693
FXUS66 KMFR 191109
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
409 AM PDT Sun May 19 2024

.DISCUSSION...Conditions during the next week will be seasonable,
continued breezy during the afternoon and evening hours, a bit
cooler, and with the pattern a bit more active. Of particular
note are a cold front and associated upper level trough passage
Tuesday afternoon into Wednesday morning with the highest
probability of rain, likely for Coos and Douglas counties and
northward, and a lower 5-15% probability for northern California.

Higher uncertainty/less run to run consistency accompanies the
next trough Friday night into Saturday. There is a near even split
in the ensemble data between a weaker or stronger solution in
comparison with the earlier trough. But, it is likely to at least
start the Memorial Day weekend with slightly below normal to near
normal temperatures, near 60 at the coast, lower 70s on the west
side, and 60s on the east side.

First, the arrival of a weak trough has brought an elevated
stratus deck into southwest Oregon to start the morning. This may
produce a few light showers at the Douglas County and Coos County
coast, north of Cape Arago. Mid level clouds with bases around
6000 ft agl are likely to linger across Coos and Douglas today,
but otherwise clouds will be on the decrease today with highs
several degrees cooler than yesterday, and slightly weaker late
day breezes...still gusting at 15 to 30 mph.

Weak ridging is expected between troughs on Monday with short
lived early morning Coos and Douglas low clouds as the exception
to clear skies. This will allow for a modest bump up of high
temperatures by a few degrees on the west side, with little change
from today for the east side. -DW

LONG TERM...Tuesday morning through Saturday night.

The extended forecast starts out with an upper level wave pushing
into the Pacific Northwest from the north.  The precipitation
chances increase slightly over northern sections of our forecast
area with northern California remaining dry on Tuesday.  The
probability precipitation currently maxes out around 50 percent over
the high Cascades with lower probabilities east and west of the
Cascades. A cold front will likely accompany this wave and given the
time of year, the chance of thunderstorms should be in the cards.
Right now, the probability of thunder is only about 10 percent for
most of our Oregon areas, although that could increase as more
model data comes in. It seems like the timing is good with the
cold front pushing in the evening, which is during the time of max
heating.

Temperatures trend roughly 5 degrees lower on Wednesday as some of
the cooler air filters in behind the cold front. The upper level low
appears to sit right over us. With very little shear, less potential
instability and cold air aloft, the weather pattern suggests pop up
showers are most likely. The NBM keeps a low 10 to 20 percent chance
of precipitation across sections of the forecast area on Wednesday
with the best chances east of the Cascades and around Douglas
County.

Thursday has a high probability of being a break in the action with
an upper level low departing the area.  The NBM still is holding on
to some low probability of precipitation chances across Oregon.
Perhaps there are a few ensemble members that are keeping the upper
level low around, or perhaps the next low is arriving a little
earlier.

In any case, the most likely solution is another upper level
approaching from the north on Friday with precipitation chances
increasing. The whole forecast area has a 10 to 15 percent chance of
precipitation on Friday afternoon and evening. Some ensemble members
are taking a bit longer to bring the low into southern Oregon and
northern California, whereas a smaller majority has it here on
Friday.

Overall, an active weather pattern with minimal weather impacts is
anticipated in the extended forecast. It`s hard to see a lot of
instability building under this cooler north to northwest flow
that is likely to persist into the weekend. This pattern is likely
to change to a southerly flow early next week, but moisture and
instability for showers and thunderstorms is most likely to hold
off until at least Tuesday.

-Smith/DW

&&

.AVIATION...19/06Z TAFs...

Along the coast, and just offshore, a mix of MVFR and VFR
ceilings will likely surge onshore tonight into Sunday morning,
mainly north of Cape Blanco. The stratus should peel back just off
the coast late Sunday morning into Sunday evening before coming
back between 3-4z Sunday evening.

Inland, the stratus will surge from the coast into the Umpqua Basin,
and over the Umpqua Divide into the Rogue and Applegate valleys.
The stratus is mainly VFR, but will obscure the higher terrain. It
will dissipate in the morning leading to mostly clear skies once
again. Gusty north-northwest winds will return to most areas
Sunday afternoon into Sunday evening before diminishing.
-Petrucelli/DW

&&

.MARINE...Updated 200 AM Sunday, May 19, 2024...A strong
thermal trough along the coast will produce north gales and very
steep, wind-driven seas south of Cape Blanco through Monday evening.
Conditions will be less severe, but still hazardous to small craft
with breezy north winds and steep seas north of Cape Blanco.

Model guidance continues to suggest periods of off-and-on gales
south of Cape Blanco, and a Gale Warning is in place for the areas
where these gales are expected to surface. These conditions will be
most severe during the afternoon and evening hours each day through
Monday with both winds and seas easing late at night into the early
morning.

Low pressure approaching from the north will disrupt the thermal
trough by Tuesday with winds diminishing and seas becoming dominated
by longer period swells. -Wright/CSP

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Monday
     for PZZ350-356-370-376.

Gale Warning until 11 PM PDT Monday for PZZ356-376.

&&

$$