577
FXUS66 KMFR 041140
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
440 AM PDT Mon Aug 4 2025

.Updated Aviation Discussion.

.DISCUSSION...Satellite image shows the upper trough axis centered
west of the Cascades. At the same time radar is showing some
returns with a few isolated thunderstorms between eastern Klamath
and western Lake County. Isolated storms could linger into this
morning, then ending this afternoon as the upper trough axis moves
east of the forecast area followed by a more stable atmosphere.

After this morning, the weather will be dry for the next 7-10
days. Weak upper troughing is expected Tuesday and Wednesday which
will keep afternoon temperatures just below seasonal norms away
from the coast. Between Tuesday and Wednesday, a couple of weak
disturbances will move through that could bring a few isolated
showers in Coos and northwest Douglas County, otherwise it will
remain dry. The precipitation forecast depicted by the NBM has
been running high, too far south and inland the last couple of
days, and does not make much sense given the overall pattern
(pattern recognition), and the fact that precipitation this time
of the year based on climatology is usually hard to come by.
Additionally, none of the operational models show any
precipitation(except for the NAM which shows limited QPF in
northwest Douglas and northern Coos County. Also the majority of
the individual ensemble members suggest precipitation staying
north of the forecast area. Because of the above mentioned, pops
for Tuesday and Wednesday have been adjusted accordingly.

A stronger upper trough will drop southeast and swing through
Washington State Thursday and in it`s wake will be a developing
thermal trough along the coast and stronger upper ridging building
in from the west. This will lead to the start of much warmer
temperatures for the interior with afternoon highs getting close
to triple digits for the interior west side valleys and low 90s
east of the Cascades by the end of the week and lasting through
next weekend. The coast will remain cool, with the exception at
Brookings where the Chetco Effect could result in afternoon
temperatures in the upper 80s to low 90s Friday and Saturday.
-Petrucelli


&&

.AVIATION...04/12Z TAFs...IFR conditions in low clouds and fog are
expected at the coast and into coastal valleys from Cape Blanco
northward and Brookings southward until late this morning (17-18z).
Marine stratus has pushed inland north of the Umpqua Divide.
Ceilings at Roseburg will remain VFR, however the higher terrain
could end up partly obscured until 17z.

Otherwise, VFR conditions will continue through the TAF period. Weak
instability will bring isolated thunderstorms in portions of Lake
County this morning. -Petrucelli


&&

.MARINE...Updated 200 AM PDT Monday, August 4, 2025...Relatively
calm conditions are likely through Wednesday. A northwest swell will
increase Wednesday over the waters, but seas are expected to remain
below small craft. A thermal trough will develop Thursday and likely
persist through next weekend. This will result in increasing north
winds with moderate to strong winds likely south of Cape Blanco
along with steep wind driven seas. -Petrucelli


&&

.FIRE WEATHER...Radar image is showing isolated thunderstorms
moving northeast into portions of Lake county ahead of an upper
trough axis. Isolated storms are expected to last into the morning
hours, then as the upper trough axis shifts east of the area,
stable conditions will return with thunderstorms being a thing in
the past. Afternoon temperatures will be near or just below
seasonal norms for the interior.

Weak upper troughing sets up Tuesday and Wednesday with most, if
not all locations remaining dry. A few isolated showers are
possible in northwest Douglas and northern Coos County, but that`s
about it. Afternoon temperatures for the interior remain below
seasonal norms.

A stonger upper trough will drop southeast and swing through
Washington State Thursday. This will result in a thermal trough
developing along the coast along with warmer afternoon
temperatures for the interior. Breezy east to northeast winds will
set up near and at the ridges in southwest Oregon and western Fire
Zone 280 resulting in moderate overnight recoveries.

Stronger upper ridging builds into the area Friday through next
weekend. Meanwhile the thermal trough will remain in place. The
net result will be continued gusty east to northeast breezes near
and at the ridges in southwest Oregon and western Siskiyou County
with moderate to locally poor overnight recoveries. Temperatures
near and at the ridges at night will be warm along with warm
afternoon temperatures at Brookings and Red Mound in the
afternoons starting Friday and lasting into the weekend. At the
same time, afternoon temperatures will heat up for the interior
westside valleys with highs in the upper 90s to near triple
digits, and low 90s east of the Cascades Friday through Sunday.
-Petrucelli


&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$