146
FXUS66 KMTR 170412
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
912 PM PDT Tue Jul 16 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 214 PM PDT Tue Jul 16 2024

Seasonal temperatures continue today before a warming trend begins
tomorrow. Above average temperatures and moderate heat risk will
return by the late week and continue into next week.

&&

.UPDATE...
Issued at 910 PM PDT Tue Jul 16 2024

Despite ample sunshine this afternoon temperatures for the most part
were cooler today than Monday.  Why the cooldown?  Persistent
onshore and lingering marine layer. Regardless of the cooler
temperatures it was still a pleasant afternoon with maximum
temperatures topping out in the 60s/70s bays/coast and 70s to lower
90s interior.  The real hot spot that saw little influence from the
marine layer was interior Monterey/San Benito, which hit the upper
90s.

Once the sun sets the clouds lurking off the coast will gradually
move inland once again.  Expecting coastal clouds and low clouds
covering the inland valleys.  Can`t rule out some patchy fog and
mist too.  That being said, the marine layer will not be as deep as
Tuesday morning. 500 mb heights will gradually rise leading to a
more compressed marine layer.  The depth is forecast to be closer to
2,000 feet or even below 2,000 feet.

No update needed this evening.  Moving forward,  much warmer weather
and increasing fire weather concerns will be the focus late week and
next week.

MM

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 214 PM PDT Tue Jul 16 2024

Seasonal temperatures continue today with warmer temperatures
returning tomorrow. High temperatures today will generally be in
the mid 70s to mid 80s across inland areas and in the upper 50s to
60s along the coast. Temperatures in the 90s are possible across
mountainous terrain within the North Bay, East Bay, and
Monterey/San Benito counties. Widespread stratus is expected to
return tonight given a fairly deep marine layer with HREF showing
low level clouds extending into most of the Bay Area and Central
Coast. Stratus coverage is expected to dissipate by mid to late
Wednesday morning as the start of the next warming trend kicks off.
Temperatures warm tomorrow by on average 4-5 degrees for the Bay
Area (excluding the North Bay) and the Central Coast with
widespread highs in the 80s to low 90s expected. Closer to the
coastline, onshore flow will help keep temperatures cooler with
highs in the 60s to low 70s. For the North Bay - temperatures will
warm more significantly with highs expected to be 9-10 degrees
higher tomorrow than they are today. This pushes high temperatures
across the North Bay into the upper 80s to low to mid 90s
beginning Wednesday. Minor heat risk continues over the Bay Area
and Central Coast away from the coastline as temperatures start to
warm.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 214 PM PDT Tue Jul 16 2024

Confidence is increasing that hot weather will return across inland
portions of the Bay Area and Central Coast beginning late this week
and continuing into next week. Upper level troughing has been
lingering off the West Coast for the last few days which allowed for
us to return to seasonal temperatures for the past few days.
Beginning Thursday, the upper level ridge, which produced our early
July heat wave, will retrograde and move back westward. As a result,
temperatures will increase across our CWA with widespread
temperatures in the upper 80s to mid 90s across inland areas
Thursday and Friday. Favored hot spots across the North and East Bay
will see temperatures warm into the upper 90s to low 100s. Moderate
heat risk returns Thursday/Friday across favored hot spots and
elevated terrain in the Bay Area.

Some uncertainty remains as to how high temperatures will reach
Thursday/Friday with guidance showing drastically different max
temperature solutions. For example, ECMWF temperatures for Santa
Rosa are 10 degrees greater on Friday than those predicted by the
GFS model. Such drastically different solutions indicates that there
is uncertainty as to how far inland the marine layer will extend by
late week. This can impact overnight low/daytime high temperatures
wherein if the marine layer extends further inland it can help keep
temperatures cooler at the surface but if it is confined closer to
the coastline temperatures inland are likely to be warmer. However,
confidence remains high, with the overall ensemble guidance trend in
support, that warmer temperatures will return Thursday while some
fluctuations in the current peak forecast temperatures remains
possible.

Drier, warmer weather continues over the weekend before temperatures
look to warm more significantly early next week. By Monday, inland
highs will be in the 90s with temperatures reaching into the low
100s across favored hot spots. Moderate heat risk becomes more
widespread Sunday into Monday with portions of the North and East
Bay seeing pockets of major heat risk in areas of elevated terrain.
Looking slightly outside of this forecast period, the CPC highlights
much above normal temperatures are likely to continue through at
least mid next week.

&&

.AVIATION...
(00Z TAFS)
Issued at 343 PM PDT Tue Jul 16 2024

VFR prevails through the late night tonight for the majority of
terminals. Onshore and breezy winds will slowly decrease beyond
sunset to become light for most terminals in the overnight hours.
Stratus is expected to make a return to terminals tonight bringing
MVFR CIGs. The return and onset of stratus will likely be late, with
the majority of terminals not developing CIGs until beyond midnight.
Stratus then persists through the late morning of Wednesday, with
general clearing to VFR expected between 16-18Z for the majority of
terminals.

Vicinity of SFO...VFR through the late evening today, with moderate
westerly winds. Models indicate stratus making a return towards
midnight, however, confidence on this is only moderate. MVFR CIGs
are likely to develop overnight and persist through the morning,
though it is the onset and timing of when MVFR CIGs will begin that
is uncertain. This will be something to keep an eye on this evening.

SFO Bridge Approach...Stratus will fill much of the bay tonight,
bringing MVFR CIGs. Clearing not expected until late Wednesday
morning, generally towards 18Z.

Monterey Bay Terminals...VFR is expected to persist through at least
midnight. Low clouds will likely begin to filter into the terminal
towards sunset, though MVFR CIGs will form a few hours later. Models
indicate stratus CIGs forming much earlier than the previous night,
however, there still does lie uncertainty in the onset time of CIGs.
Stratus is likely to not clear until closer to noon Wednesday.

&&

.MARINE...

Winds this evening have begun to become more W/NW and will
continue to be northwesterly through the remainder of the week.
Although winds are currently gentle across much of the waters,
they will strengthen throughout the day Wednesday to become fresh
to strong by the late evening. Significant wave heights will
build to rough by Wednesday and conditions will continue to
deteriorate through the weekend.

&&

(Tonight through next Monday).MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Wednesday to 3 AM PDT Thursday
     for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras
     Blancas 0-10 nm.

     Small Craft Advisory from 3 PM Wednesday to 9 AM PDT Thursday
     for Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...AC
MARINE...AC

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