583
FXUS66 KMFR 042134
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
234 PM PDT Sat May 4 2024

.SHORT TERM...Through Tuesday morning...A low pressure system
continues to bring activity across northern California and southern
Oregon. Reports have indicated 2 to 3 inches of rain along the
Oregon coast in the past 24 hours, as well as 4 inches of snow in
areas around Mount Shasta. The main band of rainfall is moving
across Klamath and Lake counties while scattered showers continue
west of the Cascades. Existing daytime hazards have all expired, as
elevated winds over east side areas have slowed and the heaviest
snowfall over western Siskiyou County and the Cascades has passed.

Other hazards will continue through the night. Instability from the
low pressure system brings the possibility of thunderstorms through
the night tonight. Current chances are at 20-25% across areas west
of the Cascades, with lower 10-20% chances to the east. These
chances will remain into the last hours of Saturday before
decreasing through Sunday morning.

Additionally, a Freeze Watch has been elevated into a Freeze Warning
for the Shasta and Scott Valleys in Siskiyou County. Temperatures in
these valleys are forecast to be in the high 20s to low 30s tonight
into early Sunday morning. The Freeze Warning will be in place from
2 AM until 8 AM on Sunday morning. Other areas, including the
Illinois Valley and the southern Rogue Valley, may see temperatures
at or near freezing. But the possibility of substantial periods of
freezing temperatures are low (10-20%), so warnings were not issued
for these areas. Near-freezing temperatures in the mid-30s are
forecast, so extra care for sensitive plants and animals may still
be beneficial.

The low pressure system will follow the Oregon-California border
through Sunday, keeping cooler temperatures and precipitation in the
Forecast for Sunday. Snow levels are expected to rise to about 4000
feet, limiting snowfall to the Cascades and the highest terrain to
the east. Thunderstorm chances are not in the forecast.

A warm front will follow behind the low pressure system on Monday,
bringing another round of precipitation across the area. This front
looks to be non-impactful, with some limited thunderstorm chances
over Klamath and Lake counties on Monday evening. Precipitation
will be highest over the Cascades, with 3 to 6 inches of snow
forecast over the Cascades and unremarkable rainfall amounts over
lower elevations.
-TAD

.Long Term...Tuesday (05/07) through Saturday (05/11)...The
extended period starts as "third winter" comes to an end, and a
familiar pattern of high pressure builds in. During this period of
high pressure strong, gusty north winds will be present along the
coast and east winds will develop inland. The warm bubble around
Brookings due to the Chetco effect is expected to be on display at
the end of the work week.

This diurnal pattern of wind flow will bring in drier air to the
region, but the magnitude of the warmth will be limited. The current
forecast calls for the heat to peak either Friday or Saturday in the
low to mid 80s and overnight lows barely scraping into the upper 40s
or low 50s. The reason for this low peak in high temperatures
appears to be a retrograding low pressure center, which is expected
to undercut the ridge as it moves in from around Utah.

-Miles

&&

.AVIATION...04/18Z TAFs...Unfavorable flying conditions this
morning are expected to gradually improve through the afternoon and
evening as the potent frontal system passes through and out of the
area. Widespread MVFR ceilings, terrain obscurations and periods
of moderate rain and mountain snow can be expected. Local IFR/LIFR
can occur as well, especially in times of heavier precip.
Precipitation behind the front will become more
showery late this afternoon and evening, but we still expect plenty
of MVFR along with areas of higher terrain obscured through this
evening. Some improvement to VFR tonight, though areas of MVFR will
remain. Rain showers