Loma Mar, California Weather Forecast Discussion

971
FXUS66 KMTR 202330
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
430 PM PDT Sat Sep 20 2025
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 141 PM PDT Sat Sep 20 2025
- Warming trend through Monday and into Tuesday
- Weak offshore flow on Monday and Monday night in the higher
   terrain
- Rain showers and isolated thunderstorm chances return early
   next week
&&
.SHORT TERM...
Issued at 141 PM PDT Sat Sep 20 2025
(This evening through Sunday)
A mid/upper level cut off low pressure system remains off of the Bay
Area/Central Coast early this afternoon with 850 MB temperatures on
the rise. This is leading to the warming trend across the region
that is forecast to persist into tomorrow. Cumulus clouds are
developing across the higher terrain of the Central Coast and East
Bay where surface based CAPE is up to 650 J/kg. However, the
probability remains low (less than 10%) for any of these to develop
into showers/thunderstorms.
The HRRR is showing increasing likelihood for low clouds to return
to the coast tonight into early Sunday morning before retreating to
the coastline by early afternoon. As such, overnight low
temperatures are forecast to range from the mid 50s to lower 60 in
the valleys and mid 60s to lower 70s in the higher terrain.
For Sunday, expecting upper 80s to lower 90s across the interior,
mid 70s to lower 80s around the bayshore and around the Santa Cruz
area, and upper 60s to lower 70s near the coast.
&&
.LONG TERM...
Issued at 141 PM PDT Sat Sep 20 2025
(Sunday night through next Friday)
The warming of afternoon temperatures will continue into Monday (and
potentially into Tuesday) when we are expecting more widespread
upper 80s to mid 90s across the interior. Generally the same
aforementioned mid/upper level features will persist before the cut off
low begins to near the coast Monday night into Tuesday. There is
moderate confidence that the higher terrain will experience offshore
flow (especially across the North Bay and East Bay interior) during
this timeframe.
Sub-tropical and/or monsoonal moisture will be advected northward as
the cut off mid/upper level low pressure nears the coast brining the
potential for rain showers and isolated thunderstorms to the Central
Coast on Tuesday. The increased cloud cover is expected to keep the
Central Coast cooler on Tuesday with warmer conditions across the
north and in the interior. With PWAT values between 1.00"-1.50" and
MUCAPE values between 100-300 J/kg expected, the treat for dry
lightning will be limited. The potential for rain showers will
extend northward into the North Bay by Tuesday night into Wednesday
morning before the the low pressure shifts inland into Nevada.
Dry conditions are anticipated by Thursday in wake of the exiting
cut off low. A gradual cooling trend is then expected late in the
upcoming week and into the next weekend as a trough approaches the
West Coast. Be sure to keep up to date on the latest forecast
information as we get closer to this upcoming pattern shift.
&&
.AVIATION...
(00Z TAFS)
Issued at 430 PM PDT Sat Sep 20 2025
Marine layer should compress to around 1000 ft tonight with MVFR-IFR
CIGs expected across the Bay Area and Central Coast tonight. There
is a 20-40% chance of fog developing across the North Bay Valleys
and along the coastline overnight into tomorrow morning. Moderate
confidence in timing of stratus return tonight. Guidance pushed for
an early return tonight (pre 06Z) but confidence was low in that
scenario given the lack of stratus offshore as of 00Z. Models
already show  widespread stratus over the marine environment which
increases confidence that they are modeling a too early stratus
return tonight. Once stratus fills in, it will remain in place
through mid to late morning before clearing for the remainder of the
TAF period.
Vicinity of SFO...VFR becoming MVFR overnight. Patchy stratus
returns as early as 10Z with higher confidence in widespread stratus
returning closer to 13Z. VFR returns mid to late morning and will
continue through the end of the TAF period. Onshore winds strengthen
during the afternoon/evening with gusts peaking around 25 knots.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...IFR CIGs are expected overnight with some
potential for fog to develop early tomorrow morning. If fog does
develop it is likely to develop after 10Z. Stratus clears by late
morning with VFR persisting through the end of the TAF period. Winds
remain onshore through the TAF period and strengthen to around 8-12
knots during the day.
&&
.MARINE...
(Tonight through next Thursday)
Issued at 430 PM PDT Sat Sep 20 2025
Winds stay mostly light across the waters aside from breezy winds
across the northernmost waters and locally breezy conditions near
the favored coastal jets. Winds decrease to moderate to fresh
across the coastal waters Tuesday through late week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Sunday to 3 AM PDT Monday for Pt
     Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 3 PM Sunday to 9 AM PDT Monday for Pt
     Arena to Pt Reyes 10-60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Kennedy
MARINE...Canepa
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NWS MTR Office Area Forecast Discussion