FXUS66 KMTR 280457
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
957 PM PDT Wed May 27 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 1215 PM PDT Wed May 27 2026
- Cooler, unsettled weather conditions continue through Thursday
- Warming and drying trend Friday and beyond
&&
.UPDATE...
Issued at 921 PM PDT Wed May 27 2026
We have been able to continue to benefit from the upper level
disturbance that has been slowly churning overhead the past couple
of days with beneficial rainfall in the bumper portion of our
transition into the dry season. Most locations that have received
some rainfall got less than a tenth of an inch, but numerous
locations in the Myacama's, Diablo Range and Santa Lucia's have
seen 0.25"-0.50" or more the past 48hrs. The Santa Cruz Mountain
are likely to catch up somewhat overnight into Thursday as the
upper low ends its retrograde and starts to exit to the east on
Thursday morning. Portions of the Santa Lucia's and Santa Cruz
mountains will see more rainfall tomorrow with ensembles
indicating a roughly 30%-50% chance of exceeding 0.50" of rainfall
by sunset tomorrow across those areas.
&&
.SHORT TERM...
Issued at 1215 PM PDT Wed May 27 2026
(This evening through Thursday)
We have already seen showers and an isolated thunderstorm develop
late this morning across the Eastern Santa Clara Hills and in the
Mountains of San Benito County. As daytime heating continues, we are
expecting convection to fire up in the East Bay Hills, Eastern Santa
Clara Hills, the Santa Cruz Mountains and the Central Coast (County
of Monterey/San Benito) this afternoon and evening. This is as the
atmosphere becomes more unstable with CAPE values between 100-400
J/kg. However, vertical wind profiles don't favor organized
convection, with little to no 0-6km wind shear. Therefore,
probabilities for thunderstorms remain less than 10% through the
afternoon and early evening. Any stronger cell (shower and/or
thunderstorm) that develops over any one given location has the
potential to produce 0.25"-0.50" per hour of rainfall.
The mid/upper level low will begin to retrograde back over the
Pacific tonight into early Thursday morning and begin to pull in
PWAT values of around 1.00". This will increase rain chances
offshore late tonight and then will move onshore along the Central
Coast through Thursday morning. However, with the loss of daytime
heating, the thunderstorm threat will lessen. Forecast rainfall
amounts have increased in the Santa Cruz Mountains and Santa Lucia
Range now having a greater than 60% probability of seeing more than
0.25" through Thursday afternoon (this would include rainfall from
today). These probabilities of seeing greater than 1.00" (40%-75%)
remain confined to the Santa Lucia Range.
Conditions begin to dry out from north to south during the day
Thursday as the mid/upper level low shifts further inland. However,
rain showers look to linger over the Central Coast through the early
evening.
&&
.LONG TERM...
Issued at 1215 PM PDT Wed May 27 2026
(Thursday night through next Tuesday)
Cannot rule out rain showers to linger across the North Bay late
Thursday night into early Friday morning as deeper moisture (PWAT
values approaching 1.00") move across this region. In wake of the
exiting trough, a warming and drying trend will kick off by Friday
afternoon with temperatures gradually returning to near average this
weekend as zonal flow develops over the region. Temperatures are
currently forecast to warm above seasonal averages by Sunday and
into the middle of the upcoming week.
&&
.AVIATION...
(06Z TAFS)
Issued at 957 PM PDT Wed May 27 2026
Scattered showers are expected to arrive tonight becoming widespread
rain by early morning. Rain generally continues through late
morning/early afternoon before conditions dry out. There is some
potential for isolated thunderstorms to develop again during the
day. Any t-storms that develop would likely impact MRY and SNS with
the highest thunderstorm probabilities across the interior Central
Coast. Breezy onshore winds are expected again during the
afternoon/evening before winds ease tomorrow night. Confidence has
increased in widespread MVFR CIGs tonight with most sites seeing
MVFR conditions through late morning. Temporary decreases in
visibility are possible if a stronger shower moves directly over the
airport.
Vicinity of SFO...Shower chances are expected to increase overnight
and continue through late morning. Winds remain relatively light
overnight before breezy onshore winds return during the
afternoon/evening. MVFR CIGs generally expected overnight with CIGs
rising to the MVFR/VFR border overnight. Winds ease tomorrow
evening/night with some potential for MVFR CIGs to return.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Shower chances increase through 10Z with
widespread rain returning afterwards through much of the day. There
is some potential for thunderstorms to develop during the day. The
highest chances for thunderstorms are to the south of MRY and SNS
but cannot rule out the potential for a stray storm or two moving
through the Monterey Peninsula (particularly during the morning into
the early afternoon). Winds remain breezy during the
afternoon/evening before starting to ease overnight. Winds at SNS
are tricky with LAMP guidance highlighting strong valley winds
during the early morning. For now put gusts to around 15 knots
during the early morning but LAMP guidance seemed a little high with
20+ knot gusts.
&&
.MARINE...
(Tonight through next Tuesday)
Issued at 921 PM PDT Wed May 27 2026
Winds diminish and waves abate across the coastal waters tonight
with a moderate northwest breeze expected late morning through
Friday. Strong to near gale force northerly winds return over the
weekend and continue into next week. Wave heights build as winds
restrengthen with wave heights between 10 to 12 feet expected this
weekend into early next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from 9 AM PDT Thursday through late
Thursday night for CAZ006-505-509-529-530.
PZ...Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt
Reyes 10-60 NM.
Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt
Pinos 10-60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Kennedy
MARINE...Kennedy
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Prepared by Boulder-Creek.com Weather at: Wed May 27 22:30:02 PDT 2026
From the National Weather Service
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