Wildfire in Oregon, September 18 to 30, 2023

Area Forecast Discussion
National Weather Service Medford OR
241 PM PDT Mon Sep 18 2023

.DISCUSSION...The forecast challenges continue to be shower and
thunderstorm chances in the short term, smoke movement, and colder
temperatures with a freeze east of the Cascades.

Satellite images show a broken line of cumulus clouds from around
the Trinity Alps into southeast Siskiyou County, northwest Modoc
County, and southern Lake counties. Another area of building
cumulus was across Lassen County into southern Modoc County.
A lightning ground-strike and in-the-cloud strikes were recently
detected just east of Lake County in Harney County. This region
will have a slight chance of showers and thunderstorms into this
evening. By Tuesday afternoon, any showers and thunderstorms
should be east of our forecast area.

The air quality has improved as wildfire smoke has dispersed and
has not been transported into the more populated areas of the I-5
corridor and Klamath Falls. Most areas should have decent air
quality on Tuesday. However, close to the fires there is an air
pollution advisory in effect by the Oregon DEQ for Curry and
southern Josephine counties due to smoke from the Anvil and Smith
River Complex fires. In California, much of the smoke from the
western Siskiyou County fires will move toward the south and
southeast through Tuesday. Smoke from fires in eastern Douglas
and Lane counties will continue to impact mainly northern Klamath
and Lake counties.

We should see our first widespread freeze across agricultural
areas east of the Cascades, including Klamath Falls, Lakeview, and
Alturas. There has not been a widespread freeze in this region yet
this season. Right now it looks like Friday morning could be the
coldest but freezing temperatures are possible both Thursday and
Saturday. There is more uncertainty with how much cloud cover
could be around Thursday and Friday mornings. More clouds would
mean slightly warmer temperatures that could result in lows being
near or just above freezing. Freeze watches may be issued later
for Wednesday night.

The general weather pattern is beginning to look more fall-like as
and upper low drops from British Columbia into southeast Oregon on
Thursday. This low will be associated with cooler temperatures as
well as freezing temperatures in the mountains and east of the
Cascades. A chance of showers will also be possible Thursday and
Thursday night east of the Cascades.

Over the weekend the major weather feature will be a big low in
the Gulf of Alaska. A mainly dry southwest flow will be across our
area ahead of this low. There will be a slight chance of rain for
the coast and the Umpqua Valley over the weekend. There is much
more uncertainty about how far inland the rain chances will
spread. The models differ with some showing dry conditions while
other models shows rain to the Cascades and even east of the
Cascades.
Sandler

&&

.AVIATION...18/18Z TAFs...Areas of coastal MVFR are gradually
dissipating, but will linger into this afternoon. Late tonight into
Tuesday morning, patchy IFR will return to the immediate coast north
of Cape Blanco. Also, gusty north winds are expected near the coast
this afternoon through Tuesday.

Otherwise, VFR will persist across northern California and southern
Oregon through Tuesday morning. There is a slight chance of showers
and thunderstorms this afternoon and evening for southern Siskiyou
County across Modoc County into southeast Lake County.

&&

.MARINE...Updated 200 PM September 18, 2023...A variety of
hazardous conditions are expected to affect all waters through at
least the middle of the week.

Northerly winds under a thermal trough will help to build very steep
and hazardous seas in waters south of Gold Beach and beyond 5 nm
from shore. A Small Craft Advisory and a Hazardous Seas Warning are
in place from 5 PM this evening to 5 PM Tuesday to highlight the
hazards in these areas.

Conditions will be similar from Tuesday evening through the day
Wednesday, with a broader area of expected very steep seas that
approaches the Oregon coast at Gold Beach and southward. Small Craft
and Hazardous Seas products are in place from 5 PM Tuesday to 5 PM
Wednesday to illustrate the wider area of expected hazardous
conditions. Additionally, localized areas of gale winds are possible
at and south of Gold Beach Tuesday afternoon and evening.

The thermal trough will be at its strongest Wednesday evening into
Thursday morning, with gale conditions expected south of Gold Beach
and beyond 5 nm from shore through this period while steep seas
continue in all other waters. A Gale Warning and a Small Craft
Advisory are in place from 5 PM Wednesday to 5 AM Thursday to
communicate the elevated hazards and areas expected to experience
them.

Hazardous conditions are expected to continue past Thursday morning,
but both the northwest swell and thermal trough are expected to
dissipate through the day Thursday. Short periods of steep or very
steep seas may continue into Thursday, but currently seas look to
calm Friday into the Saturday night. -TAD/DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Beach Hazards Statement until 8 PM PDT this evening for ORZ021-
     022.

     Red Flag Warning from 11 PM this evening to 11 AM PDT Tuesday
     for ORZ615-618-619.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 PM this
     afternoon to 5 AM PDT Thursday for PZZ350-356-370-376.

     Hazardous Seas Warning from 5 PM this afternoon to 5 PM PDT
     Wednesday for PZZ356-376.

     Gale Warning from 5 PM Wednesday to 5 AM PDT Thursday for PZZ356-
     376.

&&