Wind Advisory 19, NWS Sacramento, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1020 AM AM PST FRI NOV 27 2009

.DISCUSSION...
UPPER LEVEL FRONT HAS PUSHED OVER THE WRN HALF OF THE CWA...AND
SEEMS TO BE MUCH FASTER THAN MODELED. EVEN THE 27/12Z WRF PCPN IS
TOO SLOW AND NOT FAR ENOUGH SOUTH WITH THE QPF THIS MORNING. BACK
UPSTREAM WE ARE SEEING THE BEGINNING OF THE FORMATION OF THE CLOSED
LOW WITH A CIRCULAR BAND OF CLOUDS MOVING ALONG THE COAST. IT
CERTAINLY LOOKS LIKE THE CLOSED UPPER LOW WILL BE DROPPING S-SEWD
FOR THE REST OF THE DAY AND INTO THE WRN SAN JOAQUIN VALLEY BY
06Z...THEN SWD INTO SOCAL ON SAT. SATELLITE IMAGERY SHOWS STRONG
SUBSIDENCE BEHIND THE UPPER FRONT...DETACHING THE CLOSED LOW FROM
THE MOISTURE TO THE E. THIS IS RESULTING IN LESS CONVECTIVE SHOWERS
ALONG THE COAST DUE TO LOWER PW AIR. BUFKIT FORECAST SOUNDINGS
INDICATE FOR SUU/SAC MARGINAL INSTABILITY THIS AFTERNOON THROUGH
ABOUT 02Z AND THIN CAPE...A LITTLE OVER 100 J/KG. THE MID LEVEL CAA
FROM THE CLOSED LOW IS FORECAST TO STEEPEN LAPSE RATES TO 8-9 DEG
C/KM UP TO ABOUT 750 MBS DURING THE LATE AFTERNOON AND EVENING HRS.
THERE MAY BE A RUMBLE OR TWO OF THUNDER...BUT THE MAIN PROBLEM FOR
THE AFTERNOON WILL BE TO WORK ON THE TIMING OF THE WSW...AND THE
EVENTUAL INCREASE IN WINDS. WITH THE FAST MOVEMENT...WE CAN LET THE
WSW EXPIRE OR CANCEL IT FOR ZONE 68 WITH THE AFTERNOON PACKAGE...AND
LET IT RIDE THIS EVENING IN ZONE 69. SRN ZONE 69 WILL STILL BE IN
THE FAVORABLE NE QUAD OF THE UPPER WHERE CYCLONIC FLOW AND WRAP
AROUND MOISTURE ARE LIKELY TO RESULT IN SOME SPILL-OVER OF PCPN FROM
THE E SIDE OF THE SIERNEV TONIGHT AND INTO SAT. ELSEWHERE...WE CAN
PROBABLY CUT BACK ON THE POPS BECAUSE OF LESS AREAL COVERAGE OF THE
SHOWERS.

NORTHERLY WINDS WILL BE INCREASING TONIGHT AND CONTINUE INTO SAT AS
NLY PRESSURE GRADIENTS FROM THE PRESSURE RISES ACROSS THE PAC NW
TODAY/TONITE. THIS IS DUE TO THE CLOSED LOW DROPPING S...AND A
POSITIVELY TILTED RIDGE BUILDING INTO THE AREA. INCREASING
ANTICYCLONIC FLOW ALOFT WILL RESULT IN A STRONG OFFSHORE FLOW
PATTERN FOR THE NEXT COUPLE OF DAYS. BY 12Z SAT THE MFR-SAC GRADIENT
IS FORECAST TO BE 15 MBS. THE PRESSURE GRADIENT BECOMES MORE NE-ELY
SAT NITE AND SUN AS THE SURFACE HIGH MOVES FROM ORE INTO ID. STRONG
SUBSIDENCE IS FORECAST OVER PORTIONS OF OUR AREA TONIGHT AND
SAT...AND EVEN INTO SUN MORNING...AS MUCH AS 12 UB/S AT TIMES. CROSS
SECTIONS REVEAL WINDS ALOFT ARE FORECAST TO BE STRONGER ON SAT THAN
ON SUN...WITH STRONGER MID LEVEL CAA SAT MORNING AS WELL. WIND
SPEEDS OF 45-50 KTS UP TO 10-12 KFT ARE FORECAST TONITE AND INTO
SAT...AND IT LOOKS LIKE A PRIME TIME FOR WIND ADVSRY CRITERIA TO BE
MET OVER A LARGE PORTION OF OUR FORECAST AREA. INCREASING
ANTICYCLONIC FLOW WILL ALSO WARM THE AIR MASS ON SAT...WITH GREATER
WARMING ON SUN.  JHM

.EXTENDED DISCUSSION (TUESDAY THROUGH FRIDAY)...
UNCERTAINTY OF FORECAST INCREASES TOWARD THE END OF THE EXTENDED
PERIOD. ALL THE MEDIUM RANGE MODELS SHOW THE STRONG MEAN WEST COAST
RIDGE PERSISTING THROUGH THE EXTENDED PERIOD OF THE FORECAST...BUT
DIFFER IN TIMING AND HANDLING OF SIGNIFICANT SHORT WAVE ENERGY
MOVING INTO THE RIDGE TOWARD THE END OF NEXT WEEK. GFS IS MOST
AGGRESSIVE DIGGING ANOTHER SYSTEM SOUTHEASTWARD INTO CALIFORNIA FROM
THE GULF OF ALASKA LATE IN THE WEEK WHILE THE GEM AND ECMWF ARE
WEAKER AND SLOWER. MODELS CONTINUE TO HINT AT MORE SIGNIFICANT
CHANGES OUT AROUND DAY 10 AS THE WEST COAST RIDGE RETROGRADES TO
140W AND FORMS A STRONG BLOCK OVER THE GULF OF ALASKA/WESTERN BC
WHICH MAY EVENTUALLY BE UNDERCUT SETTING THE STAGE FOR A POTENTIALLY
MORE PROLONGED WET PERIOD FOR NORTHERN CALIFORNIA.

