Guerneville, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

149
FXUS66 KMTR 171133
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
433 AM PDT Sat May 17 2025

...New AVIATION...

.SYNOPSIS...
Issued at 300 AM PDT Sat May 17 2025

Blustery conditions and cooler temperatures begin today and last
through the weekend. Elevated fire weather concerns Monday for
inland areas of the North and East Bay areas due to wind and dry
conditions. Above normal temperatures on tap next week.

&&

.SHORT TERM...
(Today and tonight)
Issued at 300 AM PDT Sat May 17 2025

Wind gusts increasing through this morning as a potent upper low
swings through and digs into the Great Basin. As of writing, the
trough axis is situated just offshore of the NorCal/Oregon border
and will continue digging SE today thanks to a robust 130 kt
upstream jet. Surface low pressure developing ahead of the trough
axis will promote a very strong onshore pressure gradient today,
which will help get the gusty conditions going this morning. As
the trough axis moves inland, strong winds will be reinforced
throughout the column as the jet moves overhead. This will kick
off a roughly 30 hour period of robust upper level support and the
best window for gusts of up to 50 mph along ridgetops and the
immediate coastline. Held off on a Wind Advisory given the lack of
spatial extent of expected wind speeds that would meet criteria.
Areas away from the coast can still expect gusts of 35-40 mph.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 300 AM PDT Sat May 17 2025

These windy conditions persist through the weekend until the upper
level support finally moves out of the picture by Monday
afternoon. However, with wind direction changing every so slightly
more northerly overnight Sunday into Monday morning, we are
messaging a brief period of elevated fire weather concerns for
interior areas of the North Bay and East Bay. Conditions are not
critical, but gusty conditions along with dry daytime RH 15-25% on
Monday will certainly lead to some fire weather worries regarding
dry grasses. Beyond Monday, temperatures warm above average as
ridging dominates the pattern the rest of the week.

&&

.AVIATION...
(12Z TAFS)
Issued at 424 AM PDT Sat May 17 2025

Currently a mix of IFR-VFR at the terminals. High clouds from a
passing upper-level shortwave trough will continue to drift
southeastward throughout the day. A dry cold front will sweep
across the region from northwest to southeast through this
afternoon - this will provide lift for drizzle as well as mix the
marine layer out. As such, after VFR is achieved this afternoon
(outside of the Monterey Bay terminals), it is expected to
prevail. Strong and gusty onshore winds are expected through the
TAF period with widespread gusts of 20-30 knots.

Vicinity of SFO...Currently IFR with westerly flow. High confidence
in VFR prevailing by this afternoon. Westerly winds will strengthen
through the morning with gusts in excess of 35 knots expected this
afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently IFR with southerly flow at MRY
and IFR with westerly flow at SNS. Westerly winds will prevail
through the TAF period. While HREF and NBM probabilities suggest
that it is likely that sub-VFR ceilings will develop tonight, I am
not completely sold, here`s why. As the dry cold front moves
through it will mix out the marine layer. That in tandem with
northerly (drying) winds succeeding it should in theory lead to
drier conditions that are not conducive for sub-VFR conditions. I
think the limiting factor will be that the Monterey Bay is
geographically sheltered from northerly winds that are forecast
this afternoon, and thus will maintain a moist northwesterly flow
that may be just enough for MVFR ceilings to develop.

&&

.MARINE...
(Today through Thursday)
Issued at 300 AM PDT Sat May 17 2025

Hazardous marine conditions will be relentless through Wednesday.
Widespread strong to near gale northwesterly breezes with gale
force gusts are expected today. Winds will become northerly
tonight, remaining strong to near gale with gale force gusts
through Wednesday. Rough to very rough seas are expected through
Wednesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Sunday for Mry Bay-SF Bay N
     of Bay Bridge.

     Gale Warning until 9 PM PDT Sunday for Pt Arena to Pt Reyes 0-10
     nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10
     nm.

     Small Craft Advisory until 3 PM PDT Sunday for Pigeon Pt to Pt
     Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Gale Warning from 3 PM to 9 PM PDT Sunday for Pigeon Pt to Pt
     Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 10-60 NM.

     Gale Warning from 9 PM this evening to 9 PM PDT Sunday for
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Sarment
MARINE...Sarment

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