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fxus66 kmfr 191600 

Area forecast discussion
National Weather Service Medford or
900 am PDT Sat Aug 19 2017

Short upper level ridge centered offshore will
dominate the pattern today with a weak shortwave along the coast
moving south of the area this afternoon. The ridge will remain
offshore through Sunday then will shift inland on Monday. Some
weak upper level disturbances will be present in the flow but
expect continued dry weather. A moderate to stronger surface
thermal trough will persist along the coast then move inland
Monday afternoon. This thermal trough is bringing gusty winds and
dry humidities to the coastal and western Siskiyou Mountains. Also
expect gusty north to northeast winds are expected in the late
afternoon and evening over western portions of the area, mainly
west of the Cascade crest. This pattern will persist through
Sunday and will bring heightened fire weather concerns. A Fire
Weather Watch is out for the potential of critical fire weather
conditions. See the rfwmfr for details.

Numerous area wildfires will bring continued smoke impacts to the
area. The dry and breezy conditions are also allowing active
burning on area wildfires. Expect similar areas to be impacted by
smoke today as yesterday. Areas of smoke are expected in Curry,
Douglas, Josephine, Jackson, Siskiyou and Klamath counties. With
little change expected in the wind pattern through Sunday evening,
expect areas of smoke to bring continued air quality impacts to
the area. An air quality alert is in effect for many areas in
southwest Oregon. See the aqamfr for details.

For Monday, the easterly winds over the ridges will decrease late
in the morning and over southern portions of the area from around
the Siskiyous south, expect winds to gradually change to a
southeast directions late Monday morning. As the thermal trough
moves inland on Monday expect winds to shift to a north to
northwest direction. Smoke will continue to be a concern for
areas in southwest Oregon and northwest California but the areas
which see the worst conditions may fluctuate slightly.

Cloud cover is expected to be clear for mostly clear for most
inland areas on Monday, the day of the eclipse. Smoke will remain
the main concern for inland areas. Also models are showing some
low clouds and fog along the Oregon coast north of Cape Blanco and
into the Coquille Valley. However gradual clearing is expected in
the mid to late morning on Monday. Will continue to monitor this
closely with future model runs.


Aviation...19/12z taf cycle...IFR ceilings will prevail along the
coast north of Cape Blanco this morning. Some MVFR ceilings may try
to form in parts of the Umpqua basin toward sunrise, however,
confidence is low that this will occur. At 3 am the temperature-
dewpoint spread at rbg was still 7 deg. C. The rest of the area will
be VFR, but widespread smoke from wildfires will result in
visibility degradation to MVFR at times.


Marine...updated 305 am PDT Saturday 19 August 2017...high
pressure centered offshore and a thermal trough along the coast will
support moderate to strong north winds and steep to very steep seas
through this weekend. Conditions will at least be hazardous to small
craft, but warning level winds/seas will occur beyond 5 nm from
shore from Gold Beach south. Winds and seas will be highest during
the afternoons and evenings each day through Sunday, easing a bit
during the overnight and early morning hours. The thermal trough
will weaken early next week, and winds and seas will diminish then.


Previous discussion... /issued 444 am PDT Sat Aug 19 2017/

Discussion...there is relatively little change to the previous
issuance of the forecast. There is increased confidence in the
forecast through Wednesday with very good agreement between the
ensemble members of the 00z GFS and European model (ecmwf) models. The upper level
pattern will evolve slowly with a quasi-Rex block into Monday as
high pressure centered far offshore of northern California nudges
into the region and a broad trough remains centered offshore of
Southern California.

The weather this weekend will be just a bit less hot than
yesterday while the air mass remains dry and stable. Low clouds
and fog along the coast north of Cape Blanco and into western
Douglas County are expected to diminish quickly this morning then
return later this evening. This pattern will also continue
patches to areas of smoky skies into early next week. With the
northeast to east winds occuring each night then north to
northwest winds in the afternoon and evening expect most inland
areas to continue to experience smoke. Air quality alerts are in
effect for Douglas, Curry, Josephine, Jackson and Klamath
counties. With the active Chetco fire in southern Curry County and
the northeast winds expect smoke to continue to move into the
Brookings area at times. Also the northeast winds will bring a
Chetco effect with some warm temperatures in the Brookings area.

It will be slightly hotter again Monday then there is a slight
chance to chance of thunderstorms for much of the area, mainly
from the southern Oregon Cascade and Siskiyou Mountains south and
eastward on Tuesday and Wednesday. A cold front is likely to
follow on Thursday with gusty winds, little or no rain, and the
coolest temperatures of the week...near to slightly below normal.
There is uncertainty in the timing and position of the Thursday
front with the European model (ecmwf) indicating a morning passage and the GFS a
more impactful afternoon timing. The farther to the north and west,
the higher the probability the front produces rain.

The highest probability is for ridging to bring warming and
drying at the end of the week. Either rain with mid- week
thunderstorms or the frontal passage on Thursday may provide some
reduction in smoky skies. But, of course, they also have the
respective risks of creating new fires and worsening behavior of
existing fires.


Mfr watches/warnings/advisories...
or...Fire Weather Watch from 5 PM PDT this afternoon through Sunday
morning for orz619.


Pacific coastal waters...Small Craft Advisory until 11 PM PDT Sunday for
Gale Warning until 11 PM PDT Sunday for pzz356-376.

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