498
FXUS66 KMFR 021021
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
321 AM PDT Tue Sep 2 2025

.UPDATE...Aviation Discussion updated.

&&

.AVIATION...02/06Z TAFs...IFR and LIFR conditions will continue
along the coast through this morning, then clear back to the near-
shore waters by early this afternoon. IFR and MVFR conditions
will return in the evening to coastal areas.

Inland, moisture moving into the area from the south and southeast
this afternoon/evening will lead to isolated to scattered
thunderstorms. For area terminals, the best probability for a
thunderstorm (25%) is at Klamath Falls, but one could occur at
Medford/Roseburg too (10-15% chance). There is a low chance (10%)
for storms to drift westward over Coos County, including North Bend,
during evening. Then, expect some lingering isolated thunderstorms
Tuesday night across the area.

Smoke from area wildfires isn`t expected to result in lower flight
conditions for most locations, except in the immediate vicinity or
just downwind from wildfires, but brief periods of lower visibility
and/or haze are possible.

&&

.PREV DISCUSSION... /Issued 316 AM PDT Tue Sep 2 2025/

DISCUSSION...A strong high pressure ridge will be over the
region today and Wednesday resulting in hot temperatures across
inland areas. High temperatures are expected to be in the upper
90s to low 100s for valleys west of the Cascades and in the 90s
east of the Cascades.

Meanwhile, an upper level disturbance will near the area today
then track south to north across the area tonight, before shifting
northward on Wednesday. This will bring chances 20-30% for
thunderstorms from the Cascades east with a 10-25% chance for
storms west of the Cascades, including across portions western
Siskiyou, Josephine, Jackson, and Douglas counties. There is also a
low chance (10%) for storms to push westward into Coos county
this evening under easterly steering winds. Lingering chances
(10-20%) for thunderstorms are expected overnight. Of note with
these storms, strong, gusty outflow winds (35-50 mph) are
possible with thunderstorms today and tonight, as models continue
to show high cloud bases and a dry subcloud layer with storms.
Additionally, lighting will bring the potential for new fire
starts.

On Wednesday, models indicate a potential for weak disturbances
to move into the area from the south. This will bring continued
chances (10-25%) for thunderstorms, mainly for the southern Oregon
Cascades and areas east of the Cascades in Klamath, Lake, Modoc
and eastern Siskiyou counties.

Thursday and Friday, an upper low/trough will approach the
southern Oregon coast from the west. This will bring southerly
flow aloft. Under this pattern, expect temperatures to gradually
trend less hot with highs lowering slightly (1-2 degrees) on
Thursday then lowering another 3-5 degrees on Friday. High
temperatures on Friday will still be above normal though, with
afternoon temperatures reaching the upper 80s to mid 90s for
valleys west of the Cascades and in the mid to upper 80s east of
the Cascades. Additionally, as the low approaches the coast,
models show upper level disturbances rotating around the low and
into the area. This is expected to bring chances (10-25%) for
thunderstorms and showers to central and eastern portions of the
area, mainly from the Cascade east with lower chances (5-10%) for
storms west of the Cascades. Light drizzle or showers are also
possible along the coast Thursday night and Friday morning, with
light onshore flow.

Friday night and Saturday, models and ensembles indicate this
weak low/trough will move northward along the coast. This will
allow temperatures to trend cooler, near seasonal norms,  but
also will bring additional chances (10-25%) for showers and
thunderstorms. These chances are mainly from the Southern Oregon
Cascades east but, depending on the position of the low, cannot
rule out storms west of the Southern Oregon Cascades or into
Northern California.

Smoke from area wildfires will continue to be a concern this week.
For today into Wednesday, HRRR continues to show the highest
impacts from smoke across Klamath County and western/central
Siskiyou County. However, periods of smoke are also expected
across Josephine, Jackson and Douglas counties. Depending on the
amount of active burning and smoke from the Dads Creek fire in
southwest Douglas County, a plume of significant smoke impacts may
move into northeast Josephine and Jackson counties during the
evening today. This general pattern is expected to continue at
least into Wednesday. The Oregon Department of Environmental
Quality maintains an Air Quality Alert for Klamath County that is
in effect through at least Tuesday morning.


MARINE...Updated 200 AM PDT Tuesday, September 2,
2025...Northerly winds will persist this week. Winds and seas will
hover at advisory levels south of Cape Blanco through Wednesday
evening. Conditions are expected to improve for the latter half
of the week as winds ease and seas lower.

FIRE WEATHER...Updated 200 PM PDT Monday, September 1,
2025...The upper level ridge over the area will continue to
strengthen today and Wednesday with hotter temperatures expected.
Additionally, models continue to show an upper level disturbance
moving up from the south towards the area this afternoon then
moving northward across the area tonight. Confidence is
increasing in chances (15- 30%) for isolated to scattered
thunderstorms to develop from the Cascades east and Siskiyous
south Tuesday afternoon and evening, and isolated storms could
move into Josephine, Jackson and eastern/northern Douglas
counties in the late afternoon and evening. Then, with easterly
steering flow, there is a low (10-15%) chance that storms may
drift westward into western Douglas and Coos counties this
evening.

A Red Flag Warning remains in effect for Fire Weather Zones 280,
281, 284, 285, 617, 621, 623, 624, and 625 due to the potential
for abundant lightning on dry fuels. Model soundings show a very
dry low layer (inverted "V" sounding), which means storms that do
form will likely produce strong, gusty and erratic outflow winds
(35-50 mph) and may produce little rainfall.

As the disturbance slowly shifts northward over the area Tuesday
night, there are chances for lingering overnight showers and
thunderstorms (15-20%), mainly from the Cascades east and over
northern/eastern Douglas County. With east to southeasterly
steering winds, storms may drift into central/western Douglas and
Coos counties (10% chance) as well overnight.

Additionally, today and Wednesday will be the hottest days of the
week, and with dry low level humidities and breezy afternoon
winds, we may see some locations approach but not quite pass
critical thresholds. The hot temperatures, dry RH, breezy
afternoon winds, and overall instability will add to the already
heightened fire weather concerns due to lightning.

On Wednesday, there is better agreement with the ensembles that
the disturbance will shift north of the area into central/northern
Oregon. However, additional weaker disturbances moving up from the
south will bring thunderstorm chances (10-25%) in our area,
mainly from the Cascades east, Wednesday afternoon and evening.

Thursday and Friday, temperatures trend slightly less hot as a low
approaches from the west. This will also bring the potential for
additional disturbances, rotating around the low, to move into
the area Thursday and Friday. This will bring continued chances
for thunderstorms to the area, mainly from the Cascades east. Late
Friday into Saturday, a low nears the coast and will allow
temperatures to trend cooler abut expect additional chances for
showers and thunderstorms over inland areas on Saturday.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening for ORZ617-621-623>625.

CA...Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening for CAZ280-281-284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT
     Wednesday for PZZ356-376.

&&

$$

CC/CC/CC