Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 201658
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
858 AM PST Mon Nov 20 2017

.DISCUSSION...No updates necessary this morning. Rain continues
this morning and reported rainfall amounts so far are pretty much
on track. Reports so far have been around 1 to 1.5 inches in
western Siskiyou County, 1 to 2 inches in eastern Curry and
Josephine Counties, around 0.50 inches in Jackson County, and
generally less than 0.50 inches east of the Cascades. The Curry
Coastal Mountains have picked up anywhere between 1.5 to 2 inches
with Red Mound reporting 2.5 inches as of this writing. Local
spotter reports have been pretty hefty as well...around 1.5 to
1.75 inches in the Illinois Valley and 1.75 to over 2 inches in
Curry County.

There will be a relative lull in rainfall through this morning.
However, by this afternoon, rain will increase again as another
surge of moisture moves into the area, gradually lifting north of
the area by tonight. Another 2 to 3 inches is expected along the
Curry County coast with up to 4 inches possible in the higher
terrain. Because of this, there is a Flash Flood Watch out for the
Chetco Bar wildfire burn scar. Details can be found at PDXFFAMFR.
For the rest of the area, expect another half inch to an inch west
of the Cascades and generally between a quarter to a half inch
east of the Cascades.

Wind advisories continue this morning for the Shasta Valley and
east of the Cascades around Summer Lake and the higher terrain of
Lake County. Winds are gusting to 50 mph in these locations so the
advisories look on track. Winds should remain gusty through today
and possibly into Tuesday. We`ll be taking a look at this for the
afternoon package. Snow levels are high, around 8500 feet per the
MFR 12z sounding, and are expected to remain high through at least
Thanksgiving morning. For more details on upcoming weather, see
the previous discussion below. /BR-y

&&

.AVIATION...20/12Z TAF CYCLE... A warm front will move onshore
tonight through Monday morning bringing low ceilings and, eventually
increasing winds across the forecast area. As this transition occurs
there will be the potential of low level wind shear at the primary
airfields, through as late as 19Z at KMFR.

IFR low clouds remaining in some of the valleys west of the Cascades
are likely to lift some late tonight, particularly in the Medford
area. Exposed areas at the coast will become windy as the front
moves inland, and wind shear is a possibility at North Bend with
strong southwest winds aloft and lighter south to southeast winds at
the surface.

Mountain obscuration and MVFR/IFR ceilings will spread further
inland early Monday morning, affecting most areas by mid-morning.
/FB

&&

.MARINE...Updated 700 AM PST Monday 20 November 2017...Gales and
very steep seas will continue through early this morning before wind
speed decrease to small craft advisory level but will likely
increase again to gales tonight or Tuesday morning and remain
moderate to strong through Wednesday. Conditions should improve some
late in the week as the windy pattern subsides some.

Next weekend, model brings high northwest swell up to 15 feet into
the coastal waters. /FB

&&

.PREV DISCUSSION... /Issued 318 AM PST Mon Nov 20 2017/

DISCUSSION...Substantial precipitation continues to stream into
the area, and expect rainfall rates over the next 12 hours will be
similar to what we`re seeing now. Precipitation will taper off
Tuesday into Wednesday, then by late Thursday expect another round
of precipitation. Then, this weekend has the potential to be very
wet, though details are still being worked out.

Back to today...snow levels started out the night relatively low,
with several inches falling at Diamond Lake... but temperatures
there have risen to the mid 30s, and road cameras show rain, or
possible rain/snow mix. Snow levels will continue to rise from
this point on, to at least 8000 feet MSL by mid morning. Thus, the
main story will be rain. Though Sunday was a cold day, the chance
of freezing rain is low. Temperatures have either risen or been
stagnant across the area over the past few hours, and should
continue this trend tonight. So, we`ll continue to monitor
conditions, but currently not concerned. Precipitation amounts
have been the biggest challenge. Observations in the Coastal
Range have shown rates around a quarter inch per hour, and that
should persist through today, with locally higher rates at times.
The current forecast has a 24 hour total of 3 to 4 inches across
Curry County with up to 5 inches possible in the higher terrain.
The Flash Flood Watch for the Chetco Bar burn scar remains in
effect. Details on this can be found at FFAMFR. Currently, we
aren`t expected any flooding on mainstem rivers, but small stream
rises expected.

Winds are gusting close to 50 mph in Weed and Summer Lake. Wind
advisories for the usual spots, including the Shasta Valley,
Summer Lake/Winter Rim, and Warner Mountains.

Conditions will calm down Tuesday as a ridge builds in... but this
will be temporary. Winds, especially on the East Side, will start
ramping up Wednesday as a low forms in the Gulf of Alaska. That
low will push a cold front through as early as Thursday, bringing
more precipitation Thursday... dissipating to showers Friday.
Another cold front will approach Saturday, and likely stall
offshore. There is some disagreement on timing, but models
generally agree that a low will form to the southwest, which
should wrap in plenty of lower lat moisture, and hit the southern
Oregon coast as early as Saturday night. This has the potential to
be a very wet system.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 4 AM PST Tuesday for ORZ030-031.
     Flash Flood Watch through 4 AM PST Tuesday for ORZ022-024.

CA...Wind Advisory until 4 AM PST Tuesday for CAZ085.
     Wind Advisory until 4 AM PST Tuesday for CAZ081.

Pacific Coastal Waters...Small Craft Advisory until 10 AM PST this morning for
     PZZ356-376.
     Small Craft Advisory for hazardous seas until 4 AM PST Tuesday
     for PZZ350-356-370-376.
     Hazardous Seas Warning until 10 AM PST this morning for
     PZZ350-356-370-376.
     Gale Watch from late tonight through Tuesday evening for
     PZZ350-370-376.

$$

MNF/MSC/FJB



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