902
FXUS66 KMFR 111026
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
326 AM PDT Mon Aug 11 2025

.DISCUSSION...No big changes in the near term. Key message today
is the heat wave continues over the interior with high
temperatures of 100-110F for most valleys west of the Cascades
and 90-100F over the East Side. Many areas are in Extreme Heat
warnings and/or Heat advisories. Outdoor options to flee the heat
include: the coast and the mountains (your choices are limited).
Onshore winds near the coast will keep it cooler there with highs
of 60-70F at the beaches and 70-85F a few miles inland. Also, if
you`re looking for an amazing view and a place that should be
ranked WAY higher on the list of natural wonders of the world,
we`re predicting a comfortable high of 78F up at Crater Lake. A
climb up Mt. Shasta or Mt. McLoughlin might also be a good
alternative to experiencing the baking heat down at lower
altitudes. Of course, if you do set a course up into the
mountains, please make sure to carry lots of water! It`s really
dry out there and it wouldn`t take much to become dehydrated. The
heat continues for one more day tomorrow.

Then, an upper trough will swing onshore into the PacNW tomorrow
afternoon. This will result in locally gusty breezes for the west
side valleys and also for areas east of the Cascades. With
relative humidity values down around 10-15%, this will result in
elevated fire weather concerns (see fire weather section below).
We aren`t expecting any rainfall with this system (the dreaded
"dry frontal passage"). But, it will gradually lower heights along
the West Coast and set the stage for cooling back to at least near
normal levels late this week.

Speaking of late this week, models are coming in line showing a
stronger front pushing into the PacNW Friday into Saturday. This
front will almost assuredly bring wetting rainfall to western
Washington and NW Oregon (primarily areas north of us). But, we
may experience the southern reaches of this front with some shower
chances (20-40%) reaching the coast and into the Umpqua Valley.
Probabilities of rain decrease farther south and east and let`s
face it, it still is August. Fronts this time of year stand a
higher chance of falling apart than holding together this far
south. Even so, just the mention of possible showers means that
temperatures elsewhere across the region won`t be too hard to
take. We`ll see if we need to adjust shower chances any farther
south and east with time.

Beyond that, models show a strong upper ridge setting up from the
Four Corners up into Montana with the upper trough setting up over
the Gulf of Alaska/along the BC coast. We`ll be in the transition
between them with a SSW flow aloft. This will probably bring
warming again early next week and could open the door for moisture
to return from the south. That`s way out there though, so
something to keep an eye on. -Spilde

&&

.AVIATION...11/12Z TAFs...Stratus and fog are confined to the
immediate coast this morning, especially from Gold Beach
southward, though patchy fog is intermittently lowering the
visibility at North Bend. Areas of LIFR this morning will become
VFR by mid-morning, with a deeper and longer-lasting marine layer
and stratus push expected tonight into Tuesday morning. Inland,
VFR will continue with fairly typical afternoon/evening breezes.
-Spilde


&&

.MARINE...Updated 230 AM PDT Monday, August 11, 2025...Moderate
north winds will persist over most of the waters today with steep
residual northerly seas. After today, hazardous conditions should
be confined to the outer waters, due to ongoing north winds and
steep seas. A long period, secondary, southwest swell of 3 ft at
16 seconds is expected this afternoon becoming 3 ft at 14 seconds
by Thursday. Strongest north winds and steep seas shift to south
of Cape Blanco around midweek, then a period of lower seas and
weaker winds is possible late Thursday into Friday. -Spilde


&&

.FIRE WEATHER...Updated 230 AM PDT Monday, August 11, 2025...

The heat wave continues inland today through Tuesday with triple
digit heat west of the Cascades and in the 90s to near 100F over
the East Side. RH recoveries over the upper slopes/ridges are
moderate to poor this morning, generally in the 20-40% range, but
with lighter winds than previous nights. Afternoon winds will also
be lower today than they have been during the afternoons, so
other than the headline for recoveries, no RFWs are in effect for
today. That changes for Tuesday. Models are showing a weak upper
trough moving into the PacNW Tuesday afternoon/evening and this
should result in a belt of mid-level 25-30kt winds. Good mixing
should tap into some of these winds and with the lower criteria in
FWZ 624, we decided to hoist a Fire Weather Watch (2-8 pm PDT).
Expecting generally 10-20 mph SW winds Tuesday afternoon, with a
shift to WNW and gusts to 25-30 mph before subsiding Tuesday
evening. Some west side valleys will also have a couple of hours
of gusty NW winds Tuesday evening, so we did the same for FWZs
620/622. Moderate to poor RH recoveries (25-40%) can be expected
to continue for the upper slopes/ridges area wide through at least
Tuesday night/Wed morning.

There`s good agreement for upper troughing to remain over the
area through Thursday. We remain confident this will not result in
any thunderstorms, but still will be daily afternoon/evening gusty
breezes that may coincide with low relative humidities,
especially east of the Cascades. So, this will maintain an
elevated risk for fire weather conditions.

Lastly, some guidance is showing a chance of showers along and
near the coast as well as the Umpqua Basin Friday into Saturday.
Light rainfall amounts could become evident over these areas.
Thunder probabilities remain quite low (generally less than 15%),
but recent guidance has introduced a slight chance near and north
of Diamond Lake/Chemult area Saturday afternoon. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Warning until 2 AM PDT Wednesday for ORZ024-026.

     Heat Advisory until 2 AM PDT Wednesday for ORZ023-029.

     Fire Weather Watch from Tuesday afternoon through Tuesday
     evening for ORZ620-622.

     Fire Weather Watch from Tuesday afternoon through Tuesday
     evening for ORZ624.

CA...Extreme Heat Warning until 2 AM PDT Wednesday for CAZ080-081.

     Heat Advisory until 2 AM PDT Wednesday for CAZ082>085.

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

&&

$$

MAS