SPC Jul 27, 2012 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1153 PM CDT THU JUL 26 2012

VALID 271200Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SERN
STATES INTO THE MID ATLANTIC...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE OHIO
VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE NRN HIGH
PLAINS...

...SYNOPSIS...

ERN U.S. SYNOPTIC TROUGH WILL UNDERGO FURTHER AMPLIFICATION AS VORT
MAX OVER NWRN WI MOVES INTO THE LOWER GREAT LAKES. FARTHER WEST AN
UPSTREAM RIDGE WILL PERSIST OVER THE CNTRL AND NRN ROCKY MOUNTAIN
REGION...WHILE AN UPPER TROUGH WITH EMBEDDED VORTICITY MAXIMA MOVES
FARTHER INLAND ALONG THE WRN U.S. COAST. A COLD FRONT WILL ADVANCE
SEWD THROUGH THE GREAT LAKES AND OH VALLEY IN ASSOCIATION WITH THE
PROGRESSIVE VORT MAX. A CONVECTIVELY REINFORCED FRONT WILL PERSIST
FROM SRN NEW ENGLAND SWWD INTO THE TN AND LOWER MS VALLEY. THIS
BOUNDARY MAY SHIFT SLOWLY SEWD DURING THE DAY. 

...MID ATLANTIC THROUGH A PORTION OF THE SERN STATES...

CONVECTIVE OUTFLOW BOUNDARY WILL LIKELY EXTEND FROM MID ATLANTIC
AREA SWWD INTO NRN PARTS OF THE SERN STATES FRIDAY MORNING. WITH
RICH LOW LEVEL MOISTURE IN PLACE ACROSS WARM SECTOR...ATMOSPHERE
WILL LIKELY BECOME MODERATELY UNSTABLE AS DIABATIC WARMING COMMENCES
WITH MLCAPE FROM 2000-3000 J/KG. STORMS ARE EXPECTED TO REDEVELOP
ALONG RESIDUAL OUTFLOW BOUNDARIES AND IN WARM SECTOR FROM VA SWWD
THROUGH THE CAROLINAS INTO NRN PARTS OF THE SERN STATES. THIS REGION
WILL REMAIN SOUTH OF THE STRONGER FLOW ALOFT ASSOCIATED WITH THE
AMPLIFYING UPPER TROUGH WITH VERTICAL SHEAR PROFILES SUPPORTIVE OF
MULTICELLS. STEEPENING LOW LEVEL LAPSE RATES AND MODERATE
INSTABILITY WILL PROMOTE A THREAT OF ISOLATED STRONG TO LOCALLY
DAMAGING WIND GUSTS DURING THE AFTERNOON. 

...OH VALLEY AREA...

DEWPOINTS REMAIN IN THE 60S OVER THE OH VALLEY AND WILL SUPPORT
MODERATE INSTABILITY AS THE BOUNDARY LAYER WARMS. MLCAPE WILL BE
TEMPERED SOMEWHAT BY MODEST MID LEVEL LAPSE RATES WITH VALUES
GENERALLY AOB 1500 J/KG. SCATTERED STORMS SHOULD REDEVELOP ALONG AND
AHEAD OF FRONT AND WITHIN ZONE OF DEEPER ASCENT ASSOCIATED WITH SEWD
MOVING VORT MAX. FLOW IN THE SFC-700 MB LAYER IS FORECAST TO REMAIN
RELATIVELY WEAK...BUT 500 MB WINDS WILL STRENGTHEN TO AROUND 40 KT
OVER NRN PARTS OF OH VALLEY AS UPPER TROUGH AMPLIFIES. THIS
ENVIRONMENT WILL REMAIN GENERALLY SUPPORTIVE OF MULTICELLS WITH A
THREAT FOR PRIMARILY ISOLATED STRONG TO DAMAGING WIND GUSTS AS LOW
LEVEL LAPSE RATES STEEPEN. 

...NRN HIGH PLAINS...

BOUNDARY LAYER DEWPOINTS IN THE UPPER 40S TO LOW 50S WILL RESIDE IN
THIS REGION BENEATH PLUME OF STEEP MID LEVEL LAPSE RATES RESULTING
IN 1000-1200 MLCAPE AS THE SFC LAYER WARMS. AN IMPULSE IS FORECAST
TO MOVE OVER TOP OF UPPER RIDGE...WHICH IN CONJUNCTION WITH NEWD
ADVECTING SUBTROPICAL MOISTURE PLUME WILL LIKELY PROMOTE STORM
DEVELOPMENT OVER THE HIGHER TERRAIN OF WY...MT AND WRN SD. ACTIVITY
WILL SUBSEQUENTLY MOVE NEWD INTO THE HIGH PLAINS. STORMS WILL BE
HIGH BASED...BUT EFFECTIVE SHEAR WILL BE SUFFICIENT FOR SUPERCELLS
WITH LARGE HAIL AND ISOLATED DAMAGING WIND POSSIBLE THROUGH EARLY
EVENING. OVERNIGHT STORMS MAY CONSOLIDATE INTO AN MCS SUPPORTED BY
STRENGTHENING LLJ...BUT SEVERE THREAT WILL BECOME MARGINAL DUE TO
LIMITED INSTABILITY.

..DIAL/SMITH.. 07/27/2012

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