628
FXUS66 KMFR 232147
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
247 PM PDT Sun Jun 23 2024

.DISCUSSION...We are on the backside of a trough and onshore flow
is maintaining some cloud cover around Coos and Douglas County,
and is holding temperatures a few degrees cooler than yesterday;
which if you missed it, produced a record high temperature of 96
degrees at Mt. Shasta City. As the thermal trough builds, the
north winds will strengthen, clearing out the existing clouds and
limiting fog production along the immediate coast tonight. Further
inland across the Coquille and Umpqua river valleys, fog will be
possible tonight.

As high pressure builds in on Monday, temperatures will warm. By
Tuesday temperatures should be back into the 90s, with drier
conditions in the afternoon. This will bring some elevated fire
weather conditions, but the greater impact should be Wednesday
because another front will be moving onshore as a deeper trough
builds over the PNW.

This front will develop gusty WSW winds again east of the
Cascades on Wednesday afternoon/evening (shifting to WNW) with
breezy conditions (NW winds) for the west side. Moisture has
remained limited with the system, but another strong marine push
could induce some light rain/drizzle or mist along the coast and
mountains of Douglas County. The best precip chances are to our
north, but there remains a low probability (<20%) of showers
across northern Douglas County.

There still remains a non-zero chance for thunder because of some
high lapse rates. However, moisture remains limited, which is the
main limiting factor. Another is that the front moves through in
the morning hours of Wednesday, and so the instability is small
due to a lack of solar heating.

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

&&

.AVIATION...(23/18Z TAFs)...MVFR ceilings linger in the Umpqua Basin
and areas westward to the coast, including Roseburg and North Bend.
Meanwhile, LIFR visibilities and ceilings persist along and just near
shore around Brookings and areas southward. These lower conditions
will gradually improve over the next few hours, lingering longest
near Brookings, with VFR likely to return to all areas between 19z-
21z. A weaker marine push this evening is expected to bring a return
of LIFR/IFR to the coast, and into the Coquille and lower Umpqua
valleys, though the inland extent should be less than this morning.

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

&&

.MARINE...Updated 130 PM Sunday, June 23, 2024...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 late this afternoon. 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 week into next weekend. /BR-y

&&

.FIRE WEATHER...Overall, warm (above normal) and dry conditions
are forecast through next week with only a slight break Thursday.
Temperatures are likely to be about 10+ degrees above normal for
many locations through this period. However, Thursday we get a
cooler airmass, and we will be near normal with great humidity
recoveries both Thurs and Fri morning. Fire weather conditions
will unfortunately remain around elevated to near critical until
this cool down occurs.

The overlap of low RH (<20%) and breezy winds (>15mph) will be most
notable today (Red Flag for Modoc County). Conditions do improve
slightly tomorrow (Monday), but we could still see elevated fire
weather conditions across the eastside.

Fuels are of course tricky this time of year in transition to
summer, and this may be the limiting factor regarding fire weather
conditions until fuels transition over to "high". At this time,
elevated to critical fire weather conditions should be anticipated
through at least Wednesday. Even with the passage of the front, we
are only expecting a slight cool down with RH values staying on the
low side.

Another dry front approaches the area Tuesday and moves onshore
Wednesday. Currently, Tuesday looks like the driest day with
afternoon RH values dropping down to around 10% east of the
Cascades. Winds pick up again in the afternoon, but probably not
widespread critical levels. Best chances for elevated to critical
thresholds are going to be across NorCal and Oregon east of the
Cascades. 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 drop in temperature and an
increase in humidity to help mitigate this threat, but areas farther
east are more susceptible. We`ll be taking a close look at this in
the next couple of shifts.

The one caveat for Wednesday is the thunderstorm potential. We will
have to watch how this upper low tracks as the moisture fetch will
be key, but right now its not the most favorable setup for thunder
with the lack of instability Wednesday (at this time). Either way,
the track is shaping up to produce breezy/gusty winds, especially
east of the Cascades.

-Guerrero


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...Red Flag Warning until 8 PM PDT this evening for CAZ285.

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

Hazardous Seas Warning until 11 PM PDT Monday for PZZ356-376.

&&

$$