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000
FXUS66 KMTR 220557
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1057 PM PDT Sun Apr 21 2024

...New AVIATION...

.SYNOPSIS...
Issued at 205 AM PDT Sun Apr 21 2024

Warm inland temperatures expected throughout Monday before cooler,
unsettled weather returns Tuesday and continues through late week.
Light rain chances for Thursday night and into Friday.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 156 PM PDT Sun Apr 21 2024

Coastal stratus along the San Francisco Peninsula and Monterey Bay
has dissipated with sunny skies and warm weather expected through
the remainder of the day. Temperatures are running an average of 1-5
degrees higher today than they were yesterday at the same time
yesterday. The outlier is Santa Rosa which is running 10 degrees
higher today than it was at the same time yesterday when stratus was
widespread and blanketed Santa Rosa through most of the morning
hours. Comparatively today, stratus was fairly patchy and stayed
along the coastline. This allowed for increased solar heating and
for temperatures to rise faster today than yesterday throughout the
morning at Santa Rosa.

Today will be the warmest day this week with inland highs in the
upper 70`s to mid 80`s and coastal highs in the upper 50`s to mid
60`s. Monday morning lows will be in the low to mid 50`s with mostly
clear skies expected. Upper level 500 mb heights continue to build
through Monday with high pressure resulting in another day of warm
weather. While Monday highs will be 2-3 degrees lower than today`s,
highs will still remain in the upper 70`s to low 80`s inland and
upper 50`s to low 60`s along the coast. Starting late Monday
afternoon/evening, HREF shows a southerly surge bringing increased
moisture and widespread stratus back to the area. As stratus moves
inland, orographic lift may produce drizzle/traces of rain in
coastal regions and across elevated terrain. However, any measurable
precipitation will only be a few hundredths of an inch.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 156 PM PDT Sun Apr 21 2024

Unsettled weather, cooler temperatures return Tuesday as a mid/upper
level low moves through the area. Light drizzle will continue
through Tuesday morning in coastal regions and in elevated terrain.
Tuesday low temperatures will drop to the mid 40`s to low 50`s with
areas in mountainous terrain dropping into the low 40`s. Compared to
Monday, inland high temperatures will drop by 10-15 degrees with
inland highs staying in the low to upper 60`s on Tuesday. A few
inland locations may struggle to the low 70`s but this will not be
widespread. Coastal highs will continue to linger in the upper 50`s
to the very low 60`s.

Cooler temperatures and highs in the 50`s to 60`s will persist
through the end of the week as troughing lingers over the area.
Morning lows will largely stay in the upper 40`s to low 50`s. A
shortwave trough will approach the area Friday into Saturday and
bring increased chances for light rain back to the forecast. Most
locations are forecast to receive less than 0.15 inches while a few
typically rainier areas (Santa Cruz mountains, Santa Clara hills,
coastal North Bay mountains, Mayacamas Range) receive closer to 0.15-
0.25 inches.

The most notable change for this Friday system between yesterday and
today`s forecast is that the NBM now includes a slight chance (10-
15%) for thunderstorm development Friday evening into Saturday. The
highest thunderstorm probabilities look to be in the eastern
portions of the North Bay, East Bay, and easternmost portions of San
Benito County. This system looks to be fairly warm with 850 mb
temperatures between 5 to 6C and 500 mb temperatures between -16 to
-18C. Given how warm the system is, hail is not currently expected
to be widespread but will continue to watch and see how this system
turns out.

&&

.AVIATION...
(06Z TAFS)
Issued at 1057 PM PDT Sun Apr 21 2024

VFR through the TAF period for most terminals, with the exception
of Monterey Bay who are likely to see LIFR/IFR CIGs as stratus
begins to surge up the coast. Most terminals tonight will see
clear skies and generally light winds. Into the afternoon of
Monday, winds will become more southwesterly and breezy to
moderate ahead of an approaching low pressure system. These
elevated winds will last longer into the late night before finally
diminishing just beyond the TAF period. Around the end of the TAF
period, stratus will begin to start pushing inland, bringing MVFR
CIGs to the North Bay and Monterey Bay terminals to start.

Vicinity of SFO...VFR lasts through Monday night. Winds will turn to
flow out of the southwest in the afternoon Monday, with gusts up to
20 knots. Winds only ease slightly come nightfall, but gusts do
diminish. Stratus does not appear to impact the terminal until the
first hours of Tuesday morning, bringing MVFR conditions.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR/IFR conditions develop in the early
morning of Monday. Satellite currently shows clear skies over the
terminals, but near the southern end of the Monterey county coast,
stratus is slowly creeping its way northwards. Once stratus begins
to impact MRY Bay terminals, it is expected to last at least through
the late morning Monday. After the late morning, VFR should return
for a few hours alongside breezy W/SW winds. MVFR conditions develop
in the late afternoon to early evening Monday as stratus percolates
inland once more.


&&

.MARINE...
(Tonight through next Friday)
Issued at 335 PM PDT Sun Apr 21 2024

Moderate to locally strong northerly winds prevail over the
coastal waters thanks to strong high pressure to the north. Winds
will be strongest over the outer waters north of Point Reyes.
Fresh northerly swell accompanies the northerly winds. Winds ease
Sunday night and switch to southerly starting Tuesday ahead of an
approaching trough. Small southerly swell continues to move
through the waters this weekend and through the upcoming work
week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 AM PDT Monday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...AC
MARINE...MM

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