936
FXUS66 KMFR 260547
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1047 PM PDT Wed Jun 25 2025

.Updated the Aviation section...

.AVIATION...26/06Z TAFs...At the coast and into the Coquille and
Umpqua valleys, a deep marine layer with a MVFR stratus will expand
in Douglas, Coos, and Curry counties overnight into Thursday
morning, with patchy IFR possible south of Gold Beach. Ceilings are
expected to be on the edge between VFR and MVFR around Roseburg.
Meantime, any late night spillover from the Umpqua Divide into the
Rogue Basin should be limited and VFR.

Elsewhere, VFR will prevail through Thursday evening, though
scattered afternoon cumulus buildups are expected again late
Thursday, mainly from the Cascades eastward and in Siskiyou County.
Gusty late day westerly breezes should be slightly weaker than they
were today, close to seasonably typical values of 15 to 25 kt.
-DW

&&

.MARINE...Updated 830 PM PDT Wednesday, June 25, 2025...Light winds
and seas are expected through Thursday. A weak thermal trough
develops late Thursday then strengthens Friday through the weekend.
Strong north winds may bring steep seas south of Cape Blanco by
Friday afternoon. Steep seas could extend across the northern waters
during the weekend with gales and very steep seas possible south of
Cape Blanco. The outlook for next week is for the thermal trough to
remain strong and maintain hazardous conditions, especially south of
Cape Blanco. -Spilde

&&

.PREV DISCUSSION... /Issued 529 PM PDT Wed Jun 25 2025/

DISCUSSION...The overhead trough has once again provided support
for a strong marine push along the coast this morning, where
stratus and fog pushed into all the coastal valleys and into the
Umpqua Basin all the way to Roseburg. A very similar push is
expected again tonight into Thursday morning, and this one may
even be stronger, filling most of the Umpqua Basin and perhaps
spilling into portions of the Rogue Basin as well.

Temperatures this afternoon will be about 5 degrees cooler than
yesterday, and will remain right around the same through Friday.
Daily marine layer pushes will continue at the coast and coastal
valleys as well. Ridging will build into the area beginning
Saturday, along with the redevelopment of the thermal trough over
California and the southern Oregon coast, and as a result, we
will see temperatures rise by about 5 to 10 degrees Saturday, and
again on Sunday. Sunday will be the warmest day of this warm spell
for areas west of the Cascades, then Monday will be the warmest
for the East Side. The West Side valleys on Sunday will see highs
in the upper 90s to low 100s, while the highs on Monday for the
East Side will peak out around 90 to 95. Temperatures will then
cool slightly heading further into next week, but will remain
above normal.

As is typical with periods of heat in the region, it will come to
an end with the threat of thunderstorms. With the ridge passing
just to our east and strengthening as it moves over the Rockies, a
trough develops off the coast of California, which then attempts
to move onshore around Monday or Tuesday, taking on a negative
tilt as it does so. This is a classic pattern for convection here,
with the trough tapping into monsoonal moisture from the south,
and taking advantage of the warm surface temperatures and cooler
temperatures aloft to produce instability across the inland
portions of the forecast area.

It now appears that convection is possible Sunday afternoon,
focused west of the Cascades, but confidence is low and model
guidance seems hesitant to depict this. The pattern does support
the possibility, so while the forecast does not include thunder on
Sunday, this may change in the coming days. And any convection on
Sunday afternoon and evening may even carry on through Sunday
night.

There is much more confidence, however, on thunderstorms for
Monday and Tuesday, and it is nearly a certain thing that there
will be lighting somewhere within the forecast area both
afternoons. The trick will be where and when. For MOnday, based on
the expected location of the trough, it appears that the bulk of
convective activity will be centered around Siskiyou County and
the Siskiyous, Cascades, and Rogue/Umpqua Divide, and nearly the
entire East Side. That is not to say a few storms may not drift
into the West Side Valleys, but the chances are lower. Some
convection may carry on through the night, then on Tuesday,
thunderstorms are expected to be concentrated farther east,
focusing on areas along and east of the Cascades. Based on current
guidance, we do not expect very strong or severe thunderstorms,
but small hail and gusty winds are possible. Also, given the high
moisture content in the atmosphere that the models are depicting,
these storms will be wet, and could produce periods of moderate to
heavy rainfall. As always with thunderstorms, lightning will be a
threat, not only in regards to new wildfire starts, but also to
anyone attempting to enjoy outdoor recreation in the area. Keep
up to date with the latest forecasts as the details regarding
this thunderstorm threat become more clear over the next few days.
-BPN

FIRE WEATHER...Updated 200 PM PDT Wednesday, June 25, 2025...Mostly
low impact fire weather conditions are expected the rest of this
week with fairly typical diurnal (afternoon/evening) breezes,
seasonable humidity and near to above normal warmth.

A strengthening upper ridge will bring hotter weather to all but the
immediate coast this weekend with continued drying. Even the south
coast could have highs in the 70s to near 80F Saturday (maybe Sunday
too?). A brief period of enhanced E-NE winds at the mid slope/ridge
level is expected Friday night and again Saturday night with
moderate RH recoveries (especially Sat night), but probably not
enough to be concerned about any watches/warnings. Temperatures
increase across the interior Saturday with widespread highs in the
90s on Sunday. A few locations in the Rogue Basin could touch 100
degrees Sunday.

Meanwhile, an upper level low pressure system will consolidate off
the California coast. The upper ridge shifts to the Four Corners
region and this pattern sets up south to southeast flow aloft from
California into southern Oregon. This is a common thunderstorm
pattern for our area, so we`ll see t-storm risk increase as early as
Sunday afternoon/evening across the norCal mountains. We don`t
currently have thunderstorms in the forecast (PoP less than 15%),
but this may change, so keep checking back for updates). Even so,
some instability is present and small portion of ensemble members do
show activity popping over the higher terrain. As shortwave
disturbances ride northward ahead of the closed low off the Cali
coast, lightning chances increase on Monday. There is some nocturnal
risk for lightning as well Sunday night and again Monday night. The
main storm threat shifts to the Cascades and points south and east
Tuesday into mid next week. As fuels continue to dry out and the
calendar shifts from June to July, fire danger will increase. So, be
on the lookout for potential Fire Weather Watches/Red Flag Warnings
as we head into next week. -Spilde

&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$