496
FXUS66 KMTR 130920
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
220 AM PDT Sat Jul 13 2024

...New SYNOPSIS, SHORT TERM, LONG TERM, FIRE WEATHER...

.SYNOPSIS...
Issued at 204 AM PDT Sat Jul 13 2024

A Heat Advisory remains in effect for elevated inland locations,
and will expire later this evening. A welcomed cooling trend will
begin tomorrow and extend through at least the middle of the
upcoming work week.

&&

.SHORT TERM...
(Today and tonight)
Issued at 204 AM PDT Sat Jul 13 2024

An upper level low currently centered 200mi offshore of
south/central California will gradually lift north over the course
of the weekend while making little gain eastward toward land with
the persistent high over the Four Corners region driving the
synoptic pattern across western CONUS. There is little to no thermal
instability associated with weak shortwave energy and PVA shifting
south to north across our area today and tomorrow. Probability of
elevated convection is too low for mentioning in the forecast but
can`t rule it out entirely. If an isolated thunderstorm develops,
dry lightning from any high based convection could spark a wild fire
as grass fuels continue to dry. Surface based convection well inland
and east of our area is expected, where continental modified
boundary layer moisture is more robust with stronger diurnal surface
heating at higher altitudes. A Heat Advisory remains in effect
through this evening for much of our elevated interior locations,
marking the end of an historic heat wave. A strengthening marine
layer through the weekend into the beginning of next week will help
the cooling trend as the offshore disturbance slowly migrates north.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 204 AM PDT Sat Jul 13 2024

By early Monday, the upper level low begins to get absorbed by
persistent NorCal offshore troughing resulting from the
amplification of the Four Corners ridge back to the northwest across
Nevada, Oregon and Washington state. The steady fetch of cooler
onshore flow will help keep temperatures around normal through at
least the middle of next week. Warmer temperatures are expected late
next week into the weekend as the ridge migrates westward next week,
steering the jet stream and cooler temperatures aloft well to our
north.

&&

.AVIATION...
(06Z TAFS)
Issued at 1137 PM PDT Fri Jul 12 2024

IFR and LIFR CIGS are moving inland and have already filled over the
Monterey Bay terminals. OAK and the North Bay terminals look to fill
later into the night with IFR CIGs. Expect light to moderate winds
through the late morning. Patches of fog look to affect the Monterey
Bay terminals. CIGs erode into mid Saturday morning for most areas,
but CIGs around the Monterey Bay linger into the early afternoon.
Moderate to breezy winds build Saturday afternoon. Winds ease into
Saturday evening as CIGs return to the coast, portions of the SF
Bay, and Monterey Bay terminals.

Vicinity of SFO...VFR through the TAF period. Winds stay moderate
through Saturday night, turning from northwesterly to west-
southwesterly in the afternoon before becoming light and variable
Saturday night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR CIGs and mist last into the mid
morning for SNS but into the afternoon for MRY. Expect pockets of
fog to form in the area through much of the morning. As CIGs
dissipate, moderate westerly winds build into the area. These winds
reduce into the night, as IFR CIGs move inland.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 1137 PM PDT Fri Jul 12 2024

Winds out of the north continue to be fresh through much of
Saturday for the northern outer waters. Seas become calmer as
winds begin to ease to become gentle to moderate starting Sunday,
though turn to become more southerly as low pressure enters the
region. Gentle winds then last through the majority of next week.
Significant wave heights between 10 to 12 ft continue over the
outer coastal waters with peak wave heights between 10 to 13 ft
expected over the far northern outer coastal waters.

&&

.FIRE WEATHER...
Issued at 204 AM PDT Sat Jul 13 2024

A low probability of elevated convection producing dry
thunderstorm lightning strikes continues, but there is no mention
of thunderstorms in the official forecast attm. Steep midlevel
lapse rates and improving midlevel moisture today and tomorrow
will have difficulty organizing any thunderstorm activity over our
area. Our fuels continue to dry while approaching record levels,
so if isolated thunderstorms develop, they will have to be
watched carefully.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT this evening for CAZ504-510-513>515-
     517-518.

PZ...Small Craft Advisory until 9 AM PDT this morning for Pt Arena to
     Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Murdock
MARINE...SO

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