844
FXUS66 KMFR 161048
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
348 AM PDT Wed Jul 16 2025

.DISCUSSION...Upper ridging over the area will provide another hot
day today with afternoon temperatures averaging about 4-8F above
normal in NorCal and over the East Side, but as much as 10-12F
above normal for the valleys west of the Cascades. This means
highs in the upper 90s and lower 100s for Medford, Roseburg,
Grants Pass, and Yreka; and highs generally 90-95F for Klamath
Falls, Lakeview, Alturas, and Mount Shasta City. A Heat Advisory
remains in place for the west side valleys, so if you`re planning
to spend significant time outdoors this afternoon, please try to
stay hydrated and take frequent breaks to cool off. Smoke from
PacNW fires will cause haze and even reduce visibility at times in
the immediate vicinity/downwind of the fires. Some areas may
experience degraded air quality. A weakness in the ridge will
maintain some instability this afternoon/evening, but forcing and
moisture are limited. As such, we`re expecting mostly just some
cumulus buildups over the mountains. Even so, much like yesterday,
there is a low chance (generally around 10%) a stray cell pops
up, especially in the NorCal mtns. Yesterday`s lone cell
developed near Lava Beds National Monument and did manage to
produce 2 CG lightning strikes. Marine layer is persistent along
the coast and is bringing widespread low clouds/fog from Florence
to Brookings this morning. These will peel back to the immediate
coast later this morning, but may only result in a few hours of
sunshine. In fact, some places (especially at the beaches) may
hold the stratus all day. It won`t be as breezy as it has been the
last few days.

On Thursday, the ridge will continue to weaken. It`ll remain very
warm, with still some moderate heat risk for those sensitive to
heat. A minor disturbance will move northeastward across the area
during the afternoon. Mid-level winds increase to around 30kt in
advance of this feature and model CAPE is showing a few hundred
J/KG stretching from the mountains of Siskiyou County up into
portions of Klamath/Lake counties. We`ve bumped up the probability
of thunder in these areas and allowed for isolated thunderstorms
as most CAMs do produce at least some activity during the
afternoon/evening (2pm-10pm). This doesn`t look like a widespread
lightning outbreak, but we do expect a better chance than today.
Soundings are showing a well- mixed sub-cloud layer with
inverted-V profile, so any cells that do manage to get going will
have the ability to bring gusty outflows. Even without
thunderstorms, we expect breezy conditions to develop during the
afternoon/evening, highest in Modoc and into portions of Lake
County. Wind gusts could be 25-30 mph and this will coincide with
low RH values of around 10-15%. These conditions could approach
Red Flag, but we don`t think the area affected will be large
enough to warrant a warning.

Friday into this weekend, models are showing a couple of
disturbances moving southward across western Canada with a trough
axis pushing into the PacNW. This should at least take the edge
off the heat for most areas, though it will probably also result
in breezier afternoon/evening winds. Beyond that, guidance shows
one disturbance digging southward into Washington, which wold
further establish the trough early next week. We are confident
that this will drop temperatures to near or even a bit below
normal levels. But, it`s still a bit early to assess if this
trough will bring any precipitation. Time of year goes against
much, if anything, happening. But, at least a small percentage of
models do show some potential for convection across NE sections
of the CWA then. We`ll wait and see. -Spilde

&&

.AVIATION...IFR/LIFR low clouds/fog are impacting all of the
coast, including North Bend this morning. Expect this to continue
through the morning and some coastal areas (beaches) may not see
any breaks this afternoon. We do briefly break up the stratus
at North Bend, but it should return tonight. Inland, expect VFR,
though wildfire smoke/haze will bring reduced visibility at times
to Klamath Falls. Much like yesterday, expect a few cumulus
buildups, mainly in the NorCal mountains this afternoon with just
a stray (~10% chance) of a thunderstorm. -Spilde

&&

.MARINE...Updated 230 AM PDT Wednesday, July 16, 2025...North
winds are weakening across the waters, but steep fresh swell will
persist through at least Thursday morning. Seas will become less
steep with a brief period of sub-advisory conditions possible on
Friday. Then, the thermal trough may return over the weekend,
though winds are expected to be weaker than what recently
occurred. Regardless, this could result in steep seas and advisory
level conditions south of Cape Blanco over the weekend. -Spilde

&&

.FIRE WEATHER...Hot, dry weather will continue today. While we do
expect locally breezy conditions this afternoon/evening, we don`t
think it will be sufficient for Red Flag. Overall, we`re expecting
peak wind gusts in the 20-25 mph range with minRH of 15-25%
(locally lower from around the Warner Mtns eastward). In terms of
instability, similar conditions exist today that occurred
yesterday. We do expect a few cumulus buildups, especially in the
NorCal mountains, but with generally a 10% chance or less of a
thunderstorm. Mid-level winds increase on Thursday as a minor
disturbance advances northeastward across the area. This will lead
to a bit more in the way of instability and a bit better chance of
thunderstorms. Isolated storms were added to the forecast in
portions of Siskiyou County (near, north/west of Mt Shasta), but
the highest probability (15-20%) exists along the Highway 97
corridor from around Chiloquin northward and also eastward across
Klamath/northern Lake counties. Any cells that do develop will
have gusty outflows since soundings are showing a very well-mixed
and dry sub-cloud layer. Even in the absence of storms, for
locations SE of the the main thunder area, the increased mid-
level flow should mix down to the surface during the
afternoon/early evening. Local guidance is showing peak wind gusts
in the 25-30 mph range and some minRH down in the 10-15% range.
Once again, this will flirt with Red Flag criteria, but since it
will be mostly over a small area, we`ve decided to headline at the
top of the FWF instead.

This weekend into early next week, we`ll see a downward trend in
temperatures and slight uptick in humidity, but with daily
afternoon/evening breezes that will at least maintain elevated
fire weather concerns. We`ll monitor thunder potential with the
trough dropping down early next week. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 8 PM PDT this evening for ORZ023>026.

CA...Heat Advisory until 8 PM PDT this evening for CAZ080-081.

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

&&

$$

MAS/MAS/MAS