SF NWS: Growing Confidence

Yeah, this is SF, not Sacto, but as I said earlier, the train generally passes through this station on its way to the valley. And moisture and wind are now definitely on board, though it remains far from certain a storm will arrive in the valley before the race. In fact, I'm sensing (hoping?) that it'll hit the capital after we've collected our PRs, finisher medals and high fives.

This discussion relies partly on consultation with the Hydrometeorological Prediction Center—that's the HPC reference—a part of the vast National Oceanic and Atmospheric Administration apparatus that focuses on what's called "quantitative precipitation forecasting." If you read forecasts discussions much you'll come across QPF references frequently. Put simply, it's how much it's going to rain.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
218 PM PST MON NOV 30 2009

... IN THE EXTENDED...THIS WEEKEND WILL SEE THE PATTERN UNDERGO A MAJOR SHIFT. BASED ON CHATS WITH HPC AND BETTER RUN TO RUN CONSISTENCY HAVE FOLLOWED THE 12Z ECMWF. WESTERN PACIFIC TYPHOON NIDA CENTERED NEAR 20/137E WILL CONTINUE TO WEAKEN AND SHEAR APART BY THURSDAY MORNING. ENERGY FROM THE TYPHOON WILL EJECT INTO THE WESTERLIES... STRENGTHENING THE EAST ASIAN JET. ON SAT A SHORTWAVE DROPS SOUTH ALONG THE PACIFIC NW COAST...UNDERCUTTING A HIGH AMPLITUDE RIDGE CENTERED OFF THE ALASKA/BRITISH COLUMBIA COAST. THIS SHORTWAVE STALLS OFF THE COAST ALLOWING A BAROCLINIC TO DEVELOP OFF THE COAST. ON SUN THE 12Z ECMWF DEVELOPS A 992 MB LOW ALONG THE FRONT AND MOVES IT TO THE NORTHERN CA COAST...IF THIS VERIFIES SUNDAY THROUGH MONDAY COULD BE WINDY AND WET. HAVE BUMPED UP POPS A BIT...BUT HAVEN`T WENT FULL BORE ON THIS SOLUTION SINCE THE DETAILS ARE STILL IN A BIT OF FLUX (WHEREAS THE OVERALL PATTERN IS SHOWING CONSISTENCY). PER THE 12Z ECMWF...THROUGH THE MIDDLE OF THE FOLLOWING WEEK THE STORM DOOR IS OPEN WITH THE WESTERLIES BRINGING ANOTHER STRONG SYSTEM TO THE COAST
BY WEDNESDAY...