SWODY1
SPC AC 021630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT TUE JUN 02 2009
VALID 021630Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL SRN/CENTRAL
PLAINS NEWD INTO THE MID ATLANTIC STATES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NRN CA AND SRN ORE...
...SYNOPSIS...
MAIN THREAT FOR STRONGER/SEVERE STORMS WILL BE ALONG AND AHEAD OF A
COLD FRONT...STRETCHING FROM THE CENTRAL/SRN PLAINS NEWD INTO SRN
NEW ENGLAND. THE UPPER FLOW WILL BE MOSTLY WEAK...15-20 KT... FROM
THE PLAINS STATES EWD INTO THE MID MS VALLEY...THOUGH 30-40 KT WINDS
AT 500 MB...ON THE SRN FRINGE OF THE WLYS...WILL EXTEND FROM THE OH
VALLEY EWD INTO THE ATLANTIC COAST. OTHER FEATURE OF CONVECTIVE
SIGNIFICANCE IS A WEAK MID LEVEL LOW PRESSURE SYSTEM LOCATED IN FAR
WRN KS...WHICH IS FORECAST TO TRACK SLOWLY EWD THROUGH SRN KS
THROUGH TONIGHT. A BELT OF 30 KT MID LEVEL WINDS WERE LOCATED ON THE
SRN SIDE OF THIS SYSTEM FROM ERN NM INTO NWRN TX.
...CNTRL/SRN PLNS TO LWR MO VLY...
ELEVATED THUNDERSTORMS WERE LOCATED IN WRN OK THIS MORNING... WITHIN
AREA OF STRONG DIFFLUENCE ALOFT. THESE STORMS ARE LIKELY TO SPREAD
EWD AND DEVELOP NEWD ALONG THE FRONT INTO KS/MO THROUGH THE DAY. THE
STORMS SHOULD BECOME SURFACE BASED WITH A WARMING AND
DESTABILIZING BOUNDARY LAYER. MODERATE INSTABILITY AND 20-30 KT DEEP
LAYER SHEAR WILL SUPPORT SCATTERED SEVERE MULTICELL CLUSTERS WITH
HAIL/DAMAGING WINDS.
THE SLIGHTLY STRONGER MID LEVEL FLOW AND VEERING WINDS IN LOWER 3 KM
MAY PROVIDE SUFFICIENT DEEP LAYER SHEAR FOR SUPERCELLS ACROSS NWRN
TX LATE THIS AFTERNOON/EVENING. DESPITE THE STABLE MORNING BOUNDARY
LAYER FROM OVERNIGHT CONVECTION...STRONG HEATING COMBINED WITH VERY
STEEP LAPSE RATES...PER MAF 12Z SOUNDING...AND DEWPOINTS IN THE MID
60S ARE LIKELY TO RESULT IN AN EXTREMELY UNSTABLE AIR MASS BY LATE
AFTERNOON WITH MLCAPES APPROACHING 4000 J/KG. VEERING WINDS IN THE
LOWEST KM WILL SUPPORT 1 KM SHEAR NEAR 20 KTS AND ANY STORMS THAT
ARE MORE STRONGLY DRIVEN SSEWD BY PROPAGATION...HAVE THE POTENTIAL
TO PRODUCE BRIEF TORNADOES. HOWEVER...THE VERY STEEP LAPSE RATES AND
DEGREE OF INSTABILITY APPEAR MORE FAVORABLE FOR VERY LARGE HAIL.
A THREAT FOR SEVERE HAIL AND GUSTY WINDS ARE EXPECTED TO PERSIST
INTO THE OVERNIGHT HOURS AS STORMS EVOLVE INTO SEVERAL CLUSTERS AND
MOVE ESEWD/SEWD ACROSS PORTIONS OF OK AND TX.
...MID MS/OH VALLEYS EWD TO THE MID ATLANTIC COAST...
DIFFICULT TO PICK OUT ON WV IMAGERY ANY DISCERNABLE UPPER FEATURES
FOR CONVECTIVE DEVELOPMENT. HOWEVER...VISIBLE/RADAR IMAGERY HINTS AT
A MID LEVEL SYSTEM MOVING EWD ALONG THE MO/IA BORDER AND MAY BE
ENHANCING WEAK CONVECTIVE DEVELOPMENT ACROSS WRN MO/NERN KS. THIS
AREA IS ALSO LOCATED WITHIN AREA OF CONVERGENCE INDICATED ON 700 MB
12Z ANALYSIS. EXPECT STORMS TO DEVELOP EAST OF THIS FEATURE ACROSS
NERN MO EWD INTO IL/IND THIS AFTERNOON. CU HAD ALSO RECENTLY
DEVELOPED OVER THE HIGHER TERRAIN OF WV...POSSIBLY IN RESPONSE TO
LIFT ASSOCIATED WITH MCV MOVING RAPIDLY EWD THROUGH CENTRAL PA. THIS
SYSTEM MAY ALSO INITIATE STORMS EAST OF THE APPALACHIANS. ONCE
STORMS DEVELOP ...30-40 KT DEEP WLY SHEAR AND MODERATE INSTABILITY
WILL BE SUFFICIENT FOR POSSIBLE EMBEDDED FORWARD-PROPAGATING
SEGMENTS WITH SEVERE WIND/HAIL.
...PACIFIC NW/NRN GRT BASIN...
WATER VAPOR IMAGERY SUGGESTS AN UPR LEVEL IMPULSE WAS ROTATING NWD
INTO NRN CA AROUND OFFSHORE UPPER LOW. ASSOCIATED UVV AND MODERATELY
UNSTABLE AIR MASS...MLCAPES ALREADY AROUND 1000 J/KG AT 16Z...SHOULD
SUPPORT AFTERNOON/EVENING FROM THE NRN CA SIERRA/SISKIYOU INTO
SRN/CNTRL ORE. DESPITE RELATIVELY WEAK WINDS THROUGH THE LOWER 3
KM...STRONGER WINDS FROM 500-200 MB SHOULD YIELD MULTICELL STORMS
WITH THE POTENTIAL FOR HAIL AND GUSTY WINDS.
..IMY/SMITH.. 06/02/2009
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