325
FXUS66 KMFR 182248
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
348 PM PDT Sat Jul 18 2026

...Updated Aviation Discussion...

.KEY MESSAGES...

* Fire weather conditions this afternoon and evening just shy of
  critical thresholds of wind and humidity in much the same portions
  of the area that did reach those levels yesterday. This
  includes the Shasta Valley, eastern Siskiyou, Modoc, southeast
  Klamath and southwest Lake Counties.

* Hot, very dry, breezy, and unstable conditions will continue
  this weekend.

* Smoke will persist for Jackson, Klamath, and Siskiyou counties
  through the weekend, with some temporary afternoon into early
  evening improvement expected for Klamath and Siskiyou counties.
  Also, an influx of smoke into Lake County from fires in central
  Oregon.

* Thunderstorms re-enter the forecast beginning as early as
  Monday, mainly for the Cascades and east side. The highest risk
  will be on Tuesday and Wednesday, including lesser chances for
  areas west of the Cascades.


&&

.DISCUSSION...The general weather pattern will continue again this
afternoon with warm, dry, breezy, and unstable conditions across
southern Oregon and northern California. Satellite imagery is
showing some coastal stratus dissipating near Brookings. A few
cumulus are being observed northeast of Crater Lake and across the
Warners eastward in Modoc and Lake Counties. There is some smoke
from the East Evans Creek Fire funneling into the Rogue Valley.
While there may be some brief improvement this afternoon, expect
smoke to return again this evening. Sunday will be generally a
repeat of today with weaker winds.

By Sunday night and continuing into Monday, a plume of monsoonal
moisture aloft will bring high clouds into the area. This could
generate a few showers, mainly over the higher terrain, but most
of any showers would evaporate before reaching the ground. Weak
instability on Monday afternoon is expected to generate a few
thunderstorms with a focus on the Cascades into northern Klamath
County.

On Tuesday into Wednesday, southerly flow aloft is expected
between a trough offshore tracking northward and the persistent
ridge over the Great Basin. There is more uncertainty in the
convective forecast. But also, more potential for a significant
amount of thunderstorms as well as a potential for activity on the
west side. A larger portion of the suite of ensemble members does
indicate a majority of activity from the Cascades eastward and
isolated rather than scattered coverage. It would be of note that
the storms could be mixed wet and dry on Monday, but trend wetter
over time. Precipitable Waters would be around 200% of normal, and
this could cause some significant rain in thunderstorms.

Model uncertainty increases another notch on Thursday, but the
region of instability is likely to shift east-northeastward. This
could bring another day of thunderstorm activity to the east side,
or shift the activity east and northeast out of area.

For Friday into Saturday, the pattern has some resemblance to the
current picture. This would result in a dry forecast, but a slow
moving dry front would also produce enhanced afternoon and evening
winds, strongest on the east side.


&&

.AVIATION...19/00Z TAFs...Gusty winds will continue through early
this evening, strongest along the coast, in the Shasta Valley and
east of the Cascades.

VFR will prevail across inland areas through the TAF period. One
exception will be impacts from wildfire smoke that will bring
periods of MVFR visibilities and/or ceilings to the Rogue Valley,
Klamath Basin, and Shasta Valley including Medford, Klamath Falls,
and Montague. Smoke from central Oregon fires will also impact Lake
County, including Lakeview.

Along the coast, IFR/LIFR ceilings and visibilities are expected to
develop (beginning around 05-08z) with marine stratus late this
evening and overnight, persisting through late Sunday morning.
This will mainly affect areas from Cape Blanco northward and from
Brookings south.


&&

.MARINE...Updated 200 PM PDT Saturday, July 18, 2026...Gusty north
winds will continue with steep seas to very steep seas through
Sunday evening. Strongest winds and very steep seas are expected
from Port Orford south beyond 5 nm from shore. Steep, short period
seas and areas of gusty winds will linger across the waters Sunday
night into Monday. Seas will transition on Monday from wave
dominated to fresh swell. Conditions gradually improve late Monday
and Monday night. Further improvement follows Tuesday into
Wednesday. Low pressure may move up from the south late Tuesday and
Wednesday but is expected to remain well offshore.

&&

.FIRE WEATHER...Updated 200 PM PDT Saturday, July 18, 2026...

The three main aspects of the fire weather forecast for the next
week are: first, the extent of hot, dry, and breezy/windy conditions
today through Sunday, second, the potential risk and coverage of
thunderstorms while inland temperatures remain above normal during
Monday through Thursday, and lastly, a likely transition to dry and
slightly cooler weather late next week that would likely be
accompanied by stronger than normal east side westerly winds.

The forecast through Sunday is consistent and pretty straight-
forward. Hot temperatures at 5 to 10 degrees above normal will
continue to trend slightly upward, humidities will remain
significantly drier than normal, and breezy afternoon winds will
trend just slightly weaker today than yesterday, before returning to
typical strength for Sunday afternoon. The slight moistening of the
air mass on Sunday will be accompanied by a late day increase of
high clouds, and perhaps some east side cumulus buildups.

Instability could develop as early as late Sunday night into Monday
morning, with a few very light showers or virga possible over the
higher terrain. A slight chance risk of thunderstorms is expected
Monday afternoon, with the highest probability of thunderstorms over
the Cascades. Then, on Tuesday and Wednesday, there is a greater
uncertainty regarding the area of focus, but also a greater concern
that both a significant amount of lightning may develop and coverage
may include the west side...east of the Coast Range. For now, the
NBM forecast is utilized with a slight chance of mainly east side
thunderstorms on Tuesday and Wednesday. Also to be mentioned is
that there is the possibility that with the modified tropical
moisture influx in addition to the monsoonal influx of moisture,
these storms will become wetter over time.

Late in the week (Thursday/Friday), some eastward movement in the
pattern is likely, which is likely to shift the region of
instability east of our area. But, a plausible, slower solution
would keep instability and some slight thunderstorm risk over
eastern portions of Lake and Modoc counties.


&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT Monday
     for PZZ350-356-370-376.

Hazardous Seas Warning until 11 PM PDT Sunday for PZZ356-376.

&&

$$