FXUS66 KMTR 181224
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
424 AM PST Wed Feb 18 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 356 AM PST Wed Feb 18 2026
- High elevation snow continues today and Thursday with the
highest snow accumulations over the Central Coast
- Additional storm development will bring gusty winds and rain
back to the region tonight and Thursday
- Below February normal cold continues with overnight lows and
damp conditions making it feel even colder impacting people
without adequate shelter
- Near record breaking cold temperatures Thursday night into
Friday morning
- Active weather continues with additional chances for rain into
next week
&&
.SHORT TERM...
Issued at 320 AM PST Wed Feb 18 2026
(Today and tonight)
Colder air on northwest winds continues to move in across the
forecast area. Air temperatures have lowered to a mix of 30s and
40s, mildest at sea level nearest the beaches and bays. The snow
level has lowered to approx 2000 to 2500 feet while mountain top
temperatures have lowered to the lower 20s on Mt St Helena to the
mid 20s at other mountain tops in the Bay Area and north Central
Coast. Northwest wind moving across sea surface temperatures in
the 50s is resulting in surface to mid level instability and
scattered to numerous showers (snow at and above 2000-2500 feet).
KMUX shows the showers/snow are mainly confined to the coastal
North Bay southward to San Francisco and the San Francisco Bay
Shoreline and areas southward across Monterey and San Benito
counties. Across the North Bay where it is clearing, radiative
cooling is resulting in lowering visibilities in patchy mist/fog.
Cold Weather Advisories/Extreme Cold Warnings (product details
WWUS76 or NPWMTR) remain in effect through 9 am today. Winter
Weather Advisories (product details WWUS46 or WSWMTR) remain in
effect through 4 pm today.
There was at least one report of light snow falling in the Santa
Cruz Mountains at ~ 2500 feet elevation late last evening. The
cold air will remain through daybreak of course, but how much
additional showers/snow showers moves through is the question.
Current KMUX radar shows additional showers forming upstream to
the northwest of the Santa Cruz Mtns, with recent model output
showing maybe upwards of 0.10" liquid equivalent or potential for
upwards of 1" more snow. With the morning commute soon beginning,
Highway 17 summit at ~ 1900 feet may see snow flurries to snow
showers with light accumulation possible. 1900 feet elevation is
close to or may be temporarily above the melting layer through
daybreak. Travelers over the summit should keep this in mind, icy
road conditions may develop.
A quickly southeastward moving weak front will pass across the
forecast area today. This will likely cause clouds to redevelop
with additional showers /snow showers at higher elevations/ to
form. We're stuck in the cold, highs today will be 10F to 15F
below Feb normal temperatures.
Model forecasts have also been showing the next in line low
pressure system development tonight and Thursday morning. This
will bring rain /high elevation snow likely/ AND wind. With the
low moving eastward across the forecast area, gusty winds will
develop with potential for mix down to valleys and sea level.
Nocturnal timing arrival of the low pressure and gusty winds will
have to mix down through recently deposited cold air mass, i.e. it
will have to mix down through a stabilizing atmosphere. It can do
it if the dynamics with the low are strong enough to over-ride the
stability. For now will hold off on wind advisory, since winds at
the moment look to be close to but below advisory.
&&
.LONG TERM...
Issued at 320 AM PST Wed Feb 18 2026
(Thursday through Tuesday)
With all the cold air intrusion taking place, late Thursday into
Friday morning set up is very favorable for well below normal to
near record breaking low temperatures across the forecast area. We
get a dry weather break, but it will be chilly to cold. Model
forecasts show a break in the rain and clearing taking place,
however this will allow temperatures to quickly lower under
nocturnal radiative cooling. We'll be near record lows for Feb
20th at the long term sites, the records have been posted below
for reference. As we get closer to this time-frame, we'll be
looking at the need for additional Extreme Cold Warnings/Cold
Weather Advisories. And there may be carryover of cold temperatures
i.e. warnings and/or advisories needed for late Friday into
Saturday morning. Then over the weekend and early next week, the
500 mb pattern favors the return of rain with a milder southwest
flow which will have to scour out what remaining cold there'll be
initially. Will be closely watching this pattern of course since
it'll be tapping into a more water vapor rich environment to our
southwest.
&&
.AVIATION...
(12Z TAFS)
Issued at 423 AM PST Wed Feb 18 2026
Mainly VFR conditions are prevailing this morning, with
the exception being KSTS. Clearing skies, light winds, and bountiful
moisture has allowed for fog and low clouds to develop for portions
of the interior North Bay valleys. Temperatures in this region are
on the chillier end, sitting in the low 30s. Expect fog to mix out
by mid morning, with VFR conditions expected. In terms of
precipitation, showers will slip through the region from the north.
There could be periods of brief ceiling and visibility reduction, in
addition to small hail. Lightning has held off overnight, but we
should destabilize some this afternoon. For now, left any mention of
thunder out of the TAFs but this may need to be re-adjusted as we
see how the atmosphere pans out.
Vicinity of SFO...Showers will slide through the region today, with
VFR conditions generally prevailing. Winds will hold a westerly
component through the afternoon hours before shifting to the
southeast during the evening and overnight hours. Winds pick up
after 6Z as the next organized round of rain moves through, with
gusts gradually climbing to 30-35kt by 12Z-15Z Thursday. MVFR
visibilities are expected with the next round of rain. No mention of
thunder in the TAFs as the chances look to be around 10-15% chance
this morning and into the early afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Showers will continue to skirt through the
region this morning, eventually becoming more isolated in nature
throughout the day. Winds will shift from the west to west-northwest
to the southeast by the early evening, with winds picking up as
well. VFR conditions are expected to prevail through the period,
unless stronger showers move through the region and drop visibility
and/or ceilings.
&&
.MARINE...
(Today through Monday)
Issued at 423 AM PST Wed Feb 18 2026
Expect scattered showers and slight chances for to storms
continue to move through the waters. Fresh to strong westerly
winds continue across the waters with gale force winds in the
southern waters lasting through the morning. Winds slacken and
become fresh to moderate through early Thursday but quickly
become strong again with gale force gusts returning. Rough to very
rough seas will prevail through the week.
&&
.CLIMATE...
Issued at 1047 PM PST Tue Feb 17 2026
The following are the record low temperatures at the long term sites
for Friday, Feb 20th.
Location Record Low
Santa Rosa 26 in 1913
Kentfield 27 in 1913
Napa 27 in 2018
Richmond 35 in 1990
Livermore 27 in 2018
San Francisco 38 in 1897
SFO Airport 36 in 2018
Redwood City 30 in 1933
Half Moon Bay 28 in 2018
Oakland Museum 36 in 2011
San Jose 30 in 1897
Salinas Airport 28 in 1953
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 9 AM PST Friday for CAZ006-505-509-529-
530.
Cold Weather Advisory until 9 AM PST this morning for CAZ504-506-
512-513-516.
Winter Weather Advisory until 4 PM PST this afternoon for CAZ514-
517-518.
Extreme Cold Warning until 9 AM PST this morning for CAZ514-517-
518.
PZ...Small Craft Advisory until 9 AM PST this morning for Mry Bay.
Small Craft Advisory until 3 AM PST Thursday for Pigeon Pt to Pt
Pinos 0-10 nm-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 Reyes to
Pigeon Pt 0-10 nm.
Gale Warning until 9 AM PST this morning for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...KR
MARINE...KR
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Prepared by Boulder-Creek.com Weather at: Wed Feb 18 08:30:03 PST 2026
From the National Weather Service
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