SPC AC 141740
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1240 PM CDT FRI AUG 14 2009
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS
AND CNTRL PLAINS...
CORRECTED FOR 5 % PROBABILITY ADJUSTMENT
...NRN PLAINS...
SOUTHWEST FLOW WILL BE IN PLACE ACROSS THE NCNTRL U.S. SATURDAY AS A
CLOSED-OFF LOW MOVES SLOWLY EWD NEAR THE MONTANA-CANADA BORDER. AT
THE SFC...A COLD FRONT IS FORECAST TO MOVE EWD ACROSS THE DAKOTAS.
ALTHOUGH MUCH OF THE REGION SHOULD BE CAPPED...SCATTERED ELEVATED
THUNDERSTORMS MAY BE ONGOING SATURDAY MORNING WITH THE MOST LIKELY
AREA FROM NWRN ND SEWD INTO ERN SD WHERE WARM ADVECTION SHOULD BE
QUITE STRONG. DURING THE AFTERNOON...A SUBTLE SHORTWAVE-TROUGH IS
FORECAST TO MOVE NEWD ACROSS THE NRN PLAINS AND AMPLIFY. THIS SHOULD
PROVIDE SUPPORT FOR SCATTERED SFC-BASED THUNDERSTORM INITIATION
ESPECIALLY IN THE ERN DAKOTAS SATURDAY AFTERNOON AS SFC TEMPS
WARM...THE CAP WEAKENS AND MODERATE DESTABILIZATION TAKES PLACE.
FORECAST SOUNDINGS ACROSS THE REGION SATURDAY AFTERNOON SHOW 25-35
KT OF VERTICAL SHEAR ACROSS MUCH OF THE REGION WHICH SHOULD BE
SUFFICIENT FOR ISOLATED SEVERE STORMS. MID-LEVEL LAPSE RATES ON
FORECAST SOUNDINGS ARE ONLY MARGINALLY STEEP AND DESTABILIZATION MAY
BE HAMPERED SOME BY MORNING CONVECTION. 0-3 KM LAPSE RATES DO APPEAR
STEEP AND LOW-LEVEL FLOW IS FORECAST TO STRENGTHEN DURING THE
AFTERNOON SUGGESTING A POTENTIAL FOR DAMAGING WIND GUSTS. HAIL
SHOULD BE CONCENTRATED IN AREAS WHERE INSTABILITY BECOMES LOCALLY
MAXIMIZED.
...CNTRL HIGH PLAINS AND CNTRL PLAINS...
SOUTHWEST FLOW WILL BE IN PLACE ACROSS THE REGION AS AN UPPER-LEVEL
TROUGH OVER THE INTERMOUNTAIN WEST APPROACHES FROM THE WEST. AN AREA
WITH STRONG WARM ADVECTION SHOULD BE PRESENT IN THE CNTRL PLAINS
WITH SCATTERED MORNING CONVECTION POSSIBLE. HOWEVER...A VERY MOIST
AIRMASS SHOULD ALLOW FOR MODERATE TO STRONG DESTABILIZATION ACROSS
MOST OF THE REGION BY AFTERNOON. VERTICAL SHEAR ON FORECAST
SOUNDINGS SHOULD BE STRONG ENOUGH FOR ISOLATED SEVERE THUNDERSTORMS
THAT PERSIST OR INITIATE IN THE AFTERNOON.
FURTHER TO THE WEST ACROSS THE CNTRL HIGH PLAINS...A CLUSTER OF
THUNDERSTORMS APPEAR LIKELY TO INITIATE IN THE HIGHER TERRAIN OF SE
WY AND NRN CO BY LATE AFTERNOON. THIS ACTIVITY SHOULD BE SUPPORTED
BY A MID-LEVEL JET AND SHORTWAVE TROUGH EJECTING EWD OUT OF THE
CNTRL ROCKIES. FORECAST SOUNDINGS ACROSS THE CNTRL HIGH PLAINS
SATURDAY AFTERNOON SHOW STRONG VERTICAL SHEAR PROFILES AND ENOUGH
INSTABILITY FOR ORGANIZED SEVERE STORMS. DUE TO THE STRONG VERTICAL
SHEAR...A FEW THUNDERSTORMS MAY ROTATE AND STEEP MID-LEVEL LAPSE
RATES APPEAR FAVORABLE FOR HAIL. AS CONVECTIVE COVERAGE EXPANDS EWD
SATURDAY EVENING ACROSS NEB...A WIND DAMAGE THREAT SHOULD ALSO
DEVELOP. THE SEVERE THREAT COULD BECOME ENHANCED IF AN MCS CAN
ORGANIZE ON THE WRN SIDE OF A STRENGTHENING LOW-LEVEL JET.
..BROYLES.. 08/14/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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