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

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FXUS66 KMTR 251738
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1038 AM PDT Tue Jun 25 2019

.SYNOPSIS...A cooling trend will continue through Thursday, with
temperatures forecast to cool several degrees below seasonal
averages over the next few days. 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 still remain below average.

&&

.DISCUSSION...as of 08:49 AM PDT Tuesday...Plenty of sunshine this
morning in downtown San Francisco and around the North Bay. As the
upper level low continues to make its way to the Pacific Northwest,
onshore flow remains consistent throughout the CWA. While the marine
layer remains at about 1500 feet ASL, the onshore flow has let it
spread further inland into the valleys of San Benito and Santa Clara
counties as well as southward through the Salinas Valley towards San
Luis Obispo county. This dichotomy of clearer Northern counties
versus stratus filled Southern counties is helping to allow
temperatures to be slightly warmer than yesterday morning in the
North; while temperatures in Southern counties are cooler. Afternoon
highs should be in the mid-to-low 60s near the coast today and the
mid-80s to low-90s inland. The forecasted cooling trend continues
tomorrow and into Thursday; for additional details beyond Day 1,
please refer to the previous discussion section below.

&&

.PREV DISCUSSION...As of 3:05 AM PDT Tuesday...The cooling trend that
got off to a modest start on Monday will continue through
Thursday as an upper trough gradually deepens near the California
Coast. Model consensus indicates cooling today will be limited to
just a few degrees, and mainly across inland areas. More robust
cooling, on the order of ten degrees for inland areas, is expected
on Wednesday as a vort max rotates through the base of the trough
and across northern California. A few additional degrees of
cooling is then anticipated on Thursday when the upper trough
reaches its maximum depth over California and 850 mb temperatures
drop a bit below 10 deg C. Inland temperatures by Thursday are
forecast to be as much as 15 degrees cooler than average.

Low clouds are not as widespread early this morning as they were
at this time yesterday morning, particularly across the San
Francisco Bay Area. Expect low clouds to become more widespread
tonight and Wednesday night as the marine layer deepens. By
Thursday there may be enough cooling aloft to mix out the marine
layer.

Gradual warming is forecast from Friday into the upcoming weekend
as the upper trough slowly lifts to the northeast. However,
temperatures are expected to remain cooler than normal in most
areas through the weekend.

In the longer range, there had previously been good agreement
between the GFS and ECMWF (both deterministic and ensemble mean
versions) in forecasting warmer weather by the July 4th holiday as
an upper ridge over the Desert Southwest was forecast to build
westward across California. The latest GFS ensemble mean and
deterministic model continue to forecast warming, but the latest
ECMWF now maintains the trough position near the West Coast and
thus suggests continued cooler than average conditions into the
holiday.

&&

.AVIATION...as of 10:35 AM PDT Tuesday...For 18Z TAFs. Low
ceilings associated with stratus remain confined to the northern
portion of the Monterey Bay this morning with VFR conditions at
all forecast terminals. Light onshore flow this morning will
increase into the afternoon with locally gusty conditions around
KSFO. VFR conditions will likely persist into the evening at most
terminals with the potential for low ceilings returning around the
Monterey Bay terminals by late evening, generally after 03Z.
Meanwhile, confidence is low for the development of low clouds
around the Bay Area terminals into Wednesday morning. Thus, VFR
conditions appear most likely at this time.

Vicinity of KSFO...VFR. W to NW winds increasing to around 15 kt
with gusts 20-25 kt this afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR. Onshore winds increasings to around
10 to 15 kt through the afternoon with return of low clouds by
late this evening.

&&

.MARINE...as of 08:49 AM PDT Tuesday...Gusty northwesterly winds
will persist across the northern outer waters and along the coast
north of Point Reyes into tonight as high pressure remains over
the eastern Pacific. Additionally, expect locally gusty winds to
develop this afternoon around the  coastal gaps, over the bays,
and along the Big Sur coast south of  Point Sur. These winds will
generate steep fresh swell resulting  in hazardous conditions over
the waters, particularly for smaller  vessels. Winds will diminish
tonight as high pressure weakens and  an upper low moves offshore
of the Pacific Northwest. Expect  northwesterly winds to re-
strengthen later this week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Mry Bay
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 4 PM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 4 PM
             SCA...SF Bay from 3 PM

&&

$$

PUBLIC FORECAST: DK/Dykema
AVIATION: RGass
MARINE: RGass

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