SWODY1
SPC AC 292010
DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0310 PM CDT THU JUL 29 2010
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE
MID-ATLANTIC REGION...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE NRN PLAINS...
CORRECTED FOR PROBABILITY GRAPHICS
...MID-ATLANTIC STATES...
ONLY CHANGE WAS TO ADJUST NORTH EDGE OF SLIGHT ALONG SEWD MOVING
COLD FRONT. BROKEN BANDS OF THUNDERSTORMS CONTINUE ALONG/AHEAD OF
THE FRONT WITHIN MLCAPES 2000-3000 J/KG. WNW UNIDIRECTIONAL FLOW
REGIME WAS MARGINALLY SUPPORTIVE FOR SUPERCELLS...MORE LIKELY
MULTICELL LINE-SEGMENTS CAPABLE OF DAMAGING WINDS. ACTIVITY WILL
CONTINUE S AND SE THROUGH CNTRL/ERN VA AND INTO PARTS OF NC THIS
EVENING BEFORE DIMINISHING.
...NRN PLAINS...
ELEVATED STORM CLUSTER CONTINUES ALONG THE SD/NEB/IA BORDERS AT
1930Z. THIS ACTIVITY WAS NOT CAPTURED BY MODELS VERY WELL.
FORTUNATELY...PRIMARY SEVERE THREAT IS EXPECTED TO FORM FARTHER W
LATER THIS AFTERNOON/EVENING AHEAD OF AN IMPULSE MIGRATING EWD
ACROSS MT/NW WY. STORMS HAVE ALREADY FORMED OVER THE BLACK HILLS
AND WILL ALSO LIKELY DEVELOP NEAR A LEE TROUGH OVER ERN MT AND NE WY
LATER THIS AFTERNOON/EVENING. CONTINUED DESTABILIZATION AND DEEP
LAYER SHEAR IN EXCESS OF 40 KTS WILL AID IN SUPERCELL FORMATION WILL
LARGE HAIL /POSSIBLY SIGNIFICANT HAIL/ AND A COUPLE OF TORNADOES
POSSIBLE. AS A RESULT...HAVE EXPANDED SIGNIFICANT LARGE HAIL
PROBABILITIES AND ADDED A 5 PERCENT TORNADO PROBABILITY INTO PARTS
OF WRN/SCNTRL SD. THE ACTIVITY WILL CONGEAL AND MOVE ESE ACROSS SD
AND PERHAPS NRN NEB TONIGHT WITH A DIMINISHED THREAT FOR SEVERE
WEATHER.
...SERN AZ...
HAVE REMOVED SLIGHT RISK. VERY MOIST AND WEAKLY CAPPED ENVIRONMENT
HAS ALLOWED EARLY DEVELOPMENT OF VERY EFFICIENT HEAVY RAINFALL
THUNDERSTORMS. TROPOSPHERIC FLOW HAS NOT ACCELERATED APPRECIABLY IN
ASSOCIATION WITH THE PV-ANOMALY MOVING WWD THROUGH NM. AS
SUCH...STORM ORGANIZATION WILL BE MINIMAL WITH THREATS FOR WET
MICROBURSTS REMAINING ISOLATED AT BEST.
/JPR
..RACY.. 07/29/2010
.PREV DISCUSSION... /ISSUED 1121 AM CDT THU JUL 29 2010/
...SYNOPSIS...
SUMMERTIME UPPER RIDGE PERSISTS ACROSS MUCH OF CONUS CENTERED OVER
SRN PLAINS. WHILE TROUGH REMAINS OFF THE WEST COAST AND SYSTEM
CONTINUES TO MOVE EWD ACROSS NERN STATES...SUFFICIENT FLOW PERSISTS
ACROSS TOP OF RIDGE FROM CENTRAL STATES SEWD TO MID ATLANTIC COAST
TO PROVIDE SHEAR FOR ORGANIZED CONVECTIVE DEVELOPMENT.
...MID ATLANTIC STATES...
