SWODY1
SPC AC 092047
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0347 PM CDT SAT JUL 09 2011
VALID 092100Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS NEWD
INTO THE MID MO RIVER VALLEY...
AMENDED TO ADD THUNDER AREA FOR TX PANHANDLE AND WRN OK DUE TO
PARCELS REACHING LFC AS TEMPERATURES HIT 110F.
OPERATIONAL AND HIGH RESOLUTION MODELS CONTINUE TO SHOW DIFFERENT
SOLUTIONS IN CONVECTIVE EVOLUTION THIS AFTERNOON...THOUGH PREVIOUS
FORECAST STILL APPEARS ON TRACK.
MOST SIGNIFICANT CHANGE TO OUTLOOK WAS TO LOWER THE SEVERE
PROBABILITIES ACROSS PORTIONS OF NRN MN AND WI DUE TO MOSTLY CLOUDY
SKIES AND WEAK FORCING. A STORM OR TWO MAY STILL INITIATE ALONG THE
FRONT NEAR THE ND/MN BORDER...THOUGH ANY STORMS SHOULD BE VERY
ISOLATED.
...CENTRAL PLAINS...
LOWERED THE SEVERE PROBABILITIES FOR PORTIONS OF NERN CO DUE TO
DRIER AIR SPREADING INTO THE AREA FROM THE NW...BEHIND BOUNDARY
LOCATED NEAR SNY-LIC LINE.
STORMS HAVE RECENTLY DEVELOPED ALONG THE FRONT RANGE OF CO AND WILL
SPREAD ENEWD WITHIN 20-30 KT WSWLY MID LEVEL FLOW ALOFT. WEAK
SURFACE LOW WAS LOCATED IN SWRN KS AND THIS WAS RESULTING IN WEAK
WLY BOUNDARY WINDS ACROSS ERN CO. GIVEN THE RELATIVELY DRY BOUNDARY
LAYER...GUSTY WINDS ARE POSSIBLE AND STORM OUTFLOWS MAY EVENTUALLY
CONGEAL INTO AN MCS.
...MID MO RIVER VALLEY...
SHIFTED SLIGHT RISK SEWD SOMEWHAT INTO IA TO ACCOUNT FOR STORMS...
AND POSSIBLE MCS...TRACKING ENEWD FROM NEB EWD INTO IA...WHERE LOW
LEVEL JET IS FORECAST TO BE FOCUSED BETWEEN 06-12Z.
MINOR ADJUSTMENTS TO THUNDER LINE BASED ON CURRENT TRENDS...
OTHERWISE REST OF FORECAST ON TRACK.
..IMY.. 07/09/2011
.PREV DISCUSSION... /ISSUED 1128 AM CDT SAT JUL 09 2011/
...SD/MN/EASTERN NEB/IA
THE PRIMARY BAND OF WESTERLIES EXTENDS ACROSS THE NORTHERN TIER OF
STATES TODAY...WHILE AN UPPER RIDGE DOMINATES THE WEATHER OVER THE
CENTRAL AND SOUTHERN STATES. ONE SHORTWAVE TROUGH IS TRACKING
ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST. THIS FEATURE WILL
LEAVE PORTIONS OF THE DAKOTAS/NEB AND MN IN SHORTWAVE RIDGING MUCH
OF THE DAY. NEVERTHELESS...AMPLE LOW LEVEL MOISTURE IS IN PLACE
ALONG WITH A BREAKABLE CAP. IT APPEARS LIKELY THAT A FEW CLUSTERS
OF STRONG TO SEVERE THUNDERSTORMS WILL DEVELOP DURING THE HEAT OF
THE DAY OVER EASTERN SD/NEB AND TRACK INTO PARTS OF IA/MN DURING THE
EVENING. FORECAST SOUNDINGS SHOW OVER 30 KNOTS OF EFFECTIVE SHEAR
WHICH WILL SUPPORT ORGANIZED MULTICELL OR OCCASIONAL SUPERCELL
STRUCTURES. LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE WITH THE
STRONGER STORMS. DESPITE THE RELATIVELY FAVORABLE THERMODYNAMIC AND
SHEAR ENVIRONMENT...HAVE REMOVED THE HIGHER PROBABILITY AREAS DUE TO
UNCERTAINTIES REGARDING SEVERE STORM COVERAGE. OVERNIGHT...VARIOUS
MODEL SOLUTIONS SUGGEST CONVECTION MAY ORGANIZE UPSCALE AND SPREAD
TOWARD SOUTHEAST NEB/SOUTHWEST IA WITH A CONTINUED THREAT OF LOCALLY
GUSTY/DAMAGING WINDS.
...CENTRAL HIGH PLAINS...
CONSIDERABLE LOW LEVEL MOISTURE AND STRONG HEATING SUGGEST A RATHER
ACTIVE THUNDERSTORM DAY OVER THE MOUNTAINS AND FOOTHILLS OF CENTRAL
CO. THESE STORMS ARE EXPECTED TO SPREAD EASTWARD INTO THE PLAINS
THIS AFTERNOON AND EVENING. STEEP LOW/MID LEVEL LAPSE RATES AND
FAVORABLE DEEP LAYER SHEAR WILL PROMOTE ORGANIZED STORMS WITH A FEW
SUPERCELLS AND BOW STRUCTURES POSSIBLE. LARGE HAIL AND DAMAGING
WINDS ARE POSSIBLE IN THE STRONGER CELLS. STORMS ARE EXPECTED TO
SPREAD INTO WESTERN KS AFTER DARK BEFORE WEAKENING TONIGHT.
...SOUTHEAST...
WIDESPREAD MOISTURE IS PRESENT TODAY OVER THE SOUTHEAST STATES WITH
PWAT VALUES WELL OVER 2 INCHES AND SURFACE DEWPOINTS IN THE 70S.
DESPITE ONLY WEAK MID LEVEL LAPSE RATES...AFTERNOON SBCAPE VALUES
OVER 4000 J/KG ARE EXPECTED ALONG A CORRIDOR FROM SC INTO GA/AL.
STEEP LOW LEVEL LAPSE RATES AND RATHER WEAK STEERING FLOW SUGGEST A
POTENTIAL FOR WIDELY SCATTERED PULSE-SEVERE EVENTS WITH WET
MICROBURSTS THE PRIMARY THREAT.
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