SPC AC 061634
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1134 AM CDT MON JUL 06 2009
VALID 061630Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF MT AND ADJACENT
NRN WY INTO WRN ND...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL HIGH
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ALONG THE GULF COAST...
...NRN ROCKIES AND ADJACENT HIGH PLAINS FROM MT/NRN WY TO WRN ND...
POTENT SHORT WAVE TROUGH AND ASSOCIATED STRONG PACIFIC FRONT WILL
CONTINUE EAST ACROSS THE CONTINENTAL DIVIDE BY EARLY THIS AFTERNOON.
HEATING DOWNSTREAM FROM THE INCREASINGLY STRONG DYNAMIC FORCING FOR
ASCENT WILL CONTRIBUTE TO ADEQUATE AIRMASS BUOYANCY FOR ROBUST TSTM
DEVELOPMENT. CONVERGENCE ASSOCIATED WITH THE RAPIDLY ADVANCING FRONT
WILL ACT TO FOCUS DEEP CONVECTION AND THIS ACTIVITY WILL THEN
DEVELOP EWD INTO AN AIRMASS CHARACTERIZED BY WELL-MIXED MLCAPE AOA
1000 J/KG. ALL GUIDANCE REVIEWED FOR THIS OUTLOOK STRONGLY SUGGEST A
SEVERE QUASI-LINEAR MCS SWEEPING EAST ACROSS MUCH OF MT THROUGH LATE
AFTERNOON AND INTO THE EVENING. MAJOR CONCERN WILL BE THE POTENTIAL
FOR DAMAGING WINDS ACCOMPANYING THE PASSAGE OF THE SQUALL LINE.
GIVEN THE PRE-STORM STEEP LAPSE RATE ENVIRONMENT AND 50-60KT MID
LEVEL JET DIRECTED INTO THE BACK OF THE MCS...EXPECT WIND DAMAGE
POTENTIAL WITH THIS SYSTEM TO BE WIDESPREAD AND POSSIBLY SIGNIFICANT
WITH A COUPLE OF LOCAL TSTM WIND EVENTS PERHAPS APPROACHING 70KT.
IT IS ALSO POSSIBLE...BUT LESS LIKELY...THAT A FEW DISCRETE CELLS
COULD ATTAIN SUPERCELL CHARACTERISTICS EITHER EARLY IN THE
DEVELOPMENT CYCLE...OR EMBEDDED IN OR AHEAD OF THE SQUALL LINE. A
LOW PROBABILITY TORNADO THREAT COULD EVOLVE FROM STORMS EXHIBITING
THIS BEHAVIOR. LARGE HAIL WILL ALSO BE A THREAT.
...CENTRAL ROCKIES AND ADJACENT HIGH PLAINS...
AIRMASS BACKED INTO THE HIGHER TERRAIN CONTINUES TO CONTAIN
RELATIVELY HIGH MOISTURE/PW VALUES TODAY /AROUND 150 PCT OF NORMAL/.
STORMS WILL ONCE AGAIN FIRE AS DIFFERENTIAL HEATING CONTRIBUTES TO
ELIMINATING ANY INHIBITION. WHILE LOW LEVEL ELY/SELY UPSLOPE FLOW
HAS WEAKENED CONSIDERABLY COMPARED TO PRIOR DAYS...25-30KT NWLY MID
LEVEL FLOW SHOULD PROVIDE MARGINALLY SUPPORTIVE SHEAR FOR A FEW
BETTER ORGANIZED/PERSISTENT STORMS EVENTUALLY GENERATING HAIL AND
LOCALLY DAMAGING WINDS. FORECAST STORM MOTION TO THE SOUTH SUGGESTS
THIS ACTIVITY MAY NOT MOVE THAT FAR OFF THE FRONT RANGE.
HOWEVER...ANOTHER AXIS OF DESTABILIZATION AND WEAK LARGE SCALE
ASCENT OVER THE HIGH PLAINS FROM NEB PNHDL SWD TO TX PNHDL MAY
CONTRIBUTE TO STORM DEVELOPMENT IN THESE AREAS. SLIGHTLY GREATER LOW
LEVEL SLY FLOW AND MOISTURE RETURN INTO THESE AREAS MAY ALLOW STORMS
OR STORM CLUSTERS TO PROPAGATE EWD/SEWD THIS EVENING WITH SOME
POTENTIAL FOR DAMAGING WINDS AND HAIL.
...GULF COAST...
A NUMBER OF STORM OUTFLOWS AND SMALL-SCALE CONVECTIVELY-INDUCED
CIRCULATIONS EXIST AMIDST A VERY MOIST/UNSTABLE AIRMASS ALONG THE
GULF COAST FROM TX TO FL. POCKETS OF INTENSE HEATING WHERE AIRMASS
HAS YET TO BE OVERTURNED BY DEEP CONVECTION WILL PROVIDE A FAVORABLE
ENVIRONMENT FOR ISOLATED TO SCATTERED DAMAGING WET MICROBURSTS. LAND
AREAS REMAINING UNAFFECTED BY ONGOING OR PRIOR STORMS ARE LIMITED
AND THEREFORE OVERALL SEVERE POTENTIAL APPEARS TO BE DIMINISHING
COMPARED TO PRIOR DAYS.
...NORTHEAST...
PRONOUNCED SHORT WAVE TROUGH /50-60KT JET STREAK/ EMBEDDED WITHIN
STRONG AND PERSISTENT BELT OF NW FLOW ACROSS SRN CANADA/NRN GREAT
LAKES WILL SWEEP SEWD ACROSS NRN ENGLAND THROUGH TONIGHT AS TRAILING
CLOSED UPPER LOW REMAINS ESSENTIALLY STATIONARY NEAR SRN
ONTARIO/QUEBEC BORDER AREA. HEATING IS WELL UNDERWAY ACROSS NEW
ENGLAND ATTM AND EXPECTED STEEPENING LAPSE RATES AND INCREASING
LARGE SCALE ASCENT WITH TROUGH AND APPROACHING COLD FRONT TO RESULT
IN SCATTERED TSTM DEVELOPMENT. AREAS OF EFFECTIVE SHEAR IN THE
20-35KT RANGE WILL PROVIDE SUPPORT FOR A FEW BETTER
ORGANIZED/PERSISTENT UPDRAFTS WITH SOME POTENTIAL FOR DAMAGING WINDS
AND SMALL HAIL. UNCERTAINTIES ABOUT STORM COVERAGE AND DURATION
GIVEN LIMITED LOW LEVEL MOISTURE PRECLUDE HIGHER SEVERE
PROBABILITIES THIS AREA AT THIS TIME.
..CARBIN/SMITH/COOK/GOSS.. 07/06/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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