997
FXUS66 KMFR 312355
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
455 PM PDT Mon Aug 31 2026

...Updated the Aviation Section...

.AVIATION (00Z TAFs)...
A mix of LIFR and IFR stratus at the coast and into the coastal
valleys will thicken this evening into Tuesday morning, and there
will be a slight chance of showers or drizzle. Late this evening
into Tuesday morning, a mix of MVFR and VFR ceilings will fill in
the Umpqua Valley, including Roseburg. After 18Z, late Tuesday
morning, ceilings in these areas will lift and breaks will form in
the overcast. Areas of MVFR will linger at the coast through the day.

Elsewhere, conditions will remain VFR, with gusty westerly diurnal
evening breezes (except southerly in the Shasta Valley). During
Tuesday afternoon into the early evening, westerly breezes (except
southerly in the Shasta Valley) will be gusty again, and a few
showers (mainly light) or thunderstorms may develop between the
Coast Range and the Cascades.

&&

.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

&&


.PREV DISCUSSION... /Issued 303 PM PDT Mon Aug 31 2026/

KEY MESSAGES...

* Cool overnight temperatures may reach frost conditions on early
  Wednesday morning.

* Widespread rainfall is expected on Wednesday, with gusty winds
  expected along the coast, into the Shasta Valley, and across the
  east side.

* Rainfall looks to continue but decrease on Thursday, with
  showers becoming more intermittent towards the end of the week.
  Cool early morning temperatures may return east of the Cascades
  as well.

DISCUSSION...Warm and dry weather continues this afternoon across
northern California and southern Oregon. Southerly flow around an
approaching cutoff low is expected to bring elevated breezes t most
areas this afternoon. Wind gusts of 35 to 40 mph are already bring
observed in the Shasta Valley and over terrain east of the Cascades.
These gusty winds and ongoing dry conditions are addressed by a Red
Flag Warning for critical fire weather conditions. Even in areas
outside of the Warning, dry and breezy conditions can still bring
rapid fire growth. Please be aware of any activity that can create
sparks or ignite a fire.

The cutoff low will move over the area on Tuesday, dropping daytime
highs by 5 to 15 degrees. Gusty winds return to the Shasta Valley
and across the east side, but rising relative humidities are
preventing critical fire weather conditions. Moisture moving with
this low looks to bring slight chances for light precipitation to
coastal areas, western Siskiyou County, and along the Cascades on
Tuesday afternoon and evening. 10-20% thunderstorm chances are
present for the Siskiyous and Cascades in this time frame,
suggesting that rain showers may be a component of any thunderstorms
that do develop. Farther east, the cooler air bring by the cutoff
may reach frost conditions early Wednesday morning for some areas
east of the Cascades. Increased humidity and overnight cloud cover
may be enough insulation to prevent those temperatures, so
confidence in frost conditions occuring is moderate. Please see
NPWMFR for a complete list of communities that may be affected.

On Wednesday, a cold front attached to an approaching low pressure
system will bring temperatures 10 to 20 degrees below normal for
most areas. The front`s approach will bring gusty winds to coastal
cities, into the Shasta Valley, and to most east side areas. Areas
west of the Cascades will see rainfall, with 1.5 to 2.5 inches
forecast for Curry COunty. Coos and northern Douglas counties as
well as the Illinois Valley could see up to an inch of rain. The
Umpqua and Klamath River Valleys are forecast to see around half an
inch. Other west side areas look to be in the 0.1 to 0.3 inch range.
Lake and southern Klamath counties could see up to 0.1 inches, while
Modoc will only see a few hundreths of an inch at most for
Wednesday.

While rainfall amounts are not hazardous, the first rain after a dry
period can bring local hazards. Areas around burn scars may see
additional water runoff or debris flows. For travel along highways
42, 38, and 138 as well as around the East Evans Creek and Fielder
Mountain or any other burn scars in the area, this is a concern.
Additionally, rainfall can locally accumulate in areas with poor or
blocked drainage. Rainfall can also lift oils on roads accumulated
through summer months to the surface and create slick conditions. In
some areas, rainfall may be enough to impair visibility. Please take
extra care if traveling is necessary on Wednesday.

For Thursday and beyond, the low pressure draws closer then lingers
in the area. The low`s approach will help widespread showers
continue into Thursday. Southwest flow around the low looks to help
light showers reach Modoc and east Lake counties. For Friday and the
weekend, rainfall becomes more intermittent. With skies clearing
somewhat, frost concerns may return on early Saturday and Sunday
mornings, but that is hard to say with significant confidence this
far out. -TAD

FIRE WEATHER...Updated 1200 PM PDT Monday, August 31, 2026...

Red Flag Warning remains in effect until 8pm today for strong winds
and low RH.

Tomorrow, gusty winds will again reach critical levels for parts of
the forecast area, but humidities will be slightly above thresholds
as temperatures trend cooler. In other words, not expecting critical
fire weather conditions to be met starting tomorrow and continuing
through the rest of the week. Through this stretch of fall-like
weather, there will also be chances for light showers, especially
the Wed-Thurs timeframe where we have the highest chances and
highest rainfall amounts. That said, there is also a 10%-20%
probability of thunderstorms Tuesday afternoon, mainly for areas
near west-central Siskiyou County, but more widespread in coverage
on Thursday with slightly higher chances around 10%-30%. However,
not expecting these lightning chances to warrant any fire weather
concerns/warnings.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 PM PDT this evening for ORZ624.

     Frost Advisory from 4 AM to 8 AM PDT Wednesday for ORZ029>031.

CA...Red Flag Warning until 8 PM PDT this evening for CAZ280-281-284-
     285.

     Frost Advisory from 4 AM to 8 AM PDT Wednesday for CAZ085.

PACIFIC COASTAL WATERS...Gale Watch from late Tuesday night through
     Wednesday afternoon for PZZ350-356-370-376.

&&

$$