SPC AC 311254
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT SAT JUL 31 2010
VALID 311300Z - 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...
...NRN INTERMOUNTAIN REGION INTO NRN PLAINS...
MIDLEVEL TROUGH CURRENTLY ALONG THE PACIFIC NW COAST WILL MOVE
INLAND TODAY WITH A STRONG VORTICITY MAXIMUM AND ATTENDANT 50+ KT
MIDLEVEL JET STREAK MOVING THROUGH BASAL PORTION OF LARGER-SCALE
TROUGH INTO THE INTERIOR PACIFIC NW AND 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 AREAS OVER THE ID
PNHDL AND SERN MT AS OF 11Z WILL CONSOLIDATE OVER ERN MT BY
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.
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 MENTIONED
ABOVE. 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.
...LOWER OH/TN VALLEYS...
MORNING WATER VAPOR IMAGERY INDICATES 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. WHILE
EARLY VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUDINESS THIS
MORNING ACROSS IL/IND/KY...STRONG DIABATIC HEATING TO THE W THROUGH
S OF THIS AREA SHOULD SUPPORT THE DEVELOPMENT OF A MODERATELY
UNSTABLE AIR MASS BY AFTERNOON AHEAD OF SURFACE LOW AND SWD-MOVING
FRONT WITH MLCAPE OF 1000-2500 J/KG.
EXPECT TSTMS TO GRADUALLY INCREASE IN COVERAGE AND INTENSITY THROUGH
THE DAY 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.
...SERN ATLANTIC COAST...
MIDLEVEL IMPULSE RESPONSIBLE FOR ONGOING TSTMS OVER NRN MIDDLE 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. VERTICAL SHEAR WILL BE SLIGHTLY
WEAKER THAN THAT OVER THE OH VALLEY. NONETHELESS...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.
..MEAD/BOTHWELL.. 07/31/2010
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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