000
FXUS66 KSTO 100531
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
930 PM PST TUE MAR 9 2010

.DISCUSSION...
UPPER LEVEL TROF AND ASSOCIATED STRONG VORT MAX ALONG THE N COAST
WAS ALREADY SPREADING PCPN INTO WRN SHASTA CO AND THE COASTAL MTNS
BY 8 PM. THE TROF IS MOVING AT ABOUT 40 KTS...AND WILL BE E OF OUR
FORECAST AREA AROUND 12Z WED...AND PCPN WILL BE WINDING DOWN.
THUS...WE HAVE ONLY ABOUT AN 8 HR WINDOW OR SO OF EXPERIENCING PCPN
IN OUR CWA. THE FAST MOVING NATURE OF THIS TROF WILL RESULT IN
RELATIVELY LOW QPFS...AND APPARENTLY A VERY LOW END ADVSRY AT BEST
FOR OUR MTN ZONES. ACCORDING TO THE SHASTA DAM PROFILER THE SNOW
LEVELS ARE AROUND 2200 FT.

THE MAIN FRONTAL BAND PCPN IS JUST UNDER 100 MILES WIDE...MOVING AT
40 KTS...WHILE A NARROW BAND OF SHOWERS HAS DEVELOPED ALONG THE
SURFACE FRONT ALONG THE N COAST. THEREFORE A VERY MARGINAL RAIN/SNOW
EVENT DUE TO THE RATHER LOW PW AIR AS ILLUSTRATED BY THE SPARSE .50
TO .60 INCH PWS ON THE BLENDED TPW PRODUCT.

MOST OF THE PCPN WILL WIND DOWN BEFORE SUNRISE WED...ALTHOUGH SOME
LIGHT SNOW SHOWERS MAY CONTINUE INTO THE MORNING HRS OVER THE
SIERNEV...AND A POSITIVELY TILTED RIDGE WILL BEGIN TO BUILD INTO
NORCAL FROM WED AFTN THROUGH THU. THIS WILL RESULT IN THE BEGINNING
OF A WARMING/DRYING TREND. BASED ON THE SYNOPTIC PATTERN AND CURRENT
TRENDS...BELIEVE THE ETA/NAM BUFKIT FOR BLU IS CONTINUING PCPN FOR
TOO LONG THROUGH 00Z THU / OR LATE INTO WED AFTN.   JHM

.PREVIOUS DISCUSSION...
WARMER AND DRIER WEATHER IS EXPECTED FOR THURSDAY AS UPPER LEVEL
RIDGING STRENGTHENS. SOME FROST IS POSSIBLE IN THE VALLEY WITH GOOD
RADIATIONAL COOLING OVERNIGHT. NEAR NORMAL HIGH TEMPERATURES FOR THE
AFTERNOON REACHING THE MID 60S FOR THE VALLEY.

YET ANOTHER SYSTEM ARRIVES FOR FRIDAY WITH SIGNIFICANT RAIN AND SNOW
POSSIBLE.

.EXTENDED DISCUSSION (SATURDAY THRU TUESDAY)...
LINGERING SHOWERS ALONG THE SIERRA ON SATURDAY AS THE SYSTEM THAT
BRINGS US PRECIPITATION FRIDAY MOVES OFF TO THE EAST. SNOW LEVELS
ARE EXPECTED TO BE AROUND 4000 FEET OVER THE SIERRA. RIDGE OF HIGH
PRESSURE BUILDS OVER NORTHERN CALIFORNIA BEHIND THE SYSTEM BRINGING
DRY AND WARMER WEATHER LATE SATURDAY INTO MONDAY.  SUNDAY AND MONDAY
SHOULD BE MOSTLY SUNNY DAYS WITH TEMPERATURES IN THE MID 60S TO
LOWER 70S IN THE VALLEYS AND 50S IN THE MOUNTAINS.  THE NEXT SYSTEM
APPROACHES MONDAY NIGHT INTO TUESDAY BRINGING A RETURN OF COOLER
TEMPERATURES MORE CLOUDS AND A CHANCE OF PRECIPITATION ON TUESDAY.
ALTHOUGH THE GFS IS STILL A LITTLE QUICKER AND FURTHER NORTH WITH
THIS SYSTEM THAN THE ECMWF SO TIMING THE PRECIPITATION MAY HOLD OFF
UNTIL TUESDAY NIGHT INTO WEDNESDAY. HSO

&&

.AVIATION...
PAC CDFNT AND ASSOCD UPR TROF MOVS THRU TNGT INTO WED MRNG THEN UPR
RDG BLDS INLD WED INTO THUR. FOR CNTRL VLY...MNLY VFR EXC AREAS
MVFR/IFR POSS TIL ARND 12Z-15Z WED. FOR NRN/CSTL MTNS...WDSPRD
MVFR/IFR WITH LCL LIFR OVNGT TIL ARND 12Z WED THEN IMPVG AFT. SN
LVLS 020-030 AMSL. FOR W SLPS SIERNEV...INCRSG MVFR/IFR WITH AREAS
LIFR IN PCPN OVNGT CONT THRU WED MRNG THEN GRDLY IMPVG CONDS WED
AFTN INTO EVE. SN LVLS LWRG TO ARND 020-030 OVNGT. NWLY FLOW ALF OVR
NORCAL WITH LCL W-NWLY SFC WND GSTS 25-35 KTS OVR HYR MTN TRRN TNGT
THRU WED MRNG.

&&

.STO WATCHES/WARNINGS/ADVISORIES...WINTER WEATHER ADVISORY FROM 10
PM THIS EVENING TO 10 AM PST WEDNESDAY ABOVE 2000 FEET FOR THE
NORTHEAST FOOTHILLS/SACRAMENTO VALLEY...WESTERN PLUMAS COUNTY/LASSEN
PARK.

WINTER WEATHER ADVISORY FROM 2 AM TO 2 PM PST WEDNESDAY ABOVE
2000 FEET FOR THE MOTHERLODE...WEST SLOPE NORTHERN SIERRA NEVADA.

WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 6 AM PST
WEDNESDAY ABOVE 2000 FEET FOR THE MOUNTAINS SOUTHWESTERN SHASTA
COUNTY TO NORTHERN LAKE COUNTY...SHASTA LAKE AREA / NORTHERN
SHASTA COUNTY.

&&

$$

NWS STO Office Area Forecast Discussion

Site Affiliations

Weather Underground

weatherforyou.com

Anything Weather.com

Mesowest