Saturday, October 3, 2009

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 031929
SWODY1
SPC AC 031925

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0225 PM CDT SAT OCT 03 2009

VALID 032000Z - 041200Z

...NO SVR TSTM AREAS FORECAST...

TWO CHANGES ARE MADE FOR THE 20Z OUTLOOK. THE FIRST IS TO EXTEND THE
SEE TEXT AREA FURTHER EAST TO THE HOUSTON/GALVESTON AREA ADDING A 2
PERCENT TORNADO FOR THE TX COASTAL PLAINS. THE WSR-88D VWP OUT OF
HOUSTON SHOWS SUBSTANTIAL DIRECTIONAL SHEAR SUGGESTING SOME OF THE
STORMS COULD ROTATE MOVING EWD ALONG A STRONG GRADIENT OF
INSTABILITY THIS AFTERNOON. THE SECOND AREA TO BE ADJUSTED IS IN THE
HUDSON RIVER VALLEY. MOVED THE SEE TEXT CORRIDOR SLIGHTLY TO THE
EAST TO ALIGN BETTER WITH AN AXIS OF MODERATE INSTABILITY ANALYZED
BY THE LATEST RUC MODEL. THUNDERSTORMS ARE FORECAST TO DEVELOP THIS
AFTERNOON ACROSS FAR ERN PA...NJ...SE NY AND PARTS OF SRN NEW
ENGLAND. THE SHEAR ENVIRONMENT ON THE NEW YORK CITY/UPTON WSR-88D
VWP SUGGESTS A FEW STORMS COULD ROTATE AND CONTAIN A MARGINAL THREAT
FOR DAMAGING WIND GUSTS.

..BROYLES.. 10/03/2009

.PREV DISCUSSION... /ISSUED 1049 AM CDT SAT OCT 03 2009/

...NERN STATES...
WV IMAGERY INDICATES SHORTWAVE TROUGH/SPEED MAXIMA ROTATING RAPIDLY
ENEWD AROUND BASE OF LARGER UPPER LOW AND ACROSS THE UPPER OH RIVER
VALLEY EARLY THIS AFTERNOON. MODELS CONTINUE TO SUGGEST A WEAK
SURFACE LOW EVOLVING NEAR LEE TROUGH OVER ERN PA IN RESPONSE TO THIS
IMPULSE THIS AFTERNOON. VISIBLE IMAGERY INDICATES MUCH OF NEW
ENGLAND WILL BE SLOW TO RECOVER THIS AFTERNOON...ALTHOUGH JUST WEST
OF THIS BAND OF LOW CLOUDS HEATING SHOULD SUPPORT MARGINAL
INSTABILITY / MLCAPE AOB 500 J/KG /. REGION WILL BE SKIRTED BY
EJECTING IMPULSE OVER THE LOWER LAKES AND SUFFICIENT LOW LEVEL
CONVERGENCE SHOULD BE IN PLACE FOR A BROKEN LINE OF LOW-TOPPED TSTMS
NEAR THE LEE TROUGH FROM FAR NERN MD ACROSS ERN PA AND INTO ERN NY
DURING THE MID TO LATE AFTERNOON. LARGE HODOGRAPHS UNDER STRONG
WSWLY FLOW ALOFT SHOULD BE SUFFICIENT FOR SOME BOWING/
ORGANIZATION...ALONG WITH EMBEDDED UPDRAFT ROTATION...WITH THE
STRONGER STORMS. DESPITE THE STRENGTH OF SHEAR...WILL MAINTAIN LOW
SEVERE PROBABILITIES GIVEN THE RELATIVELY WEAK INSTABILITY/LAPSE
RATES EXPECTED. ADDITIONAL DEVELOPMENT CAN BE EXPECTED TO PERSIST
OFF THE ATLANTIC WITHIN DEEP MOISTURE PLUME THROUGH TONIGHT WHICH
WILL SHIFT NNEWD ACROSS SERN NEW ENGLAND... HOWEVER SEVERE POTENTIAL
WITH THIS ACTIVITY SHOULD REMAIN LIMITED.


...TX...
STALLED SURFACE BOUNDARY OVER THE SRN TIP OF TX SHOULD REMAIN IN
PLACE FOR MUCH OF THE DAY...WITH SECONDARY FRONT PERSISTING ALONG
THE RED RIVER. VERY UNSTABLE CONDITIONS ARE EXPECTED OVER FAR SRN
TX WITHIN MOIST WARM SECTOR...ALTHOUGH CAPPING MAY PRECLUDE EWD
MOVING...ELEVATED STORMS OVER SRN/CENTRAL TX FROM TAPPING THIS
RESERVOIR OF INSTABILITY. HOWEVER...MODEST WLY FLOW ALOFT COULD
SUPPORT SOME ORGANIZATION WITH PERSISTENT UPDRAFTS AND WILL OPT TO
MAINTAIN LOW SEVERE PROBABILITIES ACCORDINGLY. MORE WIDESPREAD
DEVELOPMENT WILL OCCUR WITHIN BROAD LOW LEVEL WAA REGIME ACROSS
CENTRAL TX THROUGH TODAY...WITH INCREASED WAA AND ELEVATED TSTM
DEVELOPMENT EXPECTED THROUGH TONIGHT INTO N-CENTRAL/NERN TX AND SRN
OK. SOME HAIL COULD ACCOMPANY THIS LATE NIGHT ACTIVITY INTO THE RED
RIVER VALLEY...ALTHOUGH ACTIVITY SHOULD MAINLY EVOLVE AS MODERATE TO
HEAVY RAIN GIVEN FAIRLY WARM MID LEVEL TEMPERATURES AND DEEP
MOISTURE/WEAK LAPSE RATES.

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