Wildfire in Oregon, October 1 to 21, 2021

Area Forecast Discussion
National Weather Service Medford OR
800 PM PDT Thu Sep 30 2021

.DISCUSSION...01/00Z NAM in.

A weak front that moved onshore this afternoon and evening is
weakening as it sags southeast through the Medford forecast area.
What's left of it will clear to the east of the area Friday.

Precipitation will be light with this front and mostly limited to
a slight chance of rain or drizzle along the coast, the Umpqua
Basin, and the adjacent Cascades. Enough moisture may also bank up
against the Siskiyous for a slight chance of drizzle late
tonight into Friday morning. So far, a few RAWS in the Umpqua
Basin have recorded 0.01 inches of rain. Nothing has been
measured anywhere else yet.

Behind the front tonight, north to northeast winds will increase
over the upper slopes/ridges of southwest Oregon and western
Siskiyou County, with gusts in the 20-30 mph range. Winds will
increase the coast and offshore waters as well. Breezy north to
northeast winds will also develop in the Umpqua Valley and the
Illinois Valley.

It will remain windy into Saturday morning with dry conditions
prevailing after the drizzle dissipates Friday morning. High
temperatures on Friday will be a degree or two cooler than the
Thursday highs over most of the area, although northern California
locations may warm a degree or two.

An upper ridge will build into the area Friday night and weaken
Monday. This will make for warm and dry conditions Saturday
through Monday. Highs will be around five degrees above normal
along the coast and over the Umpqua Basin, and around ten degrees
above normal over the rest of the area.

Extended discussion from the Thursday afternoon AFD...Tuesday 5
Oct through Friday 8 Oct 2021...Guidance continues to advertise a
pattern shift to cooler, windier and wetter weather. Model
clusters and ensembles are steadfast in showing an upper trough
developing near the coast of British Columbia by Tuesday with an
offshore cold front approaching the coast. Rain chances increase
at the coast then, but many areas inland still probably stay dry.
The initial front likely pushes onshore Tuesday night into
Wednesday, but we're still not sure how strong it will be and how
much precipitation will make it inland. Right now, it doesn't look
like an overly wet front. Overall, confidence in the change to
cooler is high, since there should be some progression of the
trough eastward toward the end of next week and the expected
lowering of heights will result in the widespread cool down.
However, there is still plenty of uncertainty in just how the
trough evolves and how much precipitation there will be. With the
latest data suggesting the trough could split with some energy
pulling south and west offshore of California and a general
northwest flow aloft developing late next week, confidence in
precipitation is not as high. There is still plenty of time
between now and then to sort out the details. -Spilde

&&

.AVIATION...01/00Z TAFs...Along the coast and just offshore, a
mix of MVFR/VFR ceilings will continue to lift through this evening
as a front moves onshore. Tonight, ceilings are expected to lower
south of Cape Blanco behind the front, becoming MVFR between 6-8z.
Ceilings north of Cape Blanco could hover close to IFR, around a 30%
chance of occuring.

Inland west of the Cascades, the aforementioned front will result in
increasing onshore flow with marine stratus forming in the Coquille
and Umpqua Basin with MVFR ceilings at Roseburg overnight.
Confidence is low that IFR ceilings will develop. Clouds are
expected to bank up towards the Umpqua Divide and possibly spill
into the Illinois Valley. The chance that marine stratus could also
slip into the Rogue Valley late tonight is around 25%. Ceilings at
Medford will remain VFR, but surrounding hills and mountains will be
partly obscured.

East of the Cascades, VFR ceilings will continue through the TAF
period, but watch for partial mountain obscurations west of Klamath
Falls towards the Cascades around 12z. -Petrucelli/Miles

&&

.MARINE...Updated 730 PM PDT Thursday 30 September 2021...North
winds will increase tonight as a thermal trough develops and
strengthens behind a cold front. Moderate to strong winds are
expected from tonight into into Saturday morning which will result
in steep wind driven seas that are likely to result in Hazardous
Warning Seas conditions. Northwest swell will also increase some
which will add some to the total sea height. The strongest winds and
steepest seas are expected to be south of Port Orford initially
tonight, then expanding north west of Bandon Friday morning and
lasting into Saturday morning. As a result, have upgraded the
Hazardous Seas Watch to a warning which will include the southern
part of marine zone 370. Could not rule out brief gales south of
Gold beach and between 10 and 30 nm from shore during the same time
period, but confidence was not high enough to issue a Gale Warning.

Winds and seas will gradually diminish late Saturday morning through
Saturday night, but small Craft conditions are expected to continue
from Bandon south. Conditions should gradually improve from Sunday
into the start of next week. -Petrucelli/Miles

&&

.FIRE WEATHER...Updated 800 PM PDT Thursday 30 September 2021...
A weak and mostly dry cold front will bring a slight chance of
rain into Friday morning to the west side north of the Umpqua
divide, with a strong marine push spilling over the Siskiyous
before it moves through Friday. From late tonight into Saturday
morning northeast winds will increase on the southern coastal
ranges and western Siskiyou county with moderate overnight
recoveries. Unseasonably dry conditions with above normal
temperatures are expected Saturday through Monday, then a cooler
and wetter pattern will develop over the area for the remainder of
next week.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.

Pacific Coastal Waters...
     Small Craft Advisory until 5 AM PDT Sunday for
        PZZ350-356-370-376.
     Hazardous Seas Warning from 11 PM this evening to 11 AM PDT
        Saturday for PZZ356-370-376.

15/15/05