Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 061713
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
913 AM PST Tue Dec 6 2016

.DISCUSSION...Showers continue to move from the west northwest to
east southeast this morning. A look at the road cams show wet
roads over most of the lower elevations and roadside slush near
or just above 2000 feet and higher elevations are snow covered.
Now that its daylight, road temperatures will warm up enough to
prevent any additional snow from sticking. The exception will be
over the higher passes. Even then its not going to amount to much.
Showers will be on the decrease late this morning with most
ending by early this afternoon. A few showers could still linger
along the Cascades, but that`s it. The current winter storm
warnings and advisories are due to expire at 10 am pst and this
looks reasonable, so we`ll let this ride.

Dry weather is expected later this afternoon into most of
Wednesday. However the coldest air mass so far this season will
move into the area with cold temperatures almost everywhere. Hence
the freeze warning for the Umpqua Basin and frost advisory for the
coast.

Our next attention will be late Wednesday afternoon or evening.
The models show a warm front approaching the area Wednesday
evening and night. At the same time cold air will be in place,
especially east of the Cascades. The combination of the two could
bring a threat for freezing rain. A preliminary look at at some
data suggest the highest threat for freezing rain could be in the
Klamath Basin. Also highway 140, 66 and 138 could could also have
a higher chance for freezing rain due to colder air being funneled
in from the Cascades. Confidence on freezing rain for some of the
valleys west of the Cascades are lower. Even then, the amount and
duration of freezing is going to be highly dependent on timing of
the front and when the cold air get scoured out. Hence its going
to be tricky. All of this will be looked at in more detail this
morning and we`ll look into issuing winter weather products out
to highlight these threats. -Petrucelli

&&

.AVIATION...06/12Z TAF cycle...Widespread MVFR ceilings are expected
this morning into early this afternoon with terrain obscured. Snow
could lower ceilings and visibilities down to IFR at times this
morning at KMFR and KLMT. Local IFR may also occur at KRBG. Ceilings
will improve to VFR all sites this afternoon and evening, but areas
of IFR low clouds and fog/freezing fog are likely to develop in many
of the valleys overnight into Wednesday morning, including at KRBG
and KMFR. KLMT may also have some freezing fog patches around
sunrise Wednesday. -Spilde


&&

.MARINE...UPDATED 810 AM PST TUESDAY 6 DECEMBER 2016...BUOY
OBSERVATIONS ARE SHOWING THAT THE SHOWERS THIS MORNING ARE BRINGING
SMALL CRAFT ADVISORY WIND GUSTS TO THE SURFACE. THESE STRONGER WIND
GUSTS ARE EXPECTED TO STAY NEAR THE SHOWERS WITH RELATIVELY CALMER
WINDS ELSEWHERE. STEEP SEAS, HOWEVER, WILL PERSIST ACROSS THE MARINE
ZONES THROUGH LATE THIS AFTERNOON. THE SHOWERS WILL GRADUALLY
DIMINISH THIS AFTERNOON. HIGH PRESSURE WILL BRIEFLY BUILD INTO THE
AREA TONIGHT INTO WEDNESDAY MORNING, THEN EAST TO SOUTHEAST WINDS
WILL BEGIN TO INCREASE WEDNESDAY AFTERNOON. A STRONG FRONT WILL MOVE
THROUGH THE AREA WEDNESDAY EVENING THROUGH THURSDAY. MODEL BOUNDARY
LAYER WINDS DURING THIS TIME ARE IN EXCESS OF 40KT, SO CONFIDENCE IS
HIGH ENOUGH TO ISSUE A GALE WATCH. STEEP TO VERY STEEP SEAS WILL
ALSO ECMWF THIS FRONT. WEAKER SYSTEMS WILL THEN MOVE THROUGH
THURSDAY INTO THE WEEKEND. -SCHAAF/SPILDE


