127
FXUS66 KMTR 142128
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
228 PM PDT Fri Jun 14 2024

...New SYNOPSIS, SHORT TERM, LONG TERM, FIRE WEATHER...

.SYNOPSIS...
Issued at 107 PM PDT Fri Jun 14 2024

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

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 107 PM PDT Fri Jun 14 2024

Clear across the area this afternoon as N-S gradients strengthen
further with the passing of a shortwave trough this evening. Today
will likely be the warmest day until late next week by a few
degrees for inland locations. Expecting winds to increase
initially overnight tonight in coastal gaps and high elevation
areas. Currently seeing this as winds at major sites showing
mostly a northerly component and increasing in magnitude as of the
last few hours. The ridge ultimately gets flattened by a deeper
upper level trough that will move into the West Coast. This will
keep temps down over the next several days as well as further
strengthen the N-S gradients that will promote windy conditions
into early next week.

&&

.LONG TERM...
(Sunday through next Thursday)
Issued at 107 PM PDT Fri Jun 14 2024

The most noteworthy period of wind and elevated fire weather
conditions looks like Sunday into early Monday morning when the
N-S gradient is expected to increase to around -8.5mb (SFO-ACV).
For context, this gradient peaked at -5.8 this afternoon, and -4.8
Thursday afternoon. This type of setup will support wind gusts of
35-45 mph, with some areas near the coast and higher terrain
seeing gusts up to 50 mph. Confidence remains high in this
scenario. Have decided to forgo any fire weather highlights given
the critical wind and RH values aren`t quite there. Refer to the
Fire Weather section for more.

FROM PREVIOUS DISCUSSION...Tuesday and beyond: Winds finally
ease as the N-S begins to relax mitigating Marine and Fire Weather
concerns. Interesting evolution of the longwave pattern middle of
next week. While the pattern looks "troughy" it does show rising
500 mb heights over CA. More importantly, the warming of 850 mb
temperatures. This begins to show up by Wednesday and then
continue through next week. Rising 500 mb heights and warming 850
mb temperatures will kick off a warming and trend. Latest long
range outlook from WPC highlights portions of the Central Valley
and SoCal for Excessive Heat. Cluster analysis and NBM guidance
supports this highlighting from WPC. Official forecast late next
weekend has triple heat impacting interior portions of the Bay
Area and Central Coast. Will need to monitor over the coming days.

&&

.AVIATION...
(18Z TAFS)
Issued at 1032 AM PDT Fri Jun 14 2024

Most of the stratus have cleared creating VFR conditions through the
region. VFR is expected to prevail through the TAF period. Models do
hint at a slight chance of low ceilings tonight near Monterey Bay
but confidence is low at this moment. Winds start to build to breezy
to strong, with chances of gusty winds near the coast and gaps.
Winds diminish overnight but will remain relatively moderate to
breezy with a chance of LLWS near North Bay as winds become light
at the surface. Winds rebuild towards late Saturday morning.

Vicinity of SFO...VFR through the TAF period, with high confidence
that winds will keep stratus mixed out. Onshore winds build to
breezy and gusty this afternoon, then gradually becoming stronger
into late afternoon. Models do not show that AWW winds are expected,
but winds are expected to get up to 33 knots and will continue to
monitor if there is any changes need. Gusty winds diminish overnight
but sustained winds remain breezy before becoming gusty again
Saturday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Models hint at
a small chance for MVFR/IFR conditions overnight but low confidence
at this moment. Winds become breezy in the afternoon before
returning to light to moderate overnight.

&&

.MARINE...
(Today through Wednesday)
Issued at 1032 AM PDT Fri Jun 14 2024

Gale force gusts and strong north and northwest winds build
across waters and last through much of the weekend. Significant
wave heights build up to around 12 to 15 feet in the outer waters
and 10 to 14 feet in the inner waters continue into the weekend.
Hazardous conditions continue into the next work week as winds
remain strong and seas remain elevated. Mid work week, seas start
to diminish.

&&

.FIRE WEATHER...
Issued at 107 PM PDT Fri Jun 14 2024

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

*Less impactful marine layer
*Increasing northerly winds, especially higher terrain
*Lowering relative humidity values day and night

No major changes from previous.

By tonight into early Saturday, winds become more northerly over
the higher terrain of the N and E Bay with gusts 25-35 mph. The
developing offshore flow will usher in moderate to locally poor
humidity recoveries above 1,000 feet. The drier airmass will
ultimately spread across the entire district Saturday afternoon
with 15-30% RH minimums across the interior. A slight uptick in RH
recoveries on Saturday night as the marine layer tries to re-
establish itself below 1,000 feet. Above 1,000 feet will feature
another night with moderate to locally poor humidity recoveries
Saturday night into Sunday. Despite some strong winds and lowering
humidity onshore flow never completely goes aways. It would
definitely be on the unusual side to issue a Red Flag Warning in
June with some hint of a marine layer/onshore flow. Therefore,
will keep a headline in place and continue to message elevated
fire weather concerns. It should be noted, that does not mean
grass fires will not be in the equation over the weekend. Fine
fuels like grass will support fires as seen by recent fire trends.
However, larger fires with thicker fuels (non-grass) will be less
likely. 100 and 1000 fuels are still holding onto some winter
moisture. A great way to visually see this is watching ERC trends.
The ERC forecast through the weekend does show a trend toward
seasonal levels, but not into the widespread critical range.

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

MM/DB

&&

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

     Small Craft Advisory until 3 PM PDT Saturday for Mry Bay.

     Gale Warning until 3 AM PDT Sunday 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.

     Small Craft Advisory until 3 PM PDT this afternoon for Pt Reyes
     to Pigeon Pt 0-10 nm.

     Gale Warning until 3 AM PDT Sunday for Pt Reyes to Pigeon Pt 0-
     10 nm.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer/MM
AVIATION...SO
MARINE...SO

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