SPC AC 311609
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1109 AM CDT SAT JUL 31 2010
VALID 311630Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN INTERMOUNTAIN
REGION INTO THE DAKOTAS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE LOWER OH INTO
TN VALLEYS TO THE SERN ATLANTIC COAST...
...SYNOPSIS...
WHILE RIDGE DOMINATES SRN U.S. WITH UPR HIGH CENTER SRN PLAINS...THE
TROUGH THAT HAS BEEN OFFSHORE PAC NW HAS MOVED TO THE COAST WHILE
TROUGH PERSISTS NERN STATES.
..NRN INTERMOUNTAIN REGION INTO NRN PLAINS...
AHEAD OF THE PRIMARY UPPER TROUGH AN IMPULSE/SPEED MAX MOVING NEWD
ACROSS WA/OR WILL MOVE TO NRN INTERMOUNTAIN REGION BY THIS EVENING.
MEANWHILE...A WEAKER DOWNSTREAM IMPULSE /NOW OVER CNTRL PORTIONS OF
MT INTO NRN WY/ WILL TRANSLATE EWD TODAY INTO ND AND NRN SD. IN THE
LOW LEVELS...WEAK LOW PRESSURE WILL CONSOLIDATE OVER ERN MT BY THIS
AFTERNOON WITH A NNW-SSE ORIENTED TROUGH/BAROCLINIC ZONE PERSISTING
FROM FAR ERN MT INTO THE CNTRL HIGH PLAINS. FARTHER W...A WEAK
PACIFIC FRONT WILL PROGRESS THROUGH THE PACIFIC NW INTO NRN
INTERMOUNTAIN REGION TODAY.
THE PRIMARY FOCUS FOR STRONG TO SEVERE TSTM DEVELOPMENT APPEARS TO
BE ALONG THE FAVORED TERRAIN AND EWD-ADVANCING PACIFIC FRONT BY
MID/LATE AFTERNOON FROM ERN WA/NERN ORE ACROSS THE ID PNHDL INTO WRN
MT. HERE...INCREASED HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT
ATTENDANT TO ABOVE-MENTIONED SYSTEM WILL INTERACT WITH A STEEP LAPSE
RATE THERMODYNAMIC ENVIRONMENT WHERE MLCAPE WILL APPROACH 1000 J/KG.
THE EWD PROGRESSION OF 80-90 KT UPPER-LEVEL JET STREAK AND 50+ KT
MIDLEVEL WIND MAXIMUM WILL RESULT IN 45-60 KT OF DEEP SWLY
SHEAR...SUFFICIENT FOR ORGANIZED STORM MODES...INCLUDING SUPERCELLS
AND BOWING STRUCTURES. LARGE HAIL AND DAMAGING WIND GUSTS WILL BE
THE PRIMARY HAZARDS GIVEN THE COOLING THERMODYNAMIC PROFILES AND
STEEP LAPSE RATE/HIGH LCL ENVIRONMENT.
HAVE EXTENDED THE RISK EWD ACROSS SRN ID GIVEN THE GREATER
AVAILABILITY OF THE MONSOON MOISTURE FROM THE S TO AID THE
INSTABILITY ALONG WITH UP TO 40 KT OF SHEAR.
STORM INITIATION AND EVOLUTION IS A BIT MORE UNCERTAIN FARTHER E
ACROSS ERN MT INTO THE DAKOTAS TODAY OWING TO EWD PROGRESSION OF
LEAD IMPULSE AWAY FROM N-S ORIENTED SURFACE BOUNDARY.
NONETHELESS...IT APPEARS THAT AT LEAST ISOLATED...DIURNAL
STORMS WILL BE POSSIBLE IN ADVANCE OF THE LEAD IMPULSE OVER ND...AS
WELL AS ALONG THE PRIMARY BOUNDARY WHICH SHOULD BE SITUATED OVER FAR
ERN PARTS OF MT/WY. ALSO...SOME MODEL GUIDANCE SUGGESTS THE
POSSIBILITY OF STORMS PROGRESSING SEWD FROM SERN SASKATCHEWAN/SRN
MANITOBA INTO CNTRL/ERN ND. IN ANY EVENT...THE COMBINATION OF 40-50
KT OF DEEP-LAYER SHEAR AND AFTERNOON MLCAPE VALUES APPROACHING
1000-1500 J/KG SUGGESTS THE POTENTIAL FOR SUSTAINED/ROTATING
UPDRAFTS CAPABLE OF LARGE HAIL AND DAMAGING WIND GUSTS.
TSTMS WILL LIKELY PERSIST OVERNIGHT MAINLY ACROSS ND IN ASSOCIATION
WITH STRENGTHENING WAA REGIME ATTENDANT TO 40+ KT LLJ. A FEW OF THE
MORE INTENSE STORMS WILL REMAIN CAPABLE OF HAIL AND STRONG WIND
GUSTS INTO SUNDAY MORNING.
..SERN ATLANTIC COAST...
REF MCD 1510
MIDLEVEL IMPULSE RESPONSIBLE FOR ONGOING TSTMS NOW MOVING ACROSS ERN
TN WILL CONTINUE SEWD TODAY...SUPPORTING AN INCREASE IN TSTM
COVERAGE AND INTENSITY WITHIN A VERY MOIST AND MODERATELY UNSTABLE
AIR MASS WITH MLCAPE OF 1500-3000 J/KG. THE MODERATE
INSTABILITY COUPLED WITH VEERING WIND PROFILES AND AROUND 30 KT OF
DEEP NWLY SHEAR WILL FAVOR UPSCALE GROWTH OF STORMS INTO MULTICELL
CLUSTERS WITH THE THREAT FOR DAMAGING WIND GUSTS.
...LOWER OH/TN VALLEYS...
A FAIRLY STRONG MIDLEVEL IMPULSE AND ASSOCIATED 40-45 KT WIND
MAXIMUM TRANSLATING SEWD THROUGH THE UPPER MIDWEST. THIS IMPULSE
WILL CONTINUE SEWD TODAY IN CONJUNCTION WITH A SURFACE LOW AND
ATTENDANT FRONTAL SYSTEM. STRONG DIABATIC HEATING UNDERWAY LWR OH
AND WRN TN VLYS THIS AM AND WILL SUPPORT THE DEVELOPMENT OF A
MODERATELY UNSTABLE AIR MASS BY AFTERNOON AHEAD OF SWD-MOVING FRONT
WITH MLCAPE OF 1000-2500 J/KG.
EXPECT TSTMS TO GRADUALLY INCREASE IN COVERAGE AND INTENSITY THROUGH
THE AFTERNOON IN ADVANCE OF UPPER SYSTEM WITHIN A KINEMATIC
ENVIRONMENT FEATURING VERTICALLY-VEERING WIND PROFILES AND 30-40 KT
OF DEEP NWLY SHEAR. AS SUCH...THE SETUP WILL FAVOR THE DEVELOPMENT
OF ORGANIZED STORM CLUSTERS...PERHAPS EVOLVING INTO AN MCS WITH
DAMAGING WINDS BEING THE PRIMARY HAZARD.
..HALES/DEAN.. 07/31/2010
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