SWODY1
SPC AC 021945
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0245 PM CDT THU JUL 02 2009
VALID 022000Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN AND
CNTRL HIGH PLAINS...
SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THE 20Z ISSUANCE.
THE MOST SIGNIFICANT CHANGE WAS TO DROP THE SLIGHT RISK AREA IN SRN
NEW ENGLAND AND IN SE NY...SEE MESOSCALE DISCUSSION 1405. THE
AIRMASS HAS BEEN SLOW TO DESTABILIZE AND FOR THIS REASON...ANY
SEVERE THREAT THAT DEVELOPS LATE THIS AFTERNOON SHOULD REMAIN
MARGINAL. ANOTHER CHANGE TO THE OUTLOOK IS TO TRIM THE NWRN EDGE OF
THE SLIGHT RISK AREA IN CNTRL MONTANA WHICH IS BEHIND AN EXITING
SHORTWAVE TROUGH. LARGE-SCALE SUBSIDENCE BEHIND THIS FEATURE MAY BE
ENOUGH TO LIMIT SEVERE STORM COVERAGE OR KEEP THE SEVERE THREAT
MARGINAL. IN ADDITION...THE SLIGHT RISK AREA HAS BEEN REMOVED FOR
MOST OF NERN CO WHERE INSTABILITY IS RELATIVELY WEAK AND THE
STRONGER VERTICAL SHEAR ACCORDING TO THE RUC EXISTS OVER WRN NEB AND
SE WY. ELSEWHERE...ADJUSTMENTS TO THE 5 PERCENT HAIL AND WIND
PROBABILITIES HAVE BEEN MADE TO FAVOR THE LATEST RUC MODEL AND
CURRENTLY LIGHTNING ACTIVITY.
..BROYLES.. 07/02/2009
.PREV DISCUSSION... /ISSUED 1125 AM CDT THU JUL 02 2009/
...NORTHEAST...
SEVERE THUNDERSTORM FORECAST REMAINS COMPLEX OVER THIS REGION TODAY
WITH EXTENSIVE CLOUD COVER HOLDING OVER SRN NY INTO MUCH OF NEW
ENGLAND AND LIMITED CONVERGENCE SWD INTO BETTER HEATING INTO THE MID
ATLANTIC WITH UNIFORM WLY SURFACE WINDS. ISOLATED STRONG/SEVERE
STORMS REMAIN ELEVATED SKIRTING THE MA COAST LATE THIS MORNING ON
FRINGE OF IMPULSE ROTATING NNEWD ON WV IMAGERY...WITH SUBSIDENT
REGIME EVIDENT IN WAKE OF THIS SYSTEM. UPSTREAM IMPULSE EJECTING
ACROSS WRN NY/PA THIS MORNING MAY SUPPORT REDEVELOPMENT OF
THUNDERSTORMS INTO ERN PA/NRN NJ DURING THE MID TO LATE AFTERNOON.
DESPITE THE LIMITING FACTORS LISTED ABOVE...MID LEVEL TEMPERATURES
REMAIN FAIRLY COOL AND OVERALL MODEST INSTABILITY MAY SUPPORT A FEW
SEVERE STORMS WITH HAIL/WINDS NEAR OR JUST EXCEEDING SEVERE LEVELS.
...NRN/CENTRAL HIGH PLAINS...
MODEST WLY FLOW ALOFT WILL PERSIST ACROSS THE NRN/CENTRAL HIGH
PLAINS TODAY ALONG NRN PERIPHERY OF LARGE SCALE RIDGE PERSISTING
OVER THE SRN/CENTRAL ROCKIES. SEVERAL LOW AMPLITUDE MID LEVEL
SHORTWAVE TROUGHS/SPEED MAXIMA WILL OVERSPREAD THE REGION...WITH
IMPULSE NOW MOVING ACROSS WY EXPECTED TO SHIFT OVER THE HIGH PLAINS
THROUGH THE AFTERNOON.. SUFFICIENT MOISTURE WILL REMAIN IN PLACE
FOR MODERATE INSTABILITY THIS AFTERNOON ACROSS THE HIGH PLAINS AND
SHOULD RESULT IN ANOTHER ACTIVE CONVECTIVE DAY. DESPITE THE MODEST
WLY FLOW ALOFT...SHEAR WILL BE SUFFICIENT FOR SUPERCELLS AND
ORGANIZED CLUSTERS/LINES GIVEN THE SELY LOW LEVEL WINDS...AS STORMS
SPREAD ESEWD OFF THE HIGHER TERRAIN. PRIMARY THREATS WILL ONCE
AGAIN BE FROM LARGE HAIL AND ISOLATED DAMAGING WINDS...ALTHOUGH A
TORNADO OR TWO CAN NOT BE RULED OUT WITH ANY PERSISTENT SUPERCELL.
...GREAT BASIN...
WELL DEFINED SHORTWAVE TROUGH IS ALREADY FOCUSING THUNDERSTORMS OVER
THE SRN GREAT BASIN THIS MORNING...WHICH WILL SPREAD SLOWLY NEWD
THROUGH THE DAY. THIS WILL LIKELY FOCUS SCATTERED THUNDERSTORMS
WITH CONTINUED INFLUX OF LOW-MID LEVEL MOISTURE FROM THE S AND
DAYTIME HEATING. PROFILES WITH LOW-LEVEL INVERTED-V CHARACTERISTICS
AND 50-60 KT SWLY HIGH LEVEL FLOW COULD SUPPORT A FEW STORMS CAPABLE
OF PRODUCING A FEW STRONG OUTFLOW GUSTS AND SMALL HAIL.
...CENTRAL GULF COAST INTO /NRN FL/SRN GA...
MID LEVEL AIR REMAINS FAIRLY DRY OVER THE REGION THIS
MORNING...WHICH WILL PERSIST ATOP A VERY WARM/MOIST BOUNDARY LAYER.
MODERATE TO STRONG INSTABILITY WILL DEVELOP BY THE MID AFTERNOON
ACROSS THIS REGION...WITH PULSE-STORMS LIKELY FOCUSING ALONG E-W
ORIENTED WEAK SURFACE FRONTS. STRONGER...BRIEF-LIVED CORES WILL BE
CAPABLE OF STRONG/ISOLATED SEVERE DOWNBURSTS.
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