Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 261144

Area Forecast Discussion
National Weather Service Medford OR
444 AM PDT MON SEP 26 2016

.AVIATION...26/12Z TAF CYCLE...VFR conditions will continue
through the TAF period all areas inland from the coast. Areas of
fog and stratus with IFR CIGS/VIS have formed along the immediate
coastline this morning, but will burn off to VFR by mid morning.
Some guidance suggests stratus holds in all day around KOTH, but
this seems unlikely given how clear and dry the airmass is just
above the surface. Stratus with IFR CIGS/VIS will return to the
coast this evening, and will persist through Tuesday morning.


.PREV DISCUSSION... /Issued 417 AM PDT MON SEP 26 2016/

As of 315 AM PDT, it is still in the lower 80s at a couple of the
RAWS stations in the Curry County Coastal Mountains. While winds
have diminished enough to prevent critical fire weather
conditions, a very dry and warm air mass, especially by late
September standards, remains in place. Please see the Climate
section, below, regarding the record high of 100F set at
Brookings Airport on Sunday.

Skies remain clear over land areas this morning, though some
stratus clouds offshore have begun drifting coastward about 60
nautical miles west of the coast. High temperatures today are
expected to be just a degree or two warmer than what was observed
Sunday for highs, except along the immediate coast, where lighter
winds are expected to bring a return to maritime air.

A gradual cool down will ensue tonight through Wednesday, with
a more appreciable cool down expected Thursday into the weekend.
Highs Thursday should be 15 to 20 degrees cooler than today`s.
Friday through early next week daytime highs are expected to be in
the 50s and 60s in the valleys, about 10 degrees below normal and
30 degrees cooler than today`s highs.

There will be some marine layer drizzle along mainly the Coos and
Douglas County coasts and Umpqua Basin, and possibly in and around
Brookings in the nights and mornings through Thursday. Some
showers are possible Thursday afternoon and evening, mostly along
and downwind of the Marble Mountains, Siskiyous, and Cascades.
While we have not added it to the forecast due to it being
marginal, there could be some rumbles of thunder from these
showers, mainly northeast of Crater Lake National Park if the
incoming trough were to strengthen a bit more.

Friday through early next week several shortwave troughs will
push across the forecast area bringing a good possibility of
appreciable rainfall and some mountain snow above 6kft. As usual,
chances are higher, sooner to occur, more frequent, and of greater
magnitude the farther northwest one goes in our area. Over the
last 24 hours models have trended a bit northwest with the low
pressure impulses and resultant rain chances Friday through
Saturday, and are generally indicating a more direct hit for the
majority of us in the Sunday through Tuesday time frame. Model
trends have generally been to deepen the trough in the last 24
hours, so confidence is high that we`ll be in a cool and wet
pattern. There has been some tendency in some of the ensemble
guidance to send the bulk of the wet weather across Northern
California instead of southern Oregon early next week, but this
tendency has been sporadic/inconsistent. In short, confidence is
high in wetting precipitation and cooler temperatures Friday
through Tuesday, but low in the details of the timing and
intensity of the precipitation.

It should be noted that we currently expect that clouds, wind, and
moisture to keep overnight lows near to above normal through early
next week. However, the air mass is cool enough above the surface
that any clear and calm night during the Friday through early next
week time period would yield frost/freeze concerns for
agricultural interests on the West Side. Of note, the normal low
for Medford for the next week is 42F. BTL

MARINE...Updated 200 AM PDT Monday 26 September 2016...Winds and
seas have lessened this morning as a thermal trough weakens and
moves inland. Conditions will remain below advisory level through
this afternoon. However, the thermal trough redevelops again
tonight and persists through Wednesday evening. This will lead to
winds and seas once again reaching small craft advisory levels
tonight and tomorrow. Winds will rise to gales in the expansion
fan south of Cape Blanco Tuesday evening and night with small
craft conditions elsewhere. The trough weakens and moves inland
Wednesday and Thursday with conditions gradually improving.

FIRE WEATHER...Updated 220 AM PDT Monday 26 September 2016...Hot,
dry weather peaks over inland locations today as the surface thermal
trough moves inland. High temperatures will be about 15 degrees
above normal today inland from the coast. Fortunately, winds will
not be a problem, so red flag conditions are not expected. While
conditions over the south coast are still fairly balmy this morning,
high temperatures and minimum humidities will likely occur this
morning, with cooler more humid weather surging inland later today
as winds become onshore.

With the thermal trough moving farther inland Tuesday, humidities
will creep up and inland temperatures get a modest start to a
cooling trend. After very slight additional cooling on Wednesday,
temperatures will be noticeably cooler Thursday. But, the most
notable aspect of conditions on Thursday will be increasing westerly
winds at 10 to 20 MPH on the east side in the afternoon. These winds
will likely trend stronger at 15 to 25 MPH on Friday but it will be
dramatically cooler with below normal temperatures.

The cooling will continue into the weekend as an upper low sends a
series of systems into the area. A system may bring a wetting rain
to the coast and Umpqua Valley Friday then to much of the area next
weekend. It is too early to know exactly how much rain falls or
where it falls, but confidence is fairly high that the pattern will
shift to be much cooler and wetter late this week. -DW/Wright

It reached 100 degrees at Brookings Airport on Sunday. Not only
did this break the record high of 93 set in 1937, but is also only
the 5th time on record that the temperature has reached 100F at
Brookings Airport in September. It was also one of only 10 times
that it has ever reached 100F there. Records at Brookings go back
to August of 1913. It was the warmest temperature recorded in
Brookings since it reached 101F on September 18th, 2000. BTL




Pacific Coastal Waters...Small Craft Advisory from 11 AM Tuesday to
     2 AM PDT Wednesday for PZZ350-356-370-376.
     Small Craft Advisory for hazardous seas from 8 PM this evening
     to 11 AM PDT Thursday for PZZ350-356-370-376.
     Gale Warning from 5 PM Tuesday to 2 AM PDT Wednesday for PZZ376.

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