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Convective Report

RSS Mesoscale Discussions from Storm Prediction Center

SPC Sep 8, 2010 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
      
Day 1 Outlook Thumbnail Image
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0734 AM CDT WED SEP 08 2010

VALID 081300Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL OK INTO N-CNTRL
TX...

...OK/TX...

PER LATEST NHC GUIDANCE...TD HERMINE WILL TRACK NWD TODAY THROUGH
NWRN TX BEFORE GRADUALLY VEERING TO MORE OF A NNELY DIRECTION WHILE
ACCELERATING THROUGH WRN OK INTO S-CNTRL KS TONIGHT.  REGIONAL VWPS
AND 12Z FWD SOUNDING DATA CONFIRM THAT HERMINE STILL POSSESSES A
STRONG LOW TO MID-TROPOSPHERIC WIND FIELD WITH 40-50+ KT FLOW FROM
JUST ABOVE THE GROUND UPWARD THROUGH 6-7 KM AGL.  IN ADDITION...THIS
SYSTEM IS DRAWING A BROAD FETCH OF TROPICAL MOISTURE NWD THROUGH THE
RED RIVER VALLEY WITH BOUNDARY LAYER DEW POINTS RISING THROUGH THE
70S AND PW VALUES INCREASING TO 2.0-2.5 INCHES.  

SIMILAR TO TUESDAY...WIDESPREAD CLOUDS AND PRECIPITATION WILL LIMIT
DIABATIC HEATING AND RESULTANT AIR MASS DESTABILIZATION. 
NONETHELESS...DIURNAL WARMING OF THE BOUNDARY LAYER WILL LIKELY
STILL YIELD POCKETS OF MODEST INSTABILITY WITHIN THE ENVELOPE OF
MODERATE TO STRONG LOW-LEVEL SHEAR.  AS SUCH...THE THREAT WILL EXIST
FOR SMALL SUPERCELLS TO FORM WITHIN HERMINE/S CONFLUENT RAIN BAND/S/
WITH A THREAT FOR A TORNADO OR TWO...NAMELY THIS AFTERNOON INTO
EVENING.  

...CNTRL HIGH PLAINS INTO THE DAKOTAS...

SURFACE WARM FRONT WILL CONTINUE TO LIFT NWD THROUGH THE CNTRL INTO
NRN HIGH PLAINS TODAY IN RESPONSE TO LEE CYCLOGENESIS OVER SERN
MT/NERN WY.  AT THE SAME TIME...A LEE TROUGH WILL STRENGTHEN FROM
THE LOW SWD INTO ERN CO WITH BOUNDARY LAYER DEW POINTS INCREASING
THROUGH THE 50S PERHAPS INTO LOWER 60S WITHIN NWD EXPANDING WARM
SECTOR OVER WRN PARTS OF SD/NEB.  THIS MOISTURE WILL COINCIDE WITH
AN EML PLUME ADVANCING EWD FROM THE ROCKIES DOWNSTREAM FROM WRN U.S.
TROUGH...SUPPORTING AFTERNOON MLCAPE APPROACHING 1000-1500 J/KG.

SUBSIDENCE IN THE WAKE OF SHORT WAVE TROUGH PROGRESSING NEWD THROUGH
THE CNTRL HIGH PLAINS WILL LIKELY SERVE TO MAINTAIN A CAP ACROSS THE
WARM SECTOR THROUGH AT LEAST MID AFTERNOON.  HOWEVER...OBSERVED
LIGHTNING ACTIVITY AS OF 12Z NEAR SLC AND W OF GJT MAY BE INDICATIVE
OF AN ADDITIONAL UPSTREAM IMPULSE WHICH WOULD APPROACH THE REGION
LATER TODAY.  AS SUCH...THE POTENTIAL FOR AT LEAST ISOLATED STORM
DEVELOPMENT SHOULD INCREASE BY LATE AFTERNOON/EARLY EVENING INVOF
LEE TROUGH OVER ERN WY/WRN NEB PNHDL INTO NERN CO.  THE MODERATE
INSTABILITY IN CONJUNCTION WITH WLY DEEP-LAYER SHEAR STRENGTHENING
LATITUDINALLY FROM AROUND 30 KT OVER NERN CO TO 50 KT ACROSS WRN SD
WILL BE SUPPORTIVE OF ROTATING STORMS WITH A THREAT FOR SOME HAIL
AND LOCALLY STRONG WIND GUSTS.

