AREA FORECAST DISCUSSION

 
 FXUS66 KSTO 230606 AAA
 AFDSTO
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE SACRAMENTO CA
 955 PM PST SUN NOV 22 2009
 
 .UPDATE DISCUSSION...
 ONLY PATCHES OF LOWER CLOUDS REMAIN OVER THE W SLOPE SIERNEV THIS 
 EVENING AS SUBSIDENCE AND DRIER NLY FLOW HAVE ERODED MUCH OF THE LOW 
 CLOUDINESS THAT WAS OVER INTERIOR NORCAL DURING THE DAY. AS LOW 
 PRESSURE MOVES EWD ACROSS THE GREAT BASIN TONIGHT...HIGH PRESSURE 
 WILL BUILD ALONG THE W COAST...AND A BAND OF CIRRUS OVER THE AREA 
 WILL LIKELY LIFT NWD/AND OR DISSIPATE AS THE RIDGE BUILDS TONIGHT 
 AND MON. THE RIDGE IS FORECAST TO CONTINUE TO BUILD OVER OUR REGION 
 THROUGH WED...SO DRY AND SEASONAL TEMPS ARE EXPECTED THROUGH THE 
 MIDDLE OF THE WEEK. 
 
 PRESSURE RISES ACROSS ORE AND INTO THE GREAT BASIN WILL RESULT IN 
 INCREASING N-NELY GRADIENTS TONIGHT AND MON WITH DOWNSLOPE FLOW 
 PREVAILING OVER INTERIOR NORCAL. THIS WILL RESULT IN MAINLY CLEAR 
 SKIES OVER INTERIOR NORCAL FOR THE NEXT COUPLE OF DAYS...ALONG WITH 
 LOCALLY BREEZY N TO NE WINDS IN THE TERRAIN-FAVORED AREAS. THE NLY 
 RDD-SAC GRADIENT HAS INCREASED TO OVER 2 MBS...AND NLY FLOW IS 
 COMMENCING IN THE VLY. THIS FOR THE MOST PART WILL PRECLUDE 
 WIDESPREAD FOG FORMATION. AT 04Z...THE DEWPOINTS AND RHS ARE STILL 
 RUNNING HIGHER THAN LAST NITE...BUT IT LOOKS AS IF THERE WILL BE 
 ENOUGH NLY WIND AND MIXING TO PRECLUDE FOG FORMATION TONITE AND MON 
 MORNING. WITH THE BUILDING RIDGE THERE WILL BE GOOD SYNOPTIC WARMING 
 THAT WILL SPREAD SW TO NE ACROSS THE INTERIOR OF NORCAL DURING THE 
 NEXT COUPLE OF DAYS. THIS WILL RESULT IN MILD TEMPS MAINLY OVER THE 
 COASTAL RANGE AS 850 TEMPS WARM TO ABOUT 10-12 DEG C WHILE 850 MBS 
 TEMPS OVER THE W SLOPE SIERNEV REMAIN MAINLY IN THE SINGLE DIGITS. 
 THAT MEANS SITES SUCH AS LAKEPORT...ALDER SPRINGS...KONOCTI WILL 
 HAVE MILD AFTERNOON TEMPS FOR THE NEXT COUPLE OF DAYS...WELL INTO 
 THE 60S...MAYBE NEARING 70 OVER THE HIGHER TERRAIN IN LAKE COUNTY. 
 THE NLY GRADIENT WILL ALSO RESULT IN LOCAL AREAS OF ADIABATIC 
 DOWNSLOPE WARMING...VCB/SUU FOR INSTANCE. THE GRADIENTS AND WINDS 
 ARE FORECAST TO BE A LITTLE STRONGER ON MON...AND THEN WEAKEN ON TUE 
 AS THE SURFACE HIGH CENTER DRIFTS FARTHER INTO THE INTERIOR WEST. 
 WITH THE ABSENCE OF FOG...VLY TEMPS WILL BE SEASONABLY MILD DURING 
 THE NEXT COUPLE OF DAYS AS WELL.    JHM 
 
