813
FXUS66 KMFR 211744
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1044 AM PDT Fri Jun 21 2024

.UPDATE...Updated aviation and marine sections.

&&

DISCUSSION...The official/astronomical start to summer 2024
begins with a relatively typical summer weather pattern over
Northern California and Southern Oregon. The marine layer and
associated low clouds and fog cover much of the coastal waters and
spread inland into portions of Coos and Curry Counties. Farther
inland, mostly clear skies are being observed, with just some high
clouds pushing in from the northwest. A stable, warm and dry
weather pattern will continue through Saturday with high
temperatures about 10 degrees above normal for this time of year.
Another feature that is typical of summertime in Southern Oregon,
though a little earlier than normal, is a wildfire showing up on
morning satellite imagery. The Upper Applegate wildfire is located
south of Ruch, and GOES 18 satellite imagery allowed us to
observe the fire intensity through the night, from above. Fire
intensity has decreased overnight, per the imagery, likely due to
firefighting efforts and/or increasing humidity/decreasing winds
overnight. It`s not totally clear how much smoke impact from this
new fire can be expected over the next few days. The HRRR smoke
model (generally reliable) isn`t painting much in the way of smoke
near the Upper Applegate fire over the next 48 hours, but this
seems underdone, considering the heat on the fire last night, and
what looked like plenty of smoke production yesterday afternoon.
Therefore, we`ve added patchy smoke to the forecast for areas in
Jackson County west of I-5 and south of Ruch, with winds carrying
any smoke southward towards Siskiyou County. More on the fire
weather environment can be found in the fire weather discussion
below.

Given the stable, westerly to west-southwesterly flow aloft over the
next few days, no thunderstorms are expected over the forecast area.
Breezy conditions are expected this afternoon and moreso on Saturday
afternoon, especially east of the Cascades, as an upper trough
approaches from the northwest and the thermal trough that has been
at the coast the past few days, moves well inland. Speaking more to
the coast, today will feature gusty northerly winds, and then the
marine layer and gusty northerly winds will be disrupted/weakened
Saturday with the approach of the upper level trough. This
disruption won`t last for long, so expect gusty northerlies at the
coast, and marine layer stratus/fog to return Sunday into Monday at
least.

The upper trough will bring cooler conditions to the area on Sunday,
with temperatures dropping closer to normal for this time of year.
Sunday will probably be the breeziest day through at least early
next week. Winds will gust to 25 or 30 mph in areas east of the
Cascades Sunday afternoon. We`ve added some detail in that area of
the forecast to highlight these particularly gusty conditions east
of the Cascades, supported by some of our post-processed guidance
that is keying in on anomalously strong winds.

The cooldown will be shortlived though as upper troughing lifts
north and east, and heights build over the region.  We`ll return to
temperatures similar to today by Tuesday. Models show no signal for
thunderstorms over Southern Oregon or Northern California through at
least the middle of next week. Keene

AVIATION 21/18Z TAFs...IFR ceilings will persist at the coast, with
some clearing south of Cape Blanco under gusty north winds. IFR/LIFR
ceilings and visibilities will expand back on shore tonight.

Inland, VFR ceilings will persist through the TAF period. Winds
gusting up to 20 mph will be possible in the Umpqua Basin this
afternoon. A fire in the Applegate Valley could produce local IFR
visibilities near that valley Friday afternoon, but should not
restrict visibility in the Rogue Valley.

-Miles

&&

.MARINE...Updated 945 AM Friday, June 21, 2024...High pressure
offshore and a thermal trough along/near the coast will remain in
place through Monday. This will result in persistent northerly winds
and areas of steep to very steep wind-driven seas. Winds will be
strongest south of Pistol River, with hazardous seas expected in
that area. The thermal trough is expected to peak today and this
will maintain advisory seas south of Cape Blanco, but conditions
will begin to calm north of the cape.

Slight improvement is expected Saturday into Saturday night as a
front brings a surge of stratus with light showers possible.

-DW/Hermansen

FIRE WEATHER...Given the recent wildfires that have occurred in
Southern Oregon, we`ll take a look at the near-term fire weather
environment here for those interested. For areas west of the
Cascades, focused particularly near the Upper Applegate fire, over
the next couple days expect good humidity recoveries (80% and
higher) in valleys and moderate to good humidity recoveries over
upper slopes and ridges (50-70%) overnight. Afternoon humidities
will bottom out in the mid to upper teens to 20 percent for this
area, with these minimum humidity values trending similar Friday
afternoon to Saturday afternoon. Gusty north to northwest winds
are expected in the afternoons west of the Cascades, with winds a
little higher today than tomorrow afternoon, gusting to around 20
mph each afternoon. Light winds are expected tonight and Saturday
night.

East of the Cascades, the strongest breezes are expected Sunday
afternoon, with some areas gusting to 30 mph. Humidity will trend
upward some from Saturday afternoon to Sunday afternoon.

No lightning is expected over the forecast area through at least
Tuesday. Keene

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Saturday
     for PZZ356-376.

Hazardous Seas Warning from 2 PM this afternoon to 2 AM PDT
     Saturday for PZZ356-376.

     Small Craft Advisory until 2 PM PDT this afternoon for PZZ370.

&&

$$