SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT THU JUL 26 2012
VALID 262000Z - 271200Z
...THERE IS A MDT RISK OF SVR TSTMS FOR SRN OH...NRN
WV/MD/DE...PA...NJ...SERN NY...CT...WRN MA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE WRN GREAT LAKES/MID-MS
VALLEY TO THE MID-ATLANTIC/SRN NEW ENGLAND...
...WIDESPREAD DAMAGING WIND EVENT/POTENTIAL DERECHO APPEAR TO BE
UNFOLDING ACROSS PARTS OF THE NORTHEAST...
...OH TO SRN NEW ENGLAND...
ADJUSTED MODERATE RISK TO ALONG AND AHEAD OF INITIAL QLCS IN SWRN NY
TO ERN OH AND UPSTREAM DEVELOPMENT OCCURRING BACK IN WRN OH.
ALTHOUGH SEVERE WIND GUSTS HAVE YET TO BE MEASURED BY ANY ASOS/AWOS
OBSERVATIONS...50-55 KT EWD MOVEMENT HAS BEEN NOTED WITH THIS
INITIAL LINE AND 18Z PIT/OKX RAOBS ARE CERTAINLY SUPPORTIVE OF FAST
ELY PROPAGATION. CONSIDERED UPGRADE TO HIGH RISK BUT RELATIVELY
MODEST MID/HIGH-LEVEL LAPSE RATES SAMPLED IN REGIONAL 18Z RAOBS
SUGGEST MODERATE RISK APPEARS MOST APPROPRIATE ATTM.
NEVERTHELESS...NUMEROUS TO WIDESPREAD COVERAGE OF DAMAGING WINDS IS
LIKELY AS THE NUMBER OF BOWING SEGMENTS INCREASE WITH AN ASSOCIATED
THREAT OF ISOLATED INTENSE WIND DAMAGE AND BRIEF TORNADOES.
...SRN PLAINS TO MID-MS AND TN VALLEYS...
ADJUSTED SLIGHT RISK SEWD INTO THE TN VALLEY AND ENHANCED WIND
PROBABILITIES AS TSTMS WILL CONTINUE TO INCREASE FROM THE OZARK
PLATEAU TO THE LOWER OH VALLEY. ALTHOUGH ON THE FRINGE OF STRONGER
WLYS...HOT TEMPERATURES AND LARGE BUOYANCY SHOULD RESULT IN
STRENGTHENING COLD POOLS. THIS SHOULD LEAD TO PROBABLE MCS
DEVELOPMENT AND PROPAGATION SHOULD TEND TOWARDS THE TN VALLEY.
...WI AREA...
SEE PREVIOUS OUTLOOK DISCUSSION.
..GRAMS.. 07/26/2012
.PREV DISCUSSION... /ISSUED 1130 AM CDT THU JUL 26 2012/
...SYNOPSIS...
FAST ZONAL FLOW ALOFT CURRENTLY STRETCHES FROM THE MIDWEST INTO THE
NERN STATES...WITH AN EMBEDDED LOW AMPLITUDE SHORTWAVE TROUGH
CURRENTLY DEVELOPING FROM MI INTO IL. AT THE SURFACE...VERY UNSTABLE
AIR RESIDES SE OF A DIFFERENTIAL HEATING ZONE LEFT OVER FROM MORNING
CONVECTION...EXTENDING FROM SRN IL NEWD ACROSS NRN IND AND OH. TO
THE NE...A MORE SUBSTANTIAL OUTFLOW BOUNDARY REMAINS ACROSS CNTRL PA
INTO NJ...BUT HEATING WILL CONTINUE N OF THE BOUNDARY INTO SRN
NY...AND JUST S OF ANOTHER DIFFERENTIAL HEATING BOUNDARY ROUGHLY
FROM SYRACUSE TO ALBANY. WSWLY LOW LEVEL FLOW AND HEATING SHOULD
HELP ERODE CLOUDS AND ALLOW FOR A RETURN OF WARM AND UNSTABLE AIR
NWD ACROSS PA...SRN NY...AND EVENTUALLY SRN NEW ENGLAND LATER
TODAY...PROVIDING A FAVORABLE ENVIRONMENT FOR SEVERE STORM
MAINTENANCE.
