Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 230425
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
825 PM PST Sun Jan 22 2017

.SHORT TERM...A strong shortwave is moving across northern
California. Earlier this evening, this disturbance brought heavy
snow from Weed southward to Dunsmuir. Reports indicated around 11
inches of snow fell in the Mount Shasta area early this evening
and snowfall rates peaked between 2 to 4 inches per hour. A winter
storm warning is still in effect as this shortwave remains in the
area. The shortwave is forecast to shift east late this evening.
Snowfall has already decreased in the Mount Shasta area but some
moderate showers remain possible until this disturbance moves out
of the area. For other areas, this evening we saw moderate snow
showers into western Siskiyou and southern Josephine counties.
Numerous showers are continuing along the coastal areas as well.
Snow levels have been around 2000 feet but lowered in showers to
near 1500 feet elevation.

Shower activity is forecast to decrease tonight as the shortwave
lifts east-northeast. Although showers are expected to continue
near and just off the coast. On Monday, the forecast remains on
track with low pressure, which is currently well off the
Washington coast, moving south off the Oregon coast then shifting
down the Northern California coast Monday evening. This low will
bring additional showers to the area, mainly along the coast and
into Siskiyou county. Showers will result in additional light to
moderate snow accumulations Monday over the higher terrain, Mount
Shasta area and east of the Cascades. Please see the WSWMFR for
details.


&&

.AVIATION...23/00Z TAF Cycle...Isolated to scattered showers and
snow showers will linger through Monday morning except numerous
showers and also isolated thunderstorms from the coastal waters and
coastal areas into Josephine County this evening. This will result
in changeable cloud cover with areas of MVFR cigs and mountain
obscuration mainly accompanying showers and snow showers. IFR to
LIFR will occur occasionally in the Shasta Region. The freezing
level will near 3500 feet MSL this evening will fall to near 2000
feet MSL early Monday morning. VFR should return most areas Monday
afternoon, though occasional MVFR will persist in showers along the
SW Oregon coast and in northern California. -Spilde

&&

.MARINE...Updated 300 PM PST Sunday 22 January 2017...Low pressure
northwest of the waters will bring southerly gales through early
this evening. Winds will ease to small craft advisory levels late
this evening through Monday as the weakening low moves through the
southern Oregon offshore waters. However, seas will remain very high
and very steep through Monday evening. Conditions will improve late
Monday night into Wednesday. A weak front will bring a modest
increase in winds late Wednesday but will be accompanied by a
building very long period west swell that will reach a peak early
Thursday. -Spilde


&&

.PREV DISCUSSION... /Issued 337 PM PST Sun Jan 22 2017/

Short Term...Through Tuesday night...
Strong low pressure, now well occluded and in it`s dissipating
stage, continues to spin off of the Pacific Northwest coast. This
low had a central pressure around 974mb at 2100Z/1300PST this
afternoon and was located at about 46.5N 131W. Showers and
thunderstorms have occured through the day across the coastal
waters and along the coast, with a couple of Special Marine
Warnings issued for potential storm force gusts, potential
waterspouts, and substantial lightning.

The now mostly vertically stacked low will move southeastward
toward and then into Central California tonight through Tuesday
morning. As this occurs we do expect showers across the area, and
the surface air mass will gradually cool.

Tonight through Monday morning we expect snow levels to lower to
between 1400 and 2400 feet. Precipitation will be light for most
locations away from the coastal counties and Northern California,
where light to moderate amounts are expected. Winter weather
advisories have been issued for the Mount Shasta area and portions
of Western Siskiyou County above 2000 feet for light to moderate
snowfall in the 1-6 inch range. We will need to keep an eye out
for snow showers making it into Josephine County overnight into
the morning, as snow levels are expected to be low enough for
lower elevation impacts. Currently amounts look to be less than
an inch there. Flurries are possible down to about 1400 feet
across many western valleys, though most of the shower activity
tonight into the morning will be in the higher terrain.

Thunderstorms are still possible along the coast through this
evening and in the coastal waters overnight before it becomes a
bit more stable.

Tuesday morning will start off chilly, but then clearing skies
should yield a mostly sunny day. Expect some morning fog both
Tuesday and Wednesday morning in the valleys. BTL

Long Term...Wednesday through Sunday.
There is better than normal model agreement through Saturday.
This period will be relatively uneventful but with below normal
temperatures. It will be especially cold on the east side with lows
around 10 to 25 degrees below normal.

A weak ridge will push inland on Wednesday ahead of a weak split
trough in a progressive upper level pattern. There is a slight
chance of rain at the coast Wednesday afternoon ramping up to a
chance Wednesday night with a weak front expected to weaken further
as it moves inland. The GFS has trended toward the more consistent
ECMWF solution leading to higher confidence that the probability of
precipitation will be highest for Curry County and the far northern
California coast into western Siskiyou County. Snow levels are
forecast to be around 2500 to 3000 feet MSL with amounts of up to an
inch.

The probability of post-frontal showers will diminish quickly
Thursday morning as a ridge builds into the west coast. The ridge
will continue to build inland through early Friday then persist
at least through Saturday night.

By Sunday, uncertainty develops regarding the strength and track of
the next cold front. The ECMWF is stronger than the GFS with this
system but both models send the bulk of the precipitation into
Washington and far northern Oregon. -DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory until 10 PM PST Monday for ORZ021-022.

CA...Winter Weather Advisory until 4 AM PST Monday for CAZ081.
     Winter Weather Advisory until 10 AM PST Monday ABOVE 2000 FEET
     for for CAZ080.
     Winter Storm Warning until 4 AM PST Monday for CAZ082-083.

Pacific Coastal Waters...Hazardous Seas Warning until 10 PM PST Monday for
     PZZ350-356-370-376.

$$

CC



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