FXUS66 KMFR 140255
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
755 PM PDT Sun Oct 13 2024

.DISCUSSION.../Issued 229 PM PDT Sun Oct 13 2024/ High pressure
over the region today is bringing clear skies to the area. Another
warm fall afternoon is in store today, with afternoon
temperatures warming up around 5 to 10 degrees above normal (low
80s (70s) for West (East) Side valleys). Low clouds will return to
similar areas tonight (Umpqua Basin and coastal locations) and
some light drizzle along the coast is possible overnight tonight.
The pattern will gradually transition Monday into Tuesday as the
weather turns cooler and wetter and lingers through the remainder
of the week.

A couple of weak fronts will pass through the area on Monday and
Tuesday, bringing some light precipitation to the coast and areas
west of the Cascades. This will also bring a slight cooling trend on
Monday and Tuesday along with breezy winds east of the Cascades on
Tuesday. While these fronts won't bring much in the way of
precipitation amounts inland, they will help pave the way for some
stronger fronts expected late Tuesday through Thursday.

There is high confidence with excellent model agreement on an upper
level trough swinging through the Pacific Northwest Tuesday night
through Wednesday. While this will bring widespread chances of
wetting rains, there remains uncertainty regarding just how much
rain will accumulate. As is typical, chances are highest along and
west of the Cascades and north of the OR/CA border for the greatest
amount of precipitation. For a 24 hour period ending 00z Thursday
(5pm Wednesday), current guidance indicates a 50-80% chance of 0.25"
for areas along and west of the Cascades, decreasing to 25-40% for
areas east of the Cascades and south of the OR/CA border. In
addition, temperatures will feel rather cool compared to recent
weeks. High temperatures on Wednesday will peak at around 5 to 15
degrees below normal (mid 60s (upper 50s) for West (East) Side
Valleys).

There should be a brief break in the weather late Wednesday into
early Thursday morning before a secondary trough sags southward over
the area. This will bring an even cooler air mass into the region
and snow levels will lower to around 5000 ft by Thursday morning,
then hover around 5500 ft during the day Thursday. If the current
trajectory of precipitation stays on track, there could be a few
inches of snow accumulation in the high Cascades on Thursday.
Current guidance indicates about a 30-40% chance of 2-4 inches in
the Cascades (north of Lake of the Woods) with a 50-70% chance of at
least 1 inch of snow ending at 12z (5am) Friday morning. Given this
is the first snow of the season, be aware and prepared for some
wintry travel/conditions on Thursday. For the remainder of the area,
this secondary trough will likely deliver another shot of beneficial
precipitation to the region, especially west of the Cascades.

For those with agricultural concerns, temperatures could get quite
chilly west of the Cascades Thursday night into Friday morning and we
could be looking at some frost and freeze concerns for the Rogue,
Illinois and Shasta Valleys. There's about a 40% chance of
temperatures reaching frost thresholds in the Rogue/Illinois Valleys
on Friday morning, with around a 80% chance of freezing temperatures
for Montague/Shasta Valley. The amount of clearing on the back side
of the trough will influence how cold it will get, but those who
have agricultural interests should stay tuned for updates.

Ridging returns Friday into the weekend, bringing a warming and
drying trend with near normal temperatures. An active pattern is
expected to return late next weekend and into early next week.
/BR-y

&&

.AVIATION...14/00Z TAFs...LIFR ceilings have built into sections of
the coast already this evening under an area of high pressure. These
lower ceilings are anticipated to participate into the overnight
hours, although the may lift to 1000 feet overnight based on some
model sounding data. Elsewhere, MVFR ceilings will spill into the
Umpqua Basin overnight.

By the morning hours, these ceilings should start breaking up. Some
VFR ceilings are anticipated  along the coast ahead of the incoming
cold front Monday evening.

-Smith

&&

.MARINE...Updated 800 PM PDT Sunday, October 13, 2024...High
pressure resides over the coastal waters until the arrival of a
weak cold front Monday night. A long period moderate west swell
builds into the waters Monday, bringing the return of high and
steep seas that will persist into Tuesday afternoon. Active
weather is likely Tuesday afternoon through late week with low
pressure over the region and a series of cold fronts bringing
gusty north to northwest winds and showers at times. Stavish/TAD


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Beach Hazards Statement from Monday morning through Monday
     evening for ORZ021-022.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 11 AM Monday to 5
     PM PDT Tuesday for PZZ350-356-370-376.

&&

$$