FXUS66 KSTO 071247
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
445 AM PST MON DEC 7 2009
.DISCUSSION...
COLD CLOSED UPPER LOW ORIGINATING FROM WESTERN CANADA HAS ITS CENTRE
NOW OVER FAR NORTHERN CALIFORNIA. THE SYSTEM IS FORECAST TO OPEN UP
AND MOVE EAST LATER TODAY. THIS WILL SET THE STATE FOR BETTER
POTENTIAL FOR BREAKTHROUGH UNDER THE STRONG BLOCKING HIGH OVER THE
NORTHERN GULF OF ALASKA LATER THIS WEEK. NEXT SYSTEM EXPECTED TO
WEAKEN AS IT MOVES INTO THE REGION THURSDAY.
LIGHT TO MODERATE PRECIPITATION CONTINUES ALONG AND AHEAD OF THE
COLD FRONT WHICH LIES ALONG THE I-80/US-50 CORRIDOR. IN THE
VALLEY...MOST OF THE PRECIPITATION IS OCCURRING FROM AROUND TURLOCK
NORTHWARD TO JUST SOUTH OF MARYSVILLE. THIS WHOLE BAND IS ONLY
MOVING SLOWLY OFF TO THE SOUTHEAST AS IT PIVOTS AHEAD OF THE UPPER
TROUGH DIGGING OFF THE NORTH COAST. UPPER DIFFLUENCE AHEAD OF THE
TROUGH CONTINUES TO FAVOR UPWARD VERTICAL MOTION AHEAD OF IT WITH
THE HEAVIEST PRECIPITATION FOCUSED OVER SACRAMENTO COUNTY EASTWARD
INTO THE FOOTHILLS AND WEST SLOPES OF THE NORTHERN SIERRA NEVADA.
RAIN MIXED WITH SNOW IS BEING OBSERVED ON THE VALLEY FLOOR IN THE
SACRAMENTO AREA EARLY THIS MORNING (TEMPERATURES GENERALLY IN THE
MID 30S) WITH REPORTS OF SNOW STICKING TO GRASSY SURFACES ABOVE
ABOUT 500 FEET OF ELEVATION. AREAS AROUND 1000 FEET WILL LIKELY SEE
SOME ACCUMULATING SNOW THE NEXT SEVERAL HOURS AS HEAVIER
PRECIPITATION MOVES IN AND THE AIRMASS CONTINUES TO COOL.
PRECIPITATION EXPECTED TO END IN THE SACRAMENTO VALLEY BY THIS
AFTERNOON AND TAPER OFF IN THE NORTHERN SIERRA NORTH OF I-80...AND
TAPER OFF ACROSS THE REMAINDER OF THE MOTHERLODE AND NORTHERN SIERRA
BY LATE THIS AFTERNOON AND EARLY THIS EVENING. PORTIONS OF THE
MOTHERLODE AND WEST SLOPES OF THE NORTHERN SIERRA WILL SEE
IMPRESSIVE SNOWFALL TODAY.
CLEARING SKIES TONIGHT OVER THE VALLEY WILL ALLOW GOOD RADIATIONAL
COOLING AND WITH COLD AIRMASS IN PLACE...VERY COLD TEMPERATURES
EXPECTED (20S WITH SOME LOCAL SPOTS POSSIBLY DIPPING INTO THE UPPER
TEENS).
COLD DRY PATTERN CONTINUES THROUGH WEDNESDAY.
&&
.EXTENDED DISCUSSION (FRIDAY THROUGH MONDAY)...ECMWF AND GEM SHOW
SOME SHORTWAVE ENERGY SPREADS INTO THE AREA FRIDAY. MOIST WESTERLY
FLOW ALONG WITH 110 KT JET WILL BRING THE POTENTIAL FOR VALLEY RAIN
AND MOUNTAIN SNOW. LATEST OPERATION RUNS OF GFS SHOWING WEAKER
SYSTEM. A MORE SIGNIFICANT SYSTEM IS POSSIBLE SATURDAY INTO SUNDAY.
&&
.AVIATION...
A COLD STORM IS BRINGING LIFR/IFR CIGS AND VSBYS IN HEAVIER RASN IN
AREAS OF SOUTHERN SACRAMENTO VALLEY AND SN EXTENDING INTO SIERRA
FOOTHILLS AND MOUNTAINS. PRECIPITATION IN THE VALLEY WILL MAINLY END
BY AROUND 18Z WITH CLEARING CONDITIONS BY THE LATE AFTERNOON AND VFR
CONDITIONS. LIFR/IFR WITH SN CONTINUING THROUGH THE EVENING IN THE
NORTHERN SIERRA. SOUTHWEST GUSTS UP TO 50 MPH POSSIBLE IN THE HIGHER
SIERRA MOUNTAINS TODAY.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM PST THIS EVENING FOR MOTHERLODE AND
WEST SLOPES NORTHERN SIERRA NEVADA.
WINTER STORM WARNING UNTIL NOON PST TODAY FOR SOUTHERN SACRAMENTO
VALLEY.
WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR DELTA AND NORTHERN
SAN JOAQUIN VALLEY.
FREEZE WARNING FROM 2 AM TO 9 AM PST TUESDAY FOR SACRAMENTO
VALLEY...DELTA AND NORTHERN SAN JOAQUIN VALLEY AND SURROUNDING
FOOTHILLS INCLUDING SOUTHERN LAKE COUNTY.
&&
$$
