864
FXUS66 KMFR 261117
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
417 AM PDT Thu Jun 26 2025

.DISCUSSION...Today through Sunday...Stratus remains blanketed
along and west of the coastal mountains this morning with
generally clear skies for the remainder of the area. A weak trough
is passing through the region this morning, and this should
result in more coverage of marine stratus into the Umpqua Basin by
sunrise. Any cloud cover this morning should give way to sunshine
this afternoon, with the exception of along the coast where
clouds will be more persistent. Otherwise, today will be much like
yesterday with afternoon temperatures trending just a few degrees
cooler today. Rinse and repeat is the story for tonight and
Friday. Weak, persistent troughing over the Pacific Northwest will
bring another marine push tonight into Friday morning with
similar afternoon temperatures and breezes on Friday compared to
today.

The pattern transitions for the weekend as heights build over the
region and the thermal trough returns along the coast Friday and
strengthens into the weekend. Temperatures will trend warmer by
about 5 degrees Saturday, with another 5 to 10 degrees of warming
expected 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. NWS HeatRisk values
show a moderate risk for heat related illnesses for this event,
especially for those sensitive to these temperatures and those
without effective cooling means and hydration. Take it easy if you
need to be outside during this heat. Remember to seek shade, take
frequent breaks and stay hydrated! Also, if you plan to seek relief
by recreating in area water ways...please remember that the water is
still cold and cold water shock can happen to even the strongest of
swimmers. Wear a life jacket and take frequent breaks from the cold
waters.

Temperatures trend slightly cooler heading further into next week,
but will remain above normal. Meanwhile, an upper level pattern
develops Sunday into Tuesday that is a classic thunderstorm pattern
for our region. Please see the previous shift`s discussion that
follows for details, which largely remain consistent with recent
model runs...

...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

&&

.AVIATION...26/12Z TAFs...Marine layer stratus is bringing MVFR
conditions to the coastal waters and areas along the coast west of
the coastal mountains. A weak trough passing through the region this
morning should push this marine stratus into portions of the Umpqua
Basin by sunrise with some spillover possible into the Rogue Basin.
Ceilings are expected to be on the edge between VFR and MVFR around
Roseburg, with conditions more scattered and VFR south of the Rogue-
Umpqua Divide. Conditions should improve to VFR later this morning,
with the lower conditions lingering longest along the coast. Even
still, a period of clear conditions is expected this afternoon for
coastal locations.

Elsewhere, VFR will prevail through this evening, though scattered
afternoon cumulus buildups are expected again this afternoon and
evening, mainly from the Cascades eastward and in Siskiyou County.
Expect the typical increase in afternoon/evening winds, though
should be slightly weaker than they were on Wednesday and closer to
seasonable values of 15 to 25 kt.

&&

.MARINE...Updated 130 AM PDT Thursday, June 26, 2025...Relatively
calm conditions will persist today under light winds and low seas. A
thermal trough will take shape today, bringing some increasing north
winds south of Gold Beach this afternoon and evening, but winds will
remain below advisory levels today. The thermal trough strengthens
on Friday and even more so over the weekend. Conditions hazardous to
small craft will develop Friday afternoon from Gold Beach southward
as north winds increase and seas steepen. Conditions worsen on
Saturday as advisory level winds and seas likely spread north of
Cape Blanco, 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

&&

.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...Small Craft Advisory from 2 PM Friday to 11
     AM PDT Saturday for PZZ356-376.

&&

$$