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000
FXUS66 KMTR 301611
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
911 AM PDT Thu Mar 30 2023

.SYNOPSIS...Showers ending this morning with below average
temperatures into the weekend. Light rain chances return for this
weekend into early next week, but amounts should be on the light
side.

&&

.DISCUSSION...as of 08:45 AM PDT Thursday...KMUX radar shows
light, scattered showers moving south parallel to the Monterey
County coastline. Surface low pressure has weakened and moved
south, now currently moving inland near Point Conception. Will
likely be able to turn the radar back in "clear air" mode shortly
as the last of the showery activity moves out of the area.
Clearing skies, dry conditions, and highs in the upper 50s
expected today.

Temperatures this morning are generally running 2 to 5 degrees
colder than 24 hours ago. Lows early this morning bottomed out at
around upper 30s in the interior valleys and low to mid 40s for
coastal areas. With temps rising, Frost Advisory for the North
Bay valleys allowed to expire at 9 am this morning. Chilly
mornings in store through the weekend into next week. For now,
forecast remains on track and no update needed.

&&

.PREV DISCUSSION...as of 01:00 AM PDT Thursday...

Today and Tonight:

A closed upper low -- initially across the Bay Area this morning --
will progress into SoCal and the Desert Southwest while devolving to
an open-wave trough. Geopotential heights will rise in its wake as
surface high pressure noses in from the subtropical Pacific. Cool
northerly post-frontal flow will ensue with low-level winds turning
onshore this afternoon. Any showers should be waning this morning
but with residual 1000-850 mb moisture expect some lower clouds to
hang around through the day. High temperatures should be around 6 to
8 degrees below the seasonal average and mostly in the mid to upper
50s for the lower elevations. Readings will be coolest along the
immediate coast and bays given the modest onshore wind component.
Lows tonight should drop into the upper 30s to around 40 with the
coolest readings within the interior valleys. Frost is possible in
sheltered locations within the North Bay towards morning.

Friday through Sunday:

Upper troughing will prevail from the Gulf of Alaska through the
Pacific Northwest. The associated moisture tap will be modest and
largely focused to our north on Friday. However enough moisture will
accompany a weak frontal boundary drifting south over the weekend to
produce low-end (~25%) light rain chances for the North Bay over the
weekend. This is not looking to be an impactful event however as
rain totals should remain on the light side. Temperatures will
remain below seasonal norms with highs in the 50s to lower 60s and
lows in the upper 30s and 40s.

Sunday night through Tuesday:

Large-scale troughing will encompass much of the western CONUS while
dropping from the northeast Pacific through the Four Corners region.
Some precipitation may accompany this system, but the inland
progression of the trough suggests somewhat meager moisture to work
with. This is reflected in ensemble solutions which generally
produce light (to no) rain totals across the region. However the
increasing meridional flow pattern should set up a decent pressure
gradient with strong high pressure over the eastern Pacific and
lower pressures across the Great Basin. This suggests that gusty
northerly winds may become a concern towards early next week. We`ll
still need time to fine tune the details however regarding exact
wind magnitudes. No real changes in the temperature department with
readings remaining below seasonal averages.

Wednesday and Thursday:

There is increasing spread in deterministic model and ensemble
solutions during this period leading to lower than average forecast
confidence. There are some suggestions of a trough dropping south
across the eastern Pacific, however the upper features are being
handled quite differently among the various deterministic solutions.
The deterministic GFS spreads moisture and light rain chances onshore
by late week while the ECMWF keeps the better moisture well
offshore. There`s still more time for this to come into focus so for
now will stick with the dry solution in our forecast as provided by
the National Blend of Models through the end of the forecast period.
Looking forward, it`s noted in the Climate Prediction Center`s
Center`s 6-10 and 8-14 day outlooks show lessening probabilities for
above normal precipitation as we head forward into April. That would
be welcome news as I think we`re all ready for a break.

&&

.AVIATION...as of 4:20 AM Thursday....For the 12Z TAFs. Generally
VFR with some mid-level clouds, with moderate confidence (40-50%
probability) in MVFR ceilings developing in the evening. Scattered
showers will dissipate by dawn. Westerly winds with speeds around 15
knots this afternoon, diminishing in the evening.

Vicinity of SFO... Generally VFR under mid-level clouds, with a
moderate confidence of MVFR conditions (40-50% probability)
developing Thursday evening. Scattered showers moving out of the
region by dawn. Winds will pick up from the west at around 10-15
knots through the day Thursday, with winds diminishing through the
evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR to start, then a moderate confidence
(40-50% probability) of MVFR ceilings developing starting this
evening. Some mid-level clouds across the region through the TAF
period. Afternoon winds will pick up from the northwest with speeds
up to 10 to 15 knots, with winds diminishing in the evening.

&&

.MARINE...as of 08:05 AM PDT Thursday...Expect breezy northwest
flow through the day with some higher gusts in coastal jets north
of Point Reyes, south of Davenport, and south of Point Lobos. Weak
winds last through the weekend, turning southerly in the northern
waters. Seas continue to diminish through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...None.

$$

PUBLIC FORECAST: SPM/SMM
AVIATION: DialH
MARINE: Murdock

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