969
FXUS66 KMTR 161802
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1100 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.

&&

.UPDATE...
Issued at 930 AM PDT Wed Apr 16 2025

No major weather impacts this morning across the Bay Area and
Central Coast. That being said, there are however noticeable
differences with the sensible weather N to S. The N to S split is
roughly along SF Bay. To the north: another morning of a robust
marine layer with some patchy fog and low clouds. ACARS out of
SFO continues to show a decent moist level through approx 3k feet.
On top of the low stratus are mid-high level clouds. These higher
clouds will slow the clearing of low clouds. Some of the most
pessimistic guidance shows late clearing across the N Bay. To the
south: much less in the way of low clouds. There are still some
high clouds streaming overhead.

As noted below, low confidence with medium-high impact scenario
for today will be possible thunderstorms. Latest NWP guidance
continues to show instability and upper level moisture. However,
there continues to be a disconnect between the two. Moisture
isn`t linking up with the upper level instability. We may see
some CU development, but it`s looking less likely for
thunderstorms. Regardless, we`ll be watching the radar and
satellite closely.

No update needed this morning.

MM

&&

.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...
(18Z TAFS)
Issued at 1059 AM PDT Wed Apr 16 2025

A bit of a mixed bag with MVFR and VFR conditions. The North Bay
seems to be on track for clearing to VFR close to 20Z, meanwhile the
remaining MVFR terminals will see clearing around 19Z. After 20Z,
VFR will prevail until tonight where low CIGs will rebuild. Models
show some differences on ceilings becoming MVFR or remaining VFR but
most models show higher confidence for North Bay and Monterey Bay
seeing MVFR starting late this evening. Moderate confidence on the
remaining terminals seeing MVFR tonight, but if ceilings lower,
expect VFR near 18-19Z Thursday. Moderate to breezy onshore winds
this afternoon, but light to moderate winds overnight.

Vicinity of SFO...Conditions have improved to VFR. There is a chance
for MVFR conditions to return near 09Z, but confidence is moderate, as
some models show VFR prevailing through the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR/MVFR as some low CIGs have pushed over
KSNS. Expect VFR near 19-20Z. MVFR conditions expected to return
near 09-10Z with clearing near 17Z.


&&

.MARINE...
(Today through Monday)
Issued at 912 AM PDT Wed Apr 16 2025

Light to moderate southerly winds will transition to moderate
northerly by midday or so north of Point Reyes, but southerly
winds persist elsewhere. Northerly winds will spread through the
rest of the waters through Thursday and gradually build into the
weekend. Seas will build out in the northern outer waters this
afternoon through Thursday morning. Otherwise, small to moderate
seas persist into the weekend.

&&

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

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...SO
MARINE...SO

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