Coos Bay, Oregon Weather Forecast Discussion

696
FXUS66 KMFR 031748
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
1048 AM PDT Fri Oct 3 2025
.DISCUSSION...Updated aviation discussion.
&&
.AVIATION...03/18Z TAFs...IFR/LIFR along the coast will break
up with VFR developing this afternoon. Lower conditions
including IFR/LIFR will return tonight with a little light
rain/drizzle, especially from around Gold Beach/Port Orford
northward. This will last through most of Saturday morning.
Areas of moderate to heavy rainfall are impacting portions of
Modoc County (near Alturas) and also southern Lake County east
of Lakeview with MVFR ceilings/visibility. Rain should taper
off to showers this afternoon with conditions improving to VFR.
Elsewhere inland, any ceilings should lift to VFR this
afternoon. Some MVFR and terrain obscuration will redevelop
tonight into Saturday morning, especially west of the
Cascades with some light rain possible near and north of the
Umpqua Divide. Foggy areas could develop in the valleys/basins
of norCal and over the East Side where it has recently rained.
-Spilde
&&
.PREV DISCUSSION... /Issued 900 AM PDT Fri Oct 3 2025/
DISCUSSION...An update has been issued to nudge up the
probability of light showers in Coos and Douglas counties with a
weak trough late this evening into Saturday afternoon. Elsewhere,
the influence of the trough will be limited to creating mostly
cloudy to cloudy sky cover.
First, with the preceding trough continuing to shift
southeastward, showers today will be focused upon Modoc County.
Secondarily, a slight chance to chance of showers will also linger
into the early afternoon for eastern and southern Siskiyou, and
Lake counties.
West side low clouds are expected Saturday night into Sunday
morning, then a warming and drying trend will pick up steam Sunday
afternoon with clearing skies. Warm and dry conditions are
expected Sunday through Wednesday. As early as Wednesday evening,
or as late as Thursday night, the next trough is forecast to track
south-southeastward with at least a slight chance of showers, at
least for the coast. For the afternoon forecast issuance, we will
look to more precisely update the probability of an inland track
that would bring precipitation chances into our area versus the
contingent of solutions that are less progressive or even
retrograde the trough farther offshore.
PREV DISCUSSION... /Issued 304 AM PDT Fri Oct 3 2025/
DISCUSSION...Three upper level features will be the drivers of
our weather through Tuesday, and forecast confidence is high
through that time. The first is an upper trough now over the
Pacific Northwest and northern California coast area. The second
is a much weaker trough late Friday night into Saturday night, and
the third will be a strong ridge building in from the west early
next week.
The trough will track southeast into Nevada on Friday and the
shower activity will also shift in that direction. After the
morning commute, expect showers to be most numerous for Modoc and
southern Lake counties while sunny breaks in the clouds gradually
developing on the west side and northern portions of south central
Oregon.
Tonight into Saturday, there is better model agreement with a
stronger depiction of a weak shortwave and associated weakening
cold front in the northwest flow behind the trough. This has
resulted in the need to introduce a slight chance to a chance of
light showers to Coos, Douglas, and northern Curry counties. This
disturbance looks to have a shallow pool of moisture to work with
the highest probability of meager, barely measureable showers late
tonight until shortly after sunrise on Saturday. Meantime,
morning low clouds are expected in Josephine and Jackson counties.
Cloud cover will be more sparse on the east side and lead to a
chilly start to Saturday with lows in the upper 20s and lower 30s
expected. Douglas County is likely to have lifting but persistent
low cloud cover later Saturday, while other areas are expected to
see increasing sun in the afternoon.
Freezing and subfreezing temperatures are possible for many areas
east of the Cascades, with cooler temperatures following on
Saturday night and Sunday morning. A freeze watch remains in
effect for tonight and Saturday morning for these areas, and
details can be found at PDXNPWMFR.
Lower clouds return to southwest Oregon late Saturday night into
Sunday morning with a northerly flow between ridging far offshore
and the trough, which will be centered over the Rockies.
High pressure aloft will be the dominant feature with a warming
and drying trend Sunday at least into Tuesday, possibly into mid-
week. After a week of cooler temperatures, inland highs by Monday
will be slightly above normal. This also includes light easterly
winds with Brookings joining in the slightly above normal
temperatures for Monday and Tuesday.
Model uncertainty quickly increases for Wednesday with a majority
of GFS and ECMWF ensemble members holding on to a weakening ridge.
About 20% of ensemble members bring showers to the coast by
Wednesday night. As time progresses into next Thursday, the
probability of the next trough pushing out the ridge increases.
But, the track and strength of the trough are in question. The
probability of showers Thursday into Friday looks to be highest
for northern portions of our area. -DW/BPN
AVIATION...03/12Z TAFs...Marine stratus has settled over the Oregon
coast, bringing IFR to LIFR ceilings and visibilities mainly to the
north of Cape Blanco. Improvement to VFR is expected late this
morning or early in the afternoon. Areas of MVFR/IFR are likely to
return late this evening and tonight.
Area valleys and basins may see periods of MVFR ceilings and/or
visibilities early this morning, along with area of terrain
obscurations. Any areas of lower flight conditions should clear out
late this morning, with VFR expected through the rest of the TAF
period. Scattered showers are possible through this afternoon, and
brief periods of gusty winds and lower visibilities are possible in
heavier precipitation. -BPN/TAD
MARINE...Updated 200 AM PDT Friday, October 3, 2025...Seas will
gradually subside tonight with light winds. Winds become northerly
on Friday and increase, but should remain below advisory levels. A
thermal trough will strengthen along the coast Saturday with
moderate to strong north winds expected Saturday night through
Sunday night, strongest south of Cape Blanco. Steep, hazardous seas
will develop as well. Conditions should improve early next week.
-Spilde/BPN
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Watch from late tonight through Saturday morning for
     ORZ029-031.
CA...Freeze Watch from late tonight through Saturday morning for
     CAZ084-085.
PACIFIC COASTAL WATERS...None.
&&
$$
MAS/MAS/MAS

NWS MFR Office Area Forecast Discussion