Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS66 KMTR 152338
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
338 PM PST Fri Feb 15 2019

.SYNOPSIS...Cool weather conditions will persist with passing
rain showers through the weekend. Snow levels will lower Saturday
night into Sunday as a colder air mass drops southward along the
coast resulting in the potential for accumulating snowfall in the
region`s higher peaks. Overnight temperatures turn colder early
next week as precipitation ends and sky conditions clear.
Unsettled conditions could return for the latter half of next
week.

&&

.DISCUSSION...as of 01:48 PM PST Friday...A fairly unsettled
weather pattern continues to result in scattered rain showers over
the region this afternoon. This is as the core of a mid/upper
level low spins off of the Pacific Northwest coast and interacts
with decent moisture advection over the region. Given the colder
air mass aloft, instability has be strong enough to result in
isolated lightning strikes and an abundance of small hail
(covering the ground at times). This activity is likely to persist
into this evening with the potential for brief heavy downpours,
small hail and isolated lightning strikes. Each passing shower has
generally produced a few hundredths of an inch to upwards of
0.25" within the stronger showers. With this said, additional
rainfall amounts are not forecast to result in widespread flooding
concerns other than ponding on roadways and/or standing water in
poorly drained areas across the region.

The aforementioned mid/upper level low to our north will slowly
shift inland through tomorrow morning with passing showers likely to
continue. Snow levels will also remain around 3,500 feet or so
through sunrise Saturday with snow accumulations likely above this
level. A colder, reinforcing mid/upper level low will then drop down
the Pacific Northwest coast Saturday into Sunday morning which will
result in continued scattered showers over the entire region. 1000-
500MB heights will fall to around 530 DAM with 850 MB temperatures
cooling to around -2.5 deg C. This would support snow levels falling
to around 2,000 feet across the North Bay and around 3,000 feet
across the Central Coast. Therefore, it appears likely that snow
accumulations will occur in elevations above 3,000 feet if not lower
in the North Bay Saturday night into Sunday. As snow is likely
occuring in the region`s highest peaks as I type, areas such as the
Santa Lucia Mountains may see upwards of 1 foot of snow again
throughout the weekend. The Diablo Range will also be impacted by
accumulating snowfall in excess of 6" possible with other peaks over
the region seeing lesser amounts. Thus, a Winter Weather Advisory
may be needed for the aforementioned ranges within the next 24
hours. At this time, am not expecting snow levels to be as low as
from our previous snow event last week.

As the mid/upper level trough shifts inland late Sunday into Monday
morning, dry conditions are likely to develop over the region.
Overnight temperatures will turn colder as sky conditions clear and
winds relax. This will result in morning lows dropping into the
lower 30s inland to upper 30s/lower 40s near the coast. Daytime
temperatures will likely only warm into the 50s during the first
half of the week as well.

Forecast confidence remains low at this time heading into the latter
half of next week, especially when it comes to forecast
precipitation. The models are generally in good agreement with a
continued cool, unsettled weather pattern however. The GFS and ECMWF
both show weak disturbances dropping southward across the region
with the potential for light to moderate rain showers from Wednesday
into Thursday and then again by the following weekend. Will continue
to update the forecast accordingly and look for better model
consistency in the coming days.

&&

.AVIATION...As of 3:38 PM PST Friday...For 00z tafs. Scattered
showers will continue through the period with chances of isolated
thunderstorms possible through the early evening. VFR conditions
to prevail aside from MVFR vis/cigs during heavier showers or
isolated thunderstorms. SW/W winds through the period with gusts
generally 20-25 kt possible.

Vicinity of KSFO...VFR prevailing, MVFR during heavier showers.
Gusty SW/W winds to continue 20-25 kt. Scattered showers expected
to continue on and off through the forecast period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR, temporarily reduced to MVFR during
heavier showers. Scattered showers to continue through the period.
SE to SW winds through the period with gusts to 20 kt possible.

 &&

.BEACHES...25 feet swell with moderate period 16 seconds reported
from buoy 59 located 400 miles northwest of the Bay Area. Large,
dangerous surf will reach the coastal waters today, a high surf
advisory begins 10 am today continuing to 9 pm Saturday. Northwest
swell 14 to 17 feet will produce breakers as high as 18 to 25 feet
along west and northwest facing beaches. High surf will also bring
coastal flooding impacts during high tide today. A coastal flood
advisory is in effect 5 am to 10 am this morning.

&&

.MARINE...as of 03:29 PM PST Friday...Moderately strong and gusty
westerly winds will prevail through much of the weekend as
unsettled cold weather system settles in over the region.
Scattered showers with the possibility of a few  isolated
thunderstorms will continue into the weekend. A large  northwest
swell will move into the coastal waters this evening  and continue
through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...High Surf Advisory...CAZ006-505-509-529-530
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Rough Bar Advisory for SF Bar
             SCA...SF Bay until 9 PM
             SCA...Mry Bay until 9 PM

&&

$$

PUBLIC FORECAST: RGass
AVIATION: AS
MARINE: CW

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.