117
FXUS66 KMFR 100950
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
250 AM PDT Sun Aug 10 2025

.DISCUSSION...A surface thermal trough is analyzed along the coast
this morning. This led to strong offshore flow yesterday and a
significant "Chetco Effect" which sent temperatures past the
100-degree mark all the way to the beaches along the south coast
around Brookings/Harbor. The temperature sensor at Brookings
Airport failed yesterday around midday (go figure), so we don`t
have an official measurement from there, but the agrimet station
closer to the coast (BRKO) hit 101F. A few citizen weather
stations up river were in the 100-105F range.

Today, the thermal trough will weaken and move inland. Offshore
ENE winds are still blowing up on the coast range ridges. Red
Mound RAWS was still 80F at this early hour with RH<30% and gusts
in the 20-30 mph range. These winds will ease and we expect
onshore flow to resume at the coast around midday. This makes the
temperature forecast down there a little more difficult today.
Some places just inland will still have highs in the 80s/90s, but
overall, the warming effect will be cut off at the beaches and
marine air should win out with temps around more typical levels
(60s/70s) this afternoon.

Marine stratus filled into the coast north of Cape Blanco last
evening and will impact those areas this morning. These should
peel back offshore by late morning yielding sunny skies.

With the thermal trough moving inland, we expect the heat to
build over the interior today and Monday. Heat advisories and
Extreme Heat warnings are in effect with high temperatures area
wide in the 95-105F range (even some places topping out at
105-110F). So, please be sure to stay hydrated as best you can the
next few days, take frequent breaks if out during the hottest
part of the day and find ways to cool off -- in air conditioned
buildings, pools, shaded areas, misters, sprinklers, lakes,
anything that provides relief from the heat! Latest guidance shows
Tuesday will be hot as well, maybe a few degrees lower west of
the Cascades, but equally as hot over the east side. We extended
the Heat advisories in the Mt. Shasta region and east of the
Cascades to match the end time of late Tuesday evening (2 am PDT
Wed to be specific) for all heat products. Models show a weak
upper trough moving onshore Tuesday afternoon/evening. This won`t
produce any precipitation, but could bring an increase in westerly
breezes. That, combined with low RH values could lead to
heightened fire weather concerns.

Wednesday through Friday, the upper pattern across the PacNW
favors upper troughing as the strong upper ridge over the Pacific
Ocean retrogrades westward. As a result, temperatures should cool
back to levels more typical for mid-August. Recent model guidance
is showing some variability in the strength of the upper trough
across NW Canada and the NE Pacific. The ECMWF ensemble guidance
is on the stronger side of the guidance. Some members are now
showing a stronger frontal system approaching the NW coast toward
the end of the week, which, if correct, would result in some
shower chances entering the forecast, especially near the coast.
The GEFS ensembles are still weaker with the vast majority
maintaining a dry forecast. We`ll keep an eye on this and adjust
as necessary. With the upper trough nearby, we should expect
temperatures to continue to be near to below normal with perhaps
some gustier breezes east of the Cascades into next weekend.
-Spilde

&&

.AVIATION...10/12Z TAFs...LIFR is present near shore from Cape
Blanco northward. This will continue this morning, but will
dissipate and become VFR after 16Z. North winds will strengthen
again near the coast this afternoon (gusts of 25-30 kt). LIFR is
expected to surge back to the coast early this evening into Monday
morning. Inland, VFR will continue with fairly typical breezes
this afternoon/evening breezes. -Spilde

&&

.MARINE...Updated 230 AM PDT Sunday, August 10, 2025...A thermal
trough will weaken and move inland today. Even so, expect
moderate north winds and steep to very steep, hazardous seas
to continue, gradually subsiding on Monday. Beyond Monday,
hazardous conditions should be confined to the outer waters.
-Spilde

&&

.FIRE WEATHER...Updated 230 AM PDT Sunday, August 10, 2025...ENE
winds gusting 20-30 mph with RH<30% continue over the coast ranges
(Red Mound RAWS) of FWZ 618 this morning. The Red Flag warning is
out until 9 am PDT, but winds should ease as the thermal trough
weakens and moves inland this morning. RH recoveries are moderate
to poor over the upper slopes/ridges west of the Cascades.

Today and Monday, offshore flow at the coast will get cut off as
the thermal trough shifts inland over the interior. Afternoon
winds should ease for the west side valleys. Expect very hot temps
with triple digits west of the Cascades and in the 90s over the
east side, though coastal areas south of Blanco will begin to cool
off. Relative humidities will still be low in the afternoons
(10-15%) and 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 develop over the
area mid-late week. We are pretty confident this will not result
in any thunderstorms, but the tradeoff will be increasing winds,
and low relative humidities, especially east of the Cascades. At
this time, it`s too early to say with much confidence if critical
conditions will be met, but it will be something we`ll keep a
close watch on as conditions will be at least elevated. Some
guidance is showing a chance of showers along the coast Fri or
Sat. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Warning from 8 AM this morning to 2 AM PDT
     Wednesday for ORZ024-026.

     Heat Advisory from 8 AM this morning to 2 AM PDT Wednesday for
     ORZ023-029.

     Red Flag Warning until 9 AM PDT this morning for ORZ618.

CA...Extreme Heat Warning from 8 AM this morning to 2 AM PDT
     Wednesday for CAZ080-081.

     Heat Advisory from 8 AM this morning to 2 AM PDT Wednesday for
     CAZ082>085.

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

     Hazardous Seas Warning until 8 PM PDT this evening for PZZ356-
     376.

     Gale Warning until 5 AM PDT early this morning for PZZ376.

&&

$$

MAS