480
FXUS66 KMFR 171142
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
443 AM PDT Tue Jun 17 2025

.Updated Aviation Discussion.

.DISCUSSION...Satellite image shows clear skies over most of the
forecast area. Marine stratus is slowly pushing in from the west
over the outer waters. Dry weather will continue into this
evening. A weak front could bring a few showers along the coast,
north of Cape Blanco later tonight into Wednesday morning,
otherwise it will remain dry with afternoon temperatures slightly
above normal for the interior. The weak front will result in
increased onshore flow resulting in marine stratus along the
coast, and inland into the Coquille and Umpqua Basin banked up
along the Umpqua Divide. Some of the marine stratus could spill
over the divide, but the Rogue Valley should remain clear.

Thursday will be dry, then cooler and unsettled weather is in the
works Friday into the first half of the weekend. Details on this
follow below from yesterday`s afternoon discussion.

By Friday, a broad area of cyclonic flow will slide south from the
Gulf of Alaska into the PacNW and will start to usher in a cooler
airmass, increased shower activity, and breezy to gusty wind speeds.
We could see wind speeds increase as early as Thursday with the
strongest sustained speeds expected on Friday/Saturday (15-30 mph).
This may warrant a wind advisory at some point Thurs-Sun,
especially if gusts of 45+ mph comes to fruition. Thunderstorms
are possible Friday through the weekend, but given the increased
cloud cover, it may be difficult for destabilization to occur.
MUCAPE values are currently progged to be on the lower end of the
spectrum (~100-200 J/kg). Lapse rates are not impressive as
forecast soundings show an atypical deep moist column (or deeper
than normal for this time of year) for some locations that
resemble more of a tropical sounding, and this makes sense given
the lower-end CAPE values. That said, the dynamics with the
system could prove to be enough forcing and could modify the
column to some extent. We still have a couple days to really
narrow down the details, but at this time we just cannot rule out
thunderstorms across the forecast area. Fortunately, with this
system and the cooler temperatures, the overnight RH recoveries
are going to be great to exceptional starting Friday night for
most areas. But the truth is we are currently seeing dry fuels
out there, so any thunderstorms could be problematic this weekend.
The flip side is we will see cooler temperatures and great
overnight recoveries for the most part, so this should help
mitigate any fire starts or spread.

This system will bring a much cooler airmass than we typical see at
the end of June. To put this into perspective, the record minimum
high temperature for Medford is 68 degrees on June 21st (this
Saturday). This occurred in 2021. We are currently forecasting 67
degrees which is a record certainly within reach this Saturday.
However, most--if not all--of our climate sites will have record
minimum high temperatures in jeopardy this Saturday. Furthermore, we
may want to consider frost/freeze products for some eastside areas
as temperatures could be in the lower 30s overnight both Friday and
Saturday nights with enough moisture for potential frost
formation.

With the cooler airmass, forecast energy release component values
(fuels) are expected to decrease. For example, some areas that were
around the 97th percentile for fuels just a few days ago, are now
expected to go down well below normal for this time of year, and
in some cases near the minimum at the end of the week. This is
good news and it should help mitigate at least some potential for
both fire starts and spread this weekend into next week.


&&

.AVIATION...17/12Z TAFs...Along the coast and just offshore. VFR
conditions will continue into this evening, followed by VFR with
areas of MVFR and local IFR between 4-5z. Inland, VFR conditions
will continue through the TAF period. However marine stratus could
result in MVFR ceilings towards or just beyond the TAF period at
Roseburg.


&&

.MARINE...Updated 230 AM Tuesday, June 17, 2025...A weak
disturbance will result in overall light winds and lower seas over
the marine waters through tonight, with areas of stratus and
possibly even some light rain showers or drizzle tonight.  North
winds will increase again Wednesday, especially south of Cape
Blanco, with a period of steep seas possible during the afternoon
that could last into Thursday. Another system could bring showers
Friday into the weekend.


&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$