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fxus66 kmtr 141134 
afdmtr

Area forecast discussion
National Weather Service San Francisco Bay area
334 am PST Thu Dec 14 2017

Synopsis...dry weather continues this week as high pressure resides
over California. A mainly dry cold front will sweep south over
the area late Friday night and early Saturday morning which then
increases north-NE winds along the ridges and peaks Saturday. A dry
pattern may turn to a wet weather pattern next week.

&&

Discussion...as of 2:56 am PST Thursday...after an extended
period of stagnant weather with a Rex block, a pattern change is
likely this weekend and possibly rain returning next week.

Currently a Stout offshore flow set up prevails with high pressure
over the Great Basin and low pressure along the coast. Latest
offshore gradients are actually stronger than 24 hours ago at 14
mb (sfo-wmc). Needless to say, this pressure gradient is leading
to mild temperatures, dry conditions and very gusty winds over
higher elevations. Mt Diablo is once again the Winner for
strongest winds with gusts up to 53 mph. Santa Rita Peak in San
Benito County is the driest with relative humidity values sitting
about 10%. For what it's Worth, that is up about 5% from earlier
in the night. Heightened fire weather concerns exist over the
peaks tonight. Similar to last night, different story in the
valleys with much weaker winds and colder temperatures. Several
interior valleys locations are currently sitting in the upper 20s
to lower 30s. Patchy frost will be possible in these locations. A
few stations across the North Bay valleys are also reporting dense
fog.

If you liked yesterday's weather you'll like today's. Mostly sunny
skies and above normal temperatures. High pressure finally breaks
down on Friday as a weak frontal boundary and associated upper
level trough sweep through the region. Models continue to show a
dry frontal passage Friday night for the Bay area, but some light
precip is poss for far north California. This change in the pattern will bring
slightly cooler temperatures this weekend. More importantly, it's
the weather conditions that develop behind the front impacting the
Bay area. Offshore flow gradients ramp up pretty quick Friday
night into Saturday morning. The local WRF model continues to
show NE winds of 20-30 mph with gusts exceeding 50 mph over the
higher terrain of the North/East Bay and Santa Cruz Mountains.
Given that it is still several forecast periods out will hold off
on a Wind Advisory, but issue a hazardous weather outlook to
highlight winds. In addition to the wind impact, fire weather
concerns will also develop. Humidity values will recovery early
Friday night, but plummet below 30% as NE wind kick in. Breezy to
gusty NE winds persist through Sunday morning. A Fire Weather
Watch may be needed for Saturday night as humidity recoveries will
be poor all night with NE winds over higher terrain.

High pressure rebuilds over the region Sunday through Tuesday. The
much talked about precipitation chances for the middle of next
week still exist. In fact, the 00z models are much different than
24 hours ago. The big three models all show a large scale trough
sweeping through the West Coast on Wednesday. All three models
also show some quantitative precipitation forecast around the Bay area as well. It's still too far
out for exact amounts, but at this point we'll take anything we
can get. Hope the models stay locked on this solution and don't
flip flop back to drier solutions.

&&

Aviation...as of 3:30 am PST Thursday...for 12z tafs. Other than
reduced visible at ksts and areas of the North Bay valleys early this
morning, VFR prevails across the district. Expect VFR through the
day today and tonight, with light west/northwest winds by this
afternoon.

Vicinity of ksfo...VFR. Light and variable winds turning west-
northwest by late afternoon, around 10 kt.

Sfo bridge approach...similar to ksfo.

Monterey Bay terminals...VFR. Southeast winds to 10 kt in the
Salinas valley this morning. Winds should switch more onshore and
decrease some by late afternoon, before turning back southeast
late tonight.

&&

Climate...

Record high temperatures for Thursday, December 14, 2017.

Sf Bay area December 14
location................
Healdsburg.............. 77/1942
Santa Rosa.............. 72/1956
Kentfield............... 70/1942
San Rafael.............. 70/1959
Napa.................... 73/1959
San Francisco........... 69/1988
sfo Airport............. 69/1958
Oakland Airport......... 65/1958
Richmond................ 67/1983
Livermore............... 75/1958
Moffett field........... 72/1958
San Jose................ 73/1958
Gilroy.................. 72/1988

Monterey Bay area
location................
Monterey................ 78/1953
Santa Cruz.............. 82/1953
Salinas................. 80/1988
Salinas Airport......... 81/1953
King City............... 83/1958

&&

Marine...as of 3:16 am PST Thursday...light to moderate
northerly winds will continue through Friday afternoon before a
cold front sweeps southeast over the waters on Friday afternoon and
evening. A coastal trough will form along the California coast
after the frontal passage and will gradually strengthen late
Friday night and into Saturday, increasing winds significantly.
Seas will gradually increase through the rest of the week.

&&

Mtr watches/warnings/advisories...
...

&&

$$

Public forecast: mm
aviation/marine: BAM

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