ADDITIONAL MORE ELEVATED STORMS CAPABLE OF SOME HAIL APPEAR LIKELY
NEAR/N OF SURFACE WARM FRONT OVER THE DAKOTAS...DRIVEN BY
WAA/ISENTROPIC ASCENT ALONG 40-50 KT NOCTURNAL LLJ.

...ME...

IN THE WAKE OF THIS MORNING/S TSTM ACTIVITY CURRENTLY MOVING OFF THE
NEW ENGLAND COAST...EARLY VISIBLE SATELLITE IMAGERY SUGGESTS THAT
POCKETS OF STRONGER HEATING WILL LIKELY OCCUR IN ADVANCE OF COLD
FRONT PUSHING EWD THROUGH THE REGION.  THIS HEATING WILL COMBINE
WITH AN AXIS OF LOW 60S DEW POINTS TO SUPPORT AREAS OF AT LEAST
MODEST INSTABILITY /I.E. MLCAPE OF 500-1000 J PER KG/ LATER TODAY. 
WHERE THE PRE-FRONTAL AIR MASS CAN DESTABILIZE...CONVERGENCE ALONG
THE FRONT COUPLED WITH DEEPER-LAYER FORCING ATTENDANT TO UPPER
TROUGH WILL FOSTER ISOLATED TO SCATTERED TSTMS WITHIN A KINEMATIC
ENVIRONMENT FEATURING 40-50 KT OF DEEP...SWLY SHEAR.  THE GIVEN
SETUP SUGGESTS THE POTENTIAL FOR AT LEAST A FEW STORMS CAPABLE OF
SOME HAIL AND/OR LOCALLY DAMAGING WIND GUSTS THIS AFTERNOON INTO
EVENING.

..MEAD/GRAMS.. 09/08/2010



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SPC Sep 8, 2010 Day 4-8 Convective Outlook

Day 4-8 Outlook
      
Day 4-8 Outlook Thumbnail Image
DAY 4-8 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0358 AM CDT WED SEP 08 2010

VALID 111200Z - 161200Z

...DISCUSSION...
RELATIVELY GOOD LARGE SCALE AGREEMENT CONTINUES AMONG 00Z ECMWF/GEFS
GUIDANCE...WITH EXPECTATIONS FOR A CONTINUED EAST-NORTHEASTWARD
ADVANCEMENT OF THE DAY 3 UPPER TROUGH TOWARD THE GREAT LAKES
REGION/EASTERN CANADA THROUGH DAYS 4/5 SATURDAY/SUNDAY. FOR DAY
4/SATURDAY...SOME SEVERE RISK /WIND AND HAIL/ MAY EXIST ALONG THE
EASTWARD ADVANCING COLD FRONT ACROSS THE OHIO VALLEY/MIDWEST. WITH
THE BRUNT OF THE UPPER TROUGH EXPECTED TO SHIFT NORTHEASTWARD INTO
QUEBEC...CURRENT THINKING IS THAT LAPSE RATES ALOFT WILL BE WEAK
WITH MODEST VERTICAL SHEAR ACROSS THE WARM SECTOR. AS SUCH...A
PARTICULARLY CONSEQUENTIAL/WIDESPREAD SEVERE RISK IS NOT ANTICIPATED
THIS TIME.

OTHERWISE...THE LARGE SCALE PATTERN SHOULD DEAMPLIFY THIS
WEEKEND...WITH RESULTANT LOW AMPLITUDE/MODERATELY STRONG WESTERLIES
PREVALENT ACROSS THE NORTHERN TIER OF THE CONUS. THERE ARE EARLY
INDICATIONS THAT SOME SEVERE THREAT COULD INCREASE ACROSS THE
LOWER/MIDDLE MO VALLEY AND/OR UPPER MIDWEST BY AROUND DAY 5 AND/OR
DAY 6 SUNDAY/MONDAY. HOWEVER...CONSIDERABLY LIMITED PREDICTABILITY
EXISTS GIVEN THE LOW AMPLITUDE NATURE OF THE LARGE SCALE REGIME BY
THIS TIME FRAME.



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