017
FXUS66 KMFR 020349
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
849 PM PDT Fri Aug 1 2025

.DISCUSSION...It has been an active night in Northern California
with multiple severe thunderstorms in western Siskiyou County.
There were reports of small hail in these cells, but we will be
looking for more reports once the storms are over. The next storm
chance will be tomorrow east of the Cascades and in Siskiyou
County. However just like tonight, the Siskiyou County storms
could travel north into southern Jackson County. Please see the
previous discussion for details. -Hermansen

&&

.AVIATION...02/00Z TAFs...Marine stratus will remain along the
southern Oregon coast, keeping IFR and LIFR levels in place through
Saturday evening, except for patchy breaks during the late morning
into the early evening, around 19Z through 02Z. Gusty winds will be
strongest in the afternoon, and south of Cape Blanco at 15 to 25 kt.

Inland areas generally look to remain at VFR levels through Saturday
evening. Rain showers and thunderstorms are expected to taper off
after 04Z this evening. Compared with Friday, thunderstorm activity
is expected to be at least slightly diminished during Saturday
afternoon and evening. But, isolated to scattered storms are
expected for Siskiyou, Klamath, and Lake counties. This includes
Yreka, Klamath Falls, and Lakeview. Thunderstorms can present
hazardous conditions, including lightning strikes, gusty and erratic
winds, small hail,  and locally moderate to heavy rainfall.
-DW

&&

.MARINE...Updated 800 PM PDT Friday, August 1, 2025...A thermal
trough is maintaining gusty north winds south of Cape Blanco. This
will result in conditions hazardous to small craft, south of Cape
Blanco and out to 30 nm through at least Sunday morning, but
possibly into Tuesday. Winds will be strongest and seas will be
steepest during the afternoons and evenings. -DW

&&

.PREV DISCUSSION... /Issued 226 PM PDT Fri Aug 1 2025/

DISCUSSION...

Thunderstorms are ongoing this afternoon as an upper level
disturbance embedded in this deeper wave moves through the
forecast area. Convective Available Potential Energy(CAPE) remains
on the higher side than what we usually see for late July and we
should see some healthy cells tonight. The chance for severe
storms isn`t that high on the other hand with lack luster 0-6km
shear around 15 to maybe 20 knots in some spots.

We also took a gander at the PWATs on the polar orbiting
satellites and those show pretty typical values ranging from 0.6
up to 0.8, so nothing incredibly wet or dry, but storms will be
slow movers, so things should trend wetter like the last few
days.

Otherwise, the persistent threat of thunderstorms continues into
Saturday, although the probabilities and the areal extend of
storms decreases. Again, no severe concerns here as CAPE is around
500 J/kg maybe 1000 in some spots with 15 knots of shear.

Things begin to change on Sunday as a trough passes through our
forecast area and brings more rain and thunderstorms to the
region. Highs will trend notably lower into the mid 80`s to even
upper 70`s west of the Cascades. These highs are 5 to even 10
degrees below normal for early August, which could be a welcome
change to some. These relatively cooler temperatures continue
into Monday before a warming trend mid week.

Highs push towards normal values this time of year with mid 90`s
here in Medford and upper 80`s west of the Cascades. No weather
impacts are anticipated for the region for next week as heat risk
is minimal/low given the time of year and how frequently we`ve
observed temperatures like this already. Perhaps the biggest risk
is an odd fire popping up and producing a lot of smoke, but that
seems to be moderate as well at this time.

-Smith

FIRE WEATHER...Updated 200 PM PDT Friday, August 1, 2025...
Thunderstorm chances remain in the forecast for this afternoon and
evening, especially over the Siskiyou and Cascades ranges
according to the SPC HREF. Considering each model individually,
the amount of activity is not spectacular. One model (FV3) shows
developed cells with reflectivity over 40 dBZ moving over Jackson
and Josephine counties this afternoon, but other models in this
ensemble do not show this outcome. Model PWATS of 0.6-1.0 inches
west of the Cascades indicate that any thunderstorms that develop
will be wetter, and marginal winds aloft may result in activity
staying over terrain or moving slowly. Activity west of the
Cascades looks to be generally isolated and lasting a few hours
deeper into the evening. Fuel conditions are noted to be moderate
fire weather risk according to Wildland Fire Assessment
System(WFAS) and some energy release component plots. Given the
fuel conditions and the lack of ignitions gaining a foothold over
the last few events, a Red Flag Warning has not been issued this
afternoon in spite of the very good thunderstorm chances.
Activity should decrease into the nighttime hours.

Looking forward, weak forcing on Saturday afternoon and evening
currently limits thunderstorm chances to northern Lake and Klamath
counties, with additional slight chances in western Siskiyou County.
On Sunday, an upper trough will move over the area. This will bring
cooler temperatures across the area as well as periods of gusty
winds over elevated terrain. Additionally, instability around the
trough may help to bring thunderstorms on Sunday afternoon and
evening. Initial guidance shows some precipitation chances over and
east of the Cascades, but also currently has some timing variation.
There are also weak signals for activity to last into Sunday night
and early Monday morning. All of these are are relatively early
assessments. Even if a full product is not issued for Sunday
afternoon and evening, this could be a period of elevated concern.

Beyond Sunday, a more stable upper pattern has been in the forecast
for a few days and conditions for thunderstorms are not currently
expected. Warm and dry conditions are expected through the week,
with daytime highs possibly rising above seasonal averages by the
end of the week and into next weekend. -TAD/Smith

&&

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

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 AM PDT Sunday
     for PZZ356-376.

&&

$$