FXUS66 KSTO 260444
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
900 PM PST WED NOV 25 2009
.DISCUSSION...
CLEAR SKIES OVER THE FORECAST AREA TONIGHT UNDER UPPER LEVEL HIGH
PRESSURE RIDGE. AIRMASS WARMED A BIT TODAY UNDER SUBSIDENCE AND
MOST LOCATIONS ON THE ORDER OF A FEW DEGREES ABOVE TUESDAY AND 10 TO
15 DEGREES ABOVE NORMAL FOR THIS TIME OF YEAR. SURFACE GRADIENTS ARE
QUITE LIGHT AND AS A RESULT...WINDS ACROSS THE AREA ARE PRETTY MUCH
LIGHT EVERYWHERE. LIGHT WINDS AND TEMPERATURE DEW POINT SPREADS
SIMILAR TO 24 HOURS AGO DESPITE SLIGHTLY WARMER TEMPERATURES SO
PATCHY FOG LIKELY TO BE AN ISSUE AGAIN TONIGHT IN THE SOUTHERN
SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEY. WITH SIMILAR CONDITIONS
OVERNIGHT...EXPECT SIMILAR OVERNIGHT LOWS AND HANDLED IN CURRENT
FORECAST PACKAGE. FRONTAL BAND NOW APPROACHING 130 WEST AT 40 NORTH
WILL SPREAD HIGH CLOUDINESS OVER NORCAL ON THANKSGIVING DAY. COOLER
AIR FILTERING INTO THE AREA COMBINED WITH CLOUD COVER WILL BRING
DAYTIME HIGHS DOWN SEVERAL DEGREES BUT DAYTIME HIGHS STILL LIKELY TO
REMAIN ABOVE NORMAL FOR THIS TIME OF YEAR.
FRONTAL PASSAGE REMAINS ON TRACK FOR PASSAGE THROUGH THE NORTHERN
SACRAMENTO VALLEY AROUND MID DAY FRIDAY. MODELS CONTINUE TO FLIP
FLOP ON DEPTH OF SYSTEM HOWEVER WITH 00Z NAM NOW SHOWING A SHALLOWER
TROUGH AND KEEPING PRECIP A LITTLE FARTHER NORTH. WITH MODEL
INCONSISTENCIES...WILL NOT MAKE ANY MAJOR CHANGES AT THIS TIME.
EITHER WAY...QPF REMAINS LIGHT AND DESPITE RELATIVELY LOW SNOW
LEVELS...RAINFALL OR MOUNTAIN SNOWFALL SHOULD NOT BE A SIGNIFICANT
ISSUE. ISSUED AN SPS TO COVER NUISANCE FACTOR DURING THE HOLIDAY
WEEKEND. MORE COOLING FRIDAY ASSOCIATED WITH THE TROUGH WILL BRING
DOWN DAYTIME HIGHS TO NEAR NORMAL FOR THIS TIME OF YEAR. MAIN UPPER
TROUGH AXIS FORECAST TO SHIFT EAST OF THE CWA BY 12Z SATURDAY.
ISOLATED SHOWERS WILL REMAIN A THREAT OVER THE SIERRA EARLY SATURDAY
IN CYCLONIC FLOW AROUND BACK SIDE OF LOW.
SURFACE HIGH PRESSURE FORECAST TO PUSH INTO PACIFIC NORTHWEST BY
SATURDAY AFTERNOON BRINGING FAIRLY TIGHT SURFACE GRADIENT OVER
NORCAL BY SATURDAY AFTERNOON. 18Z GFS SHOWS ABOUT A 9 MB SURFACE
GRADIENT FROM MFR TO SAC. WITH GOOD UPPER LEVEL SUPPORT...BREEZY
WINDS ON TAP FOR SATURDAY. BREEZY CONDITIONS WILL ELIMINATE ANY FOG
THREAT IN THE VALLEY SATURDAY NIGHT.
&&
EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)...
LATEST RUNS OF EC/GFS/GEM IN FAIRLY GOOD AGREEMENT WITH BROAD
RIDGING IN PLACE OVER THE WEST COAST THROUGH THE REMAINDER OF THE
WEEKEND AND INTO EARLY NEXT WEEK. THE 18Z GFS FORMED A ROGUE CUTOFF
LOW NEAR 140W AND TRACKED IT SE TOWARD SRN CAL AND BAJA ON WED BUT
00Z HAS ELIMINATED THIS LOW AND NOW APPEARS ON TRACK WITH OTHER
MODELS.
&&
.AVIATION...
VFR CONDITIONS EXPECTED OVERNIGHT. AREAS WITH MVFR CIGS AND LOCAL
IFR/LIFR VSBY IN FOG WILL AGAIN IMPACT KSMF...KSAC...KMHR AND KSCK
AROUND 10-12Z THURSDAY MORNING. THICKER FOG/BR WILL LAST THROUGH
17-18Z WITH LINGERING HZ IN THE AFTERNOON. VFR CONDITIONS EXPECTED
ELSEWHERE EXCEPT IN LOCAL MOUNTAIN VALLEY FOG. LOCAL E SFC WNDS
GUSTING TO 25 KT THURSDAY MORNING ALONG W SLOPE OF THE SIERRA
CANYONS.
&&
.STO WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
