320
FXUS66 KMFR 111020
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
320 AM PDT Sun Aug 11 2024

.DISCUSSION...The forecast area is sandwiched between a weak upper
low near 38N/133W and an upstream upper trough moving into northwest
Washington state, with a weak west to southwest flow.

Much like the last few nights/early mornings, the latest satellite
image shows marine stratus along the coast and inland into the
coastal river valleys and Coquille Basin. The inland push of the
marine stratus has been slow but steady and could move into portions
of the Umpqua Basin towards daybreak. Elsewhere skies are clear.

Dry weather will continue today with the marine stratus away from
the coast gradually burning off during the morning. Meanwhile the
marine stratus is expected to persist at the coast and just offshore
through the day. Also the exception to the dry weather will be
patchy drizzle along the south coast, including Brookings this
morning.

Weak instability exist over the northern Cascades this afternoon,
but mid level moisture and trigger is lacking. This in addition to
the extent of the smoke will put a cap on the amount of
instability, therefore were not expecting thunderstorms. However,
we`ll see cumulus build ups in the afternoon.

Not much change in the pattern is expected through next week. The
general consensus among the operational models, ensemble members and
clusters all point to weak troughing over the area. This will result
in cooler afternoon temperatures that will be near normal for this
time of the year for the interior.

Monday, the weak upper trough that is currently offshore will move
inland and it will become negatively tilted by Monday afternoon.
This along with increasing instability could set the table for
Isolated thunderstorms east of the Cascades Monday afternoon into
Monday evening. The wildcard in terms of thunderstorm coverage or
lack thereof will be the extent of the smoke. If the smoke remain
extensive, it will put a cap or even result in less instability
resulting in a couple of isolated storms or nothing at all.

Weak troughing remains over the area for the rest of the week with
dry conditions. the one exception could be Thursday. The models are
in pretty good agreement showing an upper trough moving through the
area Thursday afternoon which could provide enough trigger to kick
off isolated thunderstorms Thursday afternoon and evening. Afternoon
temperatures during this time will be slightly below normal.

Next weekend, the clusters suggest the upper trough will deepen some
with the center of the upper trough over the PAC NW. The ensemble
means show some variation with the center of the upper low/trough
with the ECMWF mean showing the upper trough over the area while the
GFS mean has it centered slightly to the west. The operational
models are in similar agreement showing a rather strong upper low for
this time of the year centered over the PAC NW. Afternoon
temperatures for the interior are likely to end up below normal (6-8
degrees) for this time of the year. -Petrucelli


&&

.AVIATION (06Z TAFs)...A marine layer will continue IFR
conditions at the coast and coastal valleys, both north of Cape
Blanco and south of Gold Beach overnight, including at North Bend
(KOTH) and Brookings (BOK). This is expected to persist through
around 18Z Sunday morning, then develop again early Sunday
evening, around 03Z.

Meantime, inland TAF sites are expected to remain mostly VFR.
Wildfire smoke is thickest, with MVFR visibility likely, from
eastern Douglas County into northern Klamath County, and in
southwest Siskiyou County. Elsewhere, smoke could still cause minor
visibility restrictions. Otherwise, typical afternoon and evening
breezes are expected with clear skies.
-DW


&&

.MARINE...Updated 200 AM Sunday, August 11, 2024...Wind speeds will
peak this afternoon combined with steep seas which will result in
conditions hazardous to small craft through this evening. The
probability for wind gusts of 34 knots or greater south of Cape
Blanco is roughly 40-60% where we have the current Small Craft
Advisory. These speeds will remain breezy/gusty until sunset before
slowly decreasing overnight. Thereafter, winds and seas will both
ease through at least the middle of the week.

-Guerrero


&&

.FIRE WEATHER...Issued 200 AM Sunday August 10, 2024...The
forecast period will trend cooler through next weekend with
increasing onshore flow. The increased onshore flow will result in
good overnight recoveries for the coast, coastal valleys, Coquille
and Umpqua Basin, including the complex of fires in central and
eastern Douglas County.

Weak upper troughing is expected today with cooler afternoon
temperatures. There`s good agreement instability is marginal at
best, with little or no trigger, and dryer at the mid levels. In
addition, the extent of the smoke east of the Cascades will also
likely inhibit the formation of storms, therefore the threat for
thunderstorms are next to zero. The most likely scenario will be
cumulus build ups in the afternoon over the Cascades and higher
terrain east of the Cascades and northern Cal.

Monday, an upper trough that is currently offshore will move inland
as it gets picked up by a deepening upstream upper trough in
northwest Washington, the upper trough is expected to become
negatively tilted and this in combination with increasing
instability, mid level moisture and trigger could result in isolated
thunderstorms east of the Cascades Monday afternoon into Monday
evening. However, if the smoke remains extensive east of the
Cascades, it could put a cap or event result in less instability,
thus resulting in no thunderstorms.

Weak troughing remains over the area for the rest of the week with
dry conditions. the one exception could be Thursday. The models are
in pretty good agreement showing an upper trough moving through the
area Thursday afternoon which could provide enough trigger to kick
off isolated thunderstorms Thursday afternoon and evening. Afternoon
temperatures during this time will be slightly below normal.

Also higher afternoon relative humidities are expected with fairly
good overnight recoveries, even for the eastside and northern
California. We`ll still have to deal with gusty breezes in the
afternoon and early evening hours, but with higher humidities in the
afternoons, were not expecting critical conditions.

Next weekend is still shaping up to be cool with higher relative
humidities in the afternoons along with good overnight recoveries as
an upper trough settles near or over the forecast area. -Petrucelli


&&

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

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

&&

$$