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NWS Forecast Area Discussion - San Francisco Area

000
FXUS66 KMTR 221759
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1059 AM PDT Mon Jul 22 2019

.SYNOPSIS...A gradual warming trend will continue through midweek,
especially across the interior. This will lead to seasonably warm
temperatures inland while coastal areas remain mild under the
influence of the marine layer as onshore flow persists.

&&

.DISCUSSION...as of 08:46 AM PDT Monday...A compressed marine
layer due to building high pressure has resulted in less
widespread stratus coverage across the region this morning.
Satellite imagery shows low clouds remain along the coast, over
the Monterey Peninsula, and down the Salinas Valley as the marine
layer sits at around 1200-1500 ft AGL. Low clouds will dissipate
by late this morning leaving mainly clear skies for the afternoon.

A gradual warming trend will continue today, mainly for inland
areas, as high pressure builds over the Four Corners and westward
towards California. Highs along the coast today are forecast to
be in the upper 60s to mid 70s with 80s to low 90s across the
interior. Models continue to show an increase in mid/upper level
moisture this afternoon and evening over southern and eastern
California along with increased mid/upper level instability. Any
resulting high based convection is expected to remain outside of
our forecast area with only an increase in mid/upper level clouds
over the southeastern portion of the region. Conditions will be
closely monitored and the forecast will be updated as needed.
Seasonably warm temperatures inland will persist through the end
of the week while onshore flow and a shallow marine layer will
keep coastal areas in the mid 60s to mid 70s.

&&

.PREV DISCUSSION...as of 03:30 AM PDT Monday...High pressure over
the Four Corners continues to build westward over California
resulting in a more compressed marine layer this morning. Thus,
low clouds are not as widespread as previous days remaining
confined to the coast, locally inland around coastal North Bay,
through the Golden Gate and down around the Monterey Bay. However,
coastal stratus has made a run down into the Salinas Valley this
morning as light northwest winds persist. Under this pattern, low
clouds will quickly dissipate over inland areas by mid-morning and
give way to mostly sunny conditions region-wide this afternoon.
Inland areas will also continue on a gradual warming trend with
80s to lower 90s inland while coastal areas hold in the middle 60s
to middle 70s as a result on persistent onshore flow.

The short-range forecast models do show an increase in mid/upper
level moisture advecting across southern and eastern California by
midday. In addition, mid-level instability is forecast to increase
over this region as well by this afternoon and evening. However,
confidence remains low that all parameters will be sufficient enough
to produce high-based convection across our region. Thus, will
continue to monitor throughout the day and at the very least could
see an increase in mid/high level clouds over the southeastern
portion of the region.

The warming trend will stall a bit on Tuesday as a mid/upper level
trough over the northern Pacific lifts northeastward across the
Pacific Northwest. Additional warming across the interior is then
likely on Wednesday as the high pressure to our east strengthens.
Look for more widespread 80s and 90s inland with a few of the
region`s warmest interior spots potentially approaching the 100 deg
F mark. Meanwhile, a shallow marine layer is likely to persist near
the coast as onshore flow continues. This may result in more
widespread fog along coastal locations by Wednesday morning.

No significant changes are forecast through the remainder of the
week and into the upcoming weekend as high pressure to our east
dominates the weather pattern. This will keep inland temperatures at
or slightly above seasonal averages while coastal areas remain mild
with the presence of a shallow marine layer.

&&

.AVIATION...as of 10:58 AM PDT Monday...A shallow marine layer
with a depth of around 1200-1500 feet and building high pressure
has allowed clouds to peel back to the coastline this morning. VFR
conditions will prevail this afternoon at the TAF sites. Onshore
winds will increase this afternoon to around 10-15 kt most sites.
The marine layer will remain compressed through tonight as high
pressure continues to build overhead. For tonight and Tuesday
morning, expect stratus coverage similar to this morning with
mainly LIFR/IFR where clouds develop. Shallow depth should once
again prevent clouds from intruding too far into inland valleys.
Somewhat lower confidence on development around SF Bay, but some
cigs in the vicinity are likely to develop overnight.

Vicinity of KSFO...VFR this afternoon and evening. WNW winds
increasing this afternoon and early evening to 15-20 kt. For
tonight and Tuesday morning, moderate confidence on timing and
extent of stratus formation. May see a similar scenario to this
morning where the terminal remained VFR and some cigs developed
over the approach. Will continue to monitor and update as details
become more clear.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR conditions this afternoon. Onshore
winds increasing this afternoon to around 10-15 kt. IFR cigs
likely to return around 03-04z this evening with conditions
deteriorating to LIFR overnight.

&&

.MARINE...as of 08:42 AM PDT Monday...Gusty northwest winds will
continue over the northern coastal waters as high pressure builds
into the Pacific Northwest and northern California. Light
southerly swell coupled with short period wind waves will continue
through the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...SF Bay from 2 PM

&&

$$

PUBLIC FORECAST: AS/RGass
AVIATION: ST
MARINE: ST

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NWS MTR Office Area Forecast Discussion

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