340
FXUS66 KMFR 220335 AAA
AFDMFR

Area Forecast Discussion...UPDATED
National Weather Service Medford OR
835 PM PDT Sat Sep 21 2024

Updated Aviation section

.DISCUSSION...Only minor updates to the forecast this afternoon.
Warm to very warm and dry conditions will continue through
Tuesday, with a warming trend. East winds over ridges, strongest
over the Coast Range, will continue into Monday morning. This will
produce a Chetco Effect, with high temperatures likely into the
lower to mid 80s at Brookings again on Sunday and Monday.

Temperatures will then trend lower for the second half of next
week. A weak front will bring a 20-30% chance of light rain to
southwest Oregon with highest probability for the coast, Douglas
County and northward Wednesday afternoon into Wednesday night.
There are still model variations in the strength of the front and
probability of precipitation, but better agreement on timing of
the system, with the highest probability in southwest Oregon
during Wednesday evening. The ECMWF suite of data leans slightly
wetter than the GFS suite, with about 20% and 8% of respective
ensemble members generating at least a measureable amount of rain
for the Medford area. Meantime, the probability will be less than
10% for the east side and northern California. Another notable
feature of this front will be the development of gusty, windy,
westerly winds east of the Cascades on Wednesday
afternoon/evening.

A weaker front around Thursday night into Friday will likely be
limited to producing additional cooling, with perhaps a few light
showers for the Douglas and Coos coast. Model differences increase
beyond Friday, with the possibility of another weak/seasonable
trough following closely behind. But, a majority of ensemble
members are indicating very slight warming and a dry weekend.
-DW

&&

.FIRE WEATHER...Issued 200 PM Saturday September 21, 2024...A
thermal trough remains situated along the south Oregon coast with
gusty east to northeast breezes near and at the ridges. Overnight
recoveries at Red Mound were moderate to poor with relative humidity
bottoming out at 19 percent early this morning. Conditions are not
expected to very much tonight and we could see moderate to locally
poor overnight recoveries again near and at the ridges in Fire Zones
618, 619, and 620. However due to the recent rains, fuels are just
not there, so there is little or no concern for critical conditions.
Looking at some ensemble data and comparing to the climatology to
this time of year, nothing jumps out as extreme.

Conditions over the next couple of days won`t vary much, so we can
expect much of the same. The only difference is afternoon
temperatures will trend higher and peak out Monday and Tuesday for
the interior. The thermal trough will remain in place in southwest
Oregon into Monday.

Tuesday, the thermal trough will expand north, weaken and move
inland during the afternoon. This will result in afternoon
temperatures peaking out for the interior westside valleys.
Meanwhile weak onshore flow will set up near and at the coast,
resulting in higher afternoon humidities.

There`s good agreement that an upper trough will push into the area
Wednesday along with a surface front which could bring light
precipitation to the northwest part of Fire Zone 616 and most of 615
Wednesday night. However of bigger concern will be moderate to
occasionally strong winds east of the Cascades Wednesday afternoon
into Wednesday evening. Right now, the combination of winds and
relative humidities won`t result in critical conditions, but it will
be close and there could be brief periods of time where critical
conditions could be met in portions of fire zones 625 and 285. For
now we`ll headline the winds and low RH`s and we`ll continue to
monitor the situation.

Thursday will be dry with gusty afternoon and early evening breezes
for the interior west valleys and east of the Cascades. Another
front will push into the area Friday with the best chance for
precipitation in fire zones 616 and 615. However, rainfall amounts
will likely be less than a 0.10 of an inch.

Next weekend will be dry and there is some hint for gusty east to
northeast breezes near and at the ridges in southwest Oregon, and
gusty east breezes near and at the ridges along the Cascades.
However the evidence on this is not strong, but still something that
we`ll have to keep an eye on. -Petrucelli

&&

.AVIATION...22/00Z TAFs...VFR weather prevailing inland under high
pressure over the next 24 hrs. At the coast, despite the dry
offshore flow, conditions should fall to MVFR visibility toward
12z and last a few hours before the morning progresses beyond 9am
LT. Stavish

&&

.MARINE...Updated 200 PM Saturday, September 21, 2024...A thermal
trough and associated pressure gradient along/near the coast will
remain in place through early next week; as a result, strong
northerly winds and very steep seas are expected through at least
Sunday. May need to extend the small craft and/or additional
hazards after Sunday, but there is some wiggle room on the extent
of possible hazards northward. The southern waters will likely
need another hazard after Sunday.

The thermal trough is forecast to move inland with weakening winds
and easing seas late Tuesday into Wednesday. This will result in
relatively calm seas and light wind speeds through at least Friday.
-Guerrero/Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 2 AM to 9 AM PDT Sunday for ORZ029>031.

CA...Frost Advisory from 2 AM to 9 AM PDT Sunday for CAZ085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT Sunday
     for PZZ350-356-370-376.

     Hazardous Seas Warning until 11 PM PDT this evening for PZZ356-
     376.

&&

$$