782
FXUS66 KMFR 250600
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1000 PM PST Sun Nov 24 2024

.UPDATE...Updated Aviation discussion.

&&

.DISCUSSION...Main update for this evening was to extend the Wind
Advisory until 10 pm tonight for the Shasta Valley. Gusty winds
are generally easing west of the Cascades, but gusts to 45 mph in
the Shasta Valley will persist for a few more hours. Low pressure
lingering offshore is maintaining southerly flow over the region,
and shortwaves rotating around the base of this low are bringing
additional rain and snow to the area. A Winter Storm Warning
remains in effect through tonight for elevations above 4000 ft in
the Mt Shasta area. Snow has been falling down around 3500 ft in
the Mt Shasta City region. We`ll continue to monitor in case we
need to include this area in any winter headlines. Unsettled
weather will continue through Tuesday before this persistent
offshore trough finally moves east of the region. For more
details, see the previous discussion below. /BR-y

&&

.AVIATION...25/06Z TAFS...Gusty south to southeast winds have
eased in the Rogue Valley late this evening. Low-level wind shear is
still a concern for North Bend overnight into early Monday morning,
since surface winds are comparatively lower than wind speeds just
above the ground (2000 feet). Winds at that level are in the 30-40kt
range. This risk subsides later Monday morning as winds aloft ease.
Low-level turbulence can be expected near and west of the Cascades,
especially in the vicinity of terrain.

An occluded front near the coast will bring some precipitation
inland tonight, with the focus near the coast to the Umpqua Divide
over to the Cascades as well as in the vicinity of Mt. Shasta. There
is a risk of thunderstorms over the marine waters and along the
immediate coast. Overall, ceilings are a mix of VFR/MVFR with the
lowest ceilings in areas of rain/snow. Snow falling near Mount
Shasta will bring IFR and perhaps even LIFR at times there.

The southeast winds lasted long enough here in the Rogue Valley this
afternoon/evening that fog potential here is much less likely,
especially since dew points have dropped to the low 30s. Even if
there is some clearing and winds decouple from the boundary layer,
fog formation potential is unlikely. Other valleys that didn`t get
the wind could have patchy fog and/or low clouds toward morning.

A secondary front will push onshore Monday with light precip, mixed
MVFR/VFR ceilings and higher terrain obscurations. Local IFR/LIFR
is possible in heavier precip. -Spilde

&&

.MARINE...Updated 830 PM PST Sunday, November 24, 2024...Low
pressure moved past North Bend in the last hour or so, with gales
moving north through the waters. The gale warning was extended to
9 pm, but this will end as the low moves northward and onshore. We
still expect some showers and even isolated thunderstorms over the
coastal waters tonight into Monday. Any of the heavier
showers/thunderstorms could produce gusty winds in excess of 34 kt,
but overall, wind speeds should back off to 20-30kt. Another reason
for extending the gale through 9 pm was the sea state. Still some
very steep seas out there this evening with 10-11 ft, 8 sec at Buoys
15 and 27 at 8 pm.  These should lower to small craft conditions
(near or below 10 feet) late this evening and overnight. The sea
state improves Monday, even as an upper level low remains over head.
Conditions will further improve through the week as high pressure
builds. -Spilde

&&

.PREV DISCUSSION... /Issued 502 PM PST Sun Nov 24 2024/

DISCUSSION...A low pressure system lingering over the Pacific
continues to dictate conditions over northern California and
southern California. Southerly flow aloft will bring more showers
over Curry County ranges, western Siskiyou County, and the Mount
Shasta region. Snow levels lingering at 4000 to 5000 feet will
allow for snow showers to continue over nigher terrain in these
areas. Southerly flow is also bringing gusty winds into the Shasta
Valley and the southern Rogue Valley. Wind Advisories remain in
place for the Shasta and southern Rogue Valley through 8 PM
tonight. A Winter Storm Warning continues for areas around Mount
Shasta above 4000 feet through Tuesday at 4 AM.

Upper level pressure will move eastward, passing over the area
through Monday and Tuesday. Broadly, this will bring increased
shower chances across the area. Snow showers will continue over
those higher elevation areas around Mount Shasta and could develop
over the Cascades on Monday as winds aloft become more westerly.
Moderate to heavy snow is possible around Crater Lake, including
parts of highways 230 and 62. Current forecast snowfall amounts are
borderline for Advisory thresholds in these areas and lower in other
parts of the Cascades. A Winter Weather Advisory will not be issued
as of this moment, but additional data could change that.

Showers and winds taper off through the day Tuesday, with a dry
period in the forecast from Tuesday evening through the weekend
under an upper level ridge. Daytime temperatures do not look to
substantially change, but drier conditions and clear skies will
allow for cooler nights across the area. For Tuesday night through
Saturday night, the Oregon coast is forecast to have lows in the mid
30s to low 40s. West side valleys will be in the mid 20s to mid 30s,
and areas east of the Cascades will be in the low to high tens.

Sunday afternoon and beyond is where confidence starts to falter.
Both ECMWF and GFS long term ensemble outcomes start to show varying
possibilities for Sunday afternoon and beyond, with some staying dry
and others with varying precipitation. At this point, even these
varying possibilities do not look impactful. Meteogram guidance for
Crater Lake snowfall reflects similar possibilities, with no truly
organized signals for heavy snowfall at this point. -TAD

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...Wind Advisory until 10 PM PST this evening for CAZ081.

Winter Storm Warning until 4 AM PST Tuesday for CAZ082.

PACIFIC COASTAL WATERS...Gale Warning until 9 PM PST this evening for
     PZZ350-356-370-376.

     Small Craft Advisory until 7 AM PST Tuesday for PZZ350-356-370-
     376.

&&

$$