Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 230520 AAA

Area Forecast Discussion
National Weather Service Medford OR
920 PM PST Tue Jan 22 2019

...Updated Aviation Discussion...

.DISCUSSION...A frontal boundary is moving southward and will bring
valley rain and mountain snow to the northern portion of the
forecast area later tonight. Precipitation will spread from north
to south during the day Wednesday. Snow levels will vary
significantly Wednesday morning from west of the Cascades to east
of the Cascades. West Side areas will likely see snow above 5000
feet or so, while East Side areas will see snow down to valley
floors (around 4000 feet). Snow levels will rise during the day,
increasing to 6000 feet and higher during the afternoon. Several
inches of snow are likely in the Cascades and Siskiyous in the
morning before snow levels rise. We`ve increased the precipitation
expected based on the latest model data, likely due in part to a
moderate 40kt 700mb west-northwest flow that`s impinging upon the
Cascades and Siskiyous. Breezy west to northwest winds are
expected in the Cascades and east of the Cascades.

Please see the previous discussion below for more details on the
upcoming front and the dry weather expected after.


.AVIATION...For the 24/06Z TAFs...MVFR and VFR cigs are expected
this afternoon and evening.  Mountain obscurations are expected with
this next approaching system tonight. Freezing level will be above
6000 feet along the coast and offshore. Rain is likely along the
coast in addition to the higher Cascades. IFR CIGS are expected in
some of the showers, especially in the Umpqua valley and near North
Bend. East of the Cascades, VFR will prevail for the TAF period.


.MARINE...Updated 200 PM PST Tuesday, 22 January 2019...
A weak front will pass across the northern waters today, producing
breezy south winds and choppy, wind-driven seas. Meanwhile, westerly
swell will build through Wednesday. Resulting Small Craft Advisory
conditions will continue through Wednesday night before improving
Thursday morning. By Thursday afternoon, a thermal trough will
develop, producing gusty north winds and steep seas through the first
part of the weekend. Some improvement is expected Sunday, but models
suggest that north winds may return Monday or Tuesday of next week.


.PREV DISCUSSION... /Issued 229 PM PST Tue Jan 22 2019/

DISCUSSION...Varying amounts of high and mid level clouds are
moving northwest to southeast over the area. Radar is showing
light returns in northern Douglas County, but most likely its`s
not reaching the ground. Eugene is the closest area to us that`s
reporting light rain. Therefore we should stay dry into the early
evening hours. However could not rule out a few sprinkles in
northern Coos and northwest Douglas County. A cold front will
gradually sag south into our area tonight and bring a better
chance for light precipitation from the Cascades west and north of
the Umpqua Divide. Snow levels this evening are expected to be
between 4500 and 5000 feet tonight. Areas around Diamond and
Crater Lake could pick up a couple of inches by daybreak
Wednesday. Cloud cover will increase tonight as well and should be
enough to prevent fog from developing in the westside valleys in
Oregon. However it may not be sufficient enough to keep fog from
developing in the valleys in Siskiyou County.

The front will stall over our area Wednesday, so we`ll have plenty
of cloud cover and light steady precipitation. Snow levels Wednesday
are expected to rise between 6500 and 7000 feet, therefor snow will
be limited to the Crater Lake area. Even then, were not expecting
anything significant. The models suggest precipitation could make it
all the way into portions of Siskiyou County Wednesday, so added a
slight chance of precipitation.

The front will weaken and dissipate Wednesday night with
precipitation gradually ending. For now kept in patchy fog in
Wednesday night into Thursday morning, but it may not materialize if
enough cloud cover remains which is possible.

Dry weather returns Thursday and will continue into Friday as an
upper ridge builds into the area. Fog and low clouds are a good bet
late Thursday evening into Friday morning for the westside valleys.
High temperatures Thursday and Friday could end up lower than whats
in the forecast of the fog and low clouds are slower to burn off.
However offshore flow is expected to develop which could limit the
vertical thickness of the fog and low clouds which could lead to
clearing earlier in the day. -Petrucelli

A pretty quiet weather pattern will continue for southern Oregon as
high pressure maintains control.  The one notable feature coming up
in the extended forecast is the potential for a short wave trough to
dive down through Oregon east of the Cascades.  This will send east
winds over the Cascades, and we`ll see some major drying and heating
up over the region.  Right now we`re forecasting highs in the lower
60`s for populated areas west of the Cascades Sunday. Our record
high for Medford is 67 degrees.

The other notable feature was just how dry the airmass will become
as we see these strong east winds Sunday into Monday.  1000-500 mb
relative humidity values will decrease to 5%, so skies will be
almost completely clear except for some cirrus clouds from Sunday to
next Tuesday.





Pacific Coastal Waters...Small Craft Advisory for hazardous seas
until 4 AM PST Thursday      for PZZ350-356-370-376.      Small
Craft Advisory until 10 AM PST Wednesday for PZZ350-370.

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