245
FXUS66 KMFR 132351
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
451 PM PDT Wed Aug 13 2025

.DISCUSSION...A low pressure system developing in the Gulf of Alaska
has flattened an upper ridge that brought hazardous heat in the past
few days allowing a weak trough to settle over northern California
and southern Oregon. Daytime highs remain above seasonal averages
today, so individuals who are every sensitive to hear may still want
to be cautious if going outdoors. Instability moving with the upper
flow will increase afternoon breezes. Considering ongoing low
humidities, these dry and breeze conditions are brining elevated
fire weather concerns. Please see the Fire Weather discussion below
for more details.

Daytime high temperatures cool to seasonal levels on Thursday, with
breezy afternoon winds returning. On Friday, a weak front will
approach the area. This front, along with precipitable water values
of 1.5 to 1.8 inches for west side areas, is supporting rain shower
chances from Friday afternoon into Saturday evening. Post-frontal
showers may continue in some areas on Sunday. Given how weak the
front is and the lack of stronger forcing methods, rainfall amounts
remain unimpactful. Coastal areas north of Gold Beach could see
between 0.1 and 0.3 inches of rainfall through Saturday evening.
Higher elevation inland areas could see rainfall amounts measured in
the hundreths of an inch. Lower elevation areas (Rogue Valley,
Klamath Basin) or easternmost areas (Modoc, eastern Lake counties)
could see few to no rain showers. There are slight chances (15%) for
embedded thunderstorms east of the Cascades on Saturday afternoon,
and slightly higher chances (15-20%) for thunderstorms on Sunday
afternoon. Atmospheric moisture will be available, but the forcing
for thunderstorms is questionable. Confidence in any development
is moderate to low right now, but more detailed information will
be come available as the weekend approaches. Temperatures remain
below seasonal averages through the weekend.

Upper flow turns southwesterly to start next week, between the low
pressure system remaining in the Gulf of Alaska and high pressure
over the Four Corners area. Long-term meteograms for both the
ECMWF and GFS models show only the slightest hints of additional
activity for North Bend while inland areas are forecast to remain
dry. Temperature meteograms for Medford stay at seasonable daytime
highs through much of August. -TAD


&&

.AVIATION...14/00Z TAFs...IFR/LIFR will impact coastal areas tonight
through Thursday morning, with marine layer retreating to the
beaches Thursday afternoon. There could be a brief period of VFR
conditions, but it should be short-lived and IFR/LIFR conditions
return again by evening. Models are showing a deeper marine push
into the Umpqua Valley tonight, so we have introduced MVFR ceilings
at Roseburg after 10z that could last until late Thursday morning.
Other inland areas, VFR conditions will prevail through the TAF
period with breezy to gusty NW through early this evening and again
Thursday afternoon/evening. -Spilde

&&

.MARINE...Updated 200 PM PDT Wednesday, August 13, 2025...A weak
thermal trough is bringing gusty winds south of Cape Blanco. Steep
wind-built seas are expected south of Port Orford through Thursday
afternoon. Upper troughing approaching the area will break up the
thermal trough, easing winds on Friday. This trough will bring
chances for light marine showers late Friday and through the day
Saturday. Westerly swell will also start to build on Friday
afternoon and evening. This swell may build some steep seas in outer
waters north of Cape Blanco on Late Friday into Saturday, with other
areas remaining below advisory level. Westerly swell continues
through the weekend but decreases into early next week. -TAD

&&

.FIRE WEATHER...Updated 200 PM PDT Wednesday, August 13,
2025...Temperatures will trend cooler today, and even more so
Thursday onward as the pattern transitions back to being dominated
by an upper level trough. Expect near normal temperatures by
Thursday and below normal temperatures over the weekend.

The pattern continues to transition today as a dry front passes
through the region today. This will bring gusty winds to the region
today and with low daytime RHs, this will lead to critical fire
weather conditions across portions of the area. A Red Flag Warning
is in effect from 2p-8p today for gusty winds/low RH for portions of
Fire Weather Zones (FWZs) 620/622/624. Isolated critical conditions
are possible across FWZs 280/285/625, but at this time, it looks
like winds will remain just below criteria for those zones. While
breezy winds will continue into Thursday, improving trends in
temperatures and RHs will limit the extent of critical fire weather
conditions.

Friday into the weekend, low pressure in the Gulf of Alaska will
maintain gusty winds in the region, but also send a wetter front
through the area. This system looks quite similar to the one that
moved through the Pacific Northwest early last week, but
precipitation chances will extend farther south comparatively so.
Our region will still be on the tail end of this front so we don`t
expect much precipitation for inland locations. That said, there are
fairly high chances (60-80%) for measurable precipitation (0.01")
along the coast and into the Umpqua Basin, with around a 30-40%
chance for the Rogue/Illinois/Applegate Valleys and a 40-60% chance
for the Cascades. Precipitation chances drop off considerably for
areas farther south and east, hovering around 15-25%. Again, we
don`t expect a soaking rain, but there`s currently a 60-80% chance
for 0.10" and 40-50% chance for 0.25" along the coast north of Cape
Blanco and into the Umpqua Basin for late Friday into Saturday.
South of the Umpqua Divide, chances for even a 0.10" drop to 20-30%
here in the Rogue Valley, but remain in the 30-50% range for the
Illinois Valley. Given the time of year and that we are on the tail
end of the front, it feels too optimistic to advertise this rain
potential in mid-August, but models and ensembles are holding steady
in showing the front holding together enough for at least areas
along and west of the Cascades to see some rain. We`ll continue to
monitor trends and make adjustments as necessary. At the very least
for inland areas south of the Umpqua Divide and east of the
Cascades, we`ll see increased cloud cover, increased daytime
humidities and below normal temperatures over the weekend which will
limit fire weather concerns.

There`s some indications for thunderstorm concerns on Saturday and
Sunday along/east of the Cascades and across northern California. At
this time, convective parameters don`t look overly impressive for
Saturday and seem more related to the remnants of the front. Sunday
looks like a more clear thunderstorm signal focused from the Shasta
Valley north/northeastward into the East Side. Again,we`ll continue
to monitor model trends and make adjustments to the forecast as
needed. /BR-y


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 PM PDT this evening for ORZ620-622.

     Red Flag Warning until 8 PM PDT this evening for ORZ624.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT Thursday
     for PZZ356-376.

&&

$$

TAD/MNF/MAS