NWS Sacramento Office Discussion: Trending Wet

Weather geeks know that especially several days out, the only place to get a good sense of where the conditions are headed is to read the Weather Service "Area Forecast Discussion," available online. This is where the mets explain what they're seeing from the computer models they use, the doubts they have and their sense of how conflicting information might sort itself out. The discussion of the extended period from the Sacramento office this morning picks up on a theme from earlier discussions—that we're likely to see a shift from the dry weather of this week to a wet period next week. Questions remain, however; the models are hardly in full agreement, and at the very least there is uncertainty as to whether rain will be falling before, say, noon on Sunday, or won't arrive until later.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 AM PST MON NOV 30 2009

EXTENDED DISCUSSION (FRIDAY THROUGH MONDAY)...
GFS AND GEM MODELS SHOW A HIGH AMPLITUDE RIDGE DEVELOPING NEAR THE WEST COAST ON FRIDAY. THE ECMWF MODEL IS STILL AN OUTLIER AS IT SHOWS A CUT-OFF LOW MOVING INTO THE PAC NW/NORCAL ON FRIDAY...DESPITE RIDGING. HAVE LEANED MORE TOWARDS THE GFS/GEM SOLUTION FOR FRIDAY AND SATURDAY KEEPING DRY WEATHER IN THE EXTENDED FORECAST. BY SUNDAY...THE GFS AND GEM SHOW A LOW PRESSURE CELL DROPPING SOUTHWARD FROM CANADA AND RETROGRADING INTO CALIFORNIA...WHILE THE ECMWF MODEL SHOWS THE FRIDAY LOW LINGERING ALONG THE WEST COAST. ALL THREE MODELS INDICATE A WET PATTERN SUNDAY AS A SLUG OF MARINE MOISTURE SLAMS INTO CALIFORNIA. ON MONDAY...THE GEM MOVES THE LOW QUICKLY EAST OF OUR REGION AND INDICATES A DRIER PATTERN DEVELOPING. HAVE CHOSEN TO MAINTAIN THE WETTER PATTERN FOR SUN/MON AS INDICATED BY THE GFS/ECMWF FOR THE FAR EXTENDED FORECAST.
JBB