Thursday, September 16, 2010

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 160555
SWODY1
SPC AC 160553

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1253 AM CDT THU SEP 16 2010

VALID 161200Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE TX PANHANDLE AND FAR
WRN OK...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE OH AND
TN VALLEYS...

...SYNOPSIS...
AN UPPER SHORTWAVE TROUGH AND SURFACE LOW WILL TRACK FROM THE UPPER
MS VALLEY EARLY THIS MORNING EWD ACROSS THE OH VALLEY AND INTO THE
LOWER GREAT LAKES REGION BY LATE AFTERNOON. A SURFACE PRESSURE
TROUGH AND COLD FRONT WILL EXTEND SWWD FROM LAKE ERIE INTO THE MID
MS VALLEY BY 00Z...WITH BROAD SWLY LOW LEVEL PRECEDING THIS FRONT
AND HELPING TO BRING MOISTURE INTO THE REGION. FARTHER E...A WARM
FRONT WILL DEVELOP FROM ERN PA/NJ INTO SRN NEW ENGLAND...AS A MORE
HUMID AIR MASS FROM THE MID ATLANTIC AREA ATTEMPTS TO MOVE INLAND
LATER TODAY. THE AFOREMENTIONED COLD FRONT WILL BE THE PRIMARY FOCUS
FOR SEVERE THUNDERSTORMS TODAY IN THIS REGION.

TO THE W...A STATIONARY FRONT WILL LIE FROM NW-SE FROM THE OK/TX
PANHANDLES INTO CNTRL OK BY AFTERNOON WITH ONLY A WEAK DIURNALLY
DRIVEN SURFACE TROUGH OVER THE CNTRL/SRN HIGH PLAINS BY PEAK
HEATING. STRONG HEATING NEAR THIS BOUNDARY WILL FOCUS STORM
DEVELOPMENT LATER TODAY BENEATH A GENERALLY NEUTRAL NW FLOW REGIME
ALOFT.

...OH AND TN VALLEYS EWD INTO SRN NEW ENGLAND...
PRECIPITATION IS EXPECTED TO BE ONGOING ACROSS MUCH OF SRN MO AND IL
ALONG/AHEAD OF THE COLD FRONT AND IN A ZONE OF BROAD LOW LEVEL WARM
ADVECTION. DESPITE SOME CLOUDINESS...GRADUAL DESTABILIZATION IS
LIKELY WITH AROUND 1000 J/KG MUCAPE AHEAD OF THE FRONT BY AFTERNOON.
SWLY FLOW AND MIXING MAY EVENTUALLY RESULT IN A PLUME OF STEEPER LOW
LEVEL LAPSE RATES OUT OF THE LOWER MS VALLEY NEWD ALONG THE OH RIVER
WHICH WILL HELP TO INITIATE STORMS. STRONG AND MAINLY UNIDIRECTIONAL
WIND SHEAR PROFILES WILL FAVOR SUPERCELLS...SOME SPLITTING. MODELS
INDICATE A RELATIVE MAX IN LOW LEVEL VEERING/SHEAR OVER ERN KY...SRN
OH AND WRN WV. HERE...RIGHT MOVING SUPERCELLS WILL HAVE A BETTER
CHANCE AT PRODUCING AN ISOLATED TORNADO. ALTHOUGH TEMPERATURES ALOFT
ARE NOT EXCEPTIONALLY COOL...SUPERCELLULAR STORM MODE WILL MAXIMIZE
HAIL POTENTIAL.

FARTHER E...VERY LITTLE INSTABILITY WILL EXIST OVER MUCH OF CNTRL PA
EWD...WHERE CLOUDS AND RAIN WILL DEVELOP DURING THE DAY.
STILL...VERY STRONG SHEAR PROFILES WILL BE IN PLACE AND MAY ALLOW
FOR SMALL BOW ECHOES TO TRAVEL EWD ACROSS PA WITH A THREAT OF AT
LEAST ISOLATED DAMAGING WINDS GUSTS.

FINALLY...MODELS INDICATE LOW LEVEL MOISTURE WILL RETURN NWD ALONG
THE E COAST AND INTO SRN NEW YORK AND NEW ENGLAND BY LATE IN THE
DAY. GIVEN THAT THE MOISTURE PLUME IS LIKELY TO BE MODIFIED AS IT
ADVECTS NWD AROUND THE ATLANTIC SURFACE HIGH...SOME MIXING IS
EXPECTED AS THE HIGHER DEWPOINTS MAKE IT INLAND...AND THIS WILL
AFFECT INSTABILITY LEVELS. THE HIGHER THREAT OF SEVERE WEATHER WILL
BE AS THE MAIN SURFACE LOW TREKS EWD ACROSS THE REGION AFTER ABOUT
03Z...WHERE STRONG FORCING AND SHEAR PROFILES WILL COMBINE WITH THE
NEWLY ADVECTED MOISTURE TO ENHANCE DAMAGING WIND AND ISOLATED
TORNADO POTENTIAL. GIVEN UNCERTAINTIES WITH LOW LEVEL LAPSE RATES
AND OVERALL INSTABILITY FIELDS...WILL KEEP THIS AREA JUST BELOW
SLIGHT RISK THRESHOLDS WITH POSSIBLE UPGRADE IN SUBSEQUENT OUTLOOKS.


...SRN PLAINS INCLUDING THE TX PANHANDLE AND WRN OK...
A STATIONARY FRONT WILL LIE ACROSS CNTRL OK INTO THE TX PANHANDLE
TODAY WITH A MOIST AND UNSTABLE AIR MASS TO THE S. STRONG HEATING S
OF THIS BOUNDARY WILL COMBINE WITH RELATIVELY STEEP MID/UPPER LEVEL
LAPSE RATE PROFILES TO PRODUCE 2000-3000 J/KG MUCAPE BY LATE
AFTERNOON. OVERALL FORCING FOR THIS EVENT WILL BE SUBTLE AS LOW
LEVEL FLOW WILL LARGELY BE PARALLEL TO THE SURFACE FRONT.
HOWEVER...STRONG HEATING/LOW LEVEL LAPSE RATE PROFILES AND MOIST
SELY LOW LEVEL FLOW SHOULD EVENTUALLY RESULT IN TCU FIELDS WITH
SCATTERED STORMS DEVELOPING. DEEP LAYER FLOW FIELDS WILL BE
SUFFICIENT FOR A FEW LONGER LIVED STORMS INCLUDING SOME SUPERCELLS
ESPECIALLY ALONG THE FRONT WHERE LOW LEVEL SHEAR WILL BE MAXIMIZED.
ALSO...DAMAGING DOWNBURSTS WILL BE POSSIBLE MAINLY ON A LOCALIZED
LEVEL AS STORMS WILL MOVE QUITE SLOWLY. BY EVENING...A
STRENGTHENING LOW LEVEL JET WILL RESULT IN ISENTROPIC LIFT WHICH MAY
BE SUFFICIENT FOR ISOLATED ELEVATED HAIL STORMS OVER FAR SRN KS.

..JEWELL/GARNER.. 09/16/2010

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