPORTIVE OF ORGANIZED
CONVECTION WITH DEEP LAYER SHEAR OF 40-50 KT IN THE LOWEST 6 KM.
SATELLITE IMAGERY/BLENDED TPW ANALYSES INDICATE MID LEVEL MOISTURE
IS INCREASING INTO THE PACIFIC NW COASTAL AREA WITH GPS IPW GREATER
THAN 1 INCH ATTM. THIS MOISTURE IS EXPECTED TO OVERSPREAD PARTS OF
THE NRN INTERMOUNTAIN REGION TOMORROW AND INCREASE POTENTIAL FOR
THUNDERSTORM DEVELOPMENT. MODEL FORECAST SOUNDINGS INDICATE A
MODERATELY DEEP PBL WILL DEVELOP DURING THE AFTERNOON AND EVENING
WITH THREAT FOR HAIL AND STRONG WIND GUSTS WITH A FEW STORMS.
..WEISS.. 06/27/2011
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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