738
FXUS66 KMFR 182122
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
222 PM PDT Tue Aug 18 2026

.KEY MESSAGES...

* Dry weather is expected for inland areas through Thursday with
  above normal warmth and fairly typical afternoon breezes.

* Nightly marine pushes will bring cooler air and stratus to the
  coast, and also a chance of drizzle.

* Offshore low pressure brings heightened fire weather concerns
  Friday with gusty winds and at least a slight chance of
  thunderstorms.

* Breezy winds continue Saturday with a slight cool down.

* Dry, warmer weather returns Sunday/Monday.

&&

.DISCUSSION...Upper ridging will amplify a bit over the area
through Thursday resulting in above average warmth for inland
areas (NWS HeatRisk tops out as minor with pockets of moderate,
especially in the typically hotter valleys). Despite the elevated
risk, this type of heat is common for late August and primarily
impacts those who have heat sensitivities or lack adequate
cooling/hydration systems). Even so, this will be a hotter
period, so try to find ways to keep cool and stay hydrated. Expect
highs in the mid to upper 90s for the west side valleys south of
the Umpqua Divide with even some triple digit readings in the
lower Klamath river valley of western Siskiyou County. East side
locations and the Umpqua Basin will have highs in the upper 80s
and lower 90s. Nightly marine pushes will continue at the coast
bringing periods of low stratus/fog and even a chance of drizzle
at times. From around Port Orford to Gold Beach, it should stay
comparatively clear due to a slight offshore wind component.
Coastal areas will have highs in the 60s/low 70s.

A closed low well offshore will get a kick north-northeastward
Friday into Saturday as it gets absorbed into the westerlies.
At the very least, this will bring an increase in W-SW winds
in NorCal and from the Cascades eastward and NW winds in the west
side valleys Friday. Models continue to differ on timing,
strength and position of the low as it moves northeastward across
the PacNW. And, this has some impact on the forecast - especially
thunderstorm chances. Will the low be close enough to the coast so
that forcing is better or far enough offshore that most of the
forcing stays offshore or to our north? There should at least be
some moisture and instability available due to SSW flow aloft. So,
there`s a slight chance of showers and thunderstorms Friday
afternoon/evening, but the best chances at this time are up across
the north (easternmost Douglas, northernmost Klamath/Lake
counties). The associated upper trough should swing through on
Saturday. By then, most of the moisture will lift to the north
(mentionable PoPs stay north), but gusty afternoon/evening W-NW
breezes could persist. Either way, we should see a cooling trend
Fri/Sat compared to the mid week warmth.

It should dry out and turn warmer again Sunday/Monday with the
flow aloft turning more into the south Monday into mid next week.
This could increase chances for t-storms again, but it`s only a
low chance at this time (5-10%). -Spilde


&&

.AVIATION...18/18Z TAFs...Satellite imagery shows stubborn
marine stratus along the coast north of Cape Blanco, including
at North Bend and south of Pistol River, including at Brookings.
This is resulting in IFR ceilings currently at North Bend and LIFR
ceilings/fog at Brookings. Sandwiched in between is an area of
VFR (Gold Beach to Port Orford) due to a more offshore wind
component. Where the lower conditions are currently, we expect
conditions to improve somewhat this afternoon with some areas
scattering out to VFR around 21Z, but this will be short-lived. We
expect IFR/LIFR conditions to redevelop this evening and continue
overnight into Wednesday morning.

Inland, mainly VFR is expected through Wednesday morning with
just some high and mid level clouds. -Spilde


&&

.MARINE...Updated 230 PM PDT Tuesday, August 18, 2026...Gusty north
winds and steep seas, highest during the afternoons and evenings are
expected south of Cape Blanco through Wednesday evening. Conditions
are expected to improve Thursday and Friday. A thermal trough will
redevelop along the coast this weekend bringing a return of strong
north winds and steep seas. Once again, strongest winds and highest
seas are most likely south of Cape Blanco. -Spilde


&&

.FIRE WEATHER...Updated 130 PM PDT Tuesday, August 18, 2026...Aside
from some enhanced afternoon breezes today, fire weather concerns
will remain fairly standard for this time of year through Wednesday.
Expect typical summer conditions with dry weather across the area
and nightly marine pushes along the coast. Temperatures will trend
upward today through Thursday, resulting in a downward trend in
afternoon RHs. Overall, recoveries will remain in the moderate to
good range, though poor to moderate recoveries are expected along
and east of the Warners as well as the Salmon Mountains in western
Siskiyou County through Friday morning.

Thursday will be a transition day into a pattern that brings some
heightened fire weather concerns. A stronger upper level trough,
currently spinning out beyond 140 W, will gradually move eastward
this week, moving inside of 130 W by Thursday. This will start a
period of increased winds that will likely persist through Saturday
as this low pressure gradually moves inland into the PacNW through
the weekend. Gusty winds are expected to develop Thursday afternoon
as the trough nudges closer, and this could overlap with low RHs in
portions of northern California and east of the Cascades, possibly
resulting in critical conditions on Thursday.

There is some uncertainty regarding just how strong winds get and
this could be the limiting factor on Thursday. There are subtle
differences in the model guidance on how close to shore that low
pressure is on Thursday, which will be a player in how strong winds
are. Gusts 15 to 25 mph will be common across the region, but if the
closer to shore solutions are correct, the windiest locations
(Shasta Valley/East Side) could see gusts of 25-30 mph on Thursday.
Confidence is higher for winds to peak on Friday (gusts 25-35 mph),
but the limiting factor for critical conditions could be the uptick
in daytime humidities expected Friday as temperatures trend cooler.

In addition to winds/RH concerns for Friday, mid-level moisture
increases Thursday and Friday, raising the concern for thunderstorms
potential. Current guidance indicates that the best chance for storm
development would be along the Cascades from Crater Lake northward
and across northern Klamath/Lake Counties. With the approach of the
trough Thursday night into Friday, we`re monitoring the potential
for any nocturnal convection, but current guidance is steering clear
of that for now.

Heading into Saturday, models differ a bit on how fast that trough
moves through the region, but confidence is fairly good that the
thunderstorm threat will shift north of the area. The question that
lingers from these differing solutions is how strong will winds be
on Saturday, especially east of the Cascades. While it`s likely to
be another breezy day, most areas should see weaker winds on
Saturday compared to Friday. Some solutions would maintain another
day of stronger winds across the Modoc Plateau and east of the
Warner Mountains. Regardless, daytime RHs look similar to what`s
expected Friday, so again, that could be limiting factor for
critical conditions on Saturday. Stay tuned for updates. /BR-y


&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT
     Wednesday for PZZ356-376.

&&

$$

MAS/BR-y