Cascade Summit, Oregon Weather Forecast Discussion

906
FXUS66 KMFR 102040
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
140 PM PDT Wed Sep 10 2025
.DISCUSSION (Today through Tuesday)...
Overview:
System overhead will maintain shower chances today with isolated
thunder risk. Showers will generally spread east to west over the
Cascades by this afternoon. That said, most of the activity will be
across eastside areas, along with the greater chance for lightning.
There will be areas of slow moving showers that continue to
redevelop over the same area that could lead to isolated areas of
heavier rainfall. Shower chances continue tomorrow but will be more
focused over eastside areas as the system slowly moves east, and
then even farther east by Friday as the system exits. Isolated areas
of thunder will exist through this stretch, but today has the
highest potential for thunderstorms. Temperatures generally trend
higher with a peak by Saturday, but a system on Sunday will briefly
bring temperatures back down before another trend upward through
next week. In fact, long term data suggest we will be back above
normal through mid/late September with dry conditions returning. In
other words, fall-like conditions will transition back to more
typical summer-like conditions.
Further Details:
A stacked low pressure system remains over the forecast area today,
and will continue isolated to scattered shower chances with isolated
thunder through this evening. Main threats will be isolated areas of
heavy rainfall, and isolated areas of lightning. The low pressure
system is very stagnant, and the mean flow is generally very weak,
so we are not expecting much in terms of widespread convective
processes. This is also due to limited amounts of instability. These
conditions will limit the overall threat for lightning, but isolated
areas will experience a small threat for thunderstorms today/early
tonight with small pockets of potential cloud-to-ground strikes. The
slow nature of this system will result in slow moving storms in
addition to "training" of storms/showers. The combination of these
two factors will lead to some isolated areas picking up heavy
rainfall. Fortunately, given the limiting chances for convective
process, rainfall rates shouldn`t be too concerning overall and will
be more of a long duration rainfall event. Some areas in and around
the Crater Lake area and other parts of the southern Cascades could
see an inch of rainfall between now and Thursday morning given
terrain influences. There may be a brief lull in activity tomorrow
morning, but chances essentially continue into tomorrow. 24 hour
totals from tomorrow morning through Friday afternoon will be less
than the current 24 hour window into Thursday morning. That said,
there could be isolated areas on the eastside that see 24 hour
amounts around an inch from Thursday morning through Friday morning.
These chances are higher in Klamath and Lake counties, especially
where local terrain may help influence lift. For example, Yamsay
Mountain and other topography influences in the Fremont National
Forecast may help with the training and redevelopment of
showers/storms given the flow around the low.
By Friday our chances will only cover a small area of far eastside
locations as the system begins to exit the region. Saturday will be
the overall warmest day in the current forecast. However, other
system on Sunday will bring us back below normal with rainfall
chances increasing west to east early Sunday morning. Thunderstorm
chances on Sunday are very low, but showers chances will spread
across the entire area through Monday morning.
Thereafter, we will see temperatures trending back towards normal
with above normal conditions anticipated middle of next week. In
fact, middle to later parts of September are trending above normal
for temperatures with the return of dry/below normal precipitation
chances. This will feel much more like late summer than the recent
stretch of fall-like conditions.
&&
.AVIATION (18Z TAFs)...
A moist pattern continues. The marine stratus and fog has been
lifting this morning, with more locations along the coast and
inland returning to VFR conditions. Areas of higher terrain are
obscured. Stratus is building north of Coos County and continuing
southward, so by the early afternoon more of the Coos County coast
will return to MVFR ceilings.
Showers and thunderstorms over East Side will expand and wrap
westward to the Cascades and over some west side locations this
afternoon/evening. These could temporarily lower
ceilings/visibility to MVFR or even IFR in heavier showers. Main
risks with thunderstorms will be heavy downpours and lightning,
but gusty winds also cannot be ruled out. Tonight, a return of
MVFR conditions will come to the Umpqua Basin and areas east as
well.
-Spilde/Hermansen
&&
.MARINE...Updated 100 PM PDT Wednesday, September 10, 2025...
Breezy northerly winds be favored south of Port Orford and between
5 and 30 nm from shore through this evening and again Thursday
afternoon/evening. While sub-advisory conditions are likely to
persist through the end of the week and into the weekend, seas do
increase during the latter half of the week (from 3-5 ft to 5-7
ft) as a low northwest swell (5-6 ft @ 12-14 seconds) builds into
the waters starting Thursday and persisting into the weekend.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
PACIFIC COASTAL WATERS...None.
&&
$$

NWS MFR Office Area Forecast Discussion