584
FXUS66 KMTR 190441
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
941 PM PDT Wed Jun 18 2025

...New AVIATION...

.SYNOPSIS...
Issued at 1255 PM PDT Wed Jun 18 2025

Cooling trend begins on Thursday and continues through the weekend.
Gusty winds and low daytime humidities lead to elevated fire weather
conditions in the interior. Seasonal conditions resume early next
week.

&&

.UPDATE...
Issued at 843 PM PDT Wed Jun 18 2025

The warmest afternoon of the week is over with temps ranging from 61
at Half Moon Bay to the mid 90s for Santa Rosa, Livermore, Concord,
and even into the 100s for areas like Parkfield and the Pinnacles.

Onshore flow begins to increase in the next few days, but inland
humidities will be slow to improve. The forecasting team is keeping
a close eye on humidity values and the increasing winds associated
with our changing upper-level pattern. Luckily the driest conditions
do not look to occure during the windiest part of the forecast.
However, the interior valleys and mountains will still be breezy and
gusty over the next few days and will also still be dry. Please be
fire weather aware!

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 1255 PM PDT Wed Jun 18 2025

Satellite imagery shows patchy stratus lingering at the immediate
coast, with general clearing through the rest of the afternoon.
Overnight, a cold front currently analyzed over the North Coast
approaches the region, and while it will not progress further south
than the North Bay, the associated upper level low coming into the
Pacific Northwest will still provide enough wind aloft to disrupt
stratus formation, with any stratus overnight limited to the coastal
regions and perhaps parts of the East Bay west of the Berkeley-San
Leandro Hills. Speaking of winds, gusty onshore winds will develop
this afternoon with peak gusts up to 25 to 30 mph through gaps,
passes, and the Salinas Valley, but the winds won`t diminish as much
as they typically would overnight, especially along the coast and
across the higher elevations of the North and East Bay. These gusty
winds will lead to increased fire weather threat across the interior
(see FIRE WEATHER below).

Today sees the last day of warm conditions across the region with
high temperatures ranging in the lower 90s to near 100 inland, the
70s and lower 80s along the Bayshore, and the lower to middle 60s
along the Pacific coast. Low temperatures on Thursday morning range
from the lower to middle 50s in the lower elevations, into the 60s
for the higher elevations. Thursday`s highs will dip due to the
influence of the upper low, with highs reaching the lower 70s to the
lower 80s inland and the upper 50s to middle 60s along the coast and
Bayshore. Light coastal drizzle is also possible tonight into
Thursday morning.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 1255 PM PDT Wed Jun 18 2025

Breezy and chilly conditions continue through the weekend, with high
temperatures dropping to the 70s inland and the upper 50s to lower
60s along the coast, or around 8 to 15 degrees below the seasonal
average, on Friday and Saturday. The upper level low moves
northeastward into the Canadian prairie provinces, but some of its
energy remains trapped in the western United States, courtesy of a
very strong upper level ridge centered over the Ohio River Valley
and the Northeastern US. Temperatures will begin to rise on Sunday,
and by the middle of next week, it may still feel chilly along the
coast, but temperatures in the inland valleys should be much closer
to the seasonal averages. CPC guidance suggests that temperatures
remain near or slightly below seasonal averages into the first
couple days of July, with precipitation totals remaining near the
seasonal averages (read: almost nothing) for the same period.

&&

.AVIATION...
(06Z TAFS)
Issued at 941 PM PDT Wed Jun 18 2025

850 mb cold air and dry air advection arriving on northwest winds
are helping to keep VFR going area-wide except it`s 5 miles /MVFR/
in haze/mist at KHAF. The ACV-SFO and UKI-STS pressure gradients
are 8.2 mb and 1.7 mb respectively while the onshore pressure
gradient is 3.5 mb. Nocturnal radiative cooling to space and lower
level cold air advection may combine to produce redevelopment of
coastal stratus later tonight to the predawn hours Thursday, though
by how much areal extent of development is a very challenging
forecast. It`s moderate to high confidence the Bay Area terminals
stay VFR tonight with exception of IFR in stratus and mist/fog
developing at KHAF tonight and Thursday morning and it may be slow
for KHAF to mix out Thursday. Otherwise for the north Central
Coast it`s a moderate to high confidence VFR forecast for early to
mid evening then it`s a low to moderate confidence IFR forecast
mid to late evening and overnight. VFR inland Thursday, along the
immediate coastline patchy stratus /IFR-MVFR/ may linger.

Vicinity of SFO...VFR. Gusty west wind to 30 knots gradually
subsiding tonight. Gusty west wind near 30 knots Thursday and
Thursday evening. Stratus /MVFR/ returning Thursday evening and
night.

SFO Bridge Approach...Similar to SFO with VFR.

Monterey Bay Terminals...VFR conditions extending into late
evening, then nocturnal cooling and lower level cold air advection
favors redevelopment of stratus /IFR/ tonight and Thursday morning.
Tempo IFR forecast 04z-08z at KMRY and KSNS terminals then IFR
prevailing tonight/Thursday morning then mixing out to MVFR-VFR by
late Thursday morning or early afternoon. Stratus /MVFR-IFR/
returning Thursday evening and night.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 843 PM PDT Wed Jun 18 2025

Hazardous conditions prevail over the coastal waters into Friday
thanks to a passing dry cold front. Winds will be strongest over
the outer waters and coastal jet locations like north of Point
Reyes and south of Point Sur. Gale warnings are in effect in those
locations with fresh swell and steep wind waves. Significant wave
heights build to 10 to 12 feet across the coastal waters Thursday
into the weekend.

&&

.FIRE WEATHER...
Issued at 1255 PM PDT Wed Jun 18 2025

A period of elevated fire weather threat begins on Thursday as
strong winds gusting at 20 to 35 mph and daytime relative humidities
of 15 to 25% develop across the interior, with the biggest threat
coming in the interior mountains of the North Bay, the interior East
Bay, the eastern Santa Clara Hills, and the Gabilan Range in
interior Monterey and San Benito Counties. Fuels have been curing
across the interior, especially across the finer fuels of grass and
brush, and there`s already been several notable grass fires across
the interior portions of the region. However, the fact that winds
will remain onshore and temperatures will cool will keep fire
weather conditions below critical levels. The fire weather threat
continues into the weekend, before gusty winds begin to subside
heading into the early part of next week.

DialH

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 1 PM to 9 PM PDT Thursday for Mry Bay-
     SF Bay N of Bay Bridge.

     Gale Warning until 9 PM PDT Thursday for Pigeon Pt to Pt Pinos
     10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes
     10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 PM PDT Thursday for Pigeon Pt to Pt
     Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Canepa

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