Alturas, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

389
FXUS66 KMFR 211209
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
409 AM PST Thu Nov 21 2024

.Updated AVIATION Discussion...

&&

.AVIATION...21/12Z TAFS...Conditions are generally a mix of low end
VFR/MVFR with widespread terrain obscurations. A front remains
draped across the area, bringing areas of moderate to heavy
precipitation roughly south of the Siskiyous and east of the
Cascades. Showers persist west and north of the front, but areas
between these showers are experiencing LIFR conditions in West Side
Valleys. Gusty winds and low level wind shear (LLWS) continue over
higher terrain and east of the Cascades into the late morning hours.

This front will wobble northward some later this morning, bringing
more widespread MVFR/IFR conditions under heavier precipitation.
Otherwise, not much change in overall conditions is expected through
the afternoon. The lower conditions in West Side Valleys will
improve later this morning, and freezing levels have already risen
across the region, now hovering around 7000 ft. Another deepening
low pressure offshore will bring another round of strong winds to
the region along with additional concern for LLWS starting around 06-
08z. /BR-y

&&

.PREV DISCUSSION... /Issued 349 AM PST Thu Nov 21 2024/

DISCUSSION...The latest radar shows steady moderate to heavy
precipitation centered in northern California and southern Oregon
from about Siskiyou Summit east towards Klamath Falls. The general
consensus among the operational models and HREF ensemble means
reflectivity suggest the bullseye of moderate to heavy precipitation
will remain in Northern Cal through this afternoon. The area of
moderate to heavy precipitation will then shift north this evening
and tonight and impact the coast, and coastal mountains in southwest
Oregon, most locations west of the Cascades and the Cascades. The
exception will be in the Rogue Valley due to downsloping and
increasing winds. Even though moderate to heavy precipitation will
shift north this evening and tonight, snow levels will also rise
above the pass levels, and remain above there into Friday. Therefore
little or no snow impacts are expected.

Even through, snow will be at the highest peaks, the trade off is
rain will continue to deluge portions of norCal and SW Oregon late
tonight through Friday, although there are indications rainfall
rates will decline Friday afternoon into Friday night as the front
moves on shore with the heavier core of precipitation shifting back
south into Northern Cal. We have an areal flood warning for portions
of SW Oregon and into western Siskiyou County. With another 3-5
inches of rain likely (perhaps even more in some areas), there is
concern for flooding in and around the Mt Shasta region as well with
all the rain on top of the snow that has already fallen. We`ll see
if we need to expand the warning to include zone 82.

There`s good agreement for this low to develop rapidly and move up
from the southwest and move just inside of 130W late tonight. Right
now, the center of the low is not as deep as the previous one.
However, with the low expected to slide just inside of 130W and
pressure gradients between Arcata and North Bend have trended down
slightly between 7.3 to 7.7 mb. However with the surface low sliding
just inside of 130W and deepening, this will likely result in high
winds at the coast, especially over exposed areas along highway 101.
Therefore the High Wind Watch has been upgraded to a High Wind
Warning.

The strong winds experienced over portions of the eastside and
Shasta Valley yesterday and last night have eased a bit. However,
moderate to strong winds are expected to continue in portions of the
Scott and Shasta Valleys as well as over the east side tonight
through Friday morning. Models show 700mb winds pushing towards 80
kts this evening into Friday afternoon which typically results in
winds speeds reaching high wind criteria. Given the above, the High
Wind Warning that was extended last night looks reasonable and to
add to it was a Wind Advisory east of the Cascades outside of there
we have the High Wind Warning. The reason for this due to the
expected rapidly deepening of low pressure offshore as it moves
northward, the gradient will tighten and we expect potential 60 mph
wind gusts again this evening/night into Friday morning. A Wind
Advisory has been issued for the Rogue Valley, where some gusts to
45-50 mph are possible again with a favorable south to southeast
flow.

Active, but less impactful weather is expected for the weekend with
an upper trough over the area resulting in continued showers and
mountain snow showers, but precipitation amounts are not expected to
be a lot which will limit the amount of snow for the mountains and
mountain passes. -Petrucelli

MARINE...200 AM PST Thursday, November 21, 2024...The region is in
a relative break between systems today. Winds will hover right at or
just below advisory criteria through much of the day, but seas will
remain high and steep. Later this evening, conditions will rapidly
deteriorate again as another deepening low pressure develops in the
area. Though this system will move closer to shore than the Tuesday
system, it will still be weaker than previous storm. Even still,
winds will quickly ramp up to strong southerly gales this evening
and persist overnight in Friday afternoon. There will be a brief
period tonight when isolated areas could experience storm force wind
gusts of 55 to 60 kt. Since this will only be during about a 4 hour
window and for isolated areas, have decided to just stick with a
Gale Warning for this storm since it will be the main threat. Seas
will rapidly build again, reaching up to 20 ft late tonight through
Friday.

Conditions will begin improving overall as winds ease late Friday
into Saturday. Very steep seas will linger into Saturday, then seas
will become less steep but remain hazardous to small craft through
the weekend and possibly into early next week due to fresh southerly
swell and lingering west swell. As we head into next week, the upper
level pattern settles down a bit and the overall sea state drops
below 10 ft, but shower activity will continue as low pressure
lingers just offshore. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 4 PM PST Friday for ORZ021-022-029>031.

     Winter Weather Advisory until 7 AM PST this morning for ORZ027-
     028-030.

     Wind Advisory until 4 PM PST Friday for ORZ026-029>031.

CA...High Wind Warning until 4 PM PST Friday for CAZ081-084-085.

     Winter Weather Advisory until 7 AM PST this morning for CAZ082-
     083.

     Wind Advisory until 4 PM PST Friday for CAZ084-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 7 PM PST this
     evening for PZZ350-356-370-376.

     Gale Warning from 7 PM this evening to 4 PM PST Friday for
     PZZ350-356-370-376.

     Hazardous Seas Warning from 4 PM Friday to 4 AM PST Saturday for
     PZZ350-356-370-376.

&&

$$