053
FXUS66 KMFR 061933
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1233 PM PDT Mon Oct 6 2025

.DISCUSSION...Updated Aviation Discussion...


&&

.AVIATION...06/18Z TAFs...VFR conditions with mostly clear or clear
skies will continue across northern California and southern Oregon
today. Winds are starting to pick up this morning, and this will
continue through the afternoon. Reports of speed shear have been
coming near Medford with bumpy approaches from the south this
afternoon. Low level wind shear near 10-15 kt will be possible in
areas near the Rogue Valley (Medford) through 0-3 Z. Some locations
along ridgetops and in the Rogue Valley from Medford south will
continue seeing stronger winds tonight. Overall, lighter winds are
expected later Tuesday morning.

-DW/Hermansen

&&

.PREV DISCUSSION... /Issued 559 AM PDT Mon Oct 6 2025/

DISCUSSION...Our region is under the influence of a ridge,
sandwiched between a closed upper level low offshore from central
California and another along the coast of Alaska. After a chilly
start this morning, this will produce warming and drying today
with gusty easterly winds. These winds will be at a peak over the
mountains from the Coast Range to the Cascades early this morning,
then the late morning into early afternoon in the southern Rogue
Valley from around Ashland to Phoenix. This includes a peak east
wind gust of 33 mph recorded at 445 AM at Onion Mountain in
Josephine County, which may be matched by southeast winds in
southern Jackson County later today.

Arguably, the other most notable aspect of today`s weather will
be a Chetco Effect of downslope winds from the Coast Range, with a
high around 80 expected at Brookings this afternoon. The rest of
our coast will no be far behind with readings in the mid and upper
70s expected to be common. More broadly, widespread warming is
expected this afternoon with highs a few to a dozen degrees above
normal...in the mid 70s to upper 80s on the west side, mid 60s to
around 70 on the east side, and 50s and 60s in the mountains.

Tuesday will be more of the same with inland sites likely to reach
their peak values for the week. 80 degree values will become more
widespread. However, wind flow begins to shift towards the end of
Tuesday, so the coast should see some cooler temperatures due to
onshore flow.

By Tuesday night into Wednesday morning, a weakening cold front
will push through the forecast area. This will result in cooler
temperatures and a 15% chance of precipitation along our northern
portion of coastline near North Bend and Florence. Some locations
will see temperatures trend 10 degrees lower.

By Wednesday night into Thursday, models have an upper level low
just off the Oregon coast. Data suggests that there is a low 10 to
20% chance of precipitation Wednesday night in our region,
although ensemble members really seem to struggle where to place
it or if to produce any at all.

Eventually this low will move onshore and the chances of rain will
increase, especially for Friday into Saturday. About 70-80% of
00Z ensemble members produce rainfall in our area late in the
week, but there is still a wide range of solutions regarding
where, when, and how much rainfall to expect. This may include a
risk of thunderstorms as the trough itself moves inland, with the
highest probability centered over the east side around Saturday
afternoon.

Once the trough finally shifts inland, a scenario similar to our
most recent large trough passage may occur with the flow aloft
shifting from southerly to northwesterly and a colder, showery
start to next week.
-Smith/DW

MARINE...Updated 200 AM PDT Monday, October 6, 2025...A thermal
trough will maintain gusty north winds today through this evening,
with the highest winds and seas at 6 to 9 ft expected beyond 10 nm
from shore. This will continue a steep combination of wind wave and
fresh swell across the waters this morning, then most of the outer
waters through this evening. Specifically, all of the outer waters
south of Cape Blanco and the outer waters north of Cape Blanco
beyond 20 nm from shore.

A brief period of calmer conditions is expected late tonight into
Tuesday morning with north-northwest seas at 4 to 6 ft at 7 seconds.
North winds and steep seas likely return late Tuesday afternoon into
Wednesday before winds weaken and turn southerly Wednesday night.
The passage of a weak front is expected to bring an increase of
northwest swell dominated seas early Thursday. This brief increase
is forecast to be just shy of high and steep levels.

Southerly winds will increase Thursday night and may reach the low
end of advisory strength through Friday night as low pressure
lingers offshore. The low is expected to move inland over the
weekend with marine winds becoming northerly and increasing into
early next week. These north winds are likely to be strongest south
of Cape Blanco, and may reach advisory strength.
/BR-y/DW

FIRE WEATHER...Updated 400 AM PDT Monday, October 5, 2025...
Yesterday`s discussion is still valid, and included below. I did
want to draw special attention by reiterating a few specifics,
especially regarding winds over the area. Easterly winds over the
Coast Range and Cascades will be strongest early this morning with
peak gusts of 25 to 35 mph. Ridge top humidity recoveries will be
poorest on Tuesday morning, though with weaker easterly wind gusts
commonly expected at 15 to 20 mph. The southern end of the Rogue
Valley, from Ashland to Phoenix is expected to see southeast winds
of 10 mph with gusts to 20 mph now through Tuesday morning, except
trending up to and then back down from a three-hour-long peak of
15 to 20 mph with gusts to 30 mph between 10 AM and 1 PM today.
With fuels at moderate fire danger, (and minimum afternoon
humidity expected to be just shy of criteria besides) antecedent
conditions do not support the issuance of a Red Flag Warning.
Additionally, gusty southwest winds are expected for northern
California and south central Oregon Wednesday afternoon, then
similarly gusty, windy south winds in the same area on Thursday
with gusts of 30 mph possible for the southern Shasta Valley near
Weed. -DW

From Sunday...A thermal trough along the coast has induced offshore
(east to northeast) flow that will persist into Tuesday morning.
Gusts of 20 to 30 mph are already being observed in portions of the
Rogue River and Siskiyou National Forests and we expect things to
dry out across the landscape today through Tuesday with afternoon
humidity bottoming out in the in the 15-25% range. East winds are
expected to peak tonight over the upper slopes/ridges with gusts of
25-35 mph common, and the potential for up to 40 mph in the most
exposed areas of the Cascades. Humidity recoveries will trend lower
for Monday and (lowest) Tuesday mornings, largely remaining in the
moderate range, but could be locally poor Tuesday morning. Monday
night into Tuesday, however, east to northeast winds will be weaker,
so there is less concern for critical conditions Monday night into
Tuesday. Given that fuels have moderated substantially due to recent
wet and cool weather, and many locations have lowered the fire
danger to moderate or better, we`ll maintain a headline in the Fire
Weather Planning forecast for this easterly flow event.

Weak onshore flow returns later on Tuesday and daytime humidities
will trend somewhat higher, and recoveries Tuesday night will be
improved. But, major improvement will be limited to the coast until
Wednesday night. Gusty south to southwest winds return to the region
starting Wednesday as an upper level system moves southward just
offshore, but daytime humidities will still be trending higher.
There`s uncertainty on how far offshore this system traverses, but
there could be some light rain along the coast as early as Thursday.
While uncertainty in the details remains, confidence is increasing
for a return to cooler and wetter weather late in the week and into
the weekend. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this
     evening for PZZ370-376.

&&

$$