174
FXUS66 KMFR 172121
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
221 PM PDT Sun Aug 17 2025

.DISCUSSION...Visible satellite image shows cumulus clouds over most
locations. Another Image which shows signs of potential showers or
storms development is showing signs of that in southeast Lake and
far eastern Modoc (near and over the Warners). Guidance suggest
instability will be greatest in these areas later this afternoon and
evening. Even then, storms will be isolated. This makes sense when
looking at the mid and low level water vapor image with bothy
showing a weak upper level disturbance approaching the Oregon coast.
This disturbance should be enough to at least trigger isolated
storms in the above mentioned areas.

Isolated storms will end early this evening, with dry weather
expected tonight.

All signs are pointing towards dry weather for the upcoming week
into next weekend. Monday and Tuesday, the upper trough with a
stable southwest flow will be present which will keep afternoon
temperatures in check with values near seasonal norms for the
interior.

From mid week on, there`s good agreement the four corners ridge will
strengthen and nudge into our area with continued dry weather. It
will start to heat up Wednesday with hot weather likely Thursday
through next weekend with afternoon highs in the upper 90s for the
interior valleys Thursday followed by triple digit readings Friday
into next weekend. East of the Cascades, it will be in the upper 80s
to low 90s the latter part of next week into next weekend.

One thing we`ll have to watch closely is the potential for some
monsoonal moisture to make its way from the south into portions of
the Eastside starting as early as Friday into next weekend. It`s way
to early if there will be sufficient moisture to support
thunderstorms as details can change in the day to come. Stay tuned.
-Petrucelli


&&

.AVIATION...17/18Z TAFs...With the frontal system out of the area,
activity is absent across northern California and southern Oregon
this morning. Cloud cover remains across the area. While Klamath
Falls remains under IFR ceilings, other area terminals are under VFR
conditions. Ceilings should lift over Klamath Falls by this
afternoon, while marine stratus looks to build along this coast this
evening. Coastal areas are forecast to see IFR or LIFR conditions
into Monday morning, with inland areas remaining at VFR levels under
high ceilings or clear skies.

This afternoon and evening, there are chances for isolated showers
and thunderstorms (15-25%) over western Siskiyou County and
easternmost Lake and Modoc counties. Any thunderstorms that develop
may bring erratic and gusty winds, lightning strikes, and locally
heavy rain showers. -TAD


&&

.MARINE...Updated 200 PM PDT Sunday, August 17, 2025...Seas will
peak this afternoon, but are expected to remain just below advisory
levels. Seas lower tonight into Monday. Wednesday into Thursday,
signs are pointing towards moderate to occasionally strong north winds
and steep seas south of Cape Blanco as the thermal trough returns.
-Petrucelli


&&

.FIRE WEATHER...Updated 200 PM PDT Sunday, August 17,
2025...Saturday`s front had observations of 0.20 and 0.50 inches of
rainfall for coastal areas and elevated terrain (including east side
areas). West side valleys generally got 0.10 inches of rain or less.

Showers have been few today and isolated today. Thunderstorm chances
remain in the forecast this afternoon and evening. Forecast coverage
has decreased to western Siskiyou County and easternmost Lake and
Modoc counties. Any activity that does develop is expected to be
isolated and should dissipate into the evening.

A pattern change to southwest flow aloft on Monday will bring drier
air aloft, minimizing the chances of activity continuing into the
week. Daytime highs look to reach seasonal levels early in the week.
Midweek, high pressure over the Four Corners looks to build a ridge
that will start to could move over the area. This would support
daytime highs rising above seasonal levels. Current guidance shows
that most west side valleys (Umpqua Valley excluded) could see near
or just above triple digits by Friday or Saturday. Dry daytime
conditions are expected, but current overnight recoveries look to
remain moderate. Periods of overnight easterly flow could bring
locally poor recoveries, but this is not supported in current
forecast values. An upper level disturbance that looks to pass over
the area on Wednesday is also worth paying attention to, as these
disturbances can sometimes bring gusty to breezy winds. These
elevated winds are also not currently expected. Overall, hazardous
fire weather conditions are not expected but some factors may bring
elevated concerns through the dry period. -TAD


&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$