Onion Mountain, Oregon Weather Forecast Discussion

073
FXUS66 KMFR 262116
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
216 PM PDT Fri Sep 26 2025
.DISCUSSION...Mainly sunny, dry and warm weather is expected
today through almost the entire weekend as high pressure remains
in place; Saturday will likely be the warmest day for much of
the area.
A significant pattern change then occurs Sunday night into
Monday. On Sunday, the dominant flow will become more
southwesterly as a strong upper level trough develops over the
Gulf of Alaska. We`ll probably eke out one more dry and warm day.
By late Sunday, the trough will dig south over the northeastern
Pacific, then send a cold front into the Pacific Northwest Monday,
followed by another front Tuesday, then continuing showers
Wednesday into Thursday as onshore flow persists and the trough
axis passes onshore along the Oregon and Washington coastlines. In
short, as September closes out and October arrives, it will
definitely begin feeling much more like fall.
These fronts are likely to produce gusty south to southwest
winds, below normal temperatures, and a very high chance of much-
needed wetting rainfall area wide. It will be breezy everywhere as
these fronts pass, but wind concerns will be concentrated along
our typically wind-prone areas: the coast, the Shasta Valley, the
East Side, and higher terrain, where wind gusts could peak up to
50 mph. We`ve adjusted NBM winds upward during this period to
account for local terrain-induced effects, and should trends
continue, Wind Advisories will likely be needed for the Shasta
Valley and portions of the East Side, such as in the vicinity of
Summer Lake. Meanwhile, with water vapor transport (IVT) values
forecast to be quite healthy (especially for this time of year)
and snow levels remaining well above pass levels, widespread
rainfall is expected. Preliminary rainfall of 0.50 to 1 inch is
forecast for most of the West Side, 0.25 to 0.5 inches over the
East Side, and as much as 2-3 inches along the coast, the coastal
mountains, and western Siskiyou County from Sunday night through
Tuesday night. Showers are then expected to continue Wednesday and
Thursday as the upper level trough passes overhead and onshore
flow persists.
This will be the first event of its type this season, and the
first significant front to pass through the region since early
May. As a result of this and the usual lower skill of model
guidance during seasonal transitions, confidence is lower than
normal regarding the strength and timing of the fronts and the
passage of the upper level trough. Also, with this being the first
significant wind and rain event, some additional concerns arise.
Summer-weakened trees could be more easily susceptible to damage,
blocked drainages could result in ponding of stormwater, and rain
could combine with oil/residue buildup on area roads, making them
slicker than expected. Be aware of these hazards when out and
about early next week.
The good news is, this could be a wildfire season ending event, at
least for much of the area. That being said, dry and warm periods
are still possible and have occured during October in previous
years, so only time will tell.
Models are suggesting that high pressure will return by early
next weekend, with the area drying out and temperatures warming
back up to near normal Friday into Saturday. However, those same
models show continued activity across the Pacific which could
easily mean additional systems are possible by late in the weekend
into early next week. So, changeable weather should be expected
as we transition out of summer and into fall. -BPN/Spilde
&&
.AVIATION...26/18Z TAFs...Other than a few fog patches tonight into
early tomorrow morning near the coastal valleys north of Cape Blanco
and in the vicinity of Brookings, dry high pressure will provide VFR
area wide through tonight and into Saturday morning. Gusty north
winds over the coastal waters and near the coast this afternoon and
evening will diminish tonight. -Spilde/BPN
&&
.MARINE...Updated 200 PM PDT Friday, September 26, 2025...A
thermal trough along the Oregon Coast will maintain gusty northerly
winds south of Cape Blanco today, while winds ease across the north.
This will allow for below advisory conditions north of Cape Blanco.
But, stronger winds south of the Cape will bring steep to very steep
seas. Conditions will be at least hazardous to small craft there
with localized gale gusts and warning level seas this
afternoon/evening south of Gold Beach. These conditions persist into
early Saturday morning. A transition to northwest swell starts on
Saturday morning as winds decrease, limiting steep seas to waters
south of Port Orford into Saturday afternoon.
Seas look to remain below advisory level from Saturday afternoon
through Sunday afternoon. Then, an approaching front will bring
gusty southerly winds, with steep to very steep and hazardous seas
Sunday night into Monday. Active weather with a second front Monday
night into Tuesday could include gale gusts. Winds and swell from
this second front could support hazardous wind/sea conditions
continuing into midweek. -TAD/Spilde
&&
.FIRE WEATHER...Updated 200 PM PDT Friday, September 26, 2025...
Warm and dry conditions continue today and into Saturday. Easterly
flow over area peaks and ridgelines will bring another night of
moderate to locally poor recoveries tonight into early Saturday
morning. Recoveries across the Cascades and terrain in Siskiyou
County are forecast to be only in the 25-35% range. The easterly
winds should ease somewhat later tonight as the thermal trough
weakens. We`ll maintain a headline for the dryness and elevated east
flow, but warnings aren`t necessary.
While Saturday remains warm and dry, recoveries into Sunday morning
increase. Southerly winds develop across the area Sunday, with gusty
winds developing over east side terrain and into the southern Shasta
Valley during Sunday afternoon. These winds may reach Advisory
levels. Widespread wetting rainfall is likely as a couple of strong
fronts move through the area, one late Sunday night into Monday and
another Tuesday through Tuesday night. In addition to the wind/rain,
Mon-Wed will also see higher than usual humidity and below normal
temperatures. -Spilde/TAD
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Saturday
     for PZZ356-376.
Hazardous Seas Warning until 2 AM PDT Saturday for PZZ356-376.
&&
$$

NWS MFR Office Area Forecast Discussion