NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 280023

Area Forecast Discussion
National Weather Service San Francisco Bay Area
523 PM PDT Tue Jul 27 2021

.SYNOPSIS...Light showers have pushed northward out of our
forecast area this afternoon. Long range forecast is seasonably
warm and dry through the rest of the work week. Slight cooling
starts by Saturday as marine air pushes farther inland over the

&& of 02:53 PM PDT Tuesday...Current radar shows
that the last of the light showers has now pushed north of Sonoma
and Napa counties meaning that "Sprinkle Watch" is over for our
CWA. We had several reports on social media of folks seeing rain
drops in their neighborhoods across the Bay Area this morning into
afternoon. Much of the precipitation was just trace amounts, but
there were a few isolated spots that measured around 0.01-0.03".

The rest of this week puts us in a fairly stagnant synoptic
pattern as a broad and large high pressure cell dominates much of
the CONUS through Friday. With that high pressure stretching into
the west coast, we`ll see warm and dry weather in our region,
particularly for our interior locations. Meanwhile, coastal
locations will have more mild temperatures, but could still be a
bit warmer than normal. The temperature range for coastal areas
will be in the 60s and 70s this week while inland spots range in
the 80s and 90s...could see a few triple digit marks this week in
the hotter areas of our CWA, but nothing widespread. As stated in
prior discussions, the inland spots will generally range about
5-10 degrees above normal. However, at this time, we are not at
risk for this turning into a significant heat event. Folks in
those 90-100 degree locations will still want to make sure they
stay hydrated and avoid strenuous work during the heat of the day,

As we approach the weekend, an upper level low off the
coast of Canada will have a trough extending southward off the CA
coastline. On Saturday and Sunday, that low will nudge inland and
weaken the large CONUS high. As this occurs, we`ll start to cool
into a more seasonable range as the marine layer will build back
and usher in the cooler, moist marine air.

Have taken a look at long range models and there seems to be a
hint of another round of monsoon moisture making it`s way into CA
again. The main difference is that the moisture will likely stay
east of our forecast area and be more of an impact for the Sierra.

&& of 5:23 PM PDT Tuesday...For the 00z TAFs. VFR
across Bay Area terminals but stratus is encroaching on coastal
Monterey Bay terminals. GOES-17 shows monsoonal moisture has
pushed to the north, leaving FEW high clouds across North Bay.
Coastal stratus is present from the San Mateo coastline, down
through SoCal. However, it appears to be dissipating on the
northern fringe, as drier air works its way into the area. With a
mixed out marine layer from the SF Peninsula northward, expecting
VFR conditions for most Bay Area terminals overnight, though
models hint at possible low cloud development around the Golden
Gate and eastern SF Bay. Monterey Bay terminals will have IFR/LIFR
conditions through the morning as the marine layer remains in
place. Wednesday brings mostly clear skies with a light to
moderate sea breeze returning.

Vicinity of KSFO...VFR conditions through the period. Stratus
offshore is retreating to the south. FEW to SCT low clouds
possible over the bay in the early morning hours. Breezy WNW winds
15-20 kt settle down this evening and overnight. Wednesday
continues VFR with sea breezes returning in the afternoon 15-20

KSFO Bridge Approach...Similar to KSFO.

Monterey Bay...VFR transitioning to IFR/LIFR this evening as a
compressed marine layer remains in place. OVC003 reported at
KOAR, with stratus in the vicinity of KMRY/KSNS/KWVI. Clearing
to VFR late morning to early afternoon Wednesday. Light to
moderate sea breeze returns.

&& of 02:33 PM PDT Tuesday...Scattered showers remain
over the northern outer waters, but are slowly moving northward
out of the area. Drier conditions expected Tuesday evening.
Northwest winds prevail and remain fairly weak yet continue to be
the influence on the sea state at around 6 to 8 seconds along with
a weak southerly swell. Winds and gusts look to increase Tuesday
afternoon and into the evening through the Golden Gate gap into
the San Francisco Bay. Locally generated steep wind waves may be
hazardous for smaller vessels.


     .Tngt...SCA...SF Bay until 9 PM




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NWS MTR Office Area Forecast Discussion