FXUS66 KMTR 221125
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
425 AM PDT Tue Oct 22 2024
...New AVIATION, MARINE...
.SYNOPSIS...
Issued at 1233 AM PDT Tue Oct 22 2024
Quiet weather on tap through this week. Couple of chances for
light offshore wind, followed by a slight chance for rain this
weekend in the North Bay.
&&
.SHORT TERM...
(Today and tonight)
Issued at 1233 AM PDT Tue Oct 22 2024
The pattern this week is being dominated by what will ultimately
become our next weather-maker by the end of the week. A stagnant,
east-west elongated upper low situated off the PNW coast is
driving mostly zonal flow across much of CA with a weak, upper
level baroclinic zone set up across the northern half of the
state. This is evident overnight in the form of high clouds and
more subtly in the 00Z OAK sounding with a few relatively shallow
mixed layers aloft. Ultimately, this won't have much impact on
our weather locally aside from the high clouds and any minimal
local impact they may have on high temps today.
&&
.LONG TERM...
(Wednesday through Monday)
Issued at 1233 AM PDT Tue Oct 22 2024
No major changes from previous in the long term period. The most
notable impacts through midweek are the possibility of light
offshore winds Wednesday and Thursday mornings. As the
aforementioned upper low becomes pinched off by a robust jet aloft
extending over the Aleutians, a couple of shortwave troughs are
advected along the flow across the PNW into the northern plains.
These subtle pulses will be enough to briefly build surface high
pressure in their wake and reverse the San Francisco to Winnemucca
pressure gradient, promoting offshore flow most notably Thursday
morning. As these features are rather transient, we aren't
expecting any major lingering issues in regard to fire weather
beyond Thursday. Since we have a strong fire weather event in
recent memory, here's a comparison. During the last offshore wind
event last week, the Redding to Sacramento pressure gradient was
in the 99th percentile around +6 to +6.5 mb. The current forecast
max for this Thursday morning is about +2 mb. This will be enough
to help drive temps up and RH down slightly, but not expecting
critical fire weather concerns at the moment. Forecast RH across
much of the area is in the 20-25% range, and winds in the 10-15
mph range with gusts up to 25 mph in the highest terrain.
Into the latter portions of the week, the pattern strongly
supports longwave ridging across much of the CONUS and deep
troughing in the EPac across the West Coast. The most notable
thing for now is that guidance is very confident in this pattern
supporting some degree of active weather in days 6-10. The tough
question to answer is, "what kind of weather is that going to be,
Mr. Meteorologist?!" Rain continues to be included in the forecast
across much of the northern half of the CWA. However, the extent
of any rainfall is very uncertain given the low confidence
regarding the placement and exact trajectory of the upper low.
Similar to yesterday morning, ensemble cluster analysis still does
not aid in swaying confidence one way or the other to call this
our first widespread rain event or next offshore wind event. If
you're familiar with empirical orthogonal functions, there is a
whopping 56% variance by Monday regarding the location of the
upper low. If you were lucky enough to not have to learn about
empirical orthogonal functions, the previous sentence means that
confidence is very low for days 6-10. Be sure to stay tuned to
the forecast for the latest.
&&
.AVIATION...
(12Z TAFS)
Issued at 425 AM PDT Tue Oct 22 2024
Patchy fog and stratus has developed along the coastal regions, with
some inland intrusion into the Salinas Valley and the Sonoma County
valleys. Stratus should mix out later this morning, with a light
onshore breeze developing this afternoon and evening. As winds
diminish in the evening, a passing shortwave trough will again
disrupt the marine layer stratus, leaving the region generally clear
through Wednesday morning.
Vicinity of SFO... VFR with breezy onshore flow throughout the TAF
period. Winds will pick up to around 15-20 knots Tuesday afternoon
and evening, otherwise remaining lightly breezy around 8-10 knots.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... Fog and stratus has extended into the
Salinas Valley, with mixing out of the stratus expected later
this morning. At MRY, stratus has come tantalizingly close to the
terminal and there was a brief moment when the terminal reported
LIFR ceilings. For now a TEMPO extends through 16Z for a possible
second expansion over the terminal. Lightly breezy northwest winds
developing this afternoon and evening, diminishing overnight
while the skies remain generally clear.
&&
.MARINE...
(Today through Sunday)
Issued at 425 AM PDT Tue Oct 22 2024
Moderate northwesterly to northerly winds persist over the outer
waters through late week. Beginning midweek, occasional moderate
northwesterly gusts will extend into the southern inner coastal
waters from Pigeon Point extending southward. Winds will begin to
diminish over the coastal waters by late week as high pressure
weakens over the Pacific.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
evening for Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 9 AM this morning to 9 PM PDT this
evening for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt
Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
&&
$$
SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Tue Oct 22 06:30:03 PDT 2024
From the National Weather Service
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