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NWS Technical
Weather Discussion |
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FXUS66 KMTR 171207
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
505 AM PDT Fri Apr 17 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1201 AM PDT Fri Apr 17 2026
- Periods of gusty offshore winds, especially at higher
elevations, continue through early this morning
- Seasonably warm temperatures expected today through the
weekend
- Cooler temperatures and beneficial rain for the beginning of
next week
&&
.SHORT TERM...
Issued at 1201 AM PDT Fri Apr 17 2026
(Today and tonight)
Offshore flow produced gusty winds across our area today, but
especially higher elevations of the North Bay and East Bay Hills.
The highest measured wind gust was at Mt St Helena (~4400ft) shortly
after 3pm at 63mph, but is still gusting at 57mph late tonight. The
fetch of offshore flow will persist overnight through mid-morning
Friday as the upper trough responsible continues moving east.
Overnight lows from the East Bay Hills south through San Benito and
Monterey County will be chilly, especially at higher elevations,
where winds aloft are weaker and more efficient radiational cooling
will occur under clear skies. Morning winds will gradually ease by
the afternoon as progressive ridging approaches the West Coast.
Temperatures will jump about 5 degrees inland, and remain similar to
yesterday along the coast as weak onshore flow is reestablished.
&&
.LONG TERM...
Issued at 1201 AM PDT Fri Apr 17 2026
(Saturday through Thursday)
Overnight lows tonight into Saturday morning will shift closer to
normal as the progressive upper ridge moves across our area and
gradually amplifies as it moves east. Temperatures will be in the
mid-70s to near 80 inland, once again not much increase along the
coast with onshore flow. Deterministic guidance is still struggling
with the evolution and timing of the developing offshore
disturbance. Sunday now looks dry and relatively pleasant, just
slightly cooler as cloud cover increases out ahead of the upper low.
The North Bay is likely to receive rainfall Monday, however there is
plenty of uncertainty for the remainder of our area wrt to the
initial ave ejecting east onshore. Tuesday has the best chance for
scattered showers and possible thunderstorms, especially if the
trough becomes negatively tilted by Tuesday morning. Scattered
showers may linger into Wednesday, with no clear signal for what the
pattern looks like beyond the extended forecast.
&&
.AVIATION...
(12Z TAFS)
Issued at 505 AM PDT Fri Apr 17 2026
Offshore winds and a deeply dry air (continental air) intrusion
support VFR for the 12z TAFs. Gusty offshore winds in the hills
and mountains will gradually subside through morning, resulting
in a decrease in low level wind shear. Currently the ACV-SFO and
UKI-STS pressure gradients are 5.2 mb and 2.2 mb respectively.
The WMC-SFO pressure gradient is 9.6 mb. These gradients are
forecast to weaken later today and tonight with at least locally
onshore winds returning during this time. Model forecasts show a
few patchy coastal low clouds possible while high clouds move in
tonight and Saturday.
Vicinity of SFO...VFR. North wind 10 to 15 knots shifting to
northeast at times later this morning while also decreasing,
however timing the decrease in wind is a low confidence forecast.
It's very cold over the Great Basin, offshore winds are well
entrenched at this time. Cold, dense basin air has steepened the
WMC-SFO pressure gradient to 9.4 mb. The large scale pattern is
progressive, this should help flip the surface wind to onshore in
the afternoon. Westerly wind steadily decreasing to less than 10
knots tonight and Saturday morning.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. Dry air supports radiative cooling and
chilly, denser air drainage winds through daybreak then steadily
easing through morning. As mentioned for SFO the large scale pattern
is progressive and this should help flip surface winds to onshore in
the afternoon for the Monterey Bay terminals as well. Light and
variable winds shifting to light southeasterly tonight and Saturday
morning.
&&
.MARINE...
(Today through Wednesday)
Issued at 422 AM PDT Fri Apr 17 2026
Northwest winds and seas will gradually subside today through
Saturday. On Sunday winds will shift to southerly ahead of a
Pacific low pressure system that will bring rain to the area
beginning early next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
SHORT TERM...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...Canepa
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Prepared by Boulder-Creek.com Weather at: Fri Apr 17 10:30:03 PDT 2026
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From the National Weather
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reserved Boulder-Creek.com. |
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Revised:
29 Mar 2008 09:53 -0800 GMT
(Pacific) |
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