[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 161731
SWODY2
SPC AC 161731

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT WED AUG 16 2006

VALID 171200Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN PLAINS...

...SYNOPSIS...
PRONOUNCED MID-UPPER LEVEL TROUGH -- NOW MOVING INLAND PACIFIC NW --
IS EXPECTED TO SHIFT FARTHER EWD ACROSS INTERIOR NW TO NRN ROCKIES
DURING DAY2...AS ASSOCIATED SWLY FLOW ALOFT AND MIDLEVEL SPEED MAX
SPREAD OVER NRN HIGH PLANS AND ND.  MEANWHILE...WEAK SRN STREAM
PERTURBATION -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NWRN
MEX S OF SWRN NM -- IS FCST TO LIFT NEWD ACROSS SRN/CENTRAL HIGH
PLAINS DURING THIS PERIOD.

AT SFC...COLD FRONT IS EXPECTED TO MOVE SEWD FROM CANADIAN HIGH
PLAINS AND MT...ACROSS DAKOTAS AND FAR NRN MN. FRONTAL-WAVE CYCLONE
SHOULD FORM INVOF BLACK HILLS...IN ADVANCE OF APCHG MID-UPPER
TROUGH.  AS THIS OCCURS...COLD FRONT SHOULD DECELERATE ACROSS NRN
SD/SRN ND AREA AND REMAIN QUASISTATIONARY UNTIL PASSAGE OF SFC LOW
LATE DAY-2 AND EARLY DAY-3.  MEANWHILE...WARM FRONTAL ZONE NOW OVER
SRN PLAINS IS FCST TO SHIFT/REDEVELOP NNEWD TO LOWER MO VALLEY.

...NRN PLAINS...
SCATTERED TSTMS ARE EXPECTED TO DEVELOP FROM MID-LATE AFTERNOON
ONWARD...WITH EVOLUTION TO ORGANIZED MCS POSSIBLE AFTER DARK ACROSS
PORTIONS DAKOTAS INTO WRN MN.  DAMAGING GUSTS AND LARGE HAIL WILL BE
POSSIBLE.  TORNADO POTENTIAL IS MORE CONDITIONAL/MRGL...AND
DEPENDENT ON MESOSCALE TO STORM-SCALE BOUNDARY RELATED PROCESSES.

FORECAST SOUNDINGS ACROSS THIS REGION SUGGEST FAVORABLE VERTICAL
SHEAR PROFILES ALONG AND N OF FRONT FOR SUPERCELLS...WITH STRONG
DIRECTIONAL VEERING CONTRIBUTING TO EFFECTIVE SHEARS AOA 50 KT. 
THERMODYNAMICS SHOULD BECOME INCREASINGLY FAVORABLE THROUGH
AFTERNOON ALSO...AS SFC DIABATIC HEATING AND FRONTAL LIFT REDUCE
CINH IN FAVORABLY MOIST BOUNDARY LAYER ENVIRONMENT.  MOIST ADVECTION
AND EVAPOTRANSPIRATIVE EFFECTS SHOULD RESULT IN AXIS OF SFC DEW
POINTS MID 60S ALONG OR JUST N OF FRONT...COMBINING WITH STEP
MIDLEVEL LAPSE RATES TO SUPPORT MLCAPES OVER 2000 J/KG OVER
CENTRAL/WRN DAKOTAS.  ISOLATED STG-SVR STMS ALSO WILL BE POSSIBLE
WWD ACROSS MUCH OF MT IN POST-FRONTAL ZONE OF BOUNDARY LAYER UPSLOPE
FLOW...JUXTAPOSED WITH COOLING ALOFT AND AT LEAST MRGL MOISTURE.

SVR POTENTIAL IS EXPECTED TO BE CONCENTRATED IN FAIRLY DENSE FASHION
INVOF BOUNDARY LAYER MOIST AXIS FROM AFTERNOON THROUGH EVENING
HOURS. MAIN UNCERTAINTY ATTM IS POSITIONING OF FRONT AND MOIST AXIS
ON MESO BETA SCALE.  PROBABILITIES THEREFORE MAY NEED TO BE BOOSTED
WITHIN BROADER 15 PERCENT AREA...ONCE THOSE ELEMENTS BECOME MORE
CERTAIN IN SUCCEEDING OUTLOOKS.

...CENTRAL PLAINS...
VERTICAL SHEAR IS FCST TO DIMINISH WITH SWD EXTENT FROM DAKOTAS
FRONTAL ZONE.  HOWEVER...PLUME OF FAVORABLE LOW LEVEL MOISTURE WILL
BE IN PLACE FROM SRN HIGH PLAINS NNEWD ACROSS MUCH OF CENTRAL PLAINS
REGION...ALONG WITH WEAK AFTERNOON CINH IN RELATIVELY CLOUD-FREE
AREAS. MULTICELL AND PULSE STORMS WILL PREDOMINATE...MOST INTENSE
OF WHICH MAY PRODUCE GUSTS NEAR SEVERE LEVELS DURING LATE
AFTERNOON/EARLY EVENING.

...IA/IL...
SEVERAL DETERMINISTIC PROGS ARE CONSISTENT IN DEVELOPMENT OF TSTM
CLUSTER ALONG OR N OF SFC WARM FRONT DURING EVENING...WHICH WOULD
MOVE SLOWLY ESEWD ACROSS MS RIVER WITH SOME POTENTIAL FOR DAMAGING
GUSTS AND MRGL HAIL.  AIR MASS IN THIS REGION WILL BE CHARACTERIZED
BY REGIONAL MOISTURE MAXIMUM...ASSOCIATED BOTH WITH PRIOR MOIST
ADVECTION AND WITH EVAPOTRANSPIRATION AT SFC.  THIS AREA ALSO WILL
BE WITHIN WAA/MOISTURE TRANSPORT REGIME...NEAR NOSE OF 30 KT
NOCTURNAL LLJ. THIS WILL SUPPORT PERSISTENCE OF ANY LATE
AFTERNOON/EARLY EVENING DEVELOPMENT OVERNIGHT. RELATIVELY WEAK
MIDLEVEL FLOW WILL LIMIT BULK SHEAR...AND THERE IS SOME CONCERN THAT
CAP MAY NOT BREAK DIURNALLY INVOF WARM FRONT.  THEREFORE SVR
PROBABILITIES ARE KEPT MRGL ATTM.

..EDWARDS.. 08/16/2006