Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 270406

Area Forecast Discussion
National Weather Service Medford OR
806 PM PST Fri Feb 26 2021

.DISCUSSION...On radar, there are fairly strong returns in eastern
Douglas County and northern Klamath County. Road cameras in the
area show active snowfall (even blocking most of the view of the
camera), but that roads are generally clear. Of course, verify
this by checking on if you have to drive through
here. Snow levels should be lowering to a few hundred feet below
2000 kft. Over the next 3-9 hours light accumulations around 0.5"
could occur, but showers should be getting less numerous through
the night. Nonetheless, areas of higher terrain, including
portions of routes 227, 62, 138, 230, and 140 could very easily
recieve an additional 1" to 4" because of orographic lift. Winds
will generally be on the decline through the night, but as the
road cameras suggest they are still elevated enough to produce
reduced visibility. Not expecting winds to fully subside in the
Cascades until early Saturday morning.

Showers along the coast will also remain through the night. East
of the Cascades though, showers will become even more scarce.
Winds will remain elevated east of the Cascades through the night.
In the early to mid-morning, as mixing begins to pick back up,
winds will remain elevated until roughly 10 AM PST. The 00z model
runs continue to show elevated winds at 700 mb. So while these
winds may find difficulty mixing down during the night, they are
more likely to do so in the morning. The only change to the
forecast will be to extend the Wind Advisory out to at least this
time. Otherwise the forecast remains in track as we head into a
more quiet stretch of weather. -Miles


.AVIATION...For the 27/00Z TAF Cycle...Winds will be coming down
this evening west of the Cascades, but strong, gusty winds, along
and east of the Cascades will persist into tonight. This will result
in some continued turbulence and mountain waves.

Lower ceilings and showers will continue through most of the TAF
period (through Sat morning), most numerous in the Cascades and west-
facing foothills. These will cause areas of MVFR ceilings and
terrain obscurations, though periods of VFR between showers are also
likely.  -Miles


.MARINE...Updated 800 PM PST Friday 26 Feb 2021...Very steep seas
will continue for portions of the waters north of Cape Blanco
through this evening with steep seas elsewhere. Also expect
continued high surf conditions along the coast late this evening
with breakers of 20 to 23 feet. High pressure will build offshore
and a thermal trough will develop along the south Oregon coast
Saturday. Seas will gradually diminish tonight into Saturday night
but remain high and steep, due to a combination of a moderate
northwest swell and choppy wind-driven seas. On Saturday, winds
shift from northwest to north with speeds diminishing over much of
the waters -- except they`ll remain gusty and at advisory strength
into the evening from Cape Ferrelo south See MWWMFR for details.

North winds will gradually lower Saturday night with diminishing
seas expected into Monday morning as the offshore high weakens and a
low approaches the offshore waters. The low will likely bring
increasing winds Monday night into Tuesday, but its intensity and
trajectory are uncertain at this time. The next period of concern
will be around Thursday and Friday of next week as models are
suggesting waves will be around 16 to 20 feet.  There is also a
strong suggestion that most of this will be created from southerly
wind waves.  In any case, prepare for some very high seas around
next week Friday.



PREV DISCUSSION... /Issued 226 PM PST Fri Feb 26 2021/

SHORT TERM...This afternoon through Sunday night...Numerous showers continue
across the area this afternoon under swift northwest to westerly
flow. Snow levels are hovering around 3000 ft, and this is resulting
in periods of snow covered roads, especially to the Cascade passes
where showers are being enhanced by orographic lift. While the more
frequent, intense showers has subsided, periods of heavier showers
are still expected through this evening and overnight. This could
result in brief periods of snow covered roads, especially after
sunset when roads are no longer warmed by the sun. A winter weather
advisory remains in effect for this until early Saturday morning,
and details can be found at WSWMFR. In addition to snow, the other
concern remains strong, gusty winds. While the strongest wind gusts
have ebbed, gusts of 35 to 45 mph are still common across the East
Side. Wind headlines are in place for these strong winds, and
details can be found at NPWMFR. Guidance indicates another uptick in
700 mb winds late tonight, increasing back up to 40 to 50 kt. While
this is good indication of gust potential, this will be occuring
overnight when mixing is less optimal so I don`t expect those values
to fully reach the surface. However, it will still be breezy
overnight and a wind advisory will continue into early Saturday
morning. Snow levels will lower to around 2000 ft tonight, however,
shower coverage will be much less and intensity will be lower as
well so any winter impacts should be brief and minimal.

Showers continue into Saturday morning, gradually tapering off by
the afternoon. Upper level ridging and a thermal trough at the
surface builds in Saturday evening and we`ll see a break in the
weather from Saturday evening into at least Sunday night, if not
longer. Some morning fog and low clouds will be possible Saturday
night into Sunday morning. For areas that don`t see any fog/low
clouds, expect some cold temperatures overnight under clear skies.
We`ll need to monitor the potential for frost conditions along the
coast under this pattern. Any low clouds that do develop will give
way to sun by late Sunday morning with cold morning temperatures
warming seasonal normals for the afternoon. Ridging breaks to the
east Sunday night as an upper level trough approaches the area.
Overnight temperatures will trend warmer compared to Saturday
night/Sunday morning as flow becomes more southwesterly. Depending
on how much high level cloud cover arrives in advance,
overnight/morning fog and low clouds could be much more limited
Sunday night compared to Sunday morning. /BR-y

LONG TERM....LONG TERM...Monday through Friday, March 1-5,
2021...The upper ridge over the area on Sunday will push well to
the east of the area early next week with southwest flow aloft
developing on Monday in advance of the next trough moving in from
the Pacific. Recent 12z deterministic guidance, including the 12z
ECMWF, is showing the upper flow splitting on Monday with a closed
low developing out around 130W and digging southward off the
California coast Monday night. This would bring a fairly weak
trough through the Pacific Northwest during this time frame with
only slight precipitation chances, mainly from the coast to the
Cascades. GEFS ensembles, while not completely dry, also favor
this scenario of lower precip chances on Monday. ECMWF ensembles,
on the other hand, are a bit more bullish with the northern branch
trough, which would favor higher precipitation chances from the
coast to the Cascades. Given some uncertainty, we`ve largely
maintained continuity in the forecast which keeps a chance of
showers in the forecast, but with the highest PoPs at the coast.

The closed low meanders off the southern California coast Tuesday
with the main northern branch energy directed into western
Canada. We`ll be between these features and the result will be
mainly dry weather with chilly mornings and seasonably mild
afternoons through Wednesday. The closed low will eject
northeastward across the Southwest U.S. Wednesday into Thursday.
At the same time, upstream, another closed low will descend
southward into the Gulf of Alaska. This will allow an upper trough
and cold front to push toward the PacNW late next week. Of course,
timing and strength of this system at this range are uncertain,
but precipitation probabilities will increase again late next week
with some wind potential as well. Snow levels look to be in the 4000-
5000 foot range. -Spilde


OR...High Surf Advisory until 10 PM PST this evening for ORZ021-022.
     Wind Advisory until 4 AM PST Saturday for ORZ030-031.
     Winter Weather Advisory until 4 AM PST Saturday for ORZ027-028.

CA...Wind Advisory until 4 AM PST Saturday for CAZ085.

Pacific Coastal Waters...Small Craft Advisory until 2 AM PST Sunday for
     Hazardous Seas Warning until 10 PM PST this evening for PZZ370.

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