SWODY1
SPC AC 062000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT MON JUL 06 2009
VALID 062000Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE NRN
ROCKIES AND NRN HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE CNTRL AND
SRN ROCKIES AND SRN HIGH PLAINS...
...NRN ROCKIES AND ADJACENT HIGH PLAINS FROM MT/NRN WY TO WRN
...ND...
CURRENT FORECAST STILL APPEARS ON TRACK IN THIS REGION. STORMS ARE
DEVELOPING AHEAD OF COLD FRONT OVER HIGHER TERRAIN OF WRN MT...AND
STORM COVERAGE SHOULD INCREASE THIS AFTERNOON WITHIN ZONE OF LARGE
SCALE ASCENT DOWNSTREAM FROM EJECTING VORT MAX. BULK SHEAR OF 35-45
KT WILL SUPPORT SUPERCELLS WITH INITIAL DEVELOPMENT. LARGE HAIL AND
DAMAGING WIND WILL BE THE PRIMARY THREATS. STORMS SHOULD EVENTUALLY
CONSOLIDATE INTO AN MCS BY LATER THIS EVENING WITH AN INCREASING
THREAT OF DAMAGING WIND.
...CNTRL ROCKIES AND HIGH PLAINS...
A RESERVOIR OF 1000-1500 J/KG MLCAPE HAS DEVELOPED OVER THE CNTRL
AND SRN HIGH PLAINS WHERE STEEP LAPSE RATES HAVE OVERSPREAD WRN
PERIPHERY OF UPPER 50S BOUNDARY LAYER DEWPOINTS AND WHERE STRONG
DIABATIC HEATING IS OCCURRING. STORMS DEVELOPING OVER THE HIGHER
TERRAIN WILL SPREAD SEWD INTO THE UNSTABLE BOUNDARY LAYER OVER THE
HIGH PLAINS. SELY LOW LEVEL WINDS VEERING TO 20-25 KT AT ABOVE 700
MB IS RESULTING IN SUFFICIENT BULK SHEAR FOR STORMS TO DEVELOP
UPDRAFT ROTATION. ISOLATED LARGE HAIL AND DOWNBURSTS WILL BE THE
MAIN THREATS THROUGH MID EVENING.
...ERN SD AREA...
REF SWOMCD 1458.
...NERN STATES...
COOL AIR ALOFT AND ASCENT RESULTING FROM VORTICITY MAXIMA ROTATING
THROUGH UPPER TROUGH WILL PROMOTE SCATTERED THUNDERSTORMS OVER A
PORTION OF THE NERN STATES. ISOLATED MARGINALLY SEVERE HAIL AND
GUSTY WINDS COULD ACCOMPANY THE STRONGER CORES. HOWEVER...THE
MARGINAL THERMODYNAMIC ENVIRONMENT WITH MODEST LOW LEVEL MOISTURE
WILL PROBABLY REMAIN A LIMITING FACTOR FOR A MORE ROBUST SEVERE
THREAT.
...SERN STATES...
WIDESPREAD CLOUDS AND AREAS OF PRECIPITATION ASSOCIATED WITH ONGOING
STORMS AS WELL AS WEAK MID LEVEL LAPSE RATES...INSTABILITY AND
VERTICAL SHEAR WILL REMAIN LIMITING FACTORS FOR SEVERE WEATHER IN
THIS REGION. HOWEVER...POCKETS OF HEATING ARE OCCURRING AHEAD OF MCV
MOVING EAST THROUGH SERN AL/SWRN GA. SUFFICIENT BOUNDARY LAYER
DESTABILIZATION MAY TRANSPIRE IN LOCALIZED AREAS TO SUPPORT VERY
ISOLATED WET MICRO-BURSTS. HOWEVER...MORE THAN 5% SEVERE
PROBABILITIES DO NOT APPEAR WARRANTED DUE TO THE PREVIOUSLY
MENTIONED LIMITING FACTORS.
..DIAL.. 07/06/2009
.PREV DISCUSSION... /ISSUED 1134 AM CDT MON JUL 06 2009/
...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.
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