923
FXUS66 KMFR 131804
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1104 AM PDT Thu Jun 13 2024

...Updated AVIATION discussion...

.DISCUSSION...No changes are needed to the forecast. Today`s
temperatures will stay above seasonal averages across the area
under the back side of an upper ridge. Cooling is expected over
the weekend as the upper level pattern changes and two weak
troughs pass over.

Please see the previous discussion for more details about the
short- and long-term forecasts. -TAD

&&

.AVIATION...13/18Z TAFs...Patches of IFR linger at the coast near
Brookings and Cape Arago. Further dissipation to clear skies is
expected into this afternoon, but a mix of IFR/MVFR stratus is
expected to return to the coast around 04Z this evening and persist
until around 16Z Friday morning. Otherwise, conditions will remain
VFR with high level cirrus arriving Friday morning. Also, gusty
westerly breezes are expected this afternoon into the evening, with
gusts to 30 mph over the higher terrain and east of the Cascades,
including Klamath Falls.

-DW

&&

.MARINE...Updated 850 AM Thursday, June 13, 2024...Steep seas
will continue across all waters through Friday morning, with areas
of very steep seas (Hazardous Seas Warning) continuing south of
Port Orford this morning across the outer waters. Thereafter,
relatively calmer seas are expected through Sunday morning. By
Sunday afternoon, there is a lot of uncertainty with model
guidance, and there is at least some potential for a strong closed
low to pass aloft. This could bring in a strong fresh swell in
addition to stronger wind speeds than we currently have forecast
at the moment. We essentially have a scenario where either an
upper level low takes a northern track or a southern track through
the PacNW Sun-Mon. As the track becomes clearer, we should have a
much better idea of potential hazards (or lack thereof) over the
waters.

-Guerrero

&&

PREV DISCUSSION... /Issued 258 AM PDT Thu Jun 13 2024/

DISCUSSION...Fog is building in the Coquille valley and current
expectations are for there and portions of Curry county around
Brookings to be the only places where fog forms.

The thermal trough along the coast will shift inland today. This
will bring a small 1 to 3 degree bump up in temperatures from
yesterday and drier conditions along the I-5 corridor. The
displacement of the thermal trough is being driven by the
overspreading of a mid-level trough over the Pacific coast. In
addition to the small fluctuations in temperature and humidity,
the larger impact will be to winds. The west east pressure
gradient will amplify, causing the typical diurnal winds to be a
bit stronger than normal (10-20 mph, gusts around 30-35 mph). This
will be especially true in the lee of the Cascades, where the
downslope winds and humidities below 15% could lead to brief
critical fire weather conditions for 1 to 2 hours in Modoc, Lake,
and eastern Klamath County. Critical fire weather conditions may
also exist for an hour or two around the Scott Valley today.
However, it`s important to note that these conditions are fairly
typical in the summer and not really uncommon.

Friday, a noticeable cooldown is expected as the trough moves a
cooler polar air mass into the region. Conditions will again be
windy in the afternoon as the diurnal winds get an enhancement,
but with humidities trending up a few percentages, no fire weather
concerns are expected. Perhaps the bigger concern will be the
cold temperatures in the mountains and areas east of the Cascades.
Near to below freezing temperatures are expected Friday night and
continuing through the weekend. Anyone in these areas with plants
outside will want to consider covering them, and campers will
want to make sure they plan appropriately for these cold
temperatures.

There is a small chance for rain amounts less than 0.05" Friday
night across Coos, Douglas, and northern Klamath County,
especially in the higher terrain. The more moist front is
expected Sunday into Monday. Chances are peaking around 40%, so
nothing is certain with this front other than some elevated wind
speeds and a good marine push leading to increasing humidities.
If enough moisture does arrive with the front to produce
precipitation, amounts are generally expected to be less than
0.1", except in the coast range and the Cascades, where up to 0.2"
seems reasonable. There could also be a thunderstorm threat with
this system, but for right now, the greatest instability is ahead,
not along, the front and the core of the trough is too far north
to add thunderstorms to the forecast. That said, some showers will
still be strong and their heavier precipitation rates combined
with snow levels near or below below 6kft, the peaks of the
Cascades (including at Crater Lake NP) could pick up some new wet
snow cover.

We will remain in this cooler, unsettled weather pattern into the
start of next week.

-Miles

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Friday
     for PZZ350-356-370.

Hazardous Seas Warning until 11 AM PDT this morning for PZZ376.

     Small Craft Advisory until 2 AM PDT Friday for PZZ376.

&&

$$