Yountville, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

632
FXUS66 KMTR 161145
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
445 AM PDT Wed Apr 16 2025

...New AVIATION...

.SYNOPSIS...
Issued at 304 AM PDT Wed Apr 16 2025

Cooler temperatures again today, with some coastal drizzle through
the morning. Otherwise, dry weather is expected through the forecast
period. Warming trend begins tomorrow and continues into the weekend.
In terms of the isolated thunderstorm threat for today, decreased
chances to 10-14% which removed that from the point and click. See
details below.

&&

.SHORT TERM...
(Today and tonight)
Issued at 304 AM PDT Wed Apr 16 2025

Short Term Key Messages
*Cool conditions continue
*10 to 14% chance for very isolated dry storms
*Patchy Coastal Drizzle

Another morning of beautiful satellite imagery where you can see
an area of low pressure spinning of the southern portion of the
Central Coast. Much like yesterday morning, the low level water
vapor channel shows dry air over much of the our portion of the
Central Coast. Some moisture can be observed over the Bay Area,
which is reflected in other channels as high clouds. Below and
between the breaks in these higher clouds, stratus can be observed
the advanced nighttime microphysics and nighttime fog products.
You can see this in the ACARS data around the Bay Area, where the
lower levels have saturated a bit compared to the 0Z sounding.
With low level onshore flow, expect another morning of coastal
stratus and drizzle. Stratus looks to hang around for the North
Bay, while gradual clearing is expected else where.

Now, in regards to the thunderstorm forecast, after looking at the
data for the past several nights and conditions continuing to look
less favorable, opted to remove the mention of thunder in the
forecast. The most favorable ingredients are the 700-500mb lapse
rates of 8-9 C/km and cooler air aloft. While this sits plastered
across the region, other convective ingredients, such as CAPE and
moisture need to come into alignment. Most models have continued
the downward trend in CAPE, while keeping decent CIN over the
region. Additionally, convection is going to be reliant on where
the moisture plume is advected to. PWATs still appear to be
decent, around 0.6-0.8", but I`m not confident how well the column
will saturate given the dry air in place. All that being said,
shear remains weak and the lifting mechanism is a combination of
the low itself and orographic lift. Should all of these factors
come together, we could get a few isolated storms over the Central
Coast. If it looks more favorable by the morning update, I left
ghost PoPs in the forecast to re-add thunder easily back into the
forecast.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 304 AM PDT Wed Apr 16 2025

Longer Term Key Messages
*Warming trend ensues through the weekend
*Little to no precipitation forecast

No major changes to the forecast. Models and ensemble guidance
show the upper level continuing to track east Thursday and
eventually combining with a shortwave trough by early Friday.
During this time, to the west, an eastern Pacific high builds and
noeses its way into the PacNW. This will leave us with a
combination of weak ridging and quasi- zonal flow Friday into
Saturday. Weak ridging over the Gulf of Alaska tends to hold
through the rest of the forecast period, leaving us in zonal flow
for Sunday and then slight troughing into early next week.
Dry weather is expected to persist, with the warming trend
continuing into the weekend. Temperatures look to decrease by a
few degrees early next week, likely in response to the slight
troughiness that sets up.

&&

.AVIATION...
(12Z TAFS)
Issued at 426 AM PDT Wed Apr 16 2025

MVFR cigs through this morning as a weak upper level disturbance
lifts the marine layer, thus raising ceilings compared to 24 hrs
ago. Not enough confidence to include any SHRA or TS in TAFs.
However, some terminals from KSJC southward may end up with
periodic SCT/BKN throughout this afternoon due to CU forming over
terrain. Cloud cover then increases again this evening as a weak
surface trough moves through, promoting MVFR cigs.

Vicinity of SFO...MVFR cigs clearing to VFR by mid morning.
Moderate confidence in VFR timing mainly because more dense cloud
cover will likely be lingering around the airfield through most of
the day. Weak surface trough moves through the region early
Thursday morning, resulting in a more extended period of MVFR cigs
going into mid-to-late Thursday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Mostly clear this morning with a few
patches of stratus developing around the airfields. Confidence too
low to include it in the TAF, but there is a slight chance of MVFR
cigs affecting terminals for relatively short periods this
morning. Otherwise, cloud cover looks to consolidate more over the
terrain as some shallow instability is realized through peak
heating this afternoon.

&&

.MARINE...
(Today through Monday)
Issued at 304 AM PDT Wed Apr 16 2025

Southerly flow with light to moderate winds continues through  the
morning. Northerly winds will develop north of Point Reyes  by
midday or so, but southerly winds persist elsewhere. Northerly
winds will spread through the rest of the waters through Thursday
and gradually build into the weekend. Small to moderate seas
persist into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 PM this evening to 3 PM PDT Thursday
     for Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Behringer
MARINE...KR

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