ELSEWHERE...THE SWRN PORTION OF THIS UPPER SHORTWAVE TROUGH WILL
EXTEND SWWD ACROSS THE MID MS VALLEY WITH SEVERE STORMS POSSIBLE AS
FAR SW AS OK.
...INDIANA NEWD INTO SRN NEW ENGLAND...
STRONG HEATING WILL PERSIST OVER MUCH OF THE REGION...WITH SEVERE
THUNDERSTORM DEVELOPMENT LIKELY TO INITIATE FROM WRN PA SWWD ACROSS
OH AND IND BY EARLY/MID AFTERNOON. INITIATION WILL FURTHER BE
ENHANCED BY SEVERAL VORTICITY MAXIMA MOVING THROUGH THE FLOW. MUCAPE
IN EXCESS OF 3000 J/KG...ALONG WITH 40+ KT LOW TO MIDLEVEL MEAN
WINDS...SHOULD ALLOW FOR RAPID UPSCALE GROWTH OF AND MERGING OF
DEVELOPING STORM CELLS INTO LINES CAPABLE OF DAMAGING WINDS AND
HAIL. AS THESE STORMS CONTINUE EWD ACROSS THE PA/NEW ENGLAND SFC
BOUNDARIES...THEY MAY EXHIBIT ROTATION WITH PARTICULARLY DAMAGING
SWATHS OF WINDS ESPECIALLY WITH ANY BOWHEAD/MESO-LOW.
...ERN LOWER MI EWD ACROSS SWRN ONTARIO AND INTO NY...
WHILE THE PRIMARY MCS DEVELOPS TO THE S...SUBSTANTIAL MOISTURE WILL
REMAIN OVER LOWER MI EWD INTO THE LOWER GREAT LAKES...WITH PWAT IN
EXCESS OF 1.75 INCHES. FLOW ALOFT AND SHEAR WILL REMAIN FAVORABLE
FOR SEVERE STORMS HERE AS WELL...BUT THE MAIN QUESTION IS COVERAGE.
IF POCKETS OF INSTABILITY CAN DEVELOP...THEN ADDITIONAL ISOLATED
SEVERE STORMS MAY OCCUR MAINLY LATE IN THE DAY.
...SRN PLAINS TO MID MS VALLEY TODAY...
THE COMPOSITE OUTFLOW BOUNDARY GENERATED BY OVERNIGHT CONVECTION
CONTINUES TO MOVE SEWD INTO CENTRAL OK/MO/IL...JUST NW OF I-44.
THOUGH THE SYNOPTIC COLD FRONT IS LOCATED FARTHER TO THE
NW...LINGERING CLOUDS SUGGEST THAT THE GREATER RISK FOR ISOLATED
SEVERE STORMS WILL BE FOCUSED ALONG THE INITIAL WIND SHIFT AND
DIFFERENTIAL HEATING ZONE. DEEP-LAYER UNIDIRECTIONAL WIND PROFILES
WILL WEAKEN WITH SWWD EXTENT FROM IL TO OK...SUGGESTING THAT
MULTICELL CLUSTERS WILL BE MORE PREVALENT TOWARD IL...AND PULSE-TYPE
STORMS ALONG THE WIND SHIFT INTO OK. MODEST MIDLEVEL LAPSE RATES
AND INVERTED-V PROFILES WILL FAVOR DAMAGING OUTFLOW GUSTS AS THE
PRIMARY SEVERE RISK THIS AFTERNOON/EVENING.
...WI AREA THIS AFTERNOON...
RESIDUAL BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 60S AND CLEARING
OF CONVECTIVE DEBRIS CLOUDS WILL ALLOW DESTABILIZATION ACROSS
CENTRAL WI BY AFTERNOON. THE DESTABILIZATION WILL COINCIDE WITH THE
PASSAGE OF THE SOMEWHAT DIFFUSE SYNOPTIC COLD FRONT AND THE APPROACH
OF THE BAND OF LOW-MIDLEVEL ASCENT PRECEDING THE SHORTWAVE TROUGH.
GIVEN MLCAPE IN THE 1000-2000 J/KG RANGE AND STRAIGHT HODOGRAPHS
WITH 30-40 KT EFFECTIVE BULK SHEAR...A FEW ORGANIZED STORMS WILL BE
POSSIBLE WITH AN ATTENDANT RISK FOR ISOLATED LARGE HAIL AND DAMAGING
WINDS.
Read more
via SPC Convective Outlooks http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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