Winter Storm in California, February 22 to 24, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
930 PM PST SAT FEB 21 2009

.EVENING DISCUSSION UPDATE...
NO NOTABLE CHANGES TO THE FORECAST PACKAGE.  MOST SIGNIFICANT
POSSIBILITY IS FOR INCREASED WINDS IN THE FAR NORTHERN SAC VALLEY.
THE STRONGER WINDS ARE STAYING TO NORTH FOR NOW BUT THIS COULD
CHANGE AS THE JET MOVES THROUGH.  OTHERWISE... WAITING FOR WEATHER
TO BEGIN.  SOME PRECIP HAS BEGUN ALONG THE COAST BUT NONE YET IN THE
CENTRAL VALLEY OR SIERRA.  OF MOST INTEREST IS AT WHAT ELEVATION THE
SNOW WILL BEGIN AS THIS WILL HOPEFULLY HELP SOLIDIFY THE FORECAST.

.AFTERNOON DISCUSSION...
A LOW PRESSURE AREA CENTERED ABOUT 750 MILES NORTHWEST OF SACRAMENTO
WILL IMPACT THE INTERIOR REGION TONIGHT THROUGH MONDAY. UPPER LEVEL
JET BEGINS TO MOVE OVER THE INTERIOR THIS EVENING SO RAIN COULD
BREAK OUT OVER MANY AREAS AT ALMOST ANYTIME DURING THE EVENING HOURS
OVER THE SACRAMENTO VALLEY...BUT BETWEEN 10 PM AND MIDNIGHT MOST
EVERYONE SHOULD BE RECEIVING RAIN. THIS IS A WARM SYSTEM SO SNOW
LEVELS WILL BE HIGH...EXCEPT FOR INITIALLY SNOW LEVELS IN THE SIERRA
TONIGHT WILL BE BELOW PASS LEVEL POSSIBLY DOWN TO AROUND 6000 FEET.
2 TO 4 INCHES OF SNOW COULD OCCUR BELOW PASS LEVEL OVERNIGHT BEFORE
SNOW LEVELS RISE SUNDAY MORNING TO AROUND 7000 FEET OR HIGHER IN THE
SIERRA NEVADA.

THE MODELS ARE SHOWING A SIGNIFICANT AMOUNT OF PRECIPITATION SO HAVE
PUT OUT A WINTER STORM WARNING FOR THE HIGHER ELEVATIONS ABOVE 7500
FEET. SINCE THIS STORM WILL BE MUCH WARMER THAN RECENT STORMS THE
SNOW THAT IS EXPECTED TO FALL WILL BE MORE OF THE SIERRA CEMENT
TYPE...WET AND HEAVY.

1.0 TO 2.5 INCHES OF RAIN COULD FALL WITHIN THE CENTRAL VALLEY FOR
MOST PLACES WITH 2 TO 4 INCHES OVER THE WESTERN SLOPES...5 TO 7
INCHES OVER WESTERN SHASTA COUNTY AND THE FEATHER RIVER BASIN. SOME
OF THE SMALLER CREEKS MAY EXPERIENCE SOME FLOODING IN ADDITION TO
ROADWAY FLOODING OF LOW LYING AREAS WITH THIS STORM. THIS STORM WILL
WIND DOWN TUESDAY MORNING...WITH PERHAPS SOME LINGERING
SHOWERS...MAINLY OVER THE MOUNTAINS FOR TUESDAY.

.EXTENDED DISCUSSION (WEDNESDAY THROUGH SATURDAY)...LONGWAVE TROUGH
CONTINUES IN THE EPAC THROUGH THE EXTENDED. ANOTHER SHORT WAVE FROM
THE GOA DROPS ALONG THE WEST COAST TOWARDS NORCAL WED/THU. GFS DIGS
THIS SYSTEM DEEPER TOWARDS NORCAL AND THEN INLAND ACROSS OREGON
THU/THU NGT WHILE 12Z ECMWF/GEM KEEP A DEEPER LOW FARTHER
NORTH...MOVING IT INLAND ACROSS S B.C. THU NGT/FRI. GFS HAS BEEN
MORE INCONSISTENT RUN TO RUN DURING THIS TIME PERIOD HOWEVER 00Z
ECMWF HAD A MORE SOUTHERN TRACK WITH LOW ACROSS PAC NW THU
NGT/FRI...SIMILAR TO 12Z GFS. BOTH MODELS PAINT A WET SCENARIO
ACROSS INTERIOR NORCAL AGAIN WED INTO THU BUT ECMWF DRIER THU NGT
INTO EARLY FRI. MODELS ARE NOW SUGGESTING SHORT WAVE RIDGING OVER
NORCAL FRI AS ANOTHER CLOSED LOW MOVES INTO THE EPAC THEN DRIVE
ANOTHER ROUND OF SUBTROPICAL MOISTURE INTO THE FORECAST AREA NEXT
SATURDAY.

&&
.AVIATION...
STRONG JET STREAM ALOFT STARTING TO PUSH PRECIPITATION INTO INTERIOR
NORTHERN CALIFORNIA THIS EVENING...THOUGH MOST OF THE MOISTURE
REMAINS ALONG THE COAST. EXPECT RAIN TO BECOME MORE WIDESPREAD AND
REACH ALL OF THE TERMINALS BY 12Z. RAIN WILL BE STEADY THROUGH MOST
OF SUNDAY AND BE MODERATE TO HEAVY AT TIMES...RESULTING IN MVFR TO
IFR CONDITIONS. LIGHT SOUTHERLY WINDS WILL INCREASE TO 10 TO 20 KT
AND BE OCCASIONALLY GUSTY TO 30 KT IN THE VALLEY AND TO 45 KT OVER
SIERRA RIDGETOPS SUNDAY.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 10 PM PST THIS EVENING TO 4 AM PST TUESDAY
MORNING FOR WESTERN PLUMAS COUNTY/LASSEN PARK AND FOR THE WEST SLOPE
NORTHERN SIERRA NEVADA.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SACRAMENTO CA
1128 AM PST SAT FEB 21 2009

CAZ013>019-063-064-066>069-221500-
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-
1128 AM PST SAT FEB 21 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

A WET PACIFIC STORM IS TAKING AIM ON NORTHERN CALIFORNIA AND IS
FORECAST TO MOVE INTO THE REGION LATER TONIGHT. THIS STORM IS
FORECAST TO BE WARMER AND WETTER THAN THE ONE LAST WEEKEND AND WILL
TAP INTO SUBTROPICAL MOISTURE. PERIODS OF MODERATE TO HEAVY
PRECIPITATION WILL BEGIN OVER INTERIOR NORTHERN CALIFORNIA LATE
TONIGHT.

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

.DAYS TWO THROUGH SEVEN... SUNDAY THROUGH FRIDAY

A WET PACIFIC STORM IS TAKING AIM ON NORTHERN CALIFORNIA AND WILL
CONTINUE TO IMPACT THE REGION SUNDAY AND MONDAY. PERIODS OF MODERATE
TO HEAVY PRECIPITATION WILL CONTINUE OVER INTERIOR NORTHERN
CALIFORNIA THROUGH MONDAY NIGHT. SOME OF THE SMALLER CREEKS MAY
EXPERIENCE SOME FLOODING IN ADDITION TO ROADWAY FLOODING OF LOW
LYING AREAS WITH THIS STORM DURING THIS TIME PERIOD.

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

RB