Area Forecast Discussion
Issued by NWS Medford, OR

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068
FXUS66 KMFR 060601 CCA
AFDMFR

Area Forecast Discussion...Corrected
National Weather Service Medford OR
1001 PM PST Mon Dec 5 2016

Corrected wording in Discussion

.UPDATE...
Some updates have been made to the forecast for tonight through
Tuesday in Jackson and Josephine Counties. These updates were to
lower snow levels for this evening and to adjust hourly
temperature forecasts and related snow ratio and accumulations for
later tonight into early Tuesday in the valleys. The adjustments
made in these areas remain consistent with going headlines. BTL

&&

.DISCUSSION...
Snowfall has been observed down to about 1000 feet this evening,
to include here at the Medford Airport, where the temperature has
edged down from 36F earlier this evening to 35F. As radar imagery
indicates, a burst of organized snowfall is moving through
Jackson County now and is just about through the valleys.
Accumulations are likely to be confined to elevations above 2000
feet where temperatures are at or below freezing.

The latest model guidance remains consistent in bringing the bulk
of the expected snowfall across the area between midnight and 10
AM PST. Said another way, showers will generally increase in
coverage and intensity late tonight through Tuesday morning, with
the bulk of accumulations expect to occur during that time
period. In the Bear Creek portion of the Rogue Valley peak
snowfall is expected around sunrise through the morning rush
period as the coldest air moves through aloft. As one might
imagine, a key component to how much accumulation locations
receive is whether or not temperatures are at or below freezing as
the snow falls. We expect that it will be at or below freezing
during this maximum snow period at elevations above about 1500
feet. It also appears that the snowfall will be greatest in the
northeastern and southern portions of the Bear Creek portions of
Rogue Valley, specifically northeast Medford and in Ashland where
1-3 inches of snow accumulation should be expected. It should be
noted that the new NAM12 00Z run brings another round of enhanced
precipitation to this area around midday, as well. While road
temperatures should be warmer by then, this could continue travel
impacts in colder areas and in localized showers that have greater
intensity. Altogether, current winter weather headlines appear to be
on track.

Please also note there`s another wintry system expected late
Wednesday through Friday that will bring concerns for freezing and
frozen precipitation in portions of the area, mainly the mountains
and East Side. BTL

&&

.AVIATION...06/00Z TAF cycle...From the Cascades west...Areas of
MVFR cigs and local IFR cigs with areas of higher terrain obscured
will lower to MVFR cigs/vsbys with areas of IFR cigs/vsbys tonight
as rain showers become mixed with snow showers. Very low freezing
levels will bring a chance of snow to the valley floors late
tonight through Tuesday morning, lowering visibilities and making for
slick runways in heavier showers. Conditions will clear to VFR
Tuesday afternoon.  East of the Cascades...VFR conditions will
prevail initially with some higher terrain obscured...but local MVFR
vsbys in snow showers will develop later tonight and persist through
Tuesday morning.

&&

.MARINE...Updated 115 PM PST Monday 5 December 2016...Seas will
remain steep through Tuesday afternoon. Unsettled showery weather
will persist into Tuesday. High pressure will briefly build
Wednesday...then a strong front will move through Wednesday night
into Thursday. Gale force winds are possible with this front. Weaker
systems will move through Thursday into the weekend.


&&

.PREV DISCUSSION... /Issued 337 PM PST Mon Dec 5 2016/

WIND DISCUSSION...Winds will begin to increase in the Shasta
valley Wednesday evening and continue through Thursday afternoon.
The 700mb winds are not in a favorable position for strong winds
there. However, the 850 mb winds are and the the surface pressure
gradients expected to be between 8-10 mb. Winds should gradually
decrease there Thursday night. Gusty winds will also affect the
Eastside, especially over the higher terrain, including highway 31
between Paisley and Summer Lake Thursday morning into Thursday
afternoon. Winds are expected to be lighter in the valleys east of
the Cascades Thursday morning due to low level inversion, but the
stronger winds should start to surface later in the afternoon
Thursday and Thursday evening. Winds could reach advisory criteria
in the south end of the Shasta Valley near Weed and near Summer
Lake, therefore driving could be difficult for high profile
vehicles, especially near Summer Lake because they are more
susceptible to crosswinds. -Petrucelli

..Long Term...Friday through Monday Night...During the extended
term, the forecast area will remain under swift west flow aloft.
This is mainly the result of a large blocking ridge over the
northern Pacific and Bering Sea keeping a very large scale trough
trapped over the eastern Pacific. This flow pattern will have the
potential to push any number of systems through the area as upper
level waves traverse the flow overhead. However, with this type of
pattern and at this time range, the confidence in timing or strength
of any single system are extremely low. That being said, confidence
is high that we will remain under threat of precipitation throughout
the weekend and into early next week.  have kept an ongoing chance
of precipitation in the forecast, with slightly elevated chances
during periods that either the GFS or ECMWF have a system moving
through. Meanwhile, temperatures will remain close to normal for
this time of year. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 AM PST Tuesday for ORZ029>031.
     Winter Weather Advisory until 10 AM PST Tuesday ABOVE 1500 FEET
     for for ORZ021-023-024.
     Winter Storm Warning until 10 AM PST Tuesday ABOVE 2000 FEET for
     for ORZ021-023-024.
     Winter Weather Advisory until 10 AM PST Tuesday ABOVE 2000 FEET
     for for ORZ025.
     Winter Storm Warning until 10 AM PST Tuesday ABOVE 2000 FEET for
     for ORZ025.
     Winter Weather Advisory until 10 AM PST Tuesday for ORZ027-028.
     Winter Storm Warning until 10 AM PST Tuesday ABOVE 2000 FEET for
     for ORZ026.
     Winter Weather Advisory until 10 AM PST Tuesday ABOVE 1500 FEET
     for for ORZ026.

CA...Winter Weather Advisory until 10 AM PST Tuesday ABOVE 1500 FEET
     for for CAZ080-081-083.

Pacific Coastal Waters...
- Small Craft Advisory for hazardous seas until 4 PM PST Tuesday
  for PZZ350-356-370-376.

$$

BTL/BPN/15



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