000 FXUS66 KSTO 031115 AFDSTO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 400 AM PDT FRI SEP 03 2010 .DISCUSSION... WATER VAPOR IMAGERY SHOWS THE UPPER LEVEL RIDGE AXIS SHIFTING EWD INTO THE GREAT BASIN AHEAD OF THE UPPER TROF APPROACHING THE B.C. AND PAC NW COAST. STRONG LARGE SCALE SUBSIDENCE IS ALSO INDICATED AS THE FLOW TURNS SWLY WITH THE REPOSITIONING OF THE HIGH CENTER OFF THE NRN BAJA AND SOCAL COAST. THE STRATUS HAS RETURNED TO THE COAST...AND THE FT ORD PROFILER SHOWS THE DEPTH AROUND 1000 FT. THE STRONG SUBSIDENCE WILL KEEP THE MARINE LAYER RELATIVELY SHALLOW THROUGH SAT...BUT IT SHOULD DEEPEN BY SUN MORNING AS THE AFOREMENTIONED TROF MOVES ACROSS THE PAC NW AND WEAKENS THE LARGE SCALE SUBSIDENCE. OUR "MINI" HEAT WAVE WILL BE COMING TO AN END IN THE DELTA INFLUENCED AREAS TODAY...BUT IT WILL CONTINUE TO BE VERY WARM/HOT FARTHER FROM THE DELTA. THE TEMP/PRESSURE GRADIENT BETWEEN LAND AND OCEAN HAS NOW TURNED THE LOCAL GRADIENTS POSITIVE OR ONSHORE AND INITIATED THE DELTA BREEZE. WE EXPECT A BIG DROP IN MAX TEMPS IN THE SOLANO CO AREA TODAY...AND AT LEAST A COUPLE OF DEG OF COOLING SHOULD RESULT IN THE SRN SAC AND NRN SAN JOAQUIN VLY AS THE WARMING DOWNSLOPE/NLY ENDS...AND SWLY FLOW IS ESTABLISHED. HOWEVER THE SHALLOW MARINE LAYER WILL PRECLUDE ANY COOLING IN THE FOOTHILLS. IN ADDITION...THE SIERNEV WILL BE ON THE WRN EDGE OF THE THERMAL RIDGE AXIS OVER THE GREAT BASIN...AND MAY ACTUALLY EXPERIENCE SLIGHTLY WARMER TEMPS TODAY THAN YESTERDAY DUE TO A SLIGHT INCREASE IN 850 MBS TEMPS. AS THE TROF APPROACHES THE B.C./PAC NW COAST IT IS FORECAST TO ENHANCE AN UPPER JET SPEED MAX AHEAD OF IT AND FLATTEN THE RIDGING OVER NORCAL ON SAT. SOME UPPER LEVEL DIVERGENCE IS FORECAST IN THE DIRECT CIRCULATION OF THE JET MAX OVER ALONG THE CA/OR BORDER ON SAT AND SAT NITE AND SOME CLOUDINESS MAY DEVELOP IN OUR ZONES. ALTHO THE GFS RH CROSS SECTION WAS VERY DRY FOR THIS TIME...WE WOULD NOT BE SURPRISED IF SOME CLOUDINESS DID DEVELOP. THE MAIN EFFECT FROM THE SRN PORTION OF THIS TROF WILL BE COOLING AND AN INCREASE IN WLY WINDS OVER THE NRN MTNS AND SIERNEV FROM LATE SAT AND INTO SUN. THEN SOME MODERATION IN TEMPERATURE IS EXPECTED ON MON AS THIS TROF MOVES E OF THE AREA. AFTER THE HOLIDAY...MODEL DIFFERENCES AND LACK OF RUN-TO-RUN CONTINUITY ARE CREATING SOME DOUBTS ABOUT THE DETAILS. THE GFS/ECMWF/GEM ALL SHOW SECONDARY SHORT WAVE ENERGY DROPPING SWD FROM THE GULF OF AK AND INTO NORCAL TUE AND WED...AND INTO THE GREAT BASIN ON THU. THE GFS/GEM STILL ADVERTISE THE FORMATION OF A CLOSED LOW OVER THE PAC NW AND NORCAL TUE/WED...WHILE THE ECMWF SHOWS MORE OF AN OPEN WAVE AND FASTER PATTERN. FOR NOW WE HAVE LEANED THE FORECAST TO THE COOLER/MORE UNSETTLED PATTERN OF THE GFS/GEM. THE LOOP OF THE GEFS (GFS ENSEMBLE) SHOWS MORE OF AN OPEN WAVE PATTERN WITH THE SECONDARY ENERGY...AND MORE IN LINE WITH THE ECMWF BUT SLOWER. THE LATEST NEGATIVE ANOMALY OF 2.5 SD SEEMS TO SUPPORT THE COOLER/MORE UNSETTLED WX PATTERN IN THE EFP GRIDS...AND FEW IF ANY CHANGES WERE MADE...MAINLY TO ADJUST TIMING OF CHANCE OF PCPN TO TUE NITE IN SHASTA CO PER THE LATEST TIMING. JHM && .AVIATION... VFR CONDS CONTINUE THE NEXT 24 HOURS. LIGHT SFC WINDS ACROSS OUR CWA. WIND SPEEDS AT TAF SITES GENERALLY 10 KTS OR LESS. LIGHT SOUTHWESTERLY WINDS ALOFT. JBB && .STO WATCHES/WARNINGS/ADVISORIES...NONE. && $$
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