137
FXUS66 KMTR 140721
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1221 AM PDT Sun Jul 14 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 145 PM PDT Sat Jul 13 2024

Heat Advisory is in effect mainly inland portions of the Bay Area
and north Central Coast until 9 pm this evening. It`s still hot
inland, however relative cooling is taking place helping to ease
things a bit due to cloud cover along with a few isolated passing
showers through the afternoon. High temperatures will continue to
ease back to normal mid July highs in the mid 80s to 90s far inland
early to mid next week. Closer to the coast and nearby coastal
valleys a maritime influence will result in cooler daytime
temperatures.

&&

.UPDATE...
Issued at 647 PM PDT Sat Jul 13 2024

The Heat Advisory will expire 9PM tonight as the weak low pressure
system will influence some cooler temperatures tonight. Temperatures
are already showing a 5-10 degree drop compared to 24 hours ago. We
are still monitoring the instability and mid-level moisture
moving up from southern California, which has brought a slight
chance for dry lightning over our area through Sunday. With the
dry fuels, any lightning can raise fire weather concerns. So far
no changes to the forecast at the moment and although there has
not been any lightning so far, we will continue to monitor our
radar for any convection.

&&

.SHORT TERM...
(This evening through Sunday)
Issued at 155 PM PDT Sat Jul 13 2024

We continue to closely monitor satellite, radar and observations
for incoming mid level moisture and instability from southern
California. So far we`re only seeing a few passing showers and
since high resolution model output shows plenty of convective
inhibition the expectation is this will continue to greatly limit
any potential for thunderstorm development through afternoon and
evening. There`s forecast steepening of the 700-500 mb temperature
lapse rates and weak mid level convective potential out ahead and
northeast of the 500 mb low, currently 275 miles west of Point
Conception, arriving late tonight and Sunday morning however just
above this the 500-300 mb layer is stable. From approx the 700 mb
level (~ 10,000 feet) downward through the 925 mb level (~ 2,500
feet) thermal ridging, stability remains in place tonight and
Sunday morning.

Warm to hot far inland again this afternoon, however cloud cover
will help reduce incoming solar input a little bit helping reduce
highs a little compared to Friday afternoon. Cooler temperatures
prevail along the coast and in the nearby coastal valleys due to
increasing maritime influence, including coastal stratus and fog.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 155 PM PDT Sat Jul 13 2024

Summer continental surface heating continues to correspond to
strong 500 mb heights with a nearly stationary high pressure
system over the west with the center near the Four Corners. A
stable north hemispheric pattern shows signs of strengthening and
becoming unsteady again with five long wave troughs developing by
late next week. One long wave trough is forecast to slowly
progress eastward to along western North America while a long wave
ridge primarily strengthens over central Canada with an extension,
possibly the southern extension retrogressing toward the southwestern
states. The GEFS/EPS ensemble 850 mb mean temperature forecasts for
our forecast area climb back to 26 Celsius next weekend, not quite
as warm as of recent, but bears watching.

&&

.AVIATION...
(06Z TAFS)
Issued at 1220 AM PDT Sun Jul 14 2024

IFR CIGS are moving inland and have already filled over the Monterey
Bay terminals. OAK and the North Bay terminals look to fill later
into the night with IFR CIGs. Pockets of mist will affect
visibilities around the region over night as well. CIGs erode into
the mid to late morning with moderate to breezy winds arriving into
the afternoon. Winds reduce Sunday evening as more widespread CIGs
push inland.


Vicinity of SFO...VFR lasts into Sunday night with passing high
clouds through the TAF period. Winds stay moderate through the late
morning, becoming breezy and gusty in the afternoon, reducing into
into Sunday night. MVFR CIGs build into the SF Bay that evening and
look to fill over SFO after nightfall.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR/LIFR CIGs and mist last into the late
morning for SNS but into the afternoon for MRY. As CIGs dissipate,
moderate westerly winds build into the area. These winds reduce into
the night, as IFR CIGs move inland Sunday evening.


&&

.MARINE...
(Today through Friday)
Issued at 1220 AM PDT Sun Jul 14 2024

Radar currently shows a few isolated showers over the waters.
Slight chances of light rain and drizzle will persist through the
weekend over the waters. Otherwise, gentle to moderate northerly
winds continue through the afternoon today but begin to turn more
southerly starting Sunday. These light southerly winds are
expected to continue through the middle part of next week, but
then turn to become more northwesterly beyond then.

&&

.FIRE WEATHER...
Issued at 1030 AM PDT Sat Jul 13 2024

Mid level cloud cover/moisture moving up from southern California
is resulting in widely scattered showers, a few spots have reported
a trace (and possibly light measurable precipitation) reaching the
ground. Forecast soundings show widespread convective inhibition
over our forecast area today i.e. stability greatly helping to
preclude thunderstorm development. Per satellite and high
resolution model output, mid level cloud cover over our forecast
area will help reduce incoming solar input today. 12z statistical
guidance shows slightly cooler temperature trends including inland
areas today. The marine layer temperature inversion at the mountain
tops is still quite warm, however 24 hour trends show cooler temperatures
almost everywhere this morning, also resulting in positive humidity
trends.

A well established marine layer with coastal stratus has recently
shown signs of deepening per Bodega Bay and Fort Ord profiler data.
The southerly and onshore pressure gradients and winds prevail which
will help usher higher humidity to the inland valleys, hills and
eventually mountain tops.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Murdock
MARINE...AC

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea