SWODY2
SPC AC 010600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT FRI AUG 01 2008
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE NRN
PLAINS/UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SRN NEW ENGLAND AND
PARTS OF THE MID-ATLANTIC REGION....
...SYNOPSIS...
AMPLIFIED UPPER FLOW PATTERN IS FORECAST ACROSS THE NRN 2/3 OF THE
CONUS THIS PERIOD...WITH A TROUGH ALONG THE W COAST...A LARGE RIDGE
PREVAILING ACROSS THE CENTRAL 2/3 OF THE CONUS...AND AN UPPER LOW
OVER THE NORTHEAST SURROUNDED BY A BROAD ZONE OF CYCLONIC FLOW.
AT THE SURFACE...A FRONT WILL MOVE STEADILY EWD ACROSS THE EASTERN
CONUS...AND SWD ACROSS THE TN VALLEY INTO THE GULF COAST STATES.
MEANWHILE...WRN PORTIONS OF THIS FRONT WILL EXTEND NWWD FROM THE MID
MS VALLEY REGION INTO THE NRN PLAINS...WHILE A SECOND BAROCLINIC
ZONE LINGERS OVER MT AND THE NWRN CONUS.
...NRN PLAINS INTO THE UPPER MS VALLEY...
DESPITE THE PRESENCE OF STEEP LAPSE RATES SW OF THE NW-SE SURFACE
FRONT ACROSS THE NRN PLAINS...CAPPING SHOULD HINDER CONVECTIVE
DEVELOPMENT ACROSS MOST OF THE REGION THIS PERIOD.
ISOLATED STORMS AND A LOW-PROBABILITY SEVERE THREAT MAY BE ONGOING
ACROSS PARTS OF THE DAKOTAS EARLY...AIDED BY WARM ADVECTION NEAR THE
NOSE OF A SLY LOW-LEVEL JET. ANY ONGOING STORMS SHOULD DIMINISH
THROUGH THE MORNING...WITH ANY NEW STORM DEVELOPMENT NOT EXPECTED
UNTIL AT LEAST LATE AFTERNOON.
AS AIRMASS BECOMES MODERATELY UNSTABLE...MIXING MAY ALLOW CAP TO
WEAKEN SUFFICIENTLY IN A FEW AREAS TO ALLOW ISOLATED STORM
DEVELOPMENT -- LIKELY TO THE COOL SIDE OF THE SURFACE FRONT. ANY
SUSTAINED STORM WHICH WOULD DEVELOP WOULD -- DUE TO THE
FAVORABLY-SHEARED ENVIRONMENT -- BECOME SUPERCELLULAR...ACCOMPANIED
BY A THREAT FOR LARGE HAIL AND DAMAGING WINDS.
STORM DEVELOPMENT WILL BECOME INCREASINGLY LIKELY THROUGH THE
EVENING -- PARTICULARLY ACROSS THE ERN DAKOTAS/WRN MN...AS LOW-LEVEL
JET RE-INTENSIFIES. SHOULD AMPLE DEVELOPMENT OCCUR TO ALLOW UPSCALE
GROWTH INTO AN MCS...STORMS WOULD LIKELY ACCELERATE SEWD ACCOMPANIED
BY A THREAT FOR STRONG/DAMAGING WINDS. ATTM...POTENTIAL FOR MCS
DEVELOPMENT IS UNCERTAIN DUE TO CAPPING...AND THUS WILL MAINTAIN
ONLY 15% SEVERE PROBABILITY ACROSS THIS REGION.
...MID-ATLANTIC/SRN NEW ENGLAND...
AS UPPER VORTEX EVOLVES OVER THE NERN CONUS WITH TIME...A LOBE OF
VORTICITY IS EXPECTED TO CROSS NEW ENGLAND/THE MID-ATLANTIC REGION
DURING THE AFTERNOON. ATTM...THE NAM FORECASTS A LOW OVER SRN NEW
ENGLAND ALONG A N-S SURFACE TROUGH EXTENDING FROM ERN CANADA INTO
THE SOUTHEAST...AND A WARM FRONT EXTENDING E OF THIS LOW ACROSS SRN
NEW ENGLAND. THIS SYNOPTIC SETUP WOULD FAVOR AN ENHANCED THREAT FOR
SEVERE STORMS...AS WARM SECTOR AIRMASS DESTABILIZES BENEATH 30 TO 35
KT SWLY MID-LEVEL JET. THE GFS HOWEVER DEPICTS THE SURFACE LOW OFF
THE NJ COAST DURING THE AFTERNOON...AND THUS MORE STABLE/ONSHORE
FLOW OVER SRN NEW ENGLAND.
ATTM...WILL INTRODUCE A SMALL SLIGHT RISK ACROSS PARTS OF THE
MID-ATLANTIC AND SRN NEW ENGLAND...AS OVERALL SYNOPTIC SETUP APPEARS
SUPPORTIVE OF AN ENHANCED SEVERE THREAT -- BUT THREAT REMAINS
SOMEWHAT CONDITIONAL UPON LOCATION OF SURFACE LOW DEVELOPMENT --
WHICH IS LIKEWISE TIED TO THE EWD PROGRESS OF THE MAIN SURFACE
TROUGH.
...THE SOUTHEAST...
WIDESPREAD THUNDERSTORMS ARE FORECAST ACROSS THE SOUTHEAST INVOF
SWD-MOVING COLD FRONT...AND BENEATH LARGE-SCALE CYCLONIC FLOW ALOFT.
AMPLE INSTABILITY ANTICIPATED NEAR/S OF THE FRONT COMBINED WITH
MODERATE FLOW ALOFT COULD SUPPORT A FEW STRONGER/MULTICELL
CLUSTERS...ACCOMPANIED BY THE LOCALLY-DAMAGING WINDS AND PERHAPS
SOME MARGINAL HAIL. WHILE CONFIDENCE IN DEGREE OF ORGANIZATION IS
NOT HIGH ENOUGH TO INTRODUCE A SLIGHT RISK THIS FORECAST...PORTIONS
OF THE AREA MAY REQUIRE A SLIGHT RISK UPGRADE IN LATER FORECASTS.
...SRN AZ...
MARGINAL INSTABILITY ACROSS SRN AZ IN CONJUNCTION WITH MODERATE ELY
MID-LEVEL FLOW S OF RIDGE OVER THE SRN ROCKIES MAY RESULT IN
HIGH-BASED STORMS WHICH MOVE OFF THE HIGHER TERRAIN DURING THE
AFTERNOON/EVENING. ISOLATED STORMS MAY PRODUCE BRIEF GUSTY/DAMAGING
WINDS AS EVAPORATIVELY-DRIVEN DOWNDRAFTS REACH THE SURFACE.
..GOSS.. 08/01/2008
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