Winter Storm in California, October 4 to 5, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
935 AM PDT TUE OCT 4 2011

.SHORT TERM DISCUSSION...

UPPER LEVEL TROUGH SPLIT ALONG THE WEST COAST WITH ONE PART OVER
SOUTHERN CALIFORNIA AND ANOTHER ONE OFF THE PACIFIC NORTHWEST
CENTERED AROUND 135W. MODERATE TO HEAVY RAIN AT
TIMES IS EXPECTED TONIGHT INTO WEDNESDAY WITH THE NORTHERLY SYSTEM
MOVING INTO THE AREA. 160KT JET NOSES INTO THE BAY AREA 06Z
TONIGHT BRINGING GOOD UPPER LEVEL DIVERGENCE OVER THE AREA ALONG
WITH PRECIPITABLE WATER AROUND AN INCH. PRECIPITATION WILL BECOME
HEAVIER OVER THE NORTH THIS EVENING AND SOUTH OF INTERSTATE 80
AROUND MIDNIGHT. TEMPERATURES WILL BE IN THE MID 60S TO LOWER 70S
IN THE VALLEY AND IN THE UPPER 40S TO UPPER 50S IN THE MOUNTAINS
AND DROP DOWN TO THE LOW TO MID 60S IN THE VALLEY AND LOWER 30S TO
LOWER 40S IN THE MOUNTAINS TOMORROW BEHIND THE COLD FRONT. SNOW
LEVELS ARE EXPECTED TO START OUT AROUND 7000 TO 8000 FEET AND DROP
DOWN TO AROUND 5000 TO 6000 FEET WEDNESDAY MORNING. WINTER STORM
WARNING IS OUT FOR AN EARLY SEASON STORM BUT MAY MOVE UP TIMING TO
BEGIN AROUND MIDNIGHT INSTEAD OF 5 AM. UP TO ABOUT AN INCH OF RAIN
POSSIBLE IN THE VALLEY...ESPECIALLY IN THE NORTH AND ABOUT AN INCH
AND A HALF FOR THE MOUNTAINS BY TOMORROW NIGHT. SOUTHERLY WINDS
WILL INCREASE DURING THE DAY TODAY WITH 15 TO 30 MPH WITH GUSTS TO
40 MPH IN THE VALLEY AND 50 MPH IN THE MOUNTAINS. WILL LOOK A
LITTLE MORE INTO A POSSIBLE WIND ADVISORY FOR THE NORTHERN AND
CENTRAL SACRAMENTO VALLEY LATE THIS AFTERNOON AND EVENING.

SOME INSTABILITY BEHIND THE FRONT ESPECIALLY IF WE SEE SOME SUN
WEDNESDAY AFTERNOON FOR A SLIGHT CHANCE OF THUNDERSTORMS IN THE
VALLEY AND DELTA REGION. THREAT OF SHOWERS CONTINUE WITH SOME
INSTABILITY ON THURSDAY AS THE UPPER LOW MOVES OFF TO THE EAST.
WARMER AND DRIER WEATHER EXPECTED FRIDAY INTO THE WEEKEND AS HIGH
PRESSURE BUILDS IN FROM THE PACIFIC. EXTENDED MODELS TENDING
TOWARDS FLATTENING THE RIDGE TOWARDS EARLY NEXT WEEK BUT MODEL TO
MODEL CONSISTENCY BECOMES POOR. GFS BOUNCING BETWEEN IDEA OF
ANOTHER FAIRLY SIGNIFICANT FRONTAL PASSAGE AROUND THE MIDDLE OF
NEXT WEEK OR CONTINUED FLAT RIDGING. ECMWF A LITTLE MORE
CONSISTENT WITH THE FLAT RIDGING IDEA. CONFIDENCE IN EXTENDED
FORECAST WILL REMAIN LOW UNTIL MODELS COME MORE IN LINE.

.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)

WRAPAROUND SHOWERS SHOULD CEASE OVER THE NORTHERN SIERRA THURSDAY
NIGHT. HIGH PRESSURE BUILDS INTO THE REGION ON FRIDAY...BRINGING A
FEW DAYS OF WARMER AND DRIER WEATHER. TEMPERATURES ARE EXPECTED TO
REMAIN BELOW NORMAL.