THE COLD FRONT AT 16Z STRETCHES FROM SRN NEW ENGLAND WSWWD TO NEAR
THE MD/PA BORDER THEN WWD TO MO. SUFFICIENT SHEAR...AROUND 30KT
ACROSS THE VERY MOIST WRM SECTOR E OF APPALACHIANS AND S OF COLD
FRONT FOR AT LEAST A FEW SEVERE THUNDERSTORMS BY MID AFTERNOON.
CONVERGENCE ALONG COLD FRONT AS IT DROPS SEWD FROM MD EARLY THIS
AFTERNOON TO SRN VA BY THIS EVENING...COMBINED WITH MLCAPES AOA 2500
J/KG FAVOR STORMS MOVING/DEVELOPING E OFF HIGHER TERRAIN ACROSS
CHESAPEAKE BAY. AS STORMS GROW UPSCALE INTO CLUSTERS/LINE
SEGMENTS...COLD POOLS WILL FORM LEADING TO SOME WIND DAMAGE THREAT.
STORMS SHOULD DEVELOP SWD THRU ERN VA INTO NERN NC PRIOR TO
WEAKENING AFTER SUNSET.
...SERN AZ...
SOUNDINGS AT BOTH KPHX AND KTUS AT 12Z ARE VERY MOIST WITH ONLY
MINIMAL CINH. WHILE THE STEERING FLOW REMAINS GENERALLY LESS THAN
10 KTS...THE POTENTIAL FOR MLCAPES TO 2000 J/KG AND PWAT/S IN EXCESS
OF 2 INCHES...SUPPORT WET MICROBURSTS. STORMS SHOULD INITIATE BY
EARLY THIS AFTERNOON OVER THE HIGHER TERRAIN GIVEN THE WEAK CINH AND
THEN DEVELOP/PROPAGATE INTO ADJACENT DESERT VALLEYS OF SERN AZ.
WILL CONTINUE A SLIGHT RISK EVEN WITH THE RELATIVELY WEAK LAPSE
RATES AS WATER LOADING OF UPDRAFTS GIVEN THE VERY WET AIR MASS WILL
BE GREAT...LEADING TO THE WET MICROBURST THREAT.
...NRN PLNS...
WEAK DISTURBANCES MOVING E IN BAND OF ENHANCED FLOW IMMEDIATELY N OF
UPR RIDGE EXPECTED TO MAINTAIN AREAS OF ELEVATED TSTMS OVER PARTS OF
THE DAKOTAS AND PERHAPS NRN NEB TODAY. THIS ACTIVITY SHOULD REMAIN
LARGELY NON-SVR.
FARTHER W...COMBINATION OF STRONG SFC HEATING AND ASCENT WITH UPR
SYSTEM MOVING E FROM ID SHOULD FOSTER DEVELOPMENT OF SFC-BASED
STORMS THIS AFTN ALONG LEE SFC TROUGH OVER THE WRN DAKOTAS AND FAR
ERN MT/WY. LOW LVL MOISTURE/MLCAPE WILL INCREASE WITH SEWD
EXTENT...WITH POCKETS OF MLCAPE TO 3000 J/KG POSSIBLE OVER WRN/CNTRL
SD. WEAK LOW-LVL FLOW WILL LIMIT HODOGRAPH SIZE. BUT WIND PROFILES
WILL EXHIBIT CONSIDERABLE VEERING WITH HEIGHT... WITH 25-35 KT WLY
FLOW AT MID LVLS...AND WITH SPEEDS AOA 60 KTS AT 250 MB. THIS
SHOULD PROVE MORE THAN AMPLE FOR SUPERCELLS WITH A THREAT FOR LARGE
HAIL....DMGG WIND...AND PERHAPS A TORNADO.
STRENGTHENING/VEERING OF SLY LLJ THIS EVE...IN RESPONSE TO BOTH
DIURNAL CYCLE AND CONTINUED EWD MOTION OF UPR TROUGH...SUGGEST THAT
STORMS WILL MERGE INTO ONE OR TWO STRONG-SVR CONVECTIVE COMPLEXES BY
LATE EVE. THESE SHOULD MOVE SE ACROSS SD AND PERHAPS NRN NEB...WITH
A DIMINISHING THREAT FOR SVR WIND/HAIL EARLY FRI.
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