129
FXUS66 KMFR 051236
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
536 AM PDT Sat Sep 5 2026

.KEY MESSAGES...

* Unlike our recent event, the probability of showers during each
  of the next couple of days (into Sunday evening) will be lowest
  at the coast. Meantime, the probability will be highest over
  the southern Oregon Cascades and north-northeastward, to include
  the Diamond Lake and Crater Lake vicinities into northern
  Klamath County.

* Showers today will be quite limited in coverage and intensity.
  Coverage will increase after sunrise Sunday morning, especially
  from the Cascades eastward, with isolated to scattered
  thunderstorms possible during Sunday afternoon and evening.

* Temperatures trend a little warmer again today and a little
  cooler Sunday, but remain 10 to 20 degrees below normal. Dry
  weather and a stronger, gradual warming trend follows Monday
  into at least Thursday. This includes highs near normal on
  Tuesday, and above normal at mid-week.

* Higher uncertainty late in the week, Friday through next
  weekend, with dry and warm weather most likely to continue. But,
  around 20% to 30% of ensemble model solutions on each day show
  at least scattered shower activity in a portion of the area.

&&

.DISCUSSION...The main determinant of our weather today and Sunday
will be the wobbles of a nearly stationary upper level trough that
extends from western Canada into northern California. A northward
shift of the trough allowed for shower activity to diminish
yesterday, and activity today will again be focused north of our
area. But, at least the crest of the Cascades to the north of
Lake of the Woods and northern Klamath County have a chance of
measurable rain, with snow levels at around 8000 ft msl, higher
than the Crater Lake Rim but lower than the highest peaks.
Meantime, other portions of southern Oregon have a good chance of
seeing some evening virga.

Compared to yesterday, the main shift in the data regarding the
short term forecast is an increased probability of showers late
tonight into Sunday morning, roughly from the Interstate 5
corridor eastward...though still focused over the Cascades into
Klamath County. The probability of showers and thunderstorms will
reach a peak during Sunday afternoon, wit scattered activity north
of Crater Lake and isolated activity elsewhere, still roughly from
the Interstate 5 corridor eastward. There is a sizable portion of
the ensemble suite of data that has the western edge of activity a
little farther east, along the Cascade crest. Amounts on Sunday
of a tenth of an inch to a quarter of an inch should be common
from the Cascades eastward, with a meausurable amount into the
inland west side valleys. Activity looks to taper off Sunday
evening as the trough tracks eastward.

Another shift is higher confidence in dry conditions and clearing
skies on Monday/Labor Day, after areas of early to mid-morning
coastal and Umpqua Valley stratus. The clearing will aid the
warming trend, with near normal temperatures by Tuesday.

A ridge is likely to be the dominant upper level feature driving
our weather at mid-week. The 06Z GFS has introduced a little
influx of mid- level moisture to clip Modoc and southern Lake
counties on Wednesday into Thursday. But, the large majority of
ensemble solutions keep the monsoonal flow to the south and east,
out of our area. The warming and drying trend is likely to
continue at mid-week, with temperatures likely becoming a bit
above normal, but a minority of ensembles ramping temperatures up
farther. So, no, hot, summer temperatures are not necessarily done
yet.

At the end of the forecast period, Friday into next weekend,
uncertainty increases. There is disagreement over whether a
closed low offshore from California will retrograde farther
offshore (for further warming) or move closer to our area. About
20-30% (a minority) of solutions would introduce shower chances
into our area. Depending on the track of this upper low offshore,
many of the late week solutions that do favor shower development
would also include at least a slight chance of thunderstorms.

&&

.AVIATION...05/12Z TAFs...Variable cloud cover this morning is
mainly VFR, with patchy LIFR in stratus for the coastal valleys and
Umpqua Valley that is expected to linger through around 18Z.
Shower activity will be very limited, and at a minimum, this
morning.

VFR is expected to continue to prevail in most areas today into
Sunday morning, but there is a chance of showers over the Cascades
and northern Klamath County this afternoon/evening. The probability
of showers and mountain obscuration will increase late tonight into
Sunday, with the highest probability over northern portions of
Klamath and Lake counties.

&&

.MARINE...Updated 200 AM PDT Saturday, September 5, 2026...Light,
variable winds shift to northerly in the southern waters this
morning and across the area later today with subsiding seas. Low
seas along with a few showers will persist through Sunday night. A
thermal trough develops Monday, with gusty north winds and steep
seas likely south of Port Orford through mid-week.

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 2 PM Monday to 2
     AM PDT Tuesday for PZZ356-376.

&&

$$