&&

.AVIATION...
COLD FRONT AROUND SACRAMENTO AND NORTHEAST TO AROUND CARIBOU AT
1630Z AND IS MOVING SOUTHEAST THROUGH THE AREA TODAY.  VFR/MVFR
CONDITIONS EXPECTED IN THE VALLEY TODAY WITH SHOWERS AND MVFR/IFR
CONDITIONS WITH LOCAL LIFR CONDITIONS EXPECTED IN THE MOUNTAINS WITH
PRECIPITATION. CONDITIONS WILL DETERIORATE TO IFR IN SHSN AND BR
ACROSS THE NORTHERN SIERRA NEVADA THIS MORNING AND CONTINUE THROUGH
ABOUT 06Z TO 12Z SATURDAY. SNOW LEVELS AROUND 4000 IN THE NORTH TO
AROUND 5500 FEET IN THE SOUTH. GUSTY SOUTHERLY WILL TURN NORTHERLY
BEHIND THE FRONT TODAY. NORTHERLY WINDS ARE EXPECTED TO INCREASE
SATURDAY MORNING. VFR CONDITIONS WITH GUSTY NORTHERLY WINDS ARE
EXPECTED ON SATURDAY. HSO

&&

.STO WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY 8 AM THROUGH 6 PM TODAY WESTERN PLUMAS
COUNTY/LASSEN PARK.

WINTER WEATHER ADVISORY 10 AM THROUGH 10 PM TODAY WEST SLOPE
NORTHERN SIERRA NEVADA.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SACRAMENTO CA
700 AM PST FRI NOV 27 2009

CAZ013>019-063-064-066>069-281500-
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-
700 AM PST FRI NOV 27 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

A PACIFIC FRONTAL SYSTEM WILL MOVE THROUGH NORTHERN CALIFORNIA
TODAY...BRINGING RAIN TO THE VALLEY. A BAND OF RAIN WILL DEVELOP
FROM REDDING TO CHICO EARLY THIS MORNING AND SHIFT SOUTH TO
VACAVILLE...SACRAMENTO AND OROVILLE BY LATE MORNING. A PERIOD OF
MODERATE RAIN IS EXPECTED IN THE AUBURN AND PLACERVILLE AREAS EARLY
THIS AFTERNOON. RAIN WILL END BY LATE AFTERNOON IN MANY AREAS THOUGH
MORE SHOWERS MAY DEVELOP NEAR STOCKTON AND MODESTO THIS EVENING.

SNOW AND RAIN WILL DEVELOP BY 10 AM ALONG INTERSTATE 80 AND
HIGHWAY 50 AND THE LASSEN PARK AREA. PRECIPITATION WILL BECOME HEAVY AT
TIMES BY EARLY   AFTERNOON AND SHIFT FARTHER SOUTH INTO THE CARSON
PASS AREA. SNOW LEVELS INITIALLY NEAR 5000 FEET WILL RISE TO 6000 TO
6500 FEET EARLY THIS AFTERNOON BEFORE THEY FALL BACK TO 4500 FEET
LATE THIS AFTERNOON AND THIS EVENING. 4 TO 8 INCHES OF SNOW IS
EXPECTED OVER DONNER SUMMIT AND ECHO SUMMIT BY THIS EVENING. UP TO A
FOOT OF SNOW MAY FALL OVER CARSON PASS ALONG HIGHWAY 88 BY EARLY
SATURDAY MORNING. SNOW AND ICE ACCUMULATING ON ROADWAYS WILL CREATE
SLICK ROADS AND HAZARDOUS DRIVING CONDITIONS EARLY THIS AFTERNOON
THROUGH TONIGHT.

* WINTER WEATHER ADVISORY....SEE WWUS46 KSTO - WSWSTO FOR DETAILS *

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

.DAYS TWO THROUGH SEVEN... SATURDAY THROUGH THURSDAY

ALTHOUGH SNOW WILL TAPER OFF TO SCATTERED SNOW SHOWERS
TONIGHT...GUSTY EAST WINDS UP TO 50 MPH COULD CREATE HAZARDOUS
CONDITIONS IN BLOWING AND DRIFTING SNOW OVER MOUNTAIN PASSES
SATURDAY.

STRONG HIGH PRESSURE BUILDING INTO NORTHERN CALIFORNIA BEHIND THE
FRONT WILL BRING GUSTY NORTH WINDS TO THE REGION TOMORROW. NORTH
WINDS OF 15 TO 30 MPH WITH GUSTS TO 35 MPH ARE EXPECTED. WINDS COULD
GUST UP TO 40 MPH ALONG THE WEST SIDE OF THE SACRAMENTO VALLEY
TOMORROW. STRONG WINDS ARE ALSO POSSIBLE IN THE EAST FOOTHILLS AND
MOTHERLODE...ESPECIALLY THROUGH CANYONS.

* 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

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