FXUS66 KMTR 260458
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
958 PM PDT Wed Mar 25 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 911 PM PDT Wed Mar 25 2026
- Above normal temperatures persist into the weekend
- Offshore winds across the North Bay Interior Mountains thru Friday
- Pattern change with chances for largely beneficial rain next week
&&
.SHORT TERM...
Issued at 911 PM PDT Wed Mar 25 2026
(Tonight through Friday)
Generally quiescent conditions are forecast during the short term
period, with the exception being across some of the higher terrain
of the North Bay Interior Mountains as well as parts of the East Bay
Hills tonight, but especially pre-dawn Friday morning.
A dry/cool frontal boundary continues to slide southward through
portions of the North Bay this evening, with a pretty discernible
northerly wind shift evident on observations upstream across Lake
and Mendocino Counties. This frontal boundary will usher in some
cooler air and as noted previously, min temperatures should be a
touch cooler (at least across the North Bay), but sunrise Thursday
compared to the past few days. Overall, not anticipating a
potential for widespread frost/freeze conditions, though a few
spots may dip down into the upper 30s across extreme northern
Sonoma and Napa Counties.
925mb flow does increase some on Thursday morning, in the
immediate wake of the front, but the real potential for any type
of mountain wave activity is greater on Friday morning. This will
be due to building high pressure in the wake of the front through
the day on Thursday. As the MSLP gradient tightens beneath a
largely stable regime, flow will become trapped and forced
around the complex terrain. Areas such as Mt. St. Helena and other
peaks across the North Bay Mountains may see winds gust as great
as 45 mph pre-dawn Friday morning. The SJSU/PG&E WRF as well as
our in- house model highlight this potential well.
Otherwise, mid/upper level clouds will continue to invade from
the southwest resulting in partly sunny skies. Despite largely
filtered sunshine, high temperatures will remain 10 to 15 degrees
above normal. This trend will continue through the weekend.
&&
.LONG TERM...
Issued at 911 PM PDT Wed Mar 25 2026
(Friday night through next Wednesday)
The weekend is anticipated to be quite pleasant. With the
magnitude of offshore flow weakening slightly, this may allow for
the afternoon sea-breeze to bring MaxTs down a few degrees
compared to the previous days. Still highs are expected to remain
5 to 10 degrees above normal.
Our ridge pattern that has resulted in our well above normal heat
will yield to more pronounced troughing as we venture into next
week. There do remain some temporal and spatial differences in
the placement of more vigorous shortwaves in the longwave trough
and we'll continue to examine the latest guidance as it arrives
for next week.
Some of the synoptic scale progs from the deterministic guidance
advertise swift mid-level flow extending from the southwest with
favored large scale ascent beneath the exit region of a 50 knot jet.
This will equate to cooler conditions next week. At this time,
Monday appears largely precipitation-free and this is a slight
change from previous forecast cycles due to a slower evolution of
the upper trough as it amplifies across the West Coast. Overall,
NWP is in fair to good agreement with this feature. After a few
days of troughing, a corridor of 180-200% of normal precipitable
water air will stretch from the Central Pacific eastward toward
California. Both GEFS and EPS renditions of the probability of
Integrated Vapor Transport (a useful tool for quantifying moisture
transport) above 250 kilogram/meter/second have gradually
increased from less than 10% 72 hours ago to near 50% in the
latest guidance. There are some spatial differences among model
guidance with regard to the exact location of this plume of rich
moisture and thereby the placement of the greatest rainfall and
we'll continue to iron out these details through the weekend.
Current forecast rain amounts appear respectable for this time of
year, with the greatest potential for at least 1" of rainfall across
the North Bay from late Monday into Wednesday. Chances for at least
2" of rainfall (which would be the higher end rain amount) are
around 10% across the Western Sonoma Hills, Santa Cruz Mountains,
and the Diablo Range. As noted above, once we get closer, we'll be
able to refine these rain amounts.
With actual upper level dynamics, surface/low level cyclogenesis
appears that it'll give some of the higher terrain and Pacific Coast
regions around a 40-70% chance for SW'ly wind gusts near/above 40
mph. Increased onshore flow and subsequent cloud cover will also
equate to temperatures being 5 to 15 degrees below normal by the
time we get into next week with daytime highs ranging between the
mid 50s to mid 60s.
&&
.AVIATION...
(06Z TAFS)
Issued at 957 PM PDT Wed Mar 25 2026
Generally VFR conditions persist overnight with a few high clouds.
Lingering westerly flow will diminish into light winds overnight,
with some low confidence for stratus development at the immediate
coast. Thursday morning, a pulse of gentle north to northwest
winds moves through the inland terminals with the rest of the
region seeing some onshore winds developing a little later
onwards. LLWS is expected to develop in the interior North and
East Bay on Thursday evening, as the surface winds decouple from
strong northerly flow aloft.
Vicinity of SFO... VFR with a few high clouds through the TAF
period. Breezy west-northwest winds continue through the next couple
of hours. Winds gradually diminish in the late evening with light
winds Thursday morning, before the breezy west-norhtwest winds
resume during the afternoon.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... Low confidence for sub-VFR conditions
tonight at MRY, not high enough to place a ceiling in the TAF,
otherwise VFR throughout the TAF period. Breezy northwest winds at
present, with winds turning light over the next couple of hours.
Thursday morning, light northerly winds will back to a northwest
flow at MRY, with gentle northwest winds through the afternoon at
SNS, before winds diminish into the evening.
&&
.MARINE...
(Tonight through next Tuesday)
Issued at 857 PM PDT Wed Mar 25 2026
Northwesterly gales across will persist tonight into Thursday
morning across the outer waters and the inner waters north of
Pigeon Point. Conditions begin to improve south to north by
Thursday evening, persisting over the northern outer waters
through Friday afternoon. Wind and seas ease for the weekend, then
begin to increase once again by the middle of next week a
developing system begins to move toward shore.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Gale Warning until 3 AM PDT Thursday for Pt Arena to Pt Reyes 0-
10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 9 PM PDT Thursday for Pigeon Pt to Pt
Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Gale Warning until 9 AM PDT Friday for Pt Arena to Pt Reyes 10-
60 NM.
Gale Warning until 9 AM PDT Thursday for Pigeon Pt to Pt Pinos
10-60 NM.
&&
$$
SHORT TERM...Bain
LONG TERM....Bain
AVIATION...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Thu Mar 26 00:30:03 PDT 2026
From the National Weather Service
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