 
 .PREVIOUS DISCUSSION...
 ABUNDANT LOW TO MID LEVEL CLOUDINESS ACROSS MUCH OF INTERIOR 
 NORTHERN CALIFORNIA THIS AFTERNOON IN ASSOCIATION WITH LAST NIGHTS 
 SYSTEM. THIS CLOUD MASS HAS BEEN SLOW TO DISSIPATE AND DRIFTING 
 SOUTHWARD THROUGH THE COURSE OF THE DAY. A FEW LIGHT SHOWERS 
 CONTINUE OVER THE SIERRA FOOTHILLS AND MOUNTAINS AND WILL CONTINUE 
 TO DO SO THROUGH THIS EVENING. THE LOW LEVEL STRATUS WILL SLOWLY 
 DISSIPATE THIS EVENING AND TONIGHT...POTENTIALLY MAKING WAY FOR 
 PATCHY FOG TO DEVELOP THROUGH THE VALLEY AND FAVORED MOUNTAIN 
 VALLEYS. 
 
 WARMING AND DRY TREND WILL BEGIN MONDAY AS HIGH PRESSURE ALOFT 
 BUILDS ALONG THE WEST COAST. SURFACE HIGH PRESSURE WILL SET UP IN 
 THE GREAT BASIN ALLOWING FOR SOME GUSTY WINDS TO BLOW DOWN FAVORED 
 SIERRA CANYONS DURING THE OVERNIGHT HOURS. OTHERWISE...TEMPERATURES 
 WILL BE PLEASANT WITH HIGHS AT OR SLIGHTLY WARMER THAN NORMAL THE 
 NEXT SEVERAL DAYS. 
 
 .EXTENDED DISCUSSION (THANKSGIVING THROUGH SUNDAY)...
 THE MODELS ARE IN GOOD AGREEMENT WITH A TROUGH IMPACTING THE NRN CAL 
 ON THU AND INTO FRI.  BUT THE GFS...EC AND GEM ARE OFF JUST A BIT ON 
 THE TIMING WITH THE GFS NOW BEING MORE PROGRESSIVE.  YESTERDAY THE 
 EC WAS MORE PROGRESSIVE...SO STILL NOT QUITE SURE ON EXACT TIMING. 
 THE HPC SOLUTION USED A BLEND OF THE TWO...BUT FAVORED MORE TOWARD 
 THE EC.  SO WENT WITH A CHANCE OF RAIN OVER THE NRN THREE-QUARTERS 
 OF THE FORECAST MOUNTAIN AREAS AND THE NRN HALF OF THE SACRAMENTO 
 VALLEY.  THE SACRAMENTO AREA SHOULD STAY DRY WITH VARIABLE 
 CLOUDINESS.  JMC 
 
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 .AVIATION...
 WEAK FRONTAL SYSTEM MOVING EASTWARD TONIGHT. WINDS WILL REMAIN LIGHT 
 AT 10 KTS OR LESS FOR THE NEXT 24 HRS...TRANSITIONING N TO NWRLY FOR 
 ALL TAF SITES BY 06Z. WINDS WILL BE LIGHTEST OVERNIGHT THRU EARLY 
 MORNING ALLOWING PATCHY FOG TO DEVELOP IN THE CENTRAL VALLEY... 
 GENERALLY IN THE 12-17Z TIMEFRAME. MVFR CONDS WITH LOCAL IFR COULD 
 DEVELOP IN PORTIONS OF THE CENTRAL SAC VALLEY INTO THE SAN JOAQUIN 
 VALLEY WHICH MAY AFFECT THE KSMF-KSAC-KMHR-KSCK TAF SITES. KRDD-KRBL 
 VCNTY WILL REMAIN CLEAR WITH NO FOG DUE TO NEARBY DOWNSLOPE FLOW. 
 WINDS ALOFT LIGHT TO MODERATE NORTHERLY.  JBB
 
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 .STO WATCHES/WARNINGS/ADVISORIES...NONE. 
 
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