SWODY1
SPC AC 031628
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT WED JUN 03 2009
VALID 031630Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FROM
TN/KY EWD TO THE MID ATLANTIC...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR N/NE
CA...NW NV...AND SRN ORE...
...MID ATLANTIC WWD TO THE LOWER MS VALLEY TODAY...
A SERIES OF SPEED MAXIMA WILL PROGRESS EWD FROM THE UPPER GREAT
LAKES TO NRN NEW ENGLAND AROUND THE SRN PERIPHERY OF A BROAD UPPER
TROUGH OVER CENTRAL/ERN CANADA. IN THE WAKE OF THESE SPEED
MAXIMA...A SURFACE COLD FRONT WILL CONTINUE TO DRIFT SWD/SEWD ACROSS
THE VA-TN-AR-E TX CORRIDOR. S OF THE MAIN BELT OF WLYS...A WEAK MID
LEVEL TROUGH WILL DRIFT EWD OVER THE LOWER OH/MS VALLEYS. THIS
TROUGH IS QUITE COMPLEX WITH EMBEDDED MCV/S MOVING EWD FROM S
CENTRAL IL...ERN OK...AND E TX.
THE COLD FRONT IS NOW LOCATED ALONG THE SRN FRINGE OF THE 20-30 KT
WLY MID LEVEL FLOW FROM KY TO VA. SURFACE HEATING S OF THE FRONT
AND IN ADVANCE OF ONGOING THUNDERSTORM CLUSTERS IN KY WILL LEAD TO
THE DEVELOPMENT OF MODERATE INSTABILITY BY EARLY AFTERNOON /MLCAPE
VALUES ON THE ORDER OF 1500 J/KG/. THE COMBINATION OF MODERATE
INSTABILITY AND MODEST DEEP LAYER WLY FLOW WILL SUPPORT SEVERAL
MULTICELL CLUSTERS AND LINE SEGMENTS CAPABLE OF PRODUCING DAMAGING
WINDS...AIDED BY STEEP 0-3 KM AGL LAPSE RATES DURING THE AFTERNOON.
SEASONALLY COOL MID LEVEL TEMPERATURES /-10 TO -12 C AT 500 MB/ WITH
THE 1500 J/KG MLCAPE VALUES SUGGEST THAT THE STRONGER STORMS MAY
ALSO PRODUCE LARGE HAIL.
FARTHER W AND S...A FEW STORM CLUSTERS WILL LIKELY REFORM DURING THE
AFTERNOON IN ASSOCIATION WITH THE MCV/S MOVING SLOWLY EWD INTO WRN
AR AND E TX. HERE...DEEP LAYER FLOW WILL BE WEAKER COMPARED TO
AREAS FARTHER NE ALONG THE COLD FRONT...BUT SOMEWHAT LARGER
INSTABILITY /MLCAPE OF 2000-2500 J/KG/ WILL TEND TO COMPENSATE. THE
STRONGEST STORMS WILL BE CAPABLE OF PRODUCING DAMAGING DOWNBURST
WINDS AND ISOLATED LARGE HAIL.
...NRN CA/ORE THIS AFTERNOON/EVENING...
THE LARGE CLOSED LOW W OF CENTRAL CA WILL REMAIN QUASI-STATIONARY
THROUGH EARLY THURSDAY...THOUGH A PRONOUNCED SHORTWAVE TROUGH WILL
ROTATE NEWD AROUND THE ERN PERIPHERY OF THE LOW TODAY...TOWARD
CENTRAL/NRN CA AND W/NW NV. A PLUME OF UNUSUALLY RICH MOISTURE FOR
EARLY JUNE /PW VALUES OF 0.75-1 INCH/ WILL CONTINUE TO WRAP NWD/NWWD
AROUND THE MID LEVEL LOW...ACROSS NW NV/NRN CA INTO SRN ORE. A FEW
CLOUD BREAKS SHOULD ALLOW SOME SURFACE HEATING OVER THE ELEVATED
TERRAIN THIS AFTERNOON...WHERE MODIFIED 12Z SOUNDINGS SHOW THE
POTENTIAL FOR AFTERNOON MLCAPE VALUES OF 500-1000 J/KG. VERTICAL
SHEAR WILL BE SUFFICIENT FOR ORGANIZED MULTICELL CLUSTERS...AND
PERHAPS MARGINAL SUPERCELL STRUCTURES...IN THE EXIT REGION OF THE
MID-UPPER JET. ISOLATED LARGE HAIL AND DAMAGING WINDS WILL BE THE
PRIMARY SEVERE THREATS THIS AFTERNOON/EVENING.
...CO/NM FRONT RANGE THIS AFTERNOON/EVENING...
THE RECENT FRONTAL PASSAGE HAS STABILIZED MOST OF THE CENTRAL/SRN
HIGH PLAINS REGION AS A COOL AIR MASS SPREADS SWD/SWWD.
HOWEVER...THERE MAY BE A NARROW WINDOW OF OPPORTUNITY FOR STORMS TO
FORM BY LATE AFTERNOON ALONG THE FRONT RANGE IN THE UPSLOPE FLOW
REGIME. WEAK INSTABILITY AND GRADUALLY INCREASING VERTICAL SHEAR
MAY SUPPORT A FEW STORMS CAPABLE OF PRODUCING MARGINALLY SEVERE
HAIL/GUSTY WINDS FOR A SHORT TIME THIS EVENING.
...FL PENINSULA THIS AFTERNOON...
THE GULF AND ATLANTIC SEA BREEZE BOUNDARIES WILL BE ACTIVE THIS
AFTERNOON...IN AN ENVIRONMENT OF MODERATE INSTABILITY. GIVEN
MULTIPLE STORM INTERACTIONS/COLLISIONS...THE MORE INTENSE STORMS
COULD PRODUCE SOME HAIL AND STRONG DOWNBURST WINDS.
..THOMPSON/SMITH.. 06/03/2009
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