FXUS66 KMFR 190558 AAA
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1058 PM PDT Thu Jul 18 2024

Updated Aviation Discussion.

.DISCUSSION...High pressure rests over the region with a Pacific
trough grazing the PacNW coast. Temperatures are expected to
slowly climb Friday into Saturday. The main feature on satellite
is smoke from the newly ignited fires from early week
thunderstorms. These fires are seen near Diamond and Lemolo
Lakes, and scattered across eastern Douglas, southeastern Lane and
far northern Klamath counties. These fires and smoke from them
will be a focus for operations in the near future.

A weak disturbance off the southern California coast will be
making its way northward tonight through Friday, and then will
pass through the area Saturday. A slight chance (10-20%) for
thunderstorms continues or has been re-introduced to the area as
this wave lifts north Saturday afternoon and night. More 10-20
percent chances continue Sunday afternoon and evening across the
east side as weak short waves continue to target the area in SW
flow aloft.

Thereafter the main story will be drier more stable southwest
flow aloft and temperatures closer to normal as low pressure
centers near British Columbia and the 4-corners high gets pushed
to the southeast through late week. Stavish

&&

.AVIATION...July 19/06Z TAFS... VFR is expected for the
next 24 hours for all areas except for the coast from Cape Blanco
northward and Brooking southward, where IFR and LIFR ceilings are
expected through late morning on Friday.  These ceilings will push
inland overnight into the Coquille Valley but are not expected
to reach Roseburg (KRBG). Typical diurnal breezes are expected
through this cycle. -CC

&&

.MARINE...Updated 245 PM Thursday, July 18, 2024...Weak low pressure
offshore has disrupted the thermal trough pattern. Weak winds and
low seas will persist into Friday morning. A weak thermal trough is
expected to return Friday and strengthen this weekend with the
strongest winds south of Cape Blanco. Advisory strength northerly
winds and steep seas are possible Saturday, then gales and steep to
very steep seas are possible early next week. -DW/Hermansen/Sargeant

&&

.FIRE WEATHER...Issued 200 PM Thursday July 18, 2024...

A dry and stable southwest flow continues through Friday with no
concerns for thunderstorms. However, afternoon relative humidities
will trend lower for most interior locations with values in the
single digits for portions of the East Side through Friday along
with the typical gusty afternoon and early evening breezes. This
will result in near critical conditions for portions of Fire zones
624, 625 and 285, but were not expecting the combination of wind and
RH to result in Red Flag conditions.

The other concern for those involved in air attack on the various
fires in our area will be visibilities lowering to 3-4sm in the
vicinity of the Shelly and Trail Fires. The latest run of the HRRR
smoke fields show the smoke being transported east to southeast of
those fires late this afternoon and evening, therefore visibility
could be reduced to 4-6sm into early this evening. Tonight, as the
mixing height decreases, the smoke will settle and be confined to
around the fire perimeter of the fires resulting in MVFR visibility
between 3-5sm. Also smoke could also settle in the valleys adjacent
to the Shelly Fire.

There's still a concern for thunderstorm this weekend. Saturday, an
upper trough will move up from the south just off the California
coast and could tap into some monsoonal moisture with a southeast
flow aloft. At the same time, there's good agreement, the upper
trough will become negatively tilted Saturday afternoon into
Saturday night. Based in part on pattern recognition, this could be
problematic in that we could see storms break out mid to late
Saturday afternoon in portions of fire zones 280, 281 and 284.

Saturday night, the axis of the upper trough is still south of our
area which heightens the concern for nocturnal storms west of the
Cascades, and portions of the east side in Oregon Saturday night.
Many times the models will not show signs of unstable conditions
with this type of pattern, then the next thing you know something
breaks out of nowhere. The pattern that is setting up is one where
the instability is elevated, and thus the convection will be
elevated as well. Not saying this is a slam dunk, but at the same
time it cannot be discounted.

The upper trough axis shifts north during the day Sunday. Any threat
for storms could be confined to the early morning hours over the
northwest part of our area, then shifting north late Sunday morning
through Sunday afternoon with a drier and stable southwest flow
moving into the area. The exception could be in portions of Fire
zone 623, 624 and 625 where isolated storms are possible late Sunday
afternoon. Not convinced anything will happen in these areas, but
there are some signals suggesting it cannot be discounted either.

Monday, a dry and stable southwest flow will set up with any chance
for storms shifting east and northeast of our area. It will be
cooler with gusty afternoon and early evening breezes for the
interior westside valleys and east of the Cascades.

The rest of next week is pointing towards dry and cooler weather,
but afternoon temperatures will still be above normal for the
interior. However, the concern will shift towards moderate to locally
poor overnight recoveries for the mid slopes and ridges in southwest
Oregon and western Fire zone 280, and the typical gusty afternoon
and early evening breezes for the interior westside valleys and east
of the Cascades with low afternoon RH's. -Petrucelli

&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$