FXUS66 KMFR 191626

Area Forecast Discussion
National Weather Service Medford OR
826 AM PST Sun Nov 19 2017

.DISCUSSION...No updates needed this morning. Current conditions
are pretty similar to that of yesterday morning. High level
clouds are streaming across the area, but those in the valleys are
socked in with low clouds and fog. Freezing fog persists in the
Rogue Valley and is fairly dense in some places. A Freezing Fog
Advisory is in place until 10 am for this. The Frost Advisory for
the Umpqua and Coquille Basins will be expiring at 9 am. This
should be the last relatively cold morning for the area. A strong
front will move into the area this afternoon bringing strong,
gusty winds and moderate to heavy rain overnight. Wind advisories
are in place for the more traditionally windy areas and details
can be found at NPWMFR.

The focus for this afternoon's package will be fine tuning any
details on the system expected this evening and tonight. Also,
we'll be looking into the timing of multiple fronts expected to
follow this week. Snow levels will rise with tonight's system and
remain above 8,000 feet through at least Thanksgiving afternoon,
so there aren't any snow impacts expected for pre-Thanksgiving
travel. See the previous discussion below for more details on
expected weather. /BR-y


.AVIATION...19/12Z TAF CYCLE...LIFR low clouds and fog in valleys
west of the Cascades are likely to thicken into early this morning.
But, it will dissipate a little earlier than on Saturday as a front
moves into the area. Otherwise, VFR cigs will develop across the
area this afternoon into this evening. Overnight Sunday night at the
coast could be very windy as the front moves inland. Wind sheer is a
possibility tonight. /FB


.MARINE...Updated 800 AM PST Sunday 19 November 2017...South winds
will increase again ahead of the next front this afternoon with
gales and very steep seas expected by this evening, though winds
will not be as strong near shore south of Gold Beach. Confidence
remains high that seas will build rapidly to around 14 feet tonight
from Gold Beach north, with seas possibly building to 17 feet north
of Coos Bay. Winds could decrease some Monday but are expected to
increase to near gale again on Tuesday and remain strong
through mid-week. Unsettled weather will then continue into next
weekend. FB/SK


.PREV DISCUSSION... /Issued 308 AM PST Sun Nov 19 2017/

DISCUSSION...Widespread fog and freezing fog has developed in
west side valleys, with some reports of visibility less than a
quarter mile. Yesterday, the Medford airport didn't break out
until late morning... and don't see much indication that today
will be very different. Model soundings show around 40 degrees at
850 mb late morning... similar to yesterday. Afternoon highs
should be relatively low, and made some adjustments to those this

Tonight, an upper trough front will start approaching, and on the
front side of the trough, a stream of moisture with tropical
origins will bring heavy precipitation as early as this evening.
This system will be a wet one, but not absurd for this time of
year. From tonight through Monday night, expect around 2 inches
of rain near Brookings... 3 to 4 inches in the Coastal Range... 1
to 1.5 inches in the Illinois Valley... up to an inch in
Roseburg... and around a half inch in the Rogue Valley. Given the
warm moisture source, snow levels will be quite high. Crater Lake
will probably see a few inches of snow late tonight, but by early
Monday morning, snow levels will easily be above 8000 feet.
Low temperatures east of the Cascades will be near freezing
tonight, cloud cover ahead of the system should prevent
temperatures dropping to below freezing. Thus, freezing rain is
not considered a threat on the East Side, at this time, though we
will continue to monitor the potential.

Expect breezy to gusty winds in the Shasta Valley today, and
moderate to strong winds over higher terrain on the East Side
Monday as the front passes over. Tuesday will be somewhat of a
break... though precipitation will probably linger, precip rates
will diminish sharply from Monday.

The forecast gets more complex from Tuesday forward. Models show
agreement that the area will remain under southwest flow at least
through Friday. Multiple cold fronts should pass through the area the
second half of the week, bring rounds of enhanced precipitation,
then lighter precipitation. Timing is one challenge, but QPF is a
bigger one. The GFS has presented much wetter than the EC, and
ultimately went with a blend, though leaning slightly towards GFS
due to better terrain resolution. For what it's worth, while clear
dry conditions looks like a tall order on Thanksgiving, snow
levels will continue to be above pass level, so not expecting any
travel impacts at this time... besides the challenges that rain
can bring. -MSC


OR...Frost Advisory until 9 AM PST this morning for ORZ021-023.
Wind Advisory from 10 PM this evening to 4 PM PST Monday for
Freezing Fog Advisory until 10 AM PST this morning for ORZ026.

CA...Wind Advisory from 10 PM this evening to 4 PM PST Monday for
Wind Advisory until 10 PM PST Monday for CAZ081.

Pacific Coastal Waters...Small Craft Advisory until 4 PM PST this afternoon for
Gale Warning from 4 PM this afternoon to 3 PM PST Wednesday for
Hazardous Seas Warning from 4 PM this afternoon to 3 PM PST
Wednesday for PZZ350-356-376.


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