The National Weather Service's Sacramento forecast for Sunday has moved from "chance of rain" to "slight chance of rain." Why? At least one model, the GFS, now shows the low that was forecast to move through the Pacific Northwest and then slide down into California heading farther east as it drops south.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
900 PM PST WED DEC 2 2009
SIGNS OF WEATHER CHANGE BEGIN ON FRIDAY AS UPPER LOW NOW OVER WESTERN ALASKA MOVES OVER THE WEST COAST RIDGE...THROUGH WESTERN CANADA AND INTO THE PACIFIC NORTHWEST. A WEAK LOW IN THE EASTERN PACIFIC NOW BETWEEN 130 AND 140 WEST IS FORECAST TO BREAK APART AS IN ENCOUNTERS THE WESTERN U.S RIDGE. SOME HIGH CLOUDINESS FROM THIS SYSTEM IS FORECAST TO SPILL OVER NORCAL ON FRIDAY AND THIS CLOUDINESS COMBINED WITH A SLIGHT AIRMASS COOLING FROM LOW TO THE NORTH WILL BRING A SLIGHT COOLING TO MOST AREAS. PREVIOUS RUNS OF THE GFS DUG A SHORTWAVE DOWN THE BACKSIDE OF THE GREAT BASIN LOW ON SATURDAY AND INDICATED A THREAT OF PRECIP OVER THE SIERRA. 00Z KEEPS THIS FEATURE FARTHER TO THE EAST. IF THIS TREND HOLDS IN FUTURE RUNS THEN FORECASTS WILL NEED TO BE ADJUSTED TO REMOVE THIS THREAT. EITHER WAY...COOLER AIR CONTINUES TO FILTER IN FROM THE NORTH FOR COOLER TEMPERATURES SATURDAY BRINGING DAYTIME HIGHS DOWN TO NEAR NORMAL FOR THIS TIME OF YEAR.
Wednesday, December 2, 2009
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