[SWODY1] SWODY1

Sun May 21 06:05:02 UTC 2006

ACUS01 KWNS 210601
SWODY1
SPC AC 210559

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT SUN MAY 21 2006

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN ORE...SERN
WA...WRN ID...

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MT...EXTREME N-CENTRAL
WY...

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL KS TO WRN KY
AND NWRN TN...

...SYNOPSIS...
STABLE LARGE SCALE PATTERN WITH MEAN WRN RIDGE AND ERN TROUGH WILL
CONTINUE...BUT WITH SOME IMPORTANT SHORTWAVE CHANGES DURING DAY-1.
STRONG MID/UPPER LEVEL LOW INITIALLY OVER UPPER GREAT LAKES IS FCST
TO TURN EWD THEN NEWD PAST MEAN TROUGH POSITION...THEN
PRONOUNCED MID/UPPER LEVEL LOW -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY INVOF 35N130W...HAS BEGUN SLGT SEWD TURN AND SHOULD CONTINUE
THIS TREND THROUGH PERIOD.  LOW SHOULD BE LOCATED JUST OFFSHORE SRN
CA/NRN BAJA BY 22/12Z...WITH ASSOCIATED LOW LEVEL BAROCLINIC ZONE
INCREASING CONVECTIVE POTENTIAL ACROSS MUCH OF CENTRAL/SRN CA WITH
TIME THROUGH DAY-1.  HEIGHTS ALSO SHOULD FALL ACROSS PACIFIC NW
MID-LATE PERIOD IN RESPONSE TO SPEED MAX NOW DIGGING SEWD ACROSS
GULF OF AK.

AT SFC...RAGGED BAROCLINIC ZONE WITH MESOBETA SCALE OUTFLOW
ENHANCEMENTS WILL PERSIST FROM SC COAST WNWWD OVER OZARKS REGION AND
SRN KS...BECOMING DIFFUSE FARTHER WNW INTO ERN CO. 
SECONDARY/REINFORCING FRONT NOW EVIDENT FROM ERN MT SEWD ACROSS NERN
NEB SHOULD BECOME NEARLY STATIONARY OVER NRN HIGH PLAINS THROUGH
MOST OF PERIOD...AND NEARLY COLOCATED WITH LEE TROUGH IN MT.

...INTERIOR NWRN CONUS...
AS HEIGHTS FALL AND GRADIENTS TIGHTEN ACROSS THIS
REGION...DEEP-LAYER VERTICAL SHEAR PROFILES ARE EXPECTED TO BECOME
FAVORABLE FOR SEVERE DURING AFTERNOON IN TANDEM WITH PEAK SFC
WARMTH.  NEARLY STRAIGHT LOW-MIDDLE LEVEL HODOGRAPHS ARE
PROGGED...RESULTING FROM LOW LEVEL FLOW WITH WEAK SPEEDS BUT
PRONOUNCED VEERING THAT TRANSITIONS TO 50-60 KT SSWLY FLOW IN
400-600 MB LAYER...YIELDING ABOUT 50 KT EFFECTIVE SHEAR.  MODIFIED
ETA/WRF SOUNDINGS SUGGEST SFC TEMPS LOW 70S AND DEW POINTS LOW 50S F
WILL RESULT IN WELL MIXED BOUNDARY LAYERS WITH LITTLE OR NO
CINH...INVERTED-V THERMODYNAMIC PROFILES IN SUBCLOUD LAYER...AND
600-1200 J/KG MLCAPE.  THESE FACTORS SUPPORT BOTH BOW AND SUPERCELL
POTENTIAL...WITH DAMAGING GUSTS AND LARGE HAIL.  MAIN CONCERN FOR
CONVECTIVE COVERAGE AND ORGANIZATION IS STRENGTH OF AFTERNOON
HEATING GIVEN POTENTIAL FOR MID/HIGH LEVEL CLOUDS STREAMING NWD FROM
VICINITY OF LOW APCHG CA.  SVR THREAT SHOULD DIMINISH ONCE EVENING
COOLING BEGINS TO STABILIZE PRECONVECTIVE BOUNDARY LAYER...AND AS
ACTIVITY MOVES INTO MORE STABLE AMBIENT AIR MASS FARTHER NE.

