Hillsborough, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

634
FXUS66 KMTR 172136
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
236 PM PDT Sat May 17 2025

...New MARINE...

.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...
Issued at 102 PM PDT Sat May 17 2025
(This evening through Sunday)

Key Messages
-Breezy to gusty winds
-Below normal temperatures

The much talked about windy weekend has finally arrived. Afternoon
observations are showing winds of 10 to 20 mph with highest gusts
40 to 50 mph. Why so windy? Two fold: upper level jet support and
a passing upper level trough through NorCal/NV. As noted this
morning, the onshore gradient was solid at 4+ mb from SFO-SAC,
but since then it has eased and the SFO-ACV gradient is increase
as the upper level trough kicks east. Despite the transition from
onshore to northerly winds will remain breezy to gusty over the
next 24-36 hrs. Will also keep messaging breezy to gusty, but
hold off on Wind Advisory at this time as coverage/timing isn`t
high enough to warrant it. Winds will be strongest over the
coastal waters, along the coast, and higher terrain.

As for temperatures, it was cloudy to start the day with drizzle
and the sun is finally making an appearance. Increasing northerly
flow is helping to mix out the lower levels. Additionally, as the
upper trough moves east the region will feel more subsidence
aloft helping to squash widespread cloud cover. That being said,
there is some weak cold advection aloft leading to some fair
weather cu. Despite some sunshine, temperatures will remain
cooler through Sunday with the colder airmass. Additionally, the
temperatures will "feel" a little more raw given the breezy to
gusty winds. Highs will be in the upper 50s to upper 70s.

&&

.LONG TERM...
Issued at 140 PM PDT Sat May 17 2025 (Sunday night through next
Friday)

Key Messages
-Lingering gusty northerly winds Monday
-Elevated Fire Weather Concerns Sunday through Tuesday
-Winds ease by Tuesday
-Warmer and drier conditions
-Moderate HeatRisk far interior MidWeek

To kick off the workweek gusty northerly flow will persist. Still
no Wind Advisory, but borderline conditions with occasional gusts
in the 40 to 50 mph. High pressure will begin to nose its way in
kicking off a warming and drying trend. Temperatures will warm
generally 5 to 10 degrees through midweek. Warmer and drier
conditions combined with stronger northerly flow will lead to
evaluated fire weather concerns. Given the bumper crop of
grass/finer fuels this season this set up could allow for quicker
spread of grass fires, especially interior North and East Bay.

The peak of the warm up occurs on Wednesday with the max ridging
over the region. Highs across the interior will reach into the 90s
with a few flirting a 100 degrees interior Central Coast.
HeatRisk values reach the Moderate range for these locations.
Lingering onshore flow and cooler SST will keep the coastal areas
in check temperatures. Temperatures begin to cool for Thursday and
Friday as the ridge gets flattened by an fast moving shortwave
trough/developing upper low moving into NorCal.

&&

.AVIATION...
(18Z TAFS)
Issued at 1134 AM PDT Sat May 17 2025

VFR conditions are expected to prevail at the North, East, and South
Bay terminals for the period. The forecast challenge will become the
gusty west to northwest winds where gusts to 25-30kt are expected
this afternoon and perhaps into the early evening hours. KHAF should
be the only site that struggles with cig and/or vis through the TAF
cycle. Some guidance shows low cloud building back in later in the
period, while others keep skies on clearer.

Vicinity of SFO...Clouds this morning generally remain confined to
the terrain surrounding SFO, around San Bruno and along the Santa
Cruz mountains. These clouds should hold through the afternoon which
may lead to some lower clouds slinking through the airspace. Outside
of that, the main concern will turn to the westerly winds. Gusts up
to 30 to 35kt are expected through the evening, though a few
isolated gusts to 40kt might be possible from 22Z to 02Z. Skies
should remain clear at KSFO and KOAK overnight, with some of the
latest hi-res models backing off low cloud making it into the
vicinity of KSFO. Opted to keep the possibility of a FEW MVFR cigs
overnight, but will re-evaluate at the next update.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Satellite imagery shows stratus gradually
gliding along and over the Central Coast. Nearly all of the  hi-res
models show KMRY and SNS staying socked in with MVFR cigs through
early Sunday morning. Decided to follow the that trend from the
previous shift, but also started showing the signs of clearing which
should occur between 12-17Z, with the earlier times favoring KSNS.
VFR conditions are expected to prevail once this happens. In
addition to pesky low clouds, there should be an uptick in west to
west-northwest winds this afternoon at the terminals.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 235 PM 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 and storm force
gusts through Sunday evening. Winds remain strong and near gale
force 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 3 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.

     Gale Warning from 9 PM Sunday to 9 AM PDT Monday 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.

     Storm Warning from 3 PM to 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 Sunday to 9 AM PDT Monday 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 AM PDT Monday for
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...KR
MARINE...KR

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