MODEL DIFFERENCES ARISE BY SUNDAY AS THE NEXT WAVE APPROACHES THE
PACIFIC NORTHWEST. THE ECMWF BRINGS THIS FEATURE INLAND OVER
OREGON SUNDAY INTO MONDAY...WHILE THE GFS KEEPS IT WELL NORTH OVER
CANADA. THE ECMWF HAS SHOWN A BETTER TRACK RECORD LATELY IN THE
EXTENDED PERIODS...AND AS SUCH HAVE INCLUDED SLIGHT CHANCE OF
PRECIPITATION ALONG THE NORTHERN MOUNTAINS SUNDAY AND MONDAY. DANG

&&

.AVIATION...

PATCHY LOW CLOUDS HAVE DEVELOPED IN THE VALLEY THIS MORNING DUE
TO LIGHT WINDS AND MOISTURE FROM RECENT FRONTAL PASSAGE WITH CIGS
AROUND 500 FEET. CIGS ARE EXPECTED TO INCREASE TO AROUND 2500 FEET
BY THIS AFTERNOON. SOUTH AND SOUTHWESTERLY WINDS ARE EXPECTED TO
START INCREASING AFTER 18Z. WIND SPEEDS FOR VLY TAF SITES BY 00Z
SHOULD BE AROUND 15-28 KTS AND CONTINUE OVERNIGHT WITH LCL GUSTS
TO 33 KTS POSSIBLE.

ISOLATED AND BRIEF -SHRA MAY AFFECT TAF SITES TODAY BUT THE NEXT
COLD FRONT WILL ARRIVE TONIGHT. INCREASING CHANCES OF RAIN FOR
TAF SITES AFT 00Z WITH THE BULK OF RAIN ARRIVING CLOSER TO 06Z
WHICH COULD BRING PERIODS OF MDT TO HEAVY RAIN TO TAF SITES INTO
WEDNESDAY. MVFR/IFR CIGS AND VSBYS EXPECTED DURING SHOWERS.

WIND GUSTS OVER MOUNTAIN RIDGETOPS 30-40 KTS TONIGHT INTO WED
MORNING WITH MVFR/IFR CONDS DURING SHOWERS.   JBB

&&

.STO WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 5 AM TO 11 PM PDT WEDNESDAY ABOVE 6000
FEET FOR THE WESTERN PLUMAS COUNTY/LASSEN PARK.

WINTER STORM WARNING FROM 5 AM TO 11 PM PDT WEDNESDAY ABOVE 6000
FEET FOR THE WEST SLOPE NORTHERN SIERRA NEVADA.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SACRAMENTO CA
321 PM PDT MON OCT 3 2011

CAZ013>019-063-064-066>069-041400-
SHASTA LAKE AREA/NORTHERN SHASTA COUNTY-
BURNEY BASIN/EASTERN SHASTA COUNTY-NORTHERN SACRAMENTO VALLEY-
CENTRAL SACRAMENTO VALLEY-SOUTHERN SACRAMENTO VALLEY-
CARQUINEZ STRAIT AND DELTA-NORTHERN SAN JOAQUIN VALLEY-
MOUNTAINS SOUTHWESTERN SHASTA TO NORTHERN LAKE COUNTIES-
CLEAR LAKE/SOUTHERN LAKE COUNTY-MOTHERLODE-
EAST FOOTHILLS/NORTH SACRAMENTO VALLEY-
WESTERN PLUMAS COUNTY/LASSEN PARK-WEST SLOPE NORTHERN SIERRA NEVADA-
321 PM PDT MON OCT 3 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

SYSTEM NUMBER 1 WILL AFFECT INTERIOR NORTHERN CALIFORNIA TODAY AND
TONIGHT.

* SPECIAL WEATHER STATEMENT..SEE WWUS86 KSTO - SPSSTO FOR DETAILS *

.DAYS TWO THROUGH SEVEN... TUESDAY THROUGH SUNDAY

A SECOND...STRONGER AND WETTER STORM SYSTEM WILL AFFECT THE AREA
TUESDAY NIGHT AND WEDNESDAY.

* WINTER STORM WARNING.......SEE WWUS46 KSTO - WSWSTO FOR DETAILS *

* SPECIAL WEATHER STATEMENT..SEE WWUS86 KSTO - SPSSTO FOR DETAILS *

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS TO THEIR LOCAL NATIONAL WEATHER SERVICE OFFICE.

THE LATEST WEATHER INFORMATION IS AVAILABLE ON THE INTERNET AT
(LOWER CASE): HTTP://WWW.WRH.NOAA.GOV/STO