...MT...
ANOTHER EPISODE OF STRONG-SEVERE TSTMS IS POSSIBLE DURING AFTERNOON
INTO EARLY EVENING...RESULTING FROM ACTIVITY INITIATING INVOF HIGHER
TERRAIN OF SRN/WRN MT MID-LATE AFTERNOON.  TSTMS MAY ORGANIZE INTO
ONE OR MORE OUTFLOW-DOMINANT BANDS OR CLUSTERS...FORWARD PROPAGATING
WITH MAIN THREAT BEING DAMAGING WIND.  ALTHOUGH HEIGHTS ARE EXPECTED
TO RISE GRADUALLY THROUGHOUT PERIOD OVER THIS REGION AS MEAN RIDGE
AMPLIFIES...STRONG SFC HEATING AND WEAKENING CINH SHOULD SUPPORT
AFTERNOON TSTM DEVELOPMENT.  FAVORABLE DEEP-LAYER SHEAR PROFILES ARE
EXPECTED WITH 40-50 KT OVER NRN PORTION OUTLOOK AREA...TRENDING TO
ABOUT 35 KT AND LESS S OF MT/WY BORDER.  SVR POTENTIAL IS EXPECTED
TO DIMINISH MARKEDLY DURING EVENING AS FOREGOING BOUNDARY LAYER
DIABATICALLY COOLS...AND AS ACTIVITY MOVES INTO PROGRESSIVELY LESS
BUOYANT AIR MASS E OF SFC FRONT.

...CENTRAL PLAINS TO SC COAST...
AS GREAT LAKES UPPER LOW EJECTS...HEIGHTS ARE FCST TO RISE ACROSS
MOST OF CENTRAL/SERN CONUS THROUGHOUT PERIOD.  CORRESPONDING
DECREASE IN HEIGHT GRADIENT ALOFT...AND RELATED WEAKENING OF BOTH
LARGE SCALE SUPPORT AND DEEP-LAYER KINEMATIC FIELDS WITH TIME --
INDICATE MORE CONDITIONAL/DISORGANIZED SEVERE POTENTIAL THIS PERIOD
OVER MOST OF THIS CORRIDOR.  HOWEVER...WILL MAINTAIN MRGL THRESHOLD
PROBABILITIES FOR CATEGORICAL SLGT RISK ACROSS SUBSET OF THIS
CORRIDOR...FROM S-CENTRAL KS TO NWRN TN -- COMBINING
1. CONDITIONAL DIURNAL RISK OF WIND AND HAIL INVOF FRONT WITH
2. SOMEWHAT HIGHER CONFIDENCE BUT LOWER MAGNITUDE HAIL THREAT AFTER
DARK N OF FRONT.

VEERING WIND PROFILES WITH HEIGHT WILL CONTINUE DESPITE WEAKENING
LOW-MIDLEVEL SPEEDS...SUPPORTING POTENTIAL FOR STORM ORGANIZATION
WITH ANY ACTIVITY THAT DEVELOPS.  MIDLEVEL LAPSE RATES ACROSS THIS
REGION SHOULD REMAIN RELATIVELY STEEP -- 7.5-8.5 DEG C/KM -- IN
SUPPORT OF FAVORABLE BUOYANCY. AFTERNOON MLCAPES ALONG FRONT...AND
LATE EVENING ELEVATED MUCAPES FARTHER N...SHOULD BE ENHANCED BY LOW
LEVEL MOIST AXIS WITH VALUES OF EACH AROUND 1000-1500 J/KG.

...CENTRAL HIGH PLAINS...
WIDELY SCATTERED TSTMS IN LOOSELY ORGANIZED CLUSTERS MAY EVOLVE
DURING LATE AFTERNOON AND EVENING ACROSS HIGH PLAINS FROM NERN WY TO
ERN CO/WRN KS...SOME OF WHICH MAY PRODUCE GUSTS NEAR SEVERE LIMITS. 
AFTERNOON INITIATION WILL BE AIDED BY ELY/UPSLOPE COMPONENT OF SFC
FLOW...AMIDST WEAK CINH CAUSED BY AT LEAST MRGL SFC MOISTURE AND
STRONG HEATING OF ELEVATED TERRAIN.  VERY WEAK LOW/MIDLEVEL FLOWS
AND DEEP-LAYER SHEAR PROFILES ARE EXPECTED TO LIMIT POTENTIAL FOR
SUSTAINED/WELL-ORGANIZED SVR...THOUGH DEEPLY MIXED BOUNDARY LAYERS
WILL SUPPORT STRONG/POSSIBLY SVR OUTFLOW WINDS IN SOME LOCALES.

..EDWARDS/GRAMS.. 05/21/2006