SWODY3
SPC AC 170727
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 AM CDT WED SEP 17 2008
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
NO APPRECIABLE CHANGE IN THE UPR AIR PATTERN EXPECTED ON FRIDAY WITH
PRIMARY BELT OF WLYS WELL N IN CANADA. WITHIN THE
STATES...CONVECTIVE INTERESTS WILL REVOLVE AROUND A WEAK SUBTROPICAL
IMPULSE THAT WILL MOVE TO THE MID/LWR MS VLY BY FRIDAY NIGHT AND A
POLAR DISTURBANCE MOVING INTO THE NWRN CONUS.
...NWRN CONUS...
MODEL SPREAD REMAINS SIGNIFICANT ON TIMING...DEPTH AND AMPLITUDE OF
THE UPR LOW EXPECTED TO MOVE ONSHORE CA/ORE LATE THU NIGHT/EARLY
FRIDAY MORNING. ATTM...IT APPEARS THAT THE PRIMARY HEIGHT
FALLS/LARGE SCALE ASCENT SHOULD SPREAD THROUGH PARTS OF NV/NW UT AND
INTO ID FRIDAY AFTN/EVE. PWAT VALUES WILL INCREASE...PRIMARILY VIA
MID-LVL MOISTENING...BUT IF THE SYSTEM ENDS UP TRACKING FARTHER
S...LOW-LVL MOISTURE ADVECTION MAY BE MORE ROBUST NWD FROM THE LWR
CO RVR VLY. IF THAT OCCURS...ANY TSTMS THAT DEVELOP AHEAD OF THE
SYSTEM COULD BECOME MORE ORGANIZED THAN CURRENTLY EXPECTED AND
REQUIRE ADDED SVR PROBABILITIES IN LATER FCSTS.
...LWR MS VLY...
INCREASING ESE LLVL FLOW AHEAD OF THE AFOREMENTIONED SUB-TROPICAL
IMPULSE WILL CONTRIBUTE TO A GRADUAL INCREASE IN LOW-LEVEL BOUNDARY
LAYER MOISTURE INTO PARTS OF THE LWR MS VLY REGION FRIDAY.
INCREASING INSTABILITY WILL SUPPORT TSTMS AS WEAK SUPPORT ALOFT
SPREADS ACROSS THE REGION. SOME STRONG TSTMS MAY BE PSBL ALONG THE
LA CST WHERE STEEPER MID-LVL LAPSE RATES /MINUS 8-10C AT H5/ BECOME
COINCIDENT WITH RICHER BOUNDARY LAYER MOISTURE AND 50-60 KTS OF
H3-H25 FLOW. WILL AWAIT BETTER AGREEMENT AMONG GUIDANCE ON THE
TIMING OF THE UPR TROUGH AND NOT COMMIT TO SVR PROBABILITIES ATTM.
..RACY.. 09/17/2008
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