Winchester, Oregon Weather Forecast Discussion

352
FXUS66 KMFR 071143
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
443 AM PDT Sun Sep 7 2025
.Updated AVIATION Discussion...
&&
.AVIATION...07/12Z TAFs...A shortwave passing through the region
has cleared out much of the marine layer along the coast and
over the marine waters. The marine layer is slowly filling back in
from the north, but even then, ceilings are a mix of low end
VFR/MVFR with some pockets of IFR. Low clouds persist along the
coastal mountains, resulting in terrain obscurations, and MVFR
stratus persists in the Umpqua Basin. Conditions are expected to
improve later this morning and afternoon, with the marine layer
along the coast at least breaking up some today.
VFR conditions will prevail for inland locations through the TAF
period. Isolated to scattered thunderstorms are expected again
this afternoon/evening focused along the Cascades from Crater
Lake northward and into the northern portions of Klamath and Lake
Counties.
&&
.PREV DISCUSSION... /Issued 416 AM PDT Sun Sep 7 2025/
DISCUSSION...A corridor of weak instability persists over western
Siskiyou northward into the Rogue Valley this morning. Some
spotty showers are indicated on radar, and earlier there was a
handful of lightning strikes in western Siskiyou. Lightning
activity has waned for the morning and showers are weakening as
evident by warming cloud tops on satellite. Meanwhile, areas of
degraded air quality persist in southwest Oregon/northern
California this morning, and while air quality has improved
compared to 24 hours ago, it remains worst in the
Rogue/Applegate/Klamath River Valleys. Smoke from the Kelsey
Peak/Backbone fires northeast of Agness is largely what`s
responsible for the smoke in the Rogue/Applegate Valleys. Smoke
models show continued improvement/lessening smoke concentrations
again afternoon for most areas except the Klamath River Valley.
Low pressure remains offshore and continues to send shortwaves in
the region, which will maintain another day of thunderstorm activity
this afternoon/evening. Today`s focus will shift northward and
diminish in coverage compared to recent day. Areas with the highest
chances today will be along the Cascade Crest near and north of Lake
of the Woods into the northern portions of Klamath County. Overall
temperatures will continue to trend cooler today by a few degrees
compared to yesterday, hovering near to just below normal for early
September.
Later today into early Monday, this low pressure will finally move
onshore and stick around through much of the week. With low pressure
directly overhead, this pattern will result in several days of below
normal temperatures. The "coolest" days of the forecast period are
expected to be Monday and Tuesday when high temperatures bottom out
around 10-15 degrees below normal. This equates to low-mid 70s for
West Side Valleys and mid-upper 60s for East Side locations.
Overnight temperatures, however, will be closer to normal for this
time of year (50s west/40s east), likely due to persistent cloud
cover. Afternoon highs start trending warmer on Wednesday, but its
not until Thursday when we start seeing more widespread highs back
in the 80s (70s) west (east) of the Cascades. Low pressure begins to
move eastward on Friday with a shortwave ridge building in Friday
night into Saturday, resulting in temperatures trending warmer by a
few degrees compared to Thursday.
In addition to cooler temperatures, we are confident that healthy
measurable rainfall will occur across the area during the first half
of the week. With low pressure overhead, precipitation will be more
showery in nature, so some areas could end up with less than others.
Despite this, nearly every single member from both the GFS and
European ensemble suite shows rainfall for many locations across the
region, including East Side and northern California points. As low
pressure moves inland, shower activity is forecast to begin at the
coast Monday morning, then spread inland through the day Monday.
Models are indicating some instability and thunder potential in
eastern Douglas/Cascades Crater Lake northward around sunrise, so
the forecast includes this threat ahead of the main area of showers.
There will be day to day variations in precipitation amounts and
locations, but at this time, Monday looks like the day for the
highest amounts to occur along and west of the Cascades. Tuesday
features slightly less amounts and shifts eastward some to include
more of the East Side. Both of these days will include thunderstorm
potential with these showers, focused along/west of the Cascades on
Monday, then over much of the area on Tuesday.
There looks to be more of a break in precipitation Tuesday night,
but another round of showers/thunderstorms is expected Wednesday
afternoon. Again there will be a farther eastward shift with
precipitation focused along/east of the Cascades and across northern
California on Wednesday. A similar picture is forecast for Thursday,
though amounts look slightly less compared to what`s in the forecast
for Wednesday. Precipitation chances diminish and conditions trend
drier as the day goes on Friday when the upper level trough
transitions eastward.
All in all, by the time we reach Friday, multi-day rainfall totals
are forecast to be in the 0.50-0.75" range along the coast, across
the West Side/northern California and even into portions of Klamath
County. 0.75"-1.00" is forecast in the Cascades and higher terrain
of the region, with upwards of 1.50" from Crater Lake northward. For
the far eastern areas in Lake and Modoc Counties, rainfall totals
are forecast to be in the 0.25-0.50" range, highest in the terrain.
With these totals in the forecast, this pattern is certainly
expected to be helpful with local firefighting efforts, and would
likely put a large dent in fire weather concerns.
MARINE...Updated 100 AM PDT Sunday, September 7, 2025...
Sub-advisory conditions will likely persist through next week. Low
pressure overnight will continue light south winds, low seas, marine
fog, and drizzle. Early this week, expect generally calm conditions
with no significant swell, but widespread showers are expected
Monday and Tuesday as the low pressure moves inland. Winds turn
northerly Tuesday into Thursday. -DW
FIRE WEATHER...Updated 300 AM PDT Sunday, September 7, 2025...
Another round of thunderstorms is in the forecast today, but
chances are diminished in coverage and shifts to northward for this
afternoon/evening. Areas with the highest chances today will be
along the Cascade Crest, near and north of Lake of the Woods into
the northern portions of Klamath County. Though we have scattered
thunderstorms mentioned in portions of fire weather zones (FWZs)
617/623/624, we`ll hold off on any warnings with this round of
lightning since it`s fairly limited in coverage across those zones.
Temperatures will trend cooler again today by a few degrees,
continuing the trend of increased daytime RHs. The exception being
across far eastern areas (FWZs 285/southern 624 and 625) where
similar daytime RHs can be expected. Another round of breezy south
to southwest winds is expected this afternoon, though slightly
weaker compared to Saturday afternoon.
Late tonight into Monday, low pressure offshore that has been
sending shortwaves into the region and maintaining thunderstorms
this past week, will finally move inland and linger through much of
the week. This will bring weather more typical of October with well
below normal temperatures, increasing daytime RHs, and widespread
precipitation chances. Please see the discussion above for
temperature/precipitation details. While daily thunderstorm chances
are expected with this pattern, given the ample moisture and
moderated fire environment, we aren`t currently planning on any
headlines for the expected lightning activity.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
PACIFIC COASTAL WATERS...None.
&&
$$

NWS MFR Office Area Forecast Discussion