-- Discussion containing changed information from previous version are highlighted. --
450
FXUS66 KMFR 231025
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
325 AM PDT Sun Jun 23 2024

.DISCUSSION...
-- Changed Discussion --
A dry front will push to the east of the area today.
Satellite imagery is showing a good marine push behind the front
along the coast and into the Umpqua Basin where stratus has filled
in (a little drizzle has been reported as well). The clouds will
press to about the Rogue-Umpqua Divide, but moisture depth
appears to be too shallow to spill over into the Rogue Valley. So,
just expect sunny skies to prevail today for all areas from Rogue
Valley south and east. The clouds in the Umpqua Valley and coast
will gradually dissipate late morning/early this afternoon. A
strong west to east pressure gradient will develop over the area
again today causing another round of gusty west to southwest winds
from the Cascades eastward this afternoon and evening. Overall,
we`re expecting wind speeds to peak in the 15-25 mph range over
there with some gusts of 35 mph. It will turn breezy (from the
NNW) this afternoon/evening for some west side areas as well with
gusts in the 20-25 mph range. The front should take the edge off
the heat a bit, especially from the Cascades westward (and also
where there`s clouds this morning). Most areas inland from the
coast over to the mountains will have about 6-12 degrees of
cooling compared to yesterday. Cooling won`t be as noticeable
though over the east side, about 2-5 degrees lower than yesterday.

The flow aloft becomes zonal tonight, then the axis of an upper
ridge offshore on Monday will move through the PacNW Monday night
into Tuesday. This will bring continued dry weather to much of the
CWA along with sunny days and clear nights, except for patchy
marine layer clouds along the coast at night/early morning.
Daytime temperatures Monday and Tuesday will be about 5-10 degrees
above normal.

Mid-level flow increases across the area at midweek as the next
upper trough over the NE Pacific heads toward the BC coast. This
will drag another dry front onshore on Wednesday. This is
basically a repeat of the pattern from this weekend, so we expect
gusty WSW winds to develop again east of the Cascades on
Wednesday afternoon/evening (shifting to WNW) with breezy
conditions (NW winds) for the west side. With limited moisture,
precipitation is unlikely, though another expected marine push
could induce some light rain/drizzle or mist along the coast. The
upper trough will move onshore into the PacNW on Thursday. While
the NBM is mostly dry and keeps the best precip chances to our
north, there is a low probability (<20%) of showers across
northern Douglas County. By far, the most noticeable impact from
this system weather-wise will be the winds and the drop in
temperatures again, probably 5-10F lower than on Tuesday.

The cooler weather will continue on Thursday, but things should
warm up again Friday into Saturday before the next trough arrives,
probably on Sunday. -Spilde
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
23/06Z TAFs...Later tonight, LIFR/IFR conditions
along the coast and in the Coquille and Umpqua valleys, are
expected to lift slightly to IFR 06Z due to the arrival of a weak
front. This may also produce drizzle/light showers near shore into
early Sunday morning.

Conditions in the central and southern Umpqua Valley are expected to
be MVFR, including beginning around 08Z at Roseburg (KRBG). The
marine layer will not be deep enough to broadly spill over the Rogue-
Umpqua Divide, but there could be some scattered clouds that develop
over the Illinois and Applegate Valleys around sunrise Sunday
morning.

The coastal and Umpqua stratus will gradually dissipate after
sunrise, with VFR likely to develop across the area by 19Z. A weaker
marine push on Sunday evening is expected to bring a return of
LIFR/IFR to the coast, and Coquille and lower Umpqua valleys.

Elsewhere, conditions will remain VFR with gusty afternoon westerly
winds expected to resemble those from Saturday.

/DW
-- End Changed Discussion --


&&

.MARINE...
-- Changed Discussion --
Updated 215 AM Sunday, June 23, 2024...A weak front will
bring a surge of stratus through early today with light showers
possible across the northern waters. The thermal trough will
restrengthen today, bringing increasing north winds and steepening
seas. Steep seas are expected for much of the waters south of Cape
Blanco, with very steep and hazardous seas developing south of
Pistol River by this evening. These conditions will persist through
Monday evening before the approach of another front disrupts the
pattern into mid-week. The outlook is for a return of the thermal
trough pattern late in the week.

/DW/Hermansen
-- End Changed Discussion --

&&

.FIRE WEATHER...
-- Changed Discussion --
Updated 245 AM Sunday, June 23, 2024...We`ll
continue to see a fairly typical fire weather pattern across the
Pacific Northwest today right through next weekend. This will
feature a couple of dry frontal passages, marine pushes into the
coast/Umpqua Basin, and low afternoon humidity inland with breezy
to gusty pm/eve winds, especially east of the Cascades. Both
critical wind & humidity are expected today as the first dry
front pushes to the east. Modoc County, in particular, will reach
critical RH/wind thresholds this afternoon/evening with wind gusts
nearing 35 mph and RHs down around 10%. Local fuels experts have
indicated high fire danger in Modoc, so the Red Flag Warning is
warranted there for this afternoon. It will also be gusty in
parts of Klamath/Lake counties (FWZs 624/625) with dry PM RHs,
though wind criteria there are a bit higher. Given less receptive
(moderate) fuels east of the Cascades in Oregon, we have not
issued a Red Flag for those zones. It should be noted, however,
that a couple of sites there could flirt with critical weather
thresholds this afternoon/evening.

West of the Cascades, we don`t anticipate critical fire weather
conditions. The marine push onto the coast and into the Umpqua
will provide cooler, more moist conditions there. It will still be
dry in the Rogue/Illinois valleys with afternoon humidity down in
the 20-25% range and fairly typical afternoon WNW breezes (10-15
mph).

On Monday, the same areas (Modoc/east of the Cascades in Oregon)
will have elevated fire weather risk. RH values will be similar to
today, but with perhaps just a touch less wind.

Yet another dry front will approach the area Tuesday and move
onshore Wednesday. Right now, Tuesday looks like the driest day
with afternoon MinRH values down to around 10% again east of the
Cascades. Winds pick up again in the afternoon, but probably not
widespread critical levels. Best chance is in Modoc again and east
of the Cascades in Oregon. As mentioned yesterday, Wednesday
appears to be the day where we get another period of stronger,
gusty WSW winds in combination with low humidity, especially east
of the Cascades. For most of the area, guidance is showing a
sufficient drop in temperature and an increase in humidity to
mitigate the threat somewhat, but areas farther east are most
susceptible. We`ll be taking a close look at this in the next
couple of shifts.

The cooldown lasts through Thursday, followed by a warm up
Fri/Sat before the next trough/front moves through Sunday.

The good news is that while thunder chances over the next 7 days
aren`t zero, this pattern is not really favorable for lightning
since deep moisture is cut off from moving northward and the
overall storm track is too far to the north. -Spilde
-- End Changed Discussion --

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
OR...CA...Red Flag Warning from noon today to 8 PM PDT this evening for
     CAZ285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Monday
     for PZZ356-376.

Hazardous Seas Warning from 5 PM this afternoon to 11 PM PDT
     Monday for PZZ356-376.
-- End Changed Discussion --

&&

$$

MAS/ANH/DW