Walnut Heights, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

679
FXUS66 KMTR 181740
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1040 AM PDT Fri Apr 18 2025

...New AVIATION...

.SYNOPSIS...
Issued at 1226 AM PDT Fri Apr 18 2025

Overcast skies this morning will gradually clear through the
afternoon. Slightly warmer than normal temperatures are expected
for inland areas through Monday before cooler weather returns.

&&

.UPDATE...
Issued at 859 AM PDT Fri Apr 18 2025

Widespread overcast conditions persist across the region. A few
sites (Santa Rosa, Half Moon Bay) have reported fog this morning but
visibilities are either already improving or expected to improve as
we move through the late morning hours. Conditions are drier today
than they were at this time yesterday, with only two higher
elevation sites (1800-2500ft) reporting 0.01" of drizzle this
morning. The 12Z sounding shows a marine layer depth around 2000 ft
with high pressure expected to compress the marine layer to around
1000 ft by tonight. Cloud cover is expected to clear by the early
afternoon hours with some potential for overcast skies to linger
along the coastal Monterey Bay region.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1226 AM PDT Fri Apr 18 2025

A deep marine layer persists this morning. In fact, the 00Z
sounding shows it was close to 4,000 feet deep. That explains the
extensive cloud cover shown on the satellite, however no
measurable drizzle has been reported yet. The marine layer will
gradually compress through the day as a high pressure ridge
builds. This will allow the clouds to clear this afternoon. Inland
areas warm into the mid 70s, or 5-10 degrees warmer than
yesterday. Coastal areas will still be in the shallow marine
layer, and despite the decreased cloud cover, temperatures will
still stay in the 50s all day along the immediate coast. Perhaps
the greatest hazard in the short term is the potential for patchy
dense fog Saturday morning due to the compressing marine layer.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 1226 AM PDT Fri Apr 18 2025

In the big picture, the ridge continues through the weekend. The
warmer than average temperatures will continue with mostly gentle
winds. Most guidance shows a small weakness moving through late
Saturday into Sunday. This system will go unnoticed by most, but
will likely allow the marine layer to expand from around 500 feet
to 1,000 feet, and the associated morning stratus should extend a
little further inland. The weak gradient ridging continues into
early next week as the 850 mb temperature gradually rises to 14C,
which is around the 85th percentile for this time of year. The
weather will stay pretty consistent during this stretch with sunny
skies, mild coastal temperatures in the low 60s, and slightly
warmer than average inland temperatures reaching the mid to upper
70s. A fairly significant change arrives on Tuesday as a
positively tilted trough ushers in a cooling trend through the
remainder of the week. While there is some uncertainty, roughly
80% of the ensemble members are clustered around a reinforcing
cut-off low developing off the coast late next week. It`s too
early to say how strong this system will be, but we`re keeping an
eye on it mainly for a chance of late season rain.

&&

.AVIATION...
(18Z TAFS)
Issued at 1034 AM PDT Fri Apr 18 2025

Another morning with a pesky marine layer. Obs, satellite, and
ACARS show depth still 2k feet deep. As such, clearing/thinning
has been slow going. Therefore, many TAF sites were pushed back
30-60 min on clearing times or closer toward 19Z. Some stratus
lurking this afternoon, but trending toward VFR. Tonight is low
confidence as offshore flow develops at 2500 ft, but doesn`t mix
down until Saturday morning. Some compression of the marine layer
is expected with impacts closer to the coast and immediate bay
shoreline. Conf for tafs is medium today and low tonight.

Vicinity of SFO...Cigs will linger through 19z. Some thinning on
cams/satellite, but delayed from prev taf. VFR this afternoon with
onshore flow. Tonight, low cigs sneak through the GG and in the
Gap, but conf is low on impacting SFO. Therefore, SFO will remain
VFR. The same can be said across the Bay at OAK.

SFO Bridge Approach...Thinning quicker over approach and clearing
earlier is expected 1830-19z.

Monterey Bay Terminals...Cigs lingering through 19z. VFR this
afternoon and early return tonight.

&&

.MARINE...
(Today through Wednesday)
Issued at 859 AM PDT Fri Apr 18 2025

Weak high pressure off the California coast will maintain light
to moderate winds today with decreasing seas. Breezy winds build
in the northern outer waters for Friday night with lighter winds
expected for the inner waters. Seas and winds become more elevated
into the weekend into the next work week.

&&

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

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...MM
MARINE...MM

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
X.com/nwsbayarea
www.youtube.com/nwsbayarea