-- Discussion containing changed information from previous version are highlighted. --
203
FXUS66 KMTR 151622
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
922 AM PDT Sat Jun 15 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 254 AM PDT Sat Jun 15 2024

Dry and windy with elevated fire concerns into early next week.
Seasonal temps and quiet weather midweek. Potential warming trend
for late next week.

&&

.UPDATE...
-- Changed Discussion --
Issued at 917 AM PDT Sat Jun 15 2024

Drier air continues to move into our area, bringing some clear
skies this morning. Observations show moments of increased winds
in the hills and mountains up to 40-60 mph out of the north. With
the drier area and northerly winds, be sure to take precaution for
any outdoor activities that may cause any "sparks". No changes to
the forecast were made, as conditions remain on track.

SO
-- End Changed Discussion --

&&

.SHORT TERM...
Issued at 254 AM PDT Sat Jun 15 2024
(Today and tonight)

What a difference 24 hours makes...June-Gloom is all but gone. The
longwave pattern over the West remains relatively unchanged with
an upper low anchored off the BC Coast and an upper level trough
covering the PacNW into NorCal. Additionally, a weak upper level
boundary pushed through the region on Friday. The passing boundary
helped to set the stage for the much talked about burst of
northerly winds. The SFO-ACV gradient ramped up to over -6mb and
the SFO-SAC gradient topped out at over 4mb. This pressure
gradient set up is perfect for gusty northerly winds and stronger
onshore flow. A sampling of winds over the last 12 hours shows
gusts 40-60 mph, with the strongest winds over the coastal
waters, immediate coastline, higher peaks, and any inland
gap/pass. The stronger N-S gradient helped to mix out the marine
layer (June- Gloom)for the most part. Latest satellite fog product
does show some patchy stratus trying to develop along the SF
Peninsula coast, Pt Reyes, and East Bay Hills. That will be it,
patchy at best through sunrise. Lastly, the better mixed low
levels has also led to slightly warmer overnight temperatures.

Rest of today and tonight - breezy to gusty winds will persist
thanks to the stronger N-S and W-E gradients. Still not strong
enough or widespread enough for a Wind Advisory, but strong enough
for minor impacts like blowing small unsecured items around. The
biggest impact will be to the marine environment with steeper
wind waves and hazardous conditions. Interestingly enough, a very
pronounced coastal jet forms south of Pt Sur. In fact, latest
forecast has winds approaching Storm Force conditions with a few
gusts flirting with the 48 kt (55mph) mark. Moderate to high
confidence on these stronger coastal waters winds as ensemble
guidance indicate high exceedance values (80+ percent) greater
than 50 mph. Additionally, the ECMWF EFI shows how unusually
strong the winds are for this time of year and a good portion of
the ensemble members are favoring the "extreme" side. One other
impact for the persistent northerly winds over the waters will be
effective Ekman transport and increased upwelling. In other word,
colder water along the coast. The change in airmass associated
with stronger northerly flow will lead to cool temperatures
today, especially over the interior.

&&

.LONG TERM...
Issued at 335 AM PDT Sat Jun 15 2024
(Sunday through Friday)

No big changes with the overall sensible weather for Sunday and
Monday. Not much in the way of night/morning clouds and associated
marine layer thanks to persistent breezy/gusty northerly flow.
Temperatures at night will be milder thanks to better mixing and
seasonably cool during the day.

By Tuesday northerly flow will begin to slowly ease as the upper
trough weakens. In fact, the longwave pattern aloft begin to
become more zonal and then favors a more ridge like pattern for
the second half of the week into the following weekend. So what
does this pattern shift mean? A gradual warming trend with a
potential for much warmer weather by next weekend. While tonight`s
guidance may have backed off from the more "extreme heat" around
June 21/22 it is still plenty warm across the interior. Both CPC
and WPC continue to highlight portions of the Bay Area and Central
Coast for excessive heat from June 21-26.  Stay tuned...

&&

.AVIATION...
(12Z TAFS)
Issued at 505 AM PDT Sat Jun 15 2024

VFR through the TAF period. Strong and gusty winds linger along the
immediate coast and at SFO into the mid morning, with more inland
areas seeing much lighter winds. Winds aloft are still strong and
will stay so into the mid morning as well, particularly over the
North Bay causing concerns for LLWS at STS. Winds aloft and at the
surface weekend in the mid morning but increase again into the
afternoon, with particularly strong winds over the ocean and at SFO.
Elevated winds last into the late night before reducing.

Vicinity of SFO...VFR through the TAF period. Winds Stay Gusty
through the mid morning before reducing. Another rough of gusty
winds starts building in the late morning and become stronger in the
mid afternoon with peak gusts  expected to be around 38 kts. These
stronger gusts last into the night, reducing to gusts of roughly 20
kts after 06z. Winds reduce further into Sunday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Light to
moderate winds last into the afternoon before more breezy westerly
winds arrive. Expect stronger and gustier winds over the immediate
coast and ocean compared to the terminals. Winds at the terminals
reduce into the night, but remain strong along the coast and ocean.

&&

.MARINE...
-- Changed Discussion --
(Today through Thursday)
Issued at 917 AM PDT Sat Jun 15 2024

A tight pressure gradient over the waters will allow for strong
northwesterly breezes and widespread gale force gusts to persist
through the weekend. Significant wave heights will be 12-17 feet
through the weekend before beginning an abating trend Monday.
Hazardous conditions will linger into early next week as winds
remain strong and seas remain elevated.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Issued at 345 AM PDT Sat Jun 14 2024

...Elevated Fire Weather Conditions Through The Weekend...

*Increasing northerly winds, especially higher terrain
*Lowering relative humidity values day and night

Forecast remains on track as northerly flow ramps up across the
district. Gusts of 30-50 mph will be more common along the coast,
higher terrain, and inland gaps/passes. Have already seen a few
isolated inland passes reach close to 60 mph as well. These
stronger winds will persist through early Monday. It should be
noted that they will not be strong the entire time, more like
bursts of stronger winds. The northerly flow has also ushered in
much drier air across the region too. 24 hour trends show some
locations 40-70% drier than 24 hours ago. While there are a few
isolated stations that may "technically" reach Red Flag criteria
conditions are not widespread enough to warrant a fire weather
zone wide Red Flag warning. Therefore, still best to message
elevated fire weather conditions through the weekend.

Regardless, individuals with outdoor activities planned this
weekend should be fire weather aware. Be mindful and don`t be
"that spark".

MM

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for SF Bay N of
     Bay Bridge.

     Small Craft Advisory from 3 PM Sunday to 3 AM PDT Monday for SF
     Bay N of Bay Bridge.

     Small Craft Advisory until 3 AM PDT Monday for Mry Bay.

     Gale Warning until 3 AM PDT Monday 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 Pinos to Pt Piedras
     Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Murdock
MARINE...Sarment

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