Mount Shasta, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

828
FXUS66 KMFR 232243
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
243 PM PST Mon Dec 23 2024

.DISCUSSION (Today through Sunday)...

Overview:

The holiday week will unfortunately have several rounds of potential
impactful weather across the forecast area starting today/tonight
with breezy/gusty wind and snowfall. For this first round, we are
not expecting much in the realm of snow impacts as snowfall
accumulations should be mainly above 5500 feet. The wind speeds
could cause loose or unsecured outdoor objects to be blown around
through tonight. There will be a brief break, but another system is
quickly on the heels of this one, and will start to impact the area
on Christmas Day. This will bring another round of breezy/gusty
winds and additional snowfall. This second round of snowfall would
have more widespread impacts, especially on some highways and
passes. Therefore, we have issued a Winter Storm Watch for the
second system to account for these more widespread impacts. Another
system will be quickly on the heels of this second system and could
start to impact the area this weekend. That being said, we are
looking at the potential for three systems this week, the latter two
which could have widespread impacts during the holiday week.

Further Details:

A stacked low will strengthen and deepen over the next 12 to 24 hours
as it pushes into British Columbia. Frontogenesis will extend down
from this low through the forecast area and will peak late
afternoon. The peak will last through the overnight hours and into
Tuesday morning before forcing weakens. This first round of
moisture lacks depth and is rather progressive, so not expecting
much in the realm of impacts where people live, but areas above 5500
feet could see snowfall accumulation. The wind will likely be more
impactful with this first system compared to the snowfall, and we do
have a Wind Advisory out for parts of the Eastside and the Rogue
Valley. Additionally, we have a High Wind Warning out for Shasta
Valley. While these products expire tonight, we will likely need
further wind advisories and warnings for the next system. Speaking
of the next system, we will have deeper moisture, stronger forcing,
and less progressive eastward movement which will all allow for a
longer duration event. We also have a stronger mid-level westerly
jet approaching the area which would allow for orthogonal wind
towards the Cascades which would create orographic lift. Crater Lake
could see 2 feet of snowfall accumulation over 24-36 hours. Mount
Shasta will likely see a couple feet of snowfall as well.  Highway
140 will likely see snowfall as well but currently the watch is for
areas in the Cascades north of Highway 140. That said, early
indications suggest snowfall levels may trend lower, so there is a
possibility for the current watch to expand down to lower
elevations. This would be especially important to keep an eye on
given the holiday and holiday travel. Then another storm will
quickly be on the heels of this Christmas system, but at this time
is too early to say with much confidence the scope of impacts this
weekend. However, we can say there will be additional snowfall for
higher elevations above 5000 feet.

-Guerrero

&&

.AVIATION (18Z TAFs)...

Clear skies and stabilizing atmosphere behind the most recent
front have allowed for LIFR conditions in fog to develop across
West Side Valleys. Meanwhile, east of the Cascades, MVFR
conditions continue, but if enough clearing happens there could be
isolated areas of LIFR conditions that develop. These conditions
will gradually improve during the late morning hours. Another
front will affect the region this afternoon, with showers arriving
at the coast then moving inland on Monday evening. Low level wind
shear will return this afternoon ahead of this next front, and
will continue through Monday night. Additionally, expect strong
winds to surface along the coast, in the Shasta and Rogue Valleys
as well as east of the Cascades this afternoon and evening. As the
front moves inland, expect conditions to lower to MVFR with the
development of widespread terrain obscurations.

-Schaaf/BR-y

&&

.MARINE...Updated 200 PM PST Monday December 23, 2024...Very high,
very steep, and chaotic mixed seas will be a persistent feature in
the marine waters through the next week. Multiple strong fronts will
pass through the area bringing multiple rounds of gale force south
winds, with storm force gusts a possibility with each front.
Residual wind wave/fresh swell along with a heavy background west
swell will keep very high and steep combined seas going through the
morning hours today.

The next strong front arrives this afternoon. A deepening low
pressure moves south-to-north near 130W this afternoon and evening,
and this will bring another round of strong gales to the waters.
It`s not out of the question for that some isolated areas experience
a brief period of storm force winds between 3-6 pm local time today.
Seas will build again this afternoon with the addition of very high
and steep wind waves to the ongoing heavy west swell, resulting in
chaotic mix seas into the overnight hours. Winds will ease below
gales tonight, but seas will remain very steep and hazardous for all
areas into early Tuesday morning.

Conditions briefly "improve" as seas lower to around 10 to 15 feet
late Tuesday into early Wednesday morning, but seas will remain high
and steep with conditions hazardous to small craft during this time.
Another deep low pressure system and strong front is expected
Christmas day through Christmas night, then yet another Thursday
afternoon into Thursday night. High end gales look likely with these
fronts, possibly even storm force. Guidance continues to fluctuate
with respect to the height of the swell train behind the Christmas
front, but seas will continue to be very high, steep to very steep,
and chaotic through next weekend.

/BR-y

&&

.BEACH HAZARDS...Updated 200 PM PST Monday, December 23, 2024...We
are getting reports of significant breaking waves creating dangerous
beach conditions in Curry County as well as debris being pushed over
roads in nearby Crescent City. Conditions are likely very similar in
Coos and Douglas County as well.

As strong fronts continue to progress over the eastern Pacific,
multiple rounds of high and very steep swells will result in
hazardous, and at times, dangerous, surf conditions this week and
into the weekend. Dangerous conditions are expected today with large
breaking waves of 25 to 33 ft expected in the surf zone. A High Surf
Warning is in effect through early Tuesday morning for this.
Conditions briefly improve Tuesday into early Wednesday, but this
improvement will be short lived. Additional fronts will bring the
return of dangerous surf conditions Wednesday night (Christmas
night) through Thursday evening, with hazardous surf conditions
likely to continue into next weekend.

During these events, extremely large breaking waves will create very
hazardous and dangerous conditions along beaches and area
shorelines. Waves will inundate beaches and surge into normally dry
areas. Infrastructure damage and significant beach erosion can be
expected. Stay away from area beaches during this period of active
weather.

-Schaaf/BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Watch from Wednesday afternoon through Friday
     morning for ORZ027-028.

     Wind Advisory from 7 PM this evening to 4 AM PST Tuesday for
     ORZ026-030-031.

     High Surf Warning until 4 AM PST Tuesday for ORZ021-022.

CA...Winter Storm Watch from Wednesday afternoon through Friday
     morning for CAZ080-082-083.

     High Wind Warning until 1 AM PST Tuesday for CAZ081.

     Wind Advisory from 7 PM this evening to 4 AM PST Tuesday for
     CAZ085.

PACIFIC COASTAL WATERS...Gale Warning until 4 AM PST Tuesday for
     PZZ350-356-370-376.

     Small Craft Advisory from 4 AM Tuesday to 10 AM PST Wednesday
     for PZZ350-356-370-376.

&&

$$