358
FXUS66 KMFR 121033
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
333 AM PDT Mon Aug 12 2024

.DISCUSSION...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.

The latest water vapor image shows a weak upper low weak upper low
near 38N and 139W. The upper low will move inland in northern Cal
early this afternoon and it will become negatively tilted late in
the afternoon. This along with increasing instability could set the
table for isolated thunderstorms east of the Cascades this afternoon
into early this 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. While
most locations will be dry, we cannot rule out a slight chance of
afternoon and early evening thunderstorms Wednesday and Thursday
east of the Cascades. Afternoon temperatures during this time will
be slightly below normal.

Friday through this weekend. All of the data remains locked in with
a common solution. The clusters still point to the upper low
deepening with the center of the upper low just west of the forecast
area. The ensemble means and operational models also in good
agreement with the placement of the low/trough with it centered
slightly to the west. Afternoon temperatures Friday through the
weekend for the interior are likely to end up below normal (6-8
degrees) for this time of the year.

While precipitation cannot be ruled out, the best chance is expected
be east of the Cascades and mainly during the afternoon and early
evening hours Friday, and Saturday, with marginal instability,
moisture and trigger. Sunday the low is still offshore, but the mid
levels are dry and there is little or no trigger, so the threat for
storms are low. -Petrucelli


&&

.AVIATION...12/06Z TAFS...IFR and LIFR ceilings have built back
into the coast and North Bend as of writing this discussion. These
ceilings will likely make a bigger push inland as an upper level
wave moves into the coast. Some MVFR ceilings are anticipated to
make it into Roseburg as well.

Smoke is still out there and a large swath of smoke was heading
towards Klamath Falls(LMT). We`re anticipating visibilities to fall
there at some time tonight potentially down to IFR thresholds.
Otherwise, plenty of smoke is covering northern Klamath and Lake
counties yet again tonight.  More smoke will be flying around on
Monday, although it should have a more eastwards trajectory compared
to what we`ve seen over the last few days.

There is also a 10-20% chance of showers and thunderstorms east of
the Cascades Monday afternoon as a strengthening cold front moves
inland. Some modest vertical lift and available moisture should get
a few storms going around the region.

-Smith


&&

.MARINE...Updated 220 AM Monday, August 12, 2024. High pressure
is weakening in the Pacific. Benign wave conditions will persist
through most of the week with no thermal trough condition. A weak
northerly short period swell will glide through the waters this week.


&&

.FIRE WEATHER...Issued 200 AM Monday August 12, 2024...The
forecast period will trend cooler through this 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.

The latest water vapor image shows a weak upper low weak upper low
near 38N and 139W. The upper low will move inland in northern Cal
early this afternoon and it will become negatively tilted late in
the afternoon. This along with increasing instability could set the
table for isolated thunderstorms east of the Cascades this afternoon
into early this 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. While
most locations will be dry, we cannot rule out a slight chance of
afternoon and early evening thunderstorms Wednesday and Thursday
east of the Cascades. Note: The models Wednesday suggest little or
no instability, but with an approaching upper trough and pattern
recognition suggest there is at least a slight chance for
thunderstorms east of the Cascades. 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
a rather strong upper low for this time of the year sets up just
west of the forecast area. -Petrucelli


&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$