902
FXUS66 KMFR 031731
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1031 AM PDT Wed Sep 3 2025

...Updated AVIATION discussion for 18Z TAFs...

.DISCUSSION...Radar is showing showers in portions of northern cal
Cascades and eastside. General movement of the showers are from east
to west as wraps around a weak upper low to the south. Isolated
showers will persist this morning, followed by isolated
thunderstorms this afternoon.

The forecast area will be sandwiched in between an upper ridge to
the east and an upper low near 137W. at the same time a weak upper
low is moving north into northern California and is expected to
slowly move north into southwest Oregon this afternoon. The net
result will be a continuation of isolated showers and afternoon and
early evening thunderstorms mainly from the Cascades east.

The upper trough will move north tonight with showers and isolated
thunderstorms ending followed by dry weather overnight tonight into
Thursday morning.

Thursday afternoon, a weak upper disturbance will rotate around the
larger upper low to the west which could trigger isolated storms
again Thursday afternoon and evening. -Petrucelli

Friday into the weekend, temperatures will trend cooler but still
remain above normal for early September (normal high for Medford
being 88 degrees). Upper level troughing will be persistent over the
eastern Pacific and we`ll see additional shortwave troughs pass
through the region through the weekend. The next is expected to
approach the region Friday, bringing the return of scattered
thunderstorm chances Friday into Saturday. It`s a bit early to try
to pinpoint details at this time, but current guidance indicates
thunderstorms possible as far west as the coast with this shortwave.
Stay tuned for updates as details become more clear.

Beyond Saturday, the parent trough over the eastern Pacific
responsible for sending these shortwaves through the area moves
closer to the West Coast. While it`s too early to say with
confidence, models generally agree on this trough moving inland
through Oregon, bringing below normal temperatures and chances of
light, but beneficial precipitation. This by no means looks like a
season ending event with the current forecast only having around a
tenth of an inch of rain in the forecast, but certainly a system to
moderate fire weather concerns. There are differences in the
guidance and ensembles on the timing of this beneficial rainfall,
with some saying early next week and others saying more towards the
middle of next week. Again, stay tuned for updates and/or changes to
the forecast as the time gets closer. /BR-y


&&

.AVIATION...03/18Z TAFs...Marine stratus remains at IFR levels this
morning. A brief period of MVFR ceilings is possible this afternoon.
with IFR to LIFR conditions expected to return this evening and
remain through the TAF period.

Inland areas remain at VFR levels under clear skies or high
ceilings. Smoke from nearby fires continue to move across the area.
While this brings the possibility of decreased visibilities to the
Medford and Klamath Falls terminals, current wind patterns are
helping to prevent impactful accumulation. Isolated to scattered
thunderstorms are possible this afternoon and evening east of the
Cascades, with chances for isolated thunderstorms over Jackson and
Siskiyou counties. These thunderstorms may bring lightning, erratic
gusty winds, and locally heavy rain showers. Activity decreases into
the evening. -TAD

&&

.MARINE...Updated 200 AM PDT Wednesday, September 3,
2025...Northerly winds will persist this week. Winds and seas will
hover at advisory levels south of Cape Blanco through tonight.
Conditions are expected to improve for the latter half of the week
as winds ease and seas lower. Winds turn westerly to southerly into
the weekend. -Petrucelli


&&

.FIRE WEATHER...Updated 200 AM PDT Wednesday, September 3, 2025...A
weak upper which is south of the area this morning with showers
rotating from east to west around the low circulation.

Instability will redevelop over portions of the area this afternoon,
with scattered thunderstorms possible yet again, but this time
mainly focused along the Cascades, the Warners, and other areas of
high terrain of the East Side.

Aside from the threat of lightning, models 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 to no rainfall.

Additionally, today will be the hottest day of the forecast period,
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.

Isolated thunderstorms are possible Thursday, again along and east
of the Cascades, as the influence from the larger upper level trough
to our west continues. Friday into Saturday, a low nears the coast
and passes onshore, resulting in cooler, more seasonable
temperatures, and additional chances for showers and thunderstorms
over inland areas Saturday. -BPN/Petrucelli


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 AM PDT this morning for ORZ617-623>625.

CA...Red Flag Warning until 8 AM PDT this morning for CAZ284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Thursday
     for PZZ356-376.

&&

$$