309
FXUS66 KMFR 302304
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
404 PM PDT Sun Aug 30 2026

.Aviation discussion updated...

&&

.AVIATION...31/00Z TAFs...VFR levels under clear skies persist
across northern California and southern Oregon. Gusty north winds
along the coast will ease into the evening. MVFR/IFR ceilings are
possible along the coast late tonight into early Monday morning, but
a slight easterly component to winds may limit ceiling development.
Any coastal ceilings that do develop look to clear out before Monday
afternoon. Elsewhere, VFR will continue to prevail for at least the
next 24 hours.

&&

.PREV DISCUSSION... /Issued 302 PM PDT Sun Aug 30 2026/

KEY MESSAGES...

* Dry and windy conditions are expected on Monday, bringing
  critical fire weather concerns to the Scott and Shasta Valleys
  as well as broad areas east of the Cascades. Other areas may not
  reach thresholds, but have elevated concerns for similar
  conditions.

* Tuesday marks a transition to active weather expected on
  Wednesday. A cold front will bring below seasonal temperatures
  across the area. Rainfall is expected west of the Cascades,
  with lighter showers possible to the east.

* Light scattered showers and cool conditions are expected for
  Thursday and Friday.

DISCUSSION...Zonal flow aloft behind a trough moving off to the
northwest will bring summery weather across northern California and
southern Oregon today. Coastal cities will see periods of gusty
winds this afternoon as well as chances for marine stratus to
develop overnight. North-northeast overnight winds may keep the
skies clear or reduce development.

An upper ridge passing over the area on Monday looks to raise
daytime highs about 5 degrees for most Oregon counties. Northern
Lake County may see temperatures increase by up to 10 degrees, while
Siskiyou and Modoc counties will see smaller fluctuations. In
addition to those warm and dry conditions, southerly flow will bring
gusty winds into the Scott and Shasta Valleys, northeast Siskiyou
County, Modoc County, southeast Klamath County, and southwest
Siskiyou Counties. A Red Flag Warning has been issued for these
areas as gusty winds and dry conditions reach critical levels.

Tuesday will be a transition day ahead of midweek active weather, so
forecasting may change as models get a better hold on that change.
The overall pattern has not changed; A weak shortwave trough will
swing over the area ahead of midweek activity. Temperatures look to
cool by 5 to 15 degrees for most areas, depending on the timing and
path of that shortwave. This trough may bring some initial activity
to western Siskiyou County and along the Cascades. While slight
thunderstorm chances (5-15%) remain in the forecast for these areas,
CAPE values trending lower and moisture trending marginally upward
might mean that some light showers be a part of any thunderstorms
that do develop. Those chances do linger into Tuesday night, then
ease on early Wednesday morning.

On Wednesday, a cold front from an approaching low pressure system
will bring cool temperatures and rainfall across areas west of the
Cascades as well as some rainfall to the east. The most rainfall is
expected over Curry County, with 1.0 to 1.5 inches at lower
elevations and over 2 inches possible over terrain. Coos and
northern Douglas counties as well as the Illinois Valley could see
0.75 to 1 inch of rainfall. Roseburg and westernmost Siskiyou County
could see around 0.5 inches, with 0.25 inches possible in the Rogue
Valley and northern Klamath counties. Eastern Siskiyou, southern
Klamath, and northern Lake counties may see a few hundreths of an
inch. Overall, impactful rainfall is not expected. However, as this
is the first substantial rainfall in a while, water accumulation is
possible in areas where debris blocks drainage routes. Additionally,
oils may rise to road surfaces and bring locally slick conditions.
Extra caution while traveling is advised.

For Thursday and Friday, the low pressure system lingers to the west
just off the Oregon coast and keeps a trough over the area. Cool
temperatures will continue through the end of the week. Shower
chances linger but decrease to 40-60% on Thursday and 20-40% through
Friday. The higher chances tend to stay west of the Cascades, but
southwest flow around the trough may help light showers reach Modoc
and southern Lake counties late Thursday into Friday morning.

Forecasting for next weekend is somewhat erratic, as ensemble
members show a variety of outcomes. Meteogram guidance shows light
activity continuing through the weekend. Beyond that, rain signals
are a minority (10-20% for the ECMWF ensemble, 5-10% for the GFS)
and are fairly erratic but are definitely not absent. -TAD

&&

MARINE...Updated 230 PM PDT Sunday, August 30, 2026...Gusty
northerly winds and steep seas continue across area water this
afternoon. Winds start to ease late tonight and seas fall below
advisory levels near sunrise on Monday.

An atmospheric pattern change will bring gusty southerly winds
and the possibility of light marine showers on Tuesday. Winds and
rain peak on Wednesday, with steep to very steep and hazardous
seas possible for most area waters. Southerly winds ease on
Thursday, but westerly swell may support continuing unsettled
seas. -TAD

&&

FIRE WEATHER...Updated 200 PM PDT Sunday, August 30, 2026...

A brief, but strong warming and drying trend will continue on
Monday. Winds will increase Monday afternoon as a trough approaches
from the west. Wind and humidity conditions will reach critical
levels in the Scott and Shasta valleys and east of the Cascades due
to gusty south to southwest winds and dry humidities. A Red Flag
Warning is in effect for portion of FWZ 280 (Scott Valley) and FWZs
281, 284, 285, and 624.

On Tuesday, gusty winds will again reach critical levels in that
area. But, humidities will be slightly above thresholds as
temperatures trend cooler. There will also be chances for light
showers and a 5%-15% probability of late of day thunderstorms,
especially near the Scott Valley in west-central Siskiyou County,
and in far northern Klamath County.

A trough dominated pattern will follow for the remainder of the week
with a strong cooling trend and increasing chances for rain. Gusty
winds, and a wetting rain are likely from the coast to the Cascades,
and in northern Klamath County. This will be followed by shower
chances Friday into Sunday while slightly warmer temperatures remain
below normal. The outlook for day 8-10, early next week, is for
warming and drying.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from noon to 8 PM PDT Monday for ORZ624.

CA...Red Flag Warning from noon to 8 PM PDT Monday for CAZ280-281-284-
     285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Monday
     for PZZ350-356-370-376.

&&

$$