Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 242058
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
158 PM PDT Sun Sep 24 2017

.SYNOPSIS...A gradual warming trend will continue through the first
half of the workweek as high pressure across the eastern Pacific
builds over California. While slightly cooling is expected late in
the week, temperatures are forecast to remain above seasonal
averages.

&&

.DISCUSSION...as of 01:58 PM PDT Sunday...Sunny conditions
persist over the region this afternoon as the air mass aloft warms
in response to weak offshore flow and building high pressure over
the eastern Pacific. Meanwhile, at the surface, winds along the
coast remain light and slightly onshore while portions of the
interior are experiencing weak north/northeast winds. These
conditions have resulted in a region- wide warming and drying
trend that will continue into the midweek time frame.

Look for temperatures overnight to remain on the cool side of
average for most valley and coastal locations while a more noticeable
warming trend begins in the hills. Temperatures region-wide will
continue on a warming trend Monday and ramp up Tuesday into
Wednesday as surface flow becomes predominantly offshore. By
midweek, 850 MB temperatures are forecast to approach 20 deg C and
will allow for afternoon high temperatures to reach into the
mid/upper 80s at the coast with widespread 90s inland. However, even
the warmest inland areas are likely to stay below 100 degrees and a
more uniform temperature spread in the 80s to mid 90s appears most
likely Tuesday through Thursday.  With this said, the threat for
heat related illnesses will likely remain in the low to moderate
category given decent overnight cooling.

Slight cooling is then forecast by Friday as weak onshore flow
returns to the coast in response to a mid/upper level trough pushing
inland over the Pacific Northwest. However, the ridge of high
pressure does not completely get replaced and temperatures region-
wide will remain at or slightly above seasonal averages. The medium
to longer range forecast models agree that an upper level ridge will
once again become the dominate weather feature across our region by
late next weekend. This will likely lead to another warming trend by
next Sunday into Monday.

&&

.AVIATION...As of 10:44 AM PDT Sunday...For 18 tafs. Dry
offshore/northerly flow over the area keeping VFR conditions with
clear skies. High confidence.

Vicinity of KSFO...VFR.

SFO Bridge Approach...similar to KSFO.

Monterey Bay Terminals...VFR.

&&

.FIRE WEATHER...As of 3:30 AM PDT Sunday...Northerly winds have
eased in the hills since yesterday, but models indicate that
north winds will increase this morning and peak during the late
morning hours. Winds are expected to be strongest across the
North Bay, although locally gusty winds are also likely in the
East Bay Hills. Relative humidity recoveries have been poor in the
hills overnight, with RH values remaining below 30 percent on the
higher peaks and ridges. Poor overnight humidity recoveries and
periods of moderate and gusty north to northeast winds are
forecast to persist through at least Tuesday morning. The most
critical fire weather conditions will remain over the North Bay
Mountains, particularly on Monday night and Tuesday morning when
winds are forecast to be at their strongest. A Red Flag Warning
remains in effect for elevations above 1000 feet in the North Bay
through Tuesday morning.

&&

.MARINE...as of 10:44 AM PDT Sunday...High pressure will continue
off the northern California coast.  A thermal trough will shift
towards the coast resulting in decreasing winds for the inner
waters today and the northern outer waters Tuesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm

&&

$$

PUBLIC FORECAST: RGass
AVIATION: RWW
MARINE: RWW
FIRE WEATHER: Dykema

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