Scientific Forecaster Discussion
fxus66 kmtr 231143
Area forecast discussion
National Weather Service San Francisco Bay area
343 am PST Thu Nov 23 2017
Synopsis...chance of rain over the North Bay today while the
rest of the region should remain dry with continued warmer than
normal temperatures. Dry weather is expected to return to all
areas on Friday and continue through most of Saturday. Rain will
return to our region late Saturday through Sunday.
Discussion...as of 3:00 am PST Thursday...kmux radar currently
indicates a few echoes off the Sonoma coast plus in far Sonoma
County. Look for these light showers to continue through the
morning and possibly tip a few buckets in the North Bay into the
Thanksgiving afternoon. For the rest of our region, a mix of
clouds and sun can be expected (more clouds the farther north you
are) with warm November temperatures. Highs will range from lower
80s in parts of Monterey County to the upper 60s around sections
of San Francisco Bay. For anyone traveling today driving
conditions will be very good. Only potential problem may be patchy
dense fog this morning in parts of the North Bay around Santa
A ridge of high pressure will attempt to build back into our
region as today's system moves off to the east. This will lead to
dry weather for Friday into almost all of Saturday. Highs will
remain warmer than normal, although should be a few degrees cooler
than what we will see today.
The synoptic pattern will undergo changes impacting the second
half of the weekend. An upper level low near the Gulf of Alaska
will dive southward and eventually to the pacnw by Sunday. At the
same time a surface cold front will move across our region and
bring rainfall back to the North Bay late starting Saturday
evening. The front will progress to the south and east leading to
rainfall spreading across our entire County Warning Area through Sunday. Rain
will briefly switch to showers behind the front before dry
weather returns again going into next work week. Rainfall amounts
continue to not look impressive, although due to the spread
between model solutions and ensemble members, some caution is
definitely in order. Right now looks like generally 1/4" to 1/2"
can be expected for many urban spots. Coastal ranges will likely
be in the 1/3" to 2/3" with isolated spots possibly seeing 1". In
addition to the rain, winds will increase with gusts from the
south of over 20 mph possible in spots.
Dry weather now looks likely for next work week with highs
averaging a bit above normal. Record values from this week look
very unlikely to continue into next week.
Aviation...as of 3:30 am PST Thursday...an upper level shortwave
passing north of the area will bring a moist southwest flow into
the sfo Bay area. VFR conditions are expected today except for
morning fog at sts but by tonight some lower level moisture may
bring some MVFR cigs to sfo and Oak.
Vicinity of ksfo...VFR for today.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...VFR.
Marine...as of 3:45 am PST Thursday...weak high pressure off the
California coast will keep light winds through Friday. Southerly
winds will increase Saturday as a low pressure system moves into
the Pacific northwest waters. Rain will spread over the area
Saturday night and Sunday.
Public forecast: Bell
aviation: west pi
marine: west pi
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