Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 211549

Area Forecast Discussion
National Weather Service Medford OR
849 AM PDT FRI OCT 21 2016

.UPDATE...Current observations show rain across much of the West
Side this morning, along with large areas of patchy fog in the
valleys. Have made some updates to the near term forecast to
account for this, but no major changes were needed. The weak front
responsible for the showers will be slow to pass through today,
and should continue to produce clouds and very light rain through
this afternoon, then bring a slight chance for showers to the
East Side this evening.

Major focus of forecast efforts today will be the upcoming rain
and wind system expected late this weekend into early next week.
For more information, see the previous discussion below. -BPN


.AVIATION...IFR will prevail at the coast,
including at KOTH through the TAF period with some improvement
expected after 21z today with terrain and coastal mountains

Inland...Areas of MVFR/IFR cigs are expected in inland
valleys west of the Cascades and IFR cigs/visibilities in the Klamath
Basin through early this morning. Conditions will improve around 16-
18z for most locations but lingering MVFR cigs are possible in the
Umpqua Valley through early afternoon. All areas except the coast
will become VFR this afternoon. -CC

Note: The ceilometer at FAA site KOTH is out of service, so there
will be no ceiling observations available generally between the
hours of 04Z and 14Z.


.MARINE...Updated 850 AM PDT Friday, October 21, 2016...Weak high
pressure over the waters this morning will edge inland this
afternoon as a weak front moves in. Winds will remain light and
variable as a result today. Moderate west swell will keep seas
elevated this morning, but it is expected to remain below small
craft advisory levels.

A storm over the Gulf of Alaska will generate high and steep west-
northwest swell over the coastal waters beginning late this afternoon
into this evening...with steep seas continuing through Saturday
night. An unsettled weather pattern is taking shape this weekend and
continuing into at least early next week. A cold front will move
through Saturday night with gusty south winds and choppy seas.
Another stronger one Sunday night into Monday will bring the
potential for gale force winds over the area along with steep
to very steep wind-driven seas. Stay tuned for updates and possible
watches regarding this period of unsettled weather. -Wright/CC


.PREV DISCUSSION... /Issued 350 AM PDT FRI OCT 21 2016/

SHORT TERM...Today through Monday...A broad upper low currently over
the Gulf of Alaska will drive the weather pattern over Southern
Oregon and Northern California through the weekend. This low will
send several disturbances through the forecast area with a general
trend towards more active, wet weather by early next week.

Today a cold front will move through from west to east and bring a
chance for showers to most areas. This front lacks deep moisture and
won`t bring much rain with it, but temperatures will be noticeably
cooler compared to Thursday. Winds will become gusty from the west
and northwest in the afternoon, especially east of the Cascades.

Saturday will feature a break in precipitation while the upper low
to the northwest digs and ridging builds ahead of it.

A frontal boundary will nudge towards the coast Saturday night and
bring a chance of rain to the coast and just inland through Sunday,
with the rest of the forecast area expected to remain dry. By Monday
the parent upper low draws near, and southerly winds increase across
the forecast area. Interstate 5 near Weed will likely become windy
and winds in the Rogue Valley could be enhanced as well due to
southeasterly flow aloft and increasing pressure gradients from MFR
to RDD.  By Monday afternoon rain should overspread most of the
area, with a front stalling somewhere over Southern Oregon and
Northern California before waving northward as a warm front.
Moderate to heavy rain is expected west of the Cascades. Southerly
flow will induce some downsloping and drying in the Rogue Valley,
potentially preventing significant rains here, at least on Monday. Snow
levels should generally be above 6500 feet through Monday.

LONG TERM...From previous discussion with minor edits...Snow
levels Monday should still remain above the major passes, but they
will come down Monday night as the front moves southeast with
accumulating snow possible near and at Crater Lake, Diamond Lake
and Mt. Ashland by daybreak Tuesday. As the front moves southeast,
the focus for heavy precipitation is expected to shift around
Mount Shasta area. Meanwhile, snow levels possibly lowering enough
to affect a few of the passes like Lake of the Woods and,
possibly, Siskiyou Summit on Tuesday, but this is still a ways out
and specific details could change, so stay tuned for the latest

The upper low will weaken, but remain just offshore after Tuesday.
The models disagree with the amount of moisture being pumped into
our area. The GFS and Canadian show ample moisture moving into our
area from the southwest. The ECMWF is not as wet and has more
ridging due to a slightly stronger upper low offshore. For now
leaned towards the GFS/Canadian solution, with pops slightly above
climo. Of note, the ECMWF and GFS ensemble means are spread out
quite a bit among the individual members, especially after next
Wednesday. -Petrucelli/SK




Pacific Coastal Waters...Small Craft Advisory from 5 PM Saturday to 5 AM PDT Sunday for
     Small Craft Advisory for hazardous seas from 5 PM this afternoon
     to 5 AM PDT Sunday for PZZ350-356-376.
     Small Craft Advisory for hazardous seas from 3 PM this afternoon
     to 5 AM PDT Sunday for PZZ370.


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