FXUS66 KMTR 250825
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
125 AM PDT Fri Apr 25 2025
...New SYNOPSIS, SHORT TERM, LONG TERM...
.SYNOPSIS...
Issued at 124 AM PDT Fri Apr 25 2025
Cloudy and cool conditions prevail with chances for rain and
isolated thunder later today into Saturday, with the risk
concentrated across the Central Coast and adjacent offshore waters.
Dry conditions and a warming trend resume after the rain moves out
early on Sunday.
&&
.SHORT TERM...
(Today and tonight)
Issued at 124 AM PDT Fri Apr 25 2025
Short Term Key Messages:
-Cool and cloudy through the day
-Rain chances arrive later today through Saturday
-Isolated thunderstorms possible in southern Monterey and San Benito
counties
-Snow possible on the peaks of the Santa Lucias and Diablo ranges
Cool and cloudy conditions are the story of the day with an upper
level low continuing to deepen and approach the state. Satellite
imagery and surface observations both support extensive and
widespread cloudiness across the region and well into the interior.
Some patches of clearing might be possible during the afternoon, but
these will be generally short-lived and will dissipate with the
approach of the low pressure system. High temperatures today and
Saturday will range from the middle 50s to the lower 60s across the
lower elevations, and the middle 40s to the lower 50s in the higher
elevations, with breezy onshore winds developing this afternoon
before a lull tonight into Saturday.
The forecast track of the low has continued to shift southwards into
San Luis Obispo and Santa Barbara Counties, with the main axis of
rainfall shifting ever so slightly southwards as a result. The main
thrust of rain is anticipated to arrive Friday evening and last into
Saturday evening. Generally beneficial rainfall is still anticipated
for the Central Coast, particularly as the region has missed out on
most of the big rainstorms during the winter storm season, with rain
totals of a tenth to a quarter of an inch in the Monterey Bay region
and the Salinas Valley, and up to half an inch in the Santa Lucias.
In Santa Cruz County and the Bay Area, rain totals are very light,
up to a tenth of an inch at most, with the region around San
Francisco and Oakland seeing a few hundredths of an inch of rain, if
any at all, from the system.
The chance for isolated convection remains across the southern
halves of Monterey and San Benito counties late on Friday into
Saturday, with the primary risk being isolated lightning strikes and
brief accumulating hail. 700-500 mb lapse rates in the core of the
upper level low will rise to around 7 to 7.5 C/km, allowing for CAPE
values of around a few hundred J/kg, although the highest CAPE
values remain displaced to SLO and Santa Barbara counties. As noted
by the previous forecaster, a more northward track to the low would
increase the risk, especially towards the northern halves of
Monterey and San Benito Counties, while a more southward track moves
the thunderstorm risk even further south.
In addition to all that, the highest peaks of the Santa Lucia and
Diablo ranges continue to see a chance for some accumulating snow,
with the blended guidance suggesting around a 50% chance of at least
2 inches of snow on the mountaintops. We do not anticipate needing
any winter weather products, as the snow accumulation remains
confined to the highest peaks.
&&
.LONG TERM...
(Saturday through Thursday)
Issued at 124 AM PDT Fri Apr 25 2025
Long Term Key Messages
-Lingering showers through Sunday morning
-Dry and warm conditions return after the showers clear.
A few lingering showers could remain across the Central Coast
through Sunday morning, with any additional accumulations limited to
a few hundredths of an inch generally, and up to a tenth of an inch
in favored mountain locations. Sunday remains rather cool, but a
drying and warming trend returns to the region as upper level
ridging returns to the western United States. The upcoming work week
should see high temperatures reach the upper 70s to the lower 80s in
the inland valleys, the upper 60s to middle 70s along the San
Francisco Bay, and the upper 50s to the middle 60s near the Pacific
coast. Longer term predictions support a lean towards temperatures
above seasonal averages into the first week of May.
&&
.AVIATION...
(06Z TAFS)
Issued at 909 PM PDT Thu Apr 24 2025
Mixed bag of MVFR and VFR cigs through out the TAF period as a
weak upper low meanders along the West Coast. Expecting at least
SCT conditions throughout period with cigs lifting slightly later
in the period as the surface trough and rain showers move through
the region. Complicated rain forecast for the next couple of days
as we will be in a very moist, onshore flow, on-again-off-again
shower regime. Not expecting any prolonged IFR due to showers, but
can't rule out a very brief heavy shower causing decreased vis,
especially later in the period.
Vicinity of SFO...Expecting to toe the line between MVFR/VFR cigs
throughout the TAF period with some low-level clearing expected
during the afternoon (mid-level cigs remain). The aforementioned
complicated rainfall timing forecast ultimately lead to the
decision to keep such a long prevailing group at the end of the
TAF period. No notable change that can be forecasted with any
confidence during the last period of the TAF.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Cigs likely to persist through the
period. VFR now, but will likely lower to MVFR overnight tonight.
Some low-level clearing Friday afternoon as widely scattered rain
showers move in. Mid-level cigs expected to begin to lower again
at the end of the TAF period as the center of the upper low
approaches the Central Coast. Rain chances increase just after the
current TAF period.
&&
.MARINE...
(Tonight through next Wednesday)
Issued at 909 PM PDT Thu Apr 24 2025
Light showers enter the forecast late Friday morning across the
waters, with the best chances late evening into Saturday morning.
Slight chance of isolated thunderstorms for waters generally south
of Pigeon Point. Strong breeze and rough seas return across the
waters late Saturday. Dreary conditions linger into Sunday
morning before drier conditions set for next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Behringer
MARINE...Behringer
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
Prepared by Boulder-Creek.com Weather at: Fri Apr 25 02:30:02 PDT 2025
From the National Weather Service
|