SWODY2
SPC AC 170538
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1238 AM CDT SUN AUG 17 2008
VALID 181200Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS UPSTATE NY TO NRN ME...
...UPSTATE NY...NRN VT/NH/ME...
LATEST SHORT RANGE MODEL GUIDANCE CONTINUES EARLIER TRENDS OF
DIGGING UPPER SHORTWAVE TROUGH ACROSS ONTARIO INTO QUEBEC/NEW
ENGLAND BY THE END OF THE PERIOD. THIS FEATURE WILL PRIMARILY
INFLUENCE CONVECTIVE DEVELOPMENT ACROSS SRN ONTARIO...NEWD ALONG THE
ST. LAWRENCE RIVER VALLEY OF CANADA THROUGH MID AFTERNOON AS SFC
FRONT IS NOT EXPECTED TO SURGE INTO NY/VT UNTIL AROUND 19/00Z...THEN
SEWD ACROSS THE REST OF NEW ENGLAND BY 12Z. BY LATE AFTERNOON IT
APPEARS A WELL DEVELOPED SQUALL LINE SHOULD BE ONGOING ALONG
STRONGLY FORCED FRONTAL BOUNDARY OVER SERN CANADA. THIS ACTIVITY
WILL EASILY SPREAD ACROSS SLIGHT RISK AREA OF NY INTO NRN ME AS DEEP
WLY FLOW WILL ENSURE A RELATIVELY STEEP LAPSE RATE ENVIRONMENT AND
MODEST INSTABILITY WELL INTO THE EVENING HOURS. GFS FORECAST
SOUNDINGS EXHIBIT CONSIDERABLY MORE INSTABILITY THAN THE LATEST NAM
GUIDANCE...ESPECIALLY ON THE CANADIAN SIDE OF THE BORDER WHERE
MLCAPE VALUES ARE PROGGED TO BE ON THE ORDER OF 2500 J/KG. IF THIS
AIRMASS EVOLVES AS GFS SUGGESTS THEN A FAIRLY STRONG/ORGANIZED
SQUALL LINE WILL PROPAGATE CONSIDERABLY FARTHER SOUTHEAST ACROSS NY
INTO ME THAN CURRENTLY OUTLOOKED. DAMAGING WINDS AND HAIL CAN BE
EXPECTED WITH THIS ACTIVITY...MAINLY AFTER 00Z.
...FL...
TROPICAL STORM FAY IS FORECAST TO CROSS THE FL STRAIGHTS AND
APPROACH THE WCNTRL COAST OF FL NEAR TPA BY 19/12Z. NEEDLESS TO SAY
ANY INTENSIFICATION WILL RESULT IN INCREASED SHEAR AND AT LEAST SOME
THREAT FOR ISOLATED TORNADOES ACROSS THE SRN HALF OF THE STATE.
...SERN NM/WEST TX...
UPPER LOW WILL GRADUALLY SAG SEWD ACROSS NWRN TX OVER THE NEXT FEW
DAYS...WELL REMOVED FROM STRONGER FLOW ALONG THE U.S./CANADIAN
BORDER. STRONGEST MID LEVEL FLOW WILL REMAIN ON BACK SIDE OF THIS
FEATURE ACROSS NM INTO WEST TX WHERE SUFFICIENT NWLY FLOW SHOULD
ENHANCE ORGANIZATIONAL POTENTIAL OF ANY THUNDERSTORMS THAT MANAGE TO
DEVELOP ACROSS THIS REGION. HAIL AND GUSTY WINDS MAY ACCOMPANY THE
STRONGER STORMS.
...PACIFIC NW...
FAIRLY IMPRESSIVE UPPER TROUGH WILL APPROACH THE PACIFIC COAST
DURING THE DAY2 PERIOD. IN ADVANCE OF THIS FEATURE IT APPEARS A
WEAK SHORTWAVE WILL EJECT NEWD ACROSS WA/ORE INTO SERN BC. THIS
LEAD FEATURE WILL ENHANCE LARGE SCALE ASCENT ACROSS INTERIOR WA AS
TIGHTENING BAROCLINIC ZONE FOCUSES EAST OF THE CASCADES WHERE STRONG
HEATING IS EXPECTED. FORECAST SOUNDINGS SUGGEST SHEAR PROFILES WILL
BE MORE THAN ADEQUATE FOR DEEP ROTATING STORMS. THE MAIN QUESTION
AT THIS TIME IS HOW MUCH MOISTURE/INSTABILITY CAN DEVELOP/HOLD
ACROSS THIS REGION. THERE IS REASON TO BELIEVE SUFFICIENT
INSTABILITY WILL EXIST FOR HIGH BASED SUPERCELLS...ESPECIALLY NEAR
THE CANADIAN BORDER. A SLIGHT RISK MAY BE NEEDED ACROSS THIS
REGION...ESPECIALLY IF IT BECOMES MORE EVIDENT THAT MOISTURE WILL
CONTRIBUTE TO SUPERCELL DEVELOPMENT.
..DARROW.. 08/17/2008
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