041
FXUS66 KMFR 220528
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
835 PM PDT Tue May 21 2024

.UPDATE...Updated aviation discussion for 06z TAFs.

&&

.DISCUSSION...Spotty precipitation is spreading across the
northern portion of the region this evening ahead of a cold front
to our northwest, through NE Douglas into northern Klamath and
Lake counties, as well as along the Cascade crest. While the
remainder of the region has seen an increase in cloudiness today,
dry weather is expected to continue south of these areas.
Precipitation will more or less end by mid to late morning
Wednesday, with the big impact following that being breezy to
windy conditions through most of the day, especially over
ridges/mountains and east of the Cascades. More information about
this, as well as the forecast for the rest of the week, can be
found in the previous discussions below. No forecast updates were
needed this evening. -CSP

&&

.AVIATION...22/06Z TAFs...Increased cloudiness and light
precipitation in the northern parts of the region are a result of a
weak upper level disturbance. Conditions along most of the Oregon
coast, including at North Bend, are IFR to LIFR as the disturbance
has brought a stonger surge of marine moisture inland. Lowered
ceilings will spread inland tonight, with MVFR conditions expected
to move into the Umpqua Valley/Roseburg and possibly briefly into
the Medford area later tonight. Conditions should improve fairly
rapidly towards morning as the weak front moves out of the area and
skies start to clear, though some scattered to broken VFR ceilings
will likely stick around in Douglas and Coos counties, and cumulus
will develop over the higher terrain as the afternoon progresses.

As low pressure moves towards NE Oregon, northwesterly winds will
start to increase aloft early Wednesday morning, and gusty winds
will start to surface late Wednesday morning into the early
afternoon, continuing through the TAF period. At the surface, winds
will be strongest over ridges and east of the Cascades. In
particular, the Klamath Basin and most of Lake County could see
gusts to 30-35 kts. -CSP

&&

.MARINE...Updated 800 PM Tuesday, May 21, 2024...Wind driven
seas have briefly diminished this evening, but steep combined seas
will build again into Wednesday night. Conditions improve Thursday
into Friday, with a break in hazardous conditions over the waters
likely through the weekend.. Low pressure late Friday into Saturday
will lead to periods of light rain and a brief build in short period
swell dominated seas. Light seas are likely early next week. -DW

&&

.PREV DISCUSSION... /Issued 254 PM PDT Tue May 21 2024/

SHORT TERM...An upper low is seen in GOES-West satellite imagery
digging southward through British Columbia this afternoon. This
system is ushering a cold front into the PacNW this afternoon with
radar showing widespread rain occuring across Washington and
northwest through north-central Oregon.

Rain has progressed southward across western Oregon to a line
roughly from Florence to Eugene as of 245 pm. Throughout the
remainder of the afternoon and through tonight the center of the
upper low will advance into south-central Washington and then
into northeast Oregon by Wednesday afternoon. This transition will
allow areas of rain and cooler air to spread into southwest
Oregon but likely leaving most of the valleys south of the Umpqua
Divide dry. Snow levels will dip to between 5000-5500 feet by
about daybreak and by 10 am or so isolated areas from Crater Lake
through Willamette Pass may see a skiff to up to an inch of snow
on the gassy/wooded areas. Winter-related road impacts should be
slim to none.

High temperatures Wednesday will wind up 5-15 degrees cooler than
today`s, coolest across the Oregon Cascades and the east side.
While temperatures will be cooler, the gusty northwest winds will
be the main story that folks will likely talk about. Afternoon
breezes on the order of 15-20 mph should be common across exposed
areas of southwest Oregon and Western Siskiyou County. The
mountains and east side will experience afternoon winds increasing
to 20-30 mph with frequent higher gusts to 40 mph. Things quickly
settle down with fair and warmer weather on tap for Thursday.
Stavish


LONG TERM...Friday through Monday, Memorial Day weekend. The main
weather feature will be upper low which will move down the British
Columbia coast on Friday. This low will drop into Washington Friday
night into Saturday. There are differences in the strength of this
low but timing is similar. This low will move away from the region
late Saturday.

Much of Friday will be dry with this approaching system along with
near normal temperatures. A cold front will pass through the region
Saturday morning with a chance of showers mainly north of the Umpqua
Divide. For those people traveling across the high passes, there
could be a mix of rain and snow or even snow showers Saturday
morning with snow levels falling to between 5500 and 5000 feet. No
appreciable accumulation is expected on the roads. Conditions dry
out Saturday afternoon as the upper low moves away from the area.
Saturday daytime temperatures will be cooler than normal with highs
in the 40s at Crater Lake, and 50s at Lake of the Woods and Howard
Prairie. Conditions on Saturday could be similar to tomorrow
(Wednesday) as the upper lows are of similar strength and their cold
fronts are forecast to move through in the morning.

Temperatures should rebound to near normal readings on Sunday with
weak high pressure possible. The models begin to differ more on
Monday. Just over half the models show stronger high pressure
nearby, a third of the models show high pressure farther east over
the Idaho/Montana border, and a small percentage of the models show
lower pressure which implies more clouds and cooler temperatures.
Right now, the warmer solutions are depicted in the forecast with
highs in the lower 80s in the western valleys but this could change
with updated forecasts.

To summarize: No heatwaves for the holiday weekend. Dry weather and
near normal temperatures are forecast Friday (morning and
afternoon), Sunday, and Monday. Saturday will likely see the most
inclement weather, especially for those in the mountains with cooler
temperatures and light rain or snow showers early in the day.
Sandler


MARINE...Updated 200 PM Tuesday, May 21, 2024...Seas are
anticipated to stay fairly consistent with current conditions
through Wednesday with small fluctuations. Periods of small craft
advisory conditions are expected through Wednesday evening. However,
conditions will subside here and there before returning again. This
is due to a low pressure system moving southward across Oregon.

By Thursday, we are expecting to see a break in hazardous conditions
over the waters through the weekend. -Schaaf/Guerrero

&&

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

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

&&

$$