SWODY1
SPC AC 210529
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 AM CDT SAT MAR 21 2009
VALID 211200Z - 221200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PROGRESSIVE SYNOPTIC-SCALE PATTERN FCST THROUGH PERIOD..AS SERIES OF
NW-FLOW SHORTWAVES REINFORCE MEAN TROUGHING THAT WILL SHIFT EWD
OFFSHORE E COAST. UPSTREAM RIDGING WILL AMPLIFY SOMEWHAT AND MOVE
EWD ACROSS PLAINS STATES...PENETRATED OVER S-CENTRAL PLAINS BY
LOW-AMPLITUDE SHORTWAVE NOW OVER NRN MEX AND SWRN NM.
MEANWHILE...SPEED MAX DIGGING SSEWD AROUND BACK SIDE OF NERN PACIFIC
TROUGH WILL LEAD TO ITS AMPLIFICATION AND EWD MOVEMENT...RESULTING
IN STG TROUGHING JUST OFFSHORE ENTIRE PACIFIC COAST BY END OF
PERIOD. BY 22/12Z...HEIGHT FALLS ALOFT WILL COVER MOST OF CONUS
FROM ROCKIES WWD.
AT SFC...ELONGATED AREA OF LEE TROUGHING WILL PERSIST FROM MT SSEWD
ACROSS ERN CO AND ERN NM. WRN PORTION OF DIFFUSE WARM FRONTAL ZONE
-- INITIALLY ANALYZED FROM NE TX NWWD ACROSS WRN KS -- WILL
MOVE/REDEVELOP NWD ACROSS CENTRAL/NRN HIGH PLAINS BY 22/12Z AS
CLOSED LEE CYCLONE DEVELOPS OVER MT.
...CENTRAL HIGH PLAINS...
ISOLATED TSTMS MAY DEVELOP DURING MID-LATE AFTERNOON OVER THIS
REGION...AS SUSTAINED SFC HEATING WEAKENS CINH OVER HIGHER
ELEVATIONS OF THIS PORTION OF GREAT PLAINS. OFFSETTING EFFECTS OF
VERTICAL MIXING...AND MOIST ADVECTION ASSOCIATED WITH SELY FLOW FROM
PORTIONS KS/NEB...SHOULD CONTRIBUTE TO SFC DEW POINTS MID 30S TO LOW
40S F...WHICH MAY CONTRIBUTE TO SUFFICIENT BUOYANCY FOR HIGH-BASED
TSTMS TO FORM BEFORE EVENING DIABATIC COOLING INCREASES SBCINH
SUBSTANTIALLY. MODIFIED ETA-KF SOUNDINGS SUGGEST MLCAPE MAY BRIEFLY
TOP 1000 J/KG LATE AFTERNOON...AMIDST LOW-MIDLEVEL LAPSE RATES 8-9
DEG C/KM. LOW LEVEL WIND PROFILES WILL BE CHARACTERIZED BY STG
VEERING WITH HEIGHT...SUPPORTING CURVED/ENLARGED HODOGRAPHS. THOUGH
MID-UPPER LEVEL FLOW APPEARS WEAK FOR SUSTAINED STORM
ROTATION...EFFECTIVE SHEAR 30-40 KT IS POSSIBLE. UNCONDITIONAL SVR
PROBABILITIES ARE MRGL BECAUSE OF CONCERNS ABOUT COVERAGE AND
DURATION OF ANY CONVECTION THAT DOES DEVELOP...BUT BOTH HAIL AND
STG-SVR GUSTS ARE POSSIBLE FROM ANY SUSTAINED ACTIVITY.
...SRN HIGH PLAINS...
SRN-STREAM SHORTWAVE TROUGH WILL WEAKEN AS IT MOVES TOWARD MEAN
RIDGE POSITION...AND MAY BE PRECEDED BY CONSIDERABLE HIGH CLOUDS
THAT COULD DAMPEN INSOLATION RELATED HEATING. FCST SOUNDINGS
SUGGEST WEAK MID-UPPER LEVEL LAPSE RATES OVER SRN HIGH
PLAINS...ASSOCIATED WITH RELATIVELY HIGH MID-UPPER RH THAT SIGNALS
SUCH CLOUD COVER. LOW-MIDLEVEL WINDS ALSO WILL BE RATHER WEAK IN
SUCH CLOSE PROXIMITY TO UPPER RIDGE...MINIMIZING VERTICAL SHEAR.
THEREFORE...CONSIDERING THOSE FACTORS AND ABSENCE OF MORE ROBUST LOW
LEVEL MOISTURE...SVR POTENTIAL WITH ANY CONVECTION THAT CAN DEVELOP
APPEARS TOO WEAK/CONDITIONAL FOR PROBABILITIES AOA 5 PERCENT ATTM.
..EDWARDS/GARNER.. 03/21/2009
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