851
FXUS66 KMFR 170505
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1005 PM PDT Mon Jun 16 2025

.UPDATE...Updated Aviation Discussion.


&&

.AVIATION...17/06Z TAFs...VFR is expected across inland areas
through Tuesday. Along the coast, expect mainly VFR with areas of
MVFR and local IFR possible late tonight and early Tuesday morning.
There is a 25% chance for MVFR at North Bend.  Due to low confidence
have kept mention out of the TAF for North Bend (KOTH) but will
monitor these conditions.


&&

.PREV DISCUSSION... /Issued 839 PM PDT Mon Jun 16 2025/

DISCUSSION...Radar showed a thunderstorm east of the Cascades
earlier this afternoon, and there were some good cumulus buildups
in that area that a spotter saw as well!

It will be a cooler night tonight with more 40s and 50s for the most
part, along with a few 30s in northern Klamath and Lake counties.
Afternoon temperatures tomorrow are back to being a few degrees
above normal with most valley locations in the low/mid-80s.

The next chance for rain will be mainly offshore, but there
have seen some chances. CAMs are indicating light shower activity
farther into the southern outer waters as well as into western
Douglas County, so a 5-20% probability has been added to these
areas. Otherwise, things are on track in the forecast with the next
wave of showers/storms and cooler temperatures this weekend. -
Hermansen

MARINE...Updated 800 PM Monday, June 16, 2025...A weak
disturbance will result in overall light winds and lower seas over
the marine waters through Tuesday, but with areas of stratus and
possibly even some light rain showers or drizzle.  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.

PREV DISCUSSION... /Issued 240 PM PDT Mon Jun 16 2025/

DISCUSSION (Today through Sunday)...

Overview:

While overall impacts remain low for most of this week, we will
start to see potential impacts towards the end of this week as an
incoming system brings chances for showers/thunderstorms and breezy
to gusty winds. At this time, its a little too early to say with
much confidence the overall threat of thunderstorms, but its hard to
believe this incoming system does not bring thunderstorms to some
areas of the Pacific Northwest. The other notable item with this
system is the cooler airmass and clouds that will bring below normal
temperatures to the area. In fact, this Saturday areas on the
westside might not hit 70 for a high, while areas on the eastside
might not reach 60 for a high. Essentially, Fri-Sun will be
noticeably cooler for this time of year. Friday night and Saturday
night could see low temperatures at or slightly below freezing for
overnight lows.

Further Details:

A trough is passing over the forecast area today and this did bring
light returns on radar for eastside areas. A few lightning strikes
have been detected with one cell in particular showing vertical
growth over Lake County as of ~2 PM. We are not expecting too
much more activity today as this weak shortwave exits to the east
by early this evening. Not expecting any strong storms to form
today but very isolated lightning may be possible for a few more
hours. We will then transition to a zonal flow pattern aloft with
no notable airmass changes anticipated until the next incoming
system develops and pushes into the PacNW later this week.

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.

&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$