&&

.PREV DISCUSSION... /Issued 429 AM PST Tue Dec 6 2016/

DISCUSSION...A potent short wave trough is moving into southern
Oregon tonight. The HRRR short term model is bringing another
burst of snow showers into Jackson county around sunrise. Snow had
been falling down to the valley floor overnight but has not
accumulated at the Medford airport. However, with temperature
hovering near freezing, the next round of snow showers could lead
to temporary accumulation on the roadway around this morning
travel. By mid morning expect snow showers to decrease in
coverage for areas west of the Cascades. Snow level on the west
side are expected to rise to around 1900 feet in Roseburg to 2300
feet in Medford...and 2600 feet in the Yreka area. Snow is
expected at the valley floor for the east side all day today.

By this evening the short wave trough is expected to push east
into the Warners with only the Goose Lake area of Lakeview and
Alturas seeing wrapped around and upslope snow showers into the
Warner Mtns. With the cold air in place, clearing tonight will
lead to a very cold night. Coos county could even see freezing
temperature tonight, especially slightly inland from the
immediate coast such as Coquille and Myrtle Point, with frost
potential at the immediate coast. Temperatures are not expected to
be as cold in Curry County and only frost is expected. Below
freezing temperatures are expected in the Umpqua Basin as well as
further south into the Rogue Valley.

We have issued a Freeze Warning for Coos County and the Umpqua
Basin as this is the first major freeze of the Fall season. To the
East, single digit temperatures will be widespread from the
Klamath Basin into the Goose Lake Basin and subzero in northern
Lake County.

Models are not deviating from this trend and today`s forecast
flows along the previous trend and our emphasis was more toward
making sure snow levels are representative of the temperature
forecasts at various time of day.

On Wednesday another low pressure will bring an occluded front
toward northern California coast. For the first half of the day,
the weather will be quiet but the warm front part of this storm
will spread warm air and precipitation into our forecast area. The
forecast going into Wednesday night will be tricky as warm air
overrunning cold air will lead to snow and areas of freezing rain.
The sequence of event is such that we can see freezing rain at the
high elevation of SW Oregon and western Siskiyou County Wednesday
evening, the potential for freezing rain spreading east into the
Klamath Basin overnight. Thursday could present a big challenge
for the East side with freezing rain potential most of the day and
spreading into the Lakeview/Alturas area by Thursday afternoon and
evening. Confidence is only moderate at this time as a lot will
depend on how deep the cold pool is. The day shift will need to
assess on this potential and we may need to issue another
statement on this development.

After Thursday, temperatures are expected to climb into the
seasonal norms but we will not be completely dry as a series of
fronts will move across the area..


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 AM PST this morning for
     ORZ029>031.
     Frost Advisory from midnight tonight to 8 AM PST Wednesday for
     ORZ021-022-024.
     Winter Weather Advisory until 10 AM PST this morning ABOVE 1500
     FEET for for ORZ021-023-024.
     Winter Storm Warning until 10 AM PST this morning ABOVE 2000
     FEET for for ORZ021-023-024.
     Winter Weather Advisory until 10 AM PST this morning ABOVE 2000
     FEET for for ORZ025.
     Winter Storm Warning until 10 AM PST this morning ABOVE 2000
     FEET for for ORZ025.
     Winter Weather Advisory until 10 AM PST this morning for
     ORZ027-028.
     Freeze Warning from 7 PM this evening to 9 AM PST Wednesday for
     ORZ023.
     Freeze Warning from 1 AM to 7 AM PST Wednesday for ORZ021.
     Winter Storm Warning until 10 AM PST this morning ABOVE 2000
     FEET for for ORZ026.
     Winter Weather Advisory until 10 AM PST this morning ABOVE 1500
     FEET for for ORZ026.

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

Pacific Coastal Waters...Gale Watch from late Wednesday night through Thursday morning
     for PZZ350-356.
     Small Craft Advisory for hazardous seas until 4 PM PST this
     afternoon for PZZ350-356-370-376.
     Gale Watch from Wednesday afternoon through Thursday morning for
     PZZ370-376.

$$



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