386
FXUS66 KMFR 181404
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
704 AM PDT Tue Jun 18 2024

.UPDATE...Updated the aviation section.

&&

.AVIATION (12Z TAFs)...
MVFR extends from the southern and central Umpqua Valley (including
Roseburg) into the southern Coquille Valley. This stratus is
expected to dissipate to VFR by 17Z. Otherwise, VFR is expected
through this evening. -DW

&&

.MARINE...Updated 230 AM Tuesday, June 18, 2024...High pressure
offshore and a thermal trough along/near the coast will likely
remain in place through at least the weekend. This will result in
persistent northerly winds and wind-driven seas through this period.
Conditions will be worst south of Cape Blanco where winds and steep
seas hazardous to small craft will persist. The thermal trough
strengthens slightly and expands northward this afternoon, which
will result in the small craft advisory conditions south of Cape
Blanco this morning, expanding across the waters north of Cape
Blanco this afternoon into Wednesday morning.

The thermal trough will strengthen further Wednesday afternoon into
Friday evening, and this may bring very steep seas and/or northerly
gales to the waters south of Cape Blanco Thursday afternoon into
Friday evening. Consequently, it is recommended mariners to stay
tuned to updates as we move through the week.

-Guerrero/DW

&&

.PREV DISCUSSION... /Issued 323 AM PDT Tue Jun 18 2024/

DISCUSSION...Active weather is largely behind us as an upper trough
moves to the east with a developing ridge taking its place. For
tonight, this stability is allowing for another night of freezing
temperatures east of the Cascades. Fort Rock has reached 29 degrees
and Cabin Lake is down to 23 degrees. Other areas farther south are
still in the mid to high 30s, but clear skies across the area will
allow for cooling to continue through the early morning. A Freeze
Warning remains in place for areas east of the Cascades through 8 AM
today. Please see NPWMFR for more detailed information.

Daytime temperatures will increase through the week under the upper
ridge. Today`s temperatures will be 5 to 10 degrees above Monday`s,
with mid to high 60s along the Oregon coast, high 70s to low 80s in
west side valleys, and mid 60s to mid 70s to the east. Wednesday`s
highs will see another 5 to 10 degree increase for most areas.
The warming trend will continue through the end of the week,
although fortunately the rate of warming will slow. Friday and
Saturday will be the warmest days of the week, with west side
valleys in the low to mid 90s and east side areas in the mid to
high 80s. Currently, heat warning products are not expected but
individuals who have difficulties acclimating to warmer
temperatures will want to be cautious participating in outdoor
activities at the end of the week into the weekend. Of course
nighttime lows will increase as well, but the only impact here is
the end of freezing temperatures east of the Cascades.

Thunderstorm chances will be considered through the week. While no
significant forcing mechanisms are expected, convective heating is
usually good for some slight afternoon thunderstorm chances. For
this week, Wednesday afternoon has some 5-10% thunderstorm chances
over eastern Douglas and northern Klamath and Lake counties. On
Thursday afternoon, those chances spread down the Cascades and into
Siskiyou County. There`s more uncertainty in thunderstorm chances
going into the weekend, but future guidance should help to clarify
those chances. Generally, given the weak forcing and absence of
available moisture, some isolated thunderstorm cells are possible
later in the week but widespread activity is not expected right now.

Overall, while temperatures warming quickly always feels unpleasant,
there`s no signal for anything extremely worrying as far as fire
conditions in the current forecast. Afternoon breezes will increase
under this stable pattern and dry vegetation is always worth being
aware of, but the expected conditions through the week are within
normal climate ranges. Of course, any changes to this expectation or
any localized hazards will be quickly communicated.

Looking to the end of the weekend and into next week, a low pressure
system approaching the Canada coast on Sunday will help to push the
upper ridge away. A pattern change to zonal flow aloft will result
in cooler temperatures down at the surface. This may also bring
cloud cover and slight 5-10% chances for showers along the Oregon
coast, especially north of Cape Blanco on Sunday morning. Current
guidance shows the low pressure system spinning in place into next
week, although there are slight variations on its location.
Probabilistic guidance for the middle of next week shows a 10 to 15
degree spread in interquartile ranges across the area (North Bend,
Roseburg, Medford, and Klamath Falls), indicating some
uncertainty in temperatures next week. However, meteograms for
both the ECMWF and GFS models expect inland areas to stay dry and
only light precipitation for North Bend through Sunday and Monday.
-TAD

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Warning until 8 AM PDT this morning for ORZ029>031.

CA...Freeze Warning until 8 AM PDT this morning for CAZ084-085.

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

     Small Craft Advisory from 2 PM this afternoon to 5 AM PDT
     Wednesday for PZZ350-370.

&&

$$