FXUS66 KMTR 191143
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
443 AM PDT Sun Jul 19 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 120 PM PDT Sat Jul 18 2026
- Near or slightly below normal temperatures and higher humidity
through the first half of the upcoming week.
- The marine layer and mid to upper level cloud cover will
continue to help keep temperatures cooler under building high
pressure.
&&
.SHORT TERM...
Issued at 109 AM PDT Sun Jul 19 2026
(Today and tonight)
Onshore winds are ushering stratus inland. Onshore winds continue
due to a 2.9 mb SFO-SAC pressure gradient. A few patches of mist/fog
may additionally develop through daybreak. High clouds are extending
far north-northeast of tropical storm Elida located 1000 miles south-
southwest of Point Conception. Elida is forecast to essentially move
northward, get drawn into the westerlies and weaken to a post tropical
remnant low by 5 am PDT Tuesday, July 21st per latest from the NHC.
Strong (warm core) high pressure remains located over the interior
west, land locked as typically this time of year due to high sun
angle surface heating. The high is surrounded by a mix of cold
core (mid-latitude) and warm core (tropical) low pressure systems
of varying strength. Upward vertical motion/expansion (lows) has
to return downward/compression (highs) somewhere via continuity.
Upper level troughing generally remains located over the eastern
Pacific. Daytime highs today will be about the same it was on
Saturday, varying from the mid to upper 60s along the coast to the
70s bayside to the 80s and 90s well inland. Tonight lows will
cool to the 50s except in the 60s in the hills and mountains.
&&
.LONG TERM...
Issued at 109 AM PDT Sun Jul 19 2026
(Monday through Saturday)
As mentioned, current tropical storm Elida is forecast to move
generally northward, get drawn into the westerlies and weaken to
a post tropical/remnant low by early Tuesday. Tropical cyclones
depend on a minimum of 80F or warmer sea surface temperatures. With
less heat flowing into northward moving tropical cyclones the
thermodynamic system diminishes. Not to mention northward moving
tropical cyclones eventually encounter the westerlies, wind shear,
drier air (destructive to convection), but may temporarily form in
to a hybrid system or become an extra-tropical cold core system
tapping energy transformation from warm/cold air temperature
advection. As of current time, the GFS and ECMWF for example
forecast the remnant low to pass ~ 500 miles to our west early-mid
week, rain is forecast to fall from the low, but of course it'll
be too far to our west to benefit from it. Good news so far, based
on the forecast low trajectory and most model forecasts, there is
minimal convective potential over our forecast area early-mid week.
Of course as always stay tuned to the latest updates.
&&
.AVIATION...
(12Z TAFS)
Issued at 441 AM PDT Sun Jul 19 2026
Currently a mixed bag of LIFR-VFR. Conditions will begin to improve
by 16Z as stratus retreats to the coast where it'll linger through
the day. Coastal terminals, namely HAF and MRY, may hold onto a
ceiling on the cusp of IFR/MVFR all day. High clouds streaming in
from the southwest will add complexity to the TAF period both from a
forecast and observation standpoint. High clouds and light winds
overnight suggest that conditions will not be as poor as they have
been overnight as radiational cooling will not be as efficient and
stratus will not be as easily advected. Moderate to high confidence
on ceilings on the cusp of IFR/MVFR returning to most terminals
tonight with lower confidence on the return to LVK and SJC. Diurnal
winds will prevail.
Vicinity of SFO...Currently IFR with westerly flow. High confidence
on VFR by late morning with conditions beginning to improve by 16Z.
Moderate confidence on the return of a ceiling on the cusp of
IFR/MVFR tonight. Reasonable best case scenario is stratus remains
confined to the north of the terminal.
SFO Bridge Approach...The San Mateo Bridge Approach has a relatively
lower probability of developing low clouds below FL045 tonight than
SFO does.
Monterey Bay Terminals...Currently LIFR with southwesterly flow at
MRY and IFR with northwesterly flow at SNS. Stratus will clear out
by late morning (SNS) to early afternoon (MRY) and remain close to
the coast. High confidence in IFR ceilings returning tonight.
&&
.MARINE...
(Today through Friday)
Issued at 441 AM PDT Sun Jul 19 2026
Moderate northwesterly breezes and moderate seas will prevail.
Moderate southerly swell will arrive today and continue next week
from distant tropical cyclone activity.
&&
.FIRE WEATHER...
Issued at 120 PM PDT Sat Jul 18 2026
Cooler than normal temperatures with assistance from onshore flow
and relatively normal diurnal intrusion of the marine layer will
continue through the weekend into next week. RH recovery will be
excellent for coastal areas and valleys, and moderate to good
farther inland. However weak offshore flow/thermal belting will
result in poor RH for higher elevations, especially above 1500-
2000ft across the East Bay Hills and Santa Lucias.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Sarment
MARINE...Sarment
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Prepared by Boulder-Creek.com Weather at: Sun Jul 19 06:30:03 PDT 2026
From the National Weather Service
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