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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 250416

Area Forecast Discussion
National Weather Service San Francisco Bay Area
916 PM PDT Mon Jun 24 2019

.SYNOPSIS...A cooling trend will get continue through Thursday, 
with temperatures forecast to cool by 10 to 20 degrees by 
Wednesday. In addition, expect an increase in night and morning 
low clouds through Wednesday morning. Temperatures will warm a 
bit late in the week and into next weekend, but remain slightly 
below seasonal averages. 

&& of 9:16 PM PDT Monday...No significant forecast 
updates planned for this evening. Highs today ranged from 64 in
Half Moon bay to 100 in the southern Salinas Valley. Satellite 
shows extensive high clouds passing over the state ahead of an 
incoming upper trough. Most of the high clouds should be to our 
east by morning. Along the immediate coast the marine layer is 
showing signs of deepening and getting more organized in the 
pre-trough environment. The Ford Ord profiler shows the depth 
currently around 1500 feet with slight deepening the last several 
hours. Nighttime fog product currently shows low clouds from Half 
Moon Bay down along the Big Sur coastline with organized stratus 
starting to inundate the Monterey Bay region from Santa Cruz to 
Salinas. Cloud heights from Half Moon Bay to Salinas are roughly 
around 600-1000 feet with vsbys above 6 miles.

Synoptic pattern features an incoming 500 mb upper trough that
will keep onshore flow firmly in place the next several days. Rain
associated with the upper trough will mainly stay over Oregon on
Weds. The main impact for the Bay Area will be a noted cooling
trend of a few degrees on Tuesday with further cooling on
Wednesday. Inland highs on Wednesday will be well below normal for
inland areas with 70s for places like Livermore, Concord and Santa
Rosa while cool 60s will prevail near the coast and bays. Expect a
solid push of marine clouds for Wednesday morning but by Wednesday
afternoon the cooling aloft may be sufficient enough to 
essentially break the marine inversion for most locations, even 
near the coast. The unseasonably cool inland temps will prevail 
through Thursday. A gradual warming trend into the weekend and 
through early next week.


.PREV of 2:22 PM PDT Monday...Visible satellite 
imagery shows some passing high clouds over the the San Francisco 
Bay Area this afternoon. Meanwhile along the immediate Pacific 
Coast, some lingering coastal stratus continues for locations such
as Point Reyes, Half Moon Bay, Moss Landing, and Pacific Grove. 
Temperatures as of 2 pm PDT this afternoon are in the 60s along 
the coast while interior communities are in the 70s and 80s. When 
compared to 24 hours ago, the present readings across the interior
have trended downward by about 4 to 8 degrees. By the time the 
afternoon wraps up, most locations will be within several degrees 
of their late June climatological normal highs.

An upper level low off the British Columbia coast is forecast to 
slide southeastward to the Pacific Northwest over the next several
days. While the stratiform rain is expected to remain far to our 
north in Oregon and Washington State, this system will promote 
further cooling for region as geopotential heights and 
temperatures aloft drop. For example, the latest NAM run has 850 
mb and 700 mb temperatures at Oakland dropping from about 20 deg C
and 10 deg C this afternoon to 7 deg C and 3 deg C, respectively,
by early Thursday morning. At the surface, this will correspond 
to high temperatures on Wednesday and Thursday in the 50s and 60s 
along the immediate coast, and 70s to isolated low 80s for the 
interior. Additionally, the trough will likely enhance the marine
layer depth over the coming days with morning low clouds.

Temperatures will begin to rebound for the Bay Area later this 
week and into the weekend as the upper low shifts eastward into 
the Northern Rockies. The long wave trough pattern over the 
eastern Pacific will try to hold on into the weekend and early 
next week as models advertise another upper level low dropping 
south from the Gulf of Alaska. Meanwhile, an upper level ridge 
will build over the Southern Plains and will gradually build 
westward toward the Desert Southwest. If this solution pans out, 
temperatures would likely continue their warming trend into the 
first week of July, particularly for the interior.

&& of 4:55 PM PDT Monday...For 00Z TAFs. An 
approaching weather system will act to deepen the marine layer and
strengthen the onshore flow over the next several days as it 
rotate through the region. Anticipate low clouds along the coast
with limited inland intrusion tonight into Tuesday morning.
Confidence is low with respect to the low clouds coverage as the
approaching trough may scour out the low clouds over the north
coast. Light to locally variable winds expected overnight with 
moderate and locally gusty winds Tuesday afternoon.

Vicinity of KSFO...VFR conditions will prevail with MVFR cigs
possible after midnight over KOAK. Confidence is low. Clearing is
anticipated around 17z. Moderate westerly winds around 15 to 20 
kt will prevail through this evening then gradually ease overnight
becoming light.

SFO Bridge Approach...Similar to KSFO. Low confidence that any 
low clouds will develop overnight.

Monterey Bay Terminals...IFR cigs anticipated to fill in by early 
evening and prevail through tonight. Clearing anticipated around
17z. Moderate westerly winds around 10 to 15 kt will prevail 
through this evening then gradually ease overnight becoming light
and locally variable.

&& of 08:59 PM PDT Monday...Gusty northwesterly winds
will continue over the northern outer  waters and along the coast
north of Point Reyes through Tuesday as high pressure remains over
the eastern Pacific. These winds will  result in steep fresh swell
creating hazardous conditions over the waters, especially for
smaller vessels. Winds will diminish briefly on Tuesday as high
pressure weakens and an upper low  moves offshore of the Pacific
Northwest. Northwesterly winds will  increase late in the week.


     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM




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