044
FXUS66 KMFR 241106
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
406 AM PDT Sun Aug 24 2025

.DISCUSSION...Tonight there is heavier high cloud cover east of
the Cascades. There is also marine stratus in areas on the Coos
County and Douglas County coasts this morning. Our warmer mornings
continue through early next week. This will mean that
temperatures will only be falling to the mid-/upper 60s west of
the Cascades, 50s at the coast, and 50s to low 60s east.

The four corners ridge is seen building in our area, making the heat
streak continue. Rain/thunderstorm chances are on their way today as
well, and this will be discussed later in the discussion. Today
includes a significant HeatRisk in the Illinois and Rogue valleys.
Heat Advisories and Extreme Heat Warnings continue through this
afternoon for all west side areas except the coast as they will be
reaching the 70s for the most part. The latest change in the
forecast has been to drop afternoon temperatures Monday and Tuesday
as cloud cover could be enough of a factor to inhibit as much
warming as seen over the weekend. Precautions need to be made to
protect yourself from the heat. Drink plenty of water, avoid peak
heating between 10 AM and 4 PM, and stay in an air-conditioned room
as much as possible. Please see NPWMFR for more details.

The rain/thunderstorm chances will be present today. Today`s chances
will mainly be east of the Cascades, and a 25-35% chance of thunder
will be present in eastern Siskiyou, southern Lake and eastern Modoc
counties. There is low confidence on nocturnal thunderstorms
tonight. If they were to develop, it would be in Klamath and Lake
counties and eastern Modoc County. Want to note that a few isolated
cells could reach farther west near the Cascades during the
nocturnal threat as well.

Monday afternoon chances expand farther west to include most of
Northern California and the Cascades with a 30-40% chance for
showers. This trend of afternoon chances continues each afternoon
through at least Thursday.

Getting into next week, the last of the heat products will be on
Monday for the Rogue and Illinois valleys and western Siskiyou
County. It is still looking like the Umpqua Basin could have
additional cloud cover Monday, and as that would limit heating, no
heat products will be issued there after the one today.

&&

.AVIATION...24/12Z TAFs...Along the coast, IFR/LIFR conditions are
impacting most coastal sites overnight. This will peel back to just
offshore later this morning and early afternoon, with local IFR
persisting along the coast. IFR/LIFR will return to coastal areas
this evening. Inland, VFR conditions continue through early this
afternoon. Then, scattered to widespread thunderstorm activity is
expected this afternoon and evening, with the focus expected to be
south of the Rogue-Umpqua Divide, east of the Cascades and across
northern California. Local MVFR conditions and strong, gusty winds
are possible with thunderstorms.

&&

.MARINE...Updated 200 AM PDT Sunday, August 24, 2025...Relatively
calm conditions conditions are expected today within 30 nm of shore,
but steep seas will continue beyond. As the thermal trough briefly
strengthens, north winds and steep seas will spread to all area
waters Sunday night into Monday, then persist through at least
Tuesday. The thermal trough will weaken and winds and seas should
ease mid to late next week. -BPN

&&

.FIRE WEATHER...Updated 200 AM PDT Sunday, August 23, 2025...Hot
and dry conditions will continue today, and although some slight
cooling is expected early next week, temperatures will remain well
above normal for several more days. Excessive heat warnings and heat
advisories remain in effect. Please see NPWMFR for more details.
Humidities will begin to slowly improve over the next few days as
monsoonal moisture flows into the region from the south, but this
also means that there will be a threat of thunderstorms daily
through at least the first half of next week.

A portion of the "Four Corners" high has reached northwestward into
our area. Only the immediate coast will be immune to the heat with
afternoon temperatures near seasonal norms along with moderate to
strong winds, especially from Cape Blanco north. At the same time,
overnight lows will be warm, especially near and at the ridges, thus
there will be little to no overnight relief from the heat.
Temperatures tomorrow will be very similar to today with highs into
triple digit territory for the interior West Side valleys and low to
mid 90s east of the Cascades.

Today, conditions are more favorable for thunderstorm development as
mid level moisture and instability continues to increase, along with
a weak to moderate trigger in the form of a weak shortwave passing
across the area from south to north. Thunderstorm chances today will
be more widespread, covering nearly all of the East Side and much of
northern California. For now, areas west of the Cascades should be
in the clear, but it`s not out of the question a couple of storms
could come off the Siskiyou Mountains and slip into the southern
portions of Fire Zones 620 and 622 late this afternoon and evening.
However with light steering winds, most likely they will remain
along the terrain. Nocturnal storms could still be a part of the
equation tonight, but confidence on this is low. Due to the more
widespread lighting threat today, a Red Flag Warning has been issued
for these most likely affected areas. Details can be found at
PDXRFWMFR.

Afternoon and early evening thunderstorms remain a concern for the
first half of next week as heat persists and moisture continues to
flow into the region. Monday, we`ll be under a south flow with
monsoonal moisture still being pushed into the area along with
marginal to moderate instability, but clouds may inhibit daytime
heating and therefore inhibit convective development. This puts a
great deal of uncertainty into the forecast, so we are holding off
on any additional headline issuances fro Monday. After Monday, we`ll
be sandwiched between the weakening ridge to the southeast and
general upper troughiness over the area. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Warning until 8 PM PDT Monday for ORZ024-026.

     Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening for ORZ621-623>625.

     Heat Advisory until 8 PM PDT this evening for ORZ023-025.

CA...Extreme Heat Warning until 8 PM PDT Monday for CAZ080-081.

     Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening for CAZ280-281-284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 PM this
     afternoon to 11 PM PDT Tuesday for PZZ350-356.

     Small Craft Advisory until 11 PM PDT Tuesday for PZZ370-376.

&&

$$