SWODY2
SPC AC 180534
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1234 AM CDT MON OCT 18 2010
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
UPPER AIR SETUP THIS PERIOD WILL BE CHARACTERIZED BY REX PATTERN
OVER WRN NORTH AMERICA...ANCHORED BY RIDGING FROM PAC NW ACROSS FAR
WRN CANADA...AND SLOW-MOVING MID-UPPER LEVEL CYCLONE NOW MOVING SEWD
JUST OFFSHORE CENTRAL CA COAST. DOWNSTREAM TROUGHING AND BROAD
CYCLONIC FLOW ALOFT WILL CHARACTERIZE MUCH OF CONUS E OF
ROCKIES...INCLUDING GENTLY CURVING SUBTROPICAL JET OVER GULF COAST
AND BROAD NRN-STREAM JET FROM UPPER MIDWEST TO OH VALLEY AND
MID-ATLANTIC REGION. STG CONSENSUS OF DETERMINISTIC AND SREF
GUIDANCE INDICATES CENTER OF 500 MB CYCLONE WILL BE JUST OFFSHORE
SAN BY 20/00Z. CYCLONE THEN SHOULD TURN EWD AND MOVE INLAND OVER
EXTREME NRN BAJA AND EXTREME SRN CA THROUGH REMAINDER PERIOD.
AT SFC...FRONTAL ZONE NOW ANALYZED OVER SERN CO...KS AND MO IS
EXPECTED TO MOVE SLOWLY SWD ACROSS OH VALLEY...OZARKS AND SRN HIGH
PLAINS DAY-1. BY 20/00Z...FRONT SHOULD BE MOVING SLOWLY SWD ACROSS
SRN APPALACHIANS...NRN AL AND MS...QUASISTATIONARY FARTHER W ACROSS
CENTRAL/SW TX.
...CENTRAL TX TO ARKLATEX REGION AND NRN LA...
SCATTERED TO WIDELY SCATTERED TSTMS -- PRIMARILY ELEVATED IN NATURE
-- MAY BE ONGOING AT BEGINNING OF PERIOD OVER PORTIONS OK...NW TX
AND AR. THIS ACTIVITY SHOULD DIMINISH DURING MORNING/EARLY
AFTERNOON AS IT MOVES SEWD...ITS OUTFLOW CONTRIBUTING TO
BAROCLINICITY IN FRONTAL ZONE.
BY MID-AFTERNOON...SECOND ROUND OF CONVECTION IS FCST TO DEVELOP
INVOF FRONTAL ZONE WHERE WEAK CONVERGENCE...DIABATIC SFC HEATING AND
ADEQUATE LOW-LEVEL MOISTURE WILL ERODE CINH. BECAUSE OF
PERSISTENT/ANTECEDENT TRAJECTORIES FROM CONTINENTAL
ANTICYCLONE...MARINE AIR MASS MODIFICATION WILL NOT BE COMPLETE OVER
WRN GULF. HOWEVER...PLUME OF 50S TO MID-60S DEW POINTS ALREADY HAS
BEEN ANALYZED ON 18/03Z SFC CHART. EXPECT BALANCE OF VERTICAL
MIXING AND MOIST ADVECTION AHEAD OF FRONT TO YIELD DEW POINTS UPPER
50S TO MID 60S F...CONTRIBUTING TO MLCAPE COMMONLY 1000-1500
J/KG...LOCALLY NEAR 2000 J/KG. WEAK LOW-MIDDLE LEVEL WINDS WILL
LIMIT SHEAR...ALTHOUGH STG UPPER FLOW BENEATH N RIM OF SUBTROPICAL
JET MAY AID IN STORM VENTILATION/ORGANIZATION. WELL-MIXED SUBCLOUD
LAYERS MAY FOSTER STG TO DAMAGING GUSTS FROM A FEW TSTMS...AND
ISOLATED SVR HAIL ALSO IS POSSIBLE.
...SRN NV/NWRN AZ TO SRN CA...
NARROW CORRIDOR OF ENHANCED MIDLEVEL WINDS -- I.E. 30-40 KT AT 500
MB -- IS FCST TO BECOME JUXTAPOSED WITH MRGL LOW-LEVEL
MOISTURE...FROM AREA BETWEEN LAS-YUM NWWD ACROSS PORTIONS SRN CA.
VEERING OF FLOW WITH HEIGHT WILL CONTRIBUTE TO 30-35 KT EFFECTIVE
SHEAR IN SOME LOCALES...ATOP WELL-MIXED BOUNDARY LAYER.
HOWEVER...MID-UPPER LAPSE RATES NOT MUCH GREATER THAN MOIST
ADIABATIC ARE PROGGED...SIGNIFICANTLY LIMITING BUOYANCY. ATTM SVR
POTENTIAL APPEARS TOO WEAK/CONDITIONAL TO ASSIGN PROBABILITIES.
..EDWARDS.. 10/18/2010
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