Technical NOAA Weather Discussion

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