Wildfire in Oregon, September 1 to 9, 2018

Area Forecast Discussion
National Weather Service Medford OR
821 PM PDT Fri Aug 31 2018

.DISCUSSION...An update will be issued to adjust the sky cover
forecast for tonight and Saturday morning. Stratus is currently
limited to the coastal waters, near shore around Gold Beach, and
near Cape Blanco. North to northeast winds will bring a
continental influenced air mass to the coast and limit expanding
stratus to the region from Cape Blanco into the Coquille Valley
from around midnight to around 7 AM Saturday morning. Brief patchy
stratus is also possible around sunrise in southern Douglas
County. The skies will clear in these areas during Saturday.

The previous discussion and fire weather discussion are included
below. They still more than adequately cover the current concerns
and details of the evolution of the weather in the next week. The
main concern will be the impact of easterly winds on the Klondike
and Natchez fires tonight through Tuesday night...especially
Saturday night and Sunday night with the Fire Weather Watch in
effect.

&&

.AVIATION...For the 01/00Z TAFs...Patchy IFR near capes will expand
along the coast north of Brookings and into the southern portion of
the Coquille Valley late this evening into Saturday morning. Another
patch of stratus is likely to form in the southern portion of the
Umpqua Valley and briefly approach Roseburg around 14Z. The stratus
will begin to dissipate around 16Z. With one exception, VFR
is expected to develop across the area.

Of course, that exception is areas affected by smoke. With a net
northerly flow over the forecast area, smoke will be most prevalent
southeast through southwest of the active wildfires. Through
Saturday, the fires will generally be less active than they have
been, except for the Natches and Klondike Fires. These two fires
will result in MVFR to IFR visibilities downwind of them primarily
from Happy Camp westward in California, and from Gold Beach and Cave
Junction in the Illinois Valley southward. -DW

&&

.MARINE...Updated 700 PM PDT Friday, 31 August 2018...North winds
and short period seas will continue to trend higher into Sunday
evening. Small craft advisory level winds and steep seas south of
Cape Blanco will continue through Saturday. A stronger thermal
trough will develop along the coast late Saturday. This will bring
strong gusty north winds and steep to very steep seas over all of
the waters through early next week. Gale force gusts are possible as
early as late Saturday afternoon/evening south of Cape Blanco, but
gales and very steep seas are more likely to develop south of Port
Orford on Sunday. As a result, a Gale Watch is in effect beginning
late Sunday morning and continuing through Monday night. The rest of
the waters will have conditions hazardous to small craft. North
winds may weaken slightly on Tuesday but expect lingering steep seas
and gusty winds into Wednesday. -Lutz/DW

&&

.PREV DISCUSSION... /Issued 256 PM PDT Fri Aug 31 2018/

DISCUSSION...

An upper level trough will continue to dig into Nevada this
afternoon and evening with a little bit of offshore flow
developing across Southern Oregon. The flow pattern will push the
smoke towards the coast and away from the inland valleys for this
weekend. The South Umpqua Complex is still outputting some smoke,
so we decided to put haze in for the Rogue Valley with some
patchy smoke near the Umpqua Divide today into this upcoming
Wednesday.

The offshore flow should keep the low level fog out of the coastal
cities tonight, but stratus should still build in some areas
along the coast. The east winds will start to pick up Saturday
into Sunday resulting in continued clear skies with the smoke
heading towards the coast. There is an elevated fire weather
concern because of these winds with Sunday night being the most
concerning. 925mb and 850mb flow over the Kalmiopsis wilderness
is about 30 to 35 knots Sunday night. Usually during the summer
its roughly 15 to 20 knots. However, the stronger offshore flow is
typical and normal as we head closer towards the Fall months.
More can be read in the fire weather discussion below, but the
biggest concern right now is how the Klondike fire will react to
the stronger winds.

After the periods of enhanced offshore flow, we'll see winds begin
to shift towards onshore flow with the next approaching trough
around the Wednesday to Thursday time period. Models are
suggesting that areas along the coast and the west facing slopes
on the Cascades could see some rain as a well defined cold front
pushes inland Thursday. Models are not really bullish on the QPF
forecast with the GFS and ECMWF only showing a few hundreths
Thursday night. Most of the QPF is expected to be north of the
Umpqua divide as the trough axis is displaced farther north
towards Washington state. As of right now, a slight chance for
some rain is completely reasonable Thursday night north of the
Umpqua divide and along portions of the coast.

The other point we would like to make here is that IF the
Klondike fire does end up becoming more active this weekend, more
smoke is likely in store for the inland valleys Wednesday.
However, the cold front will help clear things up on Thursday.

-Smith

FIRE WEATHER...Updated 230 PM PDT Friday 31 August 2018...

Dry weather will continue with no threat of thunderstorms through
most of next week. Max temperatures will trend upward Saturday and
Sunday over most of the area, the exception will be along the coast,
north of Cape Blanco where they will remain near normal.

The main concern later this weekend into early next week is moderate
to strong east to northeast winds along with moderate to possibly
poor recoveries at the mid slopes and ridges in portions of fire
zones 618, 619, 620 and western portions of 280. More on this below.

The thermal trough and east winds will return in above mentioned
fire weather zones tonight. However, overnight recoveries are not
expected to be a concern. The one exception could be on the western
fringes of the Klondike Fire. Even then were not expecting Red Flag
conditions to be met.

There's good agreement the thermal trough will strengthen Saturday
night into Sunday morning and remain strong Sunday night into Monday
morning along with moderate to poor overnight recoveries. Models
show offshore winds fairly aligned up to 850 mb in fire zones 618,
619 and 620. The high res short range models are also in pretty good
agreement with the location of the thermal trough. Thus, confidence
in gusty east to northeast winds at the mid slopes and ridges are
high. The main question will be the overnight recoveries. However
given the fire activity at the Klondike and potential for fire
growth, have decided to go with a Fire Weather Watch for fire zones
619 and 620 including portions of the Klondike Fire. You will see
the Fire Weather Watch runs from Saturday evening through Monday
morning, but this will be a porpoising event in which the best chance
for critical conditions to be met will be in the evening and
overnight hours.  Please RFWMFR for more details. For fires zones
618 and 280, we'll continue to headline for moderate to poor
overnight recoveries and winds, but keep in mind these areas could
be added should evidence becomes stronger that criteria could be
met. Stay tuned for updates.

Typically in this type of situation, overnight recoveries are not a
concern the first night/morning. However, it does become more of a
concern on the following nights.

The good news is it also appears that the pattern should be weak
enough to allow significant north to northwest winds in the
afternoons, which should help to mitigate afternoon minimum
humidities somewhat.

-Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Fire Weather Watch from Saturday evening through Monday morning
     for ORZ619-620.

CA...None.

Pacific Coastal Waters...Gale Watch from Sunday morning through late
     Monday night for PZZ356-376.
     Small Craft Advisory until 5 AM PDT Tuesday for PZZ356-376.
     Small Craft Advisory from 11 AM Saturday to 5 AM PDT Tuesday for
     PZZ350-370.

DW/BPN