FXUS66 KSTO 062310
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
300 PM PST SUN DEC 6 2009
.DISCUSSION...
SPRINKLES ARE BEGINNING TO MOVE OVER THE CENTRAL VALLEY WITH SNOW
CONTINUING OVER THE SIERRA NEVADA AND ALONG THE COASTAL RANGE. SNOW
LEVELS WILL DROP OVERNIGHT AND MONDAY MORNING TO AROUND SEA LEVEL
FOR MOST LOCATIONS. MODELS INDICATE SNOW INCREASING OVER THE SIERRA
NEVADA LATE THIS AFTERNOON AND EVENING. LOOK FOR VERY HIGH RAIN TO
SNOW RATIOS WITH THIS EVENT...ON THE ORDER OF 1 TO 30 FOR THE
WESTERN SLOPES DUE TO THE COLD DRY AIR. THE FOCUS OF THE EVENT
CONTINUES TO BE FROM AROUND QUINCY TO COLUSA AND POINTS SOUTHWARD.
BREEZY TO LOCALLY WINDY CONDITIONS OVER THE SIERRA NEVADA WILL ALSO
CAUSE BLOWING SNOW TO ADD TO THE PROBLEMS.
COLD AIR FROM THE SYSTEM CONTINUES TO SPREAD INTO THE
REGION...DROPPING SNOW LEVELS AS THE SYSTEM CONTINUES TO RETROGRADE
SOUTHWEST OVER NORTHERN CALIFORNIA TONIGHT AND ON TOP OF US ON
MONDAY. AS THE SYSTEM BACKS OVER THE PACIFIC IT WILL CONTINUE TO
PICK UP SOME MOISTURE FROM OVER THE OCEAN AS WELL AS MOISTURE FROM A
LOW PRESSURE AREA OUT OVER THE PACIFIC THE COLD AIR IN PLACE WILL
ALLOW FOR VERY LOW SNOW LEVELS...MODELS CONTINUE TO INDICATE SNOW
OVER THE CENTRAL VALLEY MONDAY MORNING. IT CONTINUE TO LOOK LIKE IT
WILL BE A VERY UNDESIRABLE COMMUTE MONDAY MORNING OVER THE SOUTHERN
SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEY.
MUCH LIGHTER PRECIPITATION IS EXPECTED OVER THE FAR NORTH WITH THE
HIGHER PRECIPITATION TOTALS AS YOU MOVE SOUTHWARD WITH THIS STORM.
PRECIPITATION AMOUNTS STILL REMAIN A LITTLE UNCERTAIN AT THIS TIME
BUT THEY COULD RANGE FROM A TRACE TO A FEW HUNDREDTHS OVER THE FAR
NORTH END OF THE VALLEY TO UP TO A THIRD OF AN INCH OR SO OVER THE
SOUTHERN SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEY...WHILE THE
WESTERN SLOPES COULD RANGE FROM A QUARTER OF AN INCH NEAR LASSEN
PARK UP TO AN INCH FOR THE WEST SLOPES OF THE SIERRA NEVADA. DUE TO
THE COLD DRY AIR RAIN TO SNOW RATIOS WILL BY VERY HIGH. THE HIGHEST
PRECIPITATION TOTALS ARE EXPECTED SOUTH OF HIGHWAY 70.
BEHIND THE SYSTEM EVEN COLDER AIR WILL ADVECT OVER THE REGION AND
SKIES SHOULD BE CLEARING MONDAY NIGHT FOR THE VALLEY WITH WINDS NOT
EXPECTED TO BE A MAJOR FACTOR BEHIND THE SYSTEM. THAT SETS THE STAGE
FOR VERY COLD TEMPERATURES AT NIGHT FOR TUESDAY MORNING. THE COLD
AIR STAYS IN PLACE THROUGH AT LEAST WEDNESDAY MORNING SO THE HARD
FREEZE WATCH INCLUDES BOTH DAYS.
.EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)...
WET WEATHER PATTERN FOR THURSDAY THROUGH THE WEEKEND AS SEVERAL
SHORTWAVES MOVE THROUGH THE WESTERLY FLOW INTO CALIFORNIA. THESE
STORMS ARE EXPECTED TO BE WARMER WITH SNOW LEVEL LEVELS AROUND 4000
FEET. AT THIS POINT...THE STORM FRIDAY NIGHT INTO SATURDAY LOOKS
LIKE THE WETTEST (WITH PRECIPITABLE WATER VALUES UP TO AN INCH) AND
STRONGEST (WITH A 120KT JET MOVING INTO NORTHERN CALIFORNIA).
&&
.AVIATION...
LIGHT TO MODERATE SOUTHEASTERLY TO SOUTHWESTERLY WINDS EXPECTED IN
THE VALLEY AND DELTA TODAY AHEAD OF THE INCOMING STORM. INCREASING
CLOUDS THROUGH TONIGHT AS THIS SYSTEM MOVES SOUTHWARD ACROSS OUR
CWA. MVFR CONDITIONS WITH AREAS OF IFR/LIFR CONDITIONS POSSIBLE
DURING SHOWERS AFT 06Z INTO MONDAY EVENING. SHOWERS WILL INITIALLY
AFFECT KRDD-KRBL VCNTY OVERNIGHT WITH ONLY LIGHT ACCUMULATION AS
SHOWERS MOVE SOUTHWARD. SNOW LEVELS MAY BE DOWN TO THE VALLEY FLOOR
SO TAFS HAVE MENTION OF RASN MIX FOR MONDAY MORNING. THE HEAVIEST
PRECIPITATION IS EXPECTED IN THE SIERRA AND AROUND INTERSTATE 80
SOUTHWARD FOR INTERIOR CALIFORNIA. LOW CLOUDS AND SNOW SHOWERS
CONTINUE IN THE MOUNTAINS WITH FLUCTUATING AREAS OF MVFR TO LIFR
CONDITIONS. PRECIPITATION IS EXPECTED TO BECOME HEAVIER AND MORE
WIDESPREAD LATER TONIGHT. LOCAL SOUTHWEST WINDS GUSTS 40 TO 50 MPH
ARE POSSIBLE OVER THE MOUNTAINS. JBB
&&
.STO WATCHES/WARNINGS/ADVISORIES...
...WINTER STORM WARNING IN EFFECT FOR THE SIERRA NEVADA FROM 3 PM
THIS AFTERNOON TO 6 PM PST MONDAY FOR HEAVY SNOW...
...WINTER STORM WARNING IN EFFECT FROM 4 AM TO NOON PST MONDAY FOR
THE SOUTHERN SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEY INCLUDING
THE DELTA FOR SNOW...
...WINTER WEATHER ADVISORY IN EFFECT FROM 4 AM TO NOON PST MONDAY
FOR THE CENTRAL SACRAMENTO VALLEY FOR SNOW...
...WINTER WEATHER ADVISORY IN EFFECT FROM 10 PM THIS EVENING TO 3 PM
PST MONDAY THE NORTHEAST FOOTHILLS/SACRAMENTO VALLEY AND SOUTHERN
LAKE COUNTY FOR SNOW...
...HARD FREEZE WATCH FOR LATE MONDAY NIGHT AND TUESDAY MORNING AND
AGAIN LATE TUESDAY NIGHT AND WEDNESDAY MORNING FOR INTERIOR NORTHERN
CALIFORNIA BELOW 2000 FEET...
&&
$$
