SWODY2
SPC AC 291716
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1216 PM CDT MON JUN 29 2009
VALID 301200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF MT INTO THE
CENTRAL HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN NY AND WRN PARTS OF
NEW ENGLAND...
...SYNOPSIS...
LARGELY STAGNANT UPPER FLOW PATTERN IS FORECAST TO CONTINUE TOMORROW
AS A STRONG UPPER LOW REMAINS OVER THE GREAT LAKES REGION AND UPPER
RIDGE IS ESTABLISHED OVER THE FOUR-CORNERS AREA. HEIGHTS ARE
FORECAST TO FALL ACROSS THE NRN INTERMOUNTAIN/NRN ROCKIES AREA AS A
SHORT WAVE TROUGH PROGRESSES ESEWD ACROSS BC.
AT THE SURFACE...AN OCCLUDED LOW WILL REMAIN OVER THE GEORGIAN BAY
AREA...WITH A FRONT ARCING SEWD INTO A SECONDARY LOW OVER SERN
NY...THEN CONTINUING SWWD INTO THE CENTRAL APPALACHIANS. A WARM
FRONT WILL EXTEND ESEWD FROM THE NY LOW ACROSS SRN NEW ENGLAND INTO
THE ATLANTIC.
A WEAK COLD FRONT WILL MOVE EWD ACROSS THE NRN INTERMOUNTAIN REGION
INTO A LOW OVER CNTRL/ERN MT. A WARM FRONT WILL EXTEND SSEWD FROM
THE MT LOW ACROSS THE HIGH PLAINS INTO THE SRN PLAINS....CONTINUING
EWD AS A QUASI-STATIONARY FRONT ACROSS THE CENTRAL/ERN GULF COAST
AND NRN FL.
...ERN NY/WRN NEW ENGLAND...
SYNOPTIC PATTERN IS FAVORABLE FOR STRONG CONVECTION TO
DEVELOP...ESPECIALLY DURING THE AFTERNOON WHEN DIURNAL HEATING WILL
BE MAXIMIZED. SURFACE DEW POINTS ARE FORECAST TO BE IN THE 60S
WITHIN THE WARM SECTOR AND ALONG THE OCCLUDED FRONT IN ERN NY...AND
WHEN COUPLED WITH RELATIVELY COOL MID LEVEL TEMPERATURES ATTENDING
THE UPPER LOW /-11 TO -13C AT 500 MB/...SHOULD RESULT IN AN UNSTABLE
ENVIRONMENT WITH MLCAPE REACHING 1000-1500 J/KG.
12Z NAM AND GFS INDICATE A SHORT WAVE TROUGH WILL ROTATE ACROSS THE
OH VALLEY AND MID ATLANTIC STATES DURING THE AFTERNOON AND
EVENING...PROVIDING INCREASING DYNAMIC SUPPORT FOR LARGE SCALE
ASCENT OVER THE SLIGHT RISK AREA. SWLY/SLY MID LEVEL WINDS OF 30-40
KT AND RESULTANT DEEP LAYER SHEAR AOA 30 KT WILL PROMOTE DEVELOPMENT
OF ORGANIZED CONVECTIVE STRUCTURES...INCLUDING SMALL-SCALE BOW
SYSTEMS. THERE WILL BE POTENTIAL FOR STRONGER STORMS TO PRODUCE
DAMAGING WIND GUSTS AND HAIL /MAINLY DURING THE AFTERNOON AND
EVENING/.
...MT INTO NRN HIGH PLAINS...
PERSISTENT SYNOPTIC SCALE MID-LEVEL UPWARD MOTION IN ADVANCE OF THE
BC SHORT WAVE IS EXPECTED TO GRADUALLY MOISTEN THE VERTICAL PROFILES
OVER PARTS OF MT...RESULTING IN INVERTED-V SOUNDINGS WITH DEEP
SURFACE-BASED MIXED LAYER STRUCTURES. WIDELY SCATTERED HIGH-BASED
THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER CENTRAL MT DURING THE
AFTERNOON IN ADVANCE OF THE APPROACHING SHORT WAVE TROUGH...AND MOVE
EWD WITHIN BAND OF 40-45 KT WLY MID LEVEL WINDS REACHING ERN MT BY
THE EVENING. SUFFICIENT DEEP LAYER SHEAR COUPLED WITH STEEP LAPSE
RATES WILL ENHANCE DOWNDRAFT STRENGTH WITH RESULTANT THREAT FOR A
FEW MICROBURSTS.
AN AXIS OF LOW LEVEL MOISTURE WITH SURFACE DEW POINTS IN THE 50S IS
EXPECTED TO EXTEND FROM ERN MT SSEWD INTO THE CENTRAL HIGH PLAINS.
SELY UPSLOPE LOW LEVEL FLOW COINCIDENT WITH NARROW N/S INSTABILITY
AXIS WILL SUPPORT DEVELOPMENT OF SCATTERED THUNDERSTORMS DURING THE
LATE AFTERNOON AND EVENING. PRONOUNCED DIRECTIONAL SHEAR /WINDS VEER
FROM A SELY DIRECTIONAL IN THE LOW LEVELS TO NWLY FLOW IN THE MID
LEVELS/ WILL ENHANCE STORM ORGANIZATION AND INTENSITY WITH POTENTIAL
FOR A FEW SUPERCELLS TO DEVELOP.
...CENTRAL HIGH PLAINS INTO THE SRN ROCKIES AREA...
STEEP MID LEVEL LAPSE RATES WILL PERSIST OVER THIS AREA...AND
DIURNAL HEATING WILL ENHANCE LOW LEVEL LAPSE RATES DURING THE
AFTERNOON AND EVENING. HIGH-BASED STORMS ARE EXPECTED TO DEVELOP
ACROSS THIS AREA WITH POTENTIAL TO PRODUCE A FEW
MICROBURSTS...ALTHOUGH WEAK WINDS ALOFT AND MINIMAL VERTICAL SHEAR
SHOULD LIMIT OVERALL SEVERE THREAT.
...FL PENINSULA...
SWLY FLOW IS FORECAST TO PERSIST ACROSS PARTS OF FL TOMORROW...WITH
ANOMALOUSLY STRONG LOW LEVEL SHEAR PREDICTED IN ASSOCIATION WITH
25-35 KT FLOW AT 850 MB. HIGH PRECIPITABLE WATER VALUES AOA 2
INCHES ARE EXPECTED TO CONTINUE WITH POTENTIAL FOR WET MICROBURSTS
TO DEVELOP...MAINLY OVER INTERIOR AND ERN PARTS OF THE PENINSULA.
..WEISS.. 06/29/2009
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