Area Forecast Discussion


787 
FXUS66 KMTR 191137
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco Bay Area
337 AM PST Mon Feb 19 2018
.SYNOPSIS...Blustery, cool conditions will persist over the 
region today with isolated to scattered showers/snow showers 
(higher elevations) possible along coastal areas this morning. Sky
conditions will clear along with subsiding winds overnight with 
widespread freezing temperatures likely Tuesday morning. Cool 
unsettled weather conditions are then expected through the 
remainder of the week and potentially into early next week as 
well.
&&
.DISCUSSION...as of 03:34 AM PST Monday...Isolated to scattered 
showers are being picked up on regional radars this morning, 
mainly over the Pacific and along coastal areas. In addition, a 
few lightning strikes have been picked up about 75 miles off of 
the Sonoma coast in the past hour. This is all occuring as a cold,
unstable air mass settles further in over the region with 850 MB 
temperatures analyzed between -3.5 and -5 deg C. With this and 
surface temperatures being reported at or below freezing in 
elevations between 2,000-2,500 feet, believe snow levels have also
fallen to around 2,000 feet early this morning. To help confirm
this, data from the Point Sur profiler reported a snow level of
1,954 feet at 1030Z. Snow levels are forecast to continue to fall
to around or below 1,500 feet by sunrise as cold air advection 
continues over the region. Thus, continue to believe snow 
accumulations will remain possible in the Santa Cruz and Santa 
Lucia Mountains through the morning hours where a Winter Weather 
Advisory remains in effect. 
Forecast models show precipitation diminishing in coverage by late 
morning and early afternoon as the mid/upper level trough axis pulls 
inland away from the coast. Cool, breezy conditions will continue 
through the day with temperatures in most urban areas only warming 
into the 50s. Winds are forecast to subside late in the day and 
through the overnight with clearing sky conditions. As the air mass 
aloft also continues to cool, look for widespread freezing 
temperatures for inland areas with overnight lows in the 20s to around 30 
deg F. Temperatures are also forecast to cool into the lower 30s 
even in many coastal areas where areas of frost will be possible. 
Thus, will continue the Freeze Warning for inland areas and Frost 
Advisory for coastal areas from late tonight into Tuesday morning. 
While the unseasonably cold air mass will remain in place through 
midweek, a weak short-wave trough is forecast to drop southward just 
off of the coast Tuesday night into Wednesday morning. This will 
bring an increase in cloud cover to inland areas and should limit 
widespread freezing temperatures. With that said, some of the 
coldest inland areas will still briefly cool into the upper 20s to 
lower 30s. For the most part, do expect any showers from this system 
to remain mostly off the coast yet an isolated shower cannot be 
ruled out along coastal areas Tuesday night into Wednesday morning. 
A cool, unsettled weather pattern is forecast to persist through 
late week as another system drops across the region Wednesday night 
into Thursday. While widespread rainfall is not currently forecast, 
do believe there will be chances for additional showers across 
portions of the region late in the week. Medium to longer range 
models continue to show the potential for this unsettled pattern to 
remain in place through the upcoming weekend and into early next 
week as well. However, details on any chances of precipitation 
remain low at this time.
&&
.AVIATION...As of 10:00 PM PST Sunday...Hi-res models indicate shower
activity is expected to pick up between 09Z and 18Z along the 
coast and over the MRY Bay Area. Strong pressure gradients between
high pressure over the waters and low pressure over Utah producing
gusty winds up to 30 kt. These winds will slowly decrease during
the night.
Vicinity of KSFO...Possible MVFR conditions between 10Z and 17Z as
showers move through west of the airport. West winds gusting to 30
kt until 10Z. 
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Shower activity will increase after 10Z
and last through 16-17Z. Predominantly MVFR cigs becoming VFR 
after 17Z.
&&
.CLIMATE...
Here are record low temperatures and the years they occurred for 
Monday through Wednesday this week.
Location          Monday          Tuesday          Wednesday
SF Bay Area
Healdsburg        28 in 1932      22 in 1922       28 in 1929
Santa Rosa        26 in 1932      26 in 1913       26 in 1913
Calistoga         25 in 1918      25 in 2006       25 in 2006
Kentfield         27 in 1932      27 in 1913       29 in 1953
San Rafael        32 in 1990      32 in 2006       33 in 1955
Napa              29 in 1990      28 in 1920       29 in 1955
San Francisco     38 in 1897      38 in 1897       36 in 1890
SFO Airport       36 in 1990      37 in 2011       34 in 1955
Half Moon Bay     34 in 1954      32 in 2013       31 in 2006
Oakland Airport   35 in 1955      34 in 2006       33 in 1955
Richmond          35 in 1990      35 in 1990       35 in 1981
Livermore         27 in 1956      28 in 1942       27 in 1955
Moffett Field     35 in 1949      34 in 2006       32 in 1955
San Jose          32 in 1990      30 in 1897       25 in 1897
Gilroy            27 in 1964      30 in 1990       31 in 1976
Monterey Bay Area
Santa Cruz        30 in 1990      29 in 1913       30 in 1955
Salinas           29 in 1990      31 in 2006       31 in 1970
Salinas Airport   29 in 1933      28 in 1953       30 in 1953
Monterey          35 in 1990      35 in 2006       36 in 1952
King City         25 in 1955      22 in 1953       23 in 1953
&&
.MARINE...as of 03:34 AM PST Monday...Northwest winds will usher
in arctic air today and generate fresh swell and steep wind waves.
Unstable air will result in showers. Another trough will swiftly
move southward over the coastal waters late Wednesday night with a
slight chance of showers.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...Winter Weather Advisory...CAZ512-517
             SCA...SF Bay
             SCA...Mry Bay
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             GLW...Pt Arena to Pigeon Pt 10-60 nm
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Rough Bar Advisory for SF Bar
&&
$$
PUBLIC FORECAST: RGass
AVIATION: W Pi
MARINE: Canepa
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