766
FXUS66 KMFR 181432
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
732 AM PDT Sat Jul 18 2026

.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.

* Conditions late next week are indicated to bear some resemblance
  to those from the past couple of days, with a dry and slightly
  cooler forecast, accompanied by enhanced afternoon winds that
  would be strongest east of the Cascades.

&&

.DISCUSSION...The upper level trough that has been offshore over
the past few days will track northeast into British Columbia
today. This will be just enough to relax pressure gradients
slightly, but breezy to windy afternoon and evening winds will
again be stronger than normal today. Humidity levels, though not
quite as extreme as yesterday, will also again be much drier than
normal. High pressure will build in Sunday and continue the
warming trend while further weakening pressure gradients. As such,
our weather for the rest of the weekend will resemble that of the
past couple of days.

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 also
mainly virga. 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.

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...18/12Z TAFs...Gusty winds will develop again this
afternoon, strongest along the coast, in the Shasta Valley and east
of the Cascades.

VFR skies will prevail across most of the
area 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.

The other exception will be marine stratus along the coast and
offshore as LIFR and IFR ceilings and visibilities persist into mid-
morning. By this afternoon, VFR conditions will return to coastal
locations.

&&

.MARINE...Updated 200 AM PDT Saturday, July 18, 2026...Gusty north
winds are maintaining steep seas south of Cape Blanco, before steep
seas spread to all waters late this morning. As north winds maintain
a lengthy peak this afternoon through Sunday evening, very steep
seas will develop south of Port Orford. Conditions gradually improve
on Monday with steep seas likely as dominant wind waves transition
to fresh swell. Further improvement follows Tuesday into Wednesday
as low pressure moves up from the south late Tuesday and Wednesday.
This low may remain well offshore and weaken as it moves north.

&&

.FIRE WEATHER...Updated 200 AM PDT Saturday, July 18, 2026...
The main update this morning is some further clarity on an
expectation of weak instability with a modest risk of thunderstorms
on Monday afternoon, as well as a heightened risk for more
signficant coverage and strength of thunderstorms on Tuesday and
Wednesday afternoons.

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 the weekend 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
thundertorms on Tuesday and Wednesday.

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 from 11 AM this morning
     to 11 PM PDT Sunday for PZZ350-356-370-376.

Hazardous Seas Warning from 5 PM this afternoon to 11 PM PDT
     Sunday for PZZ356-376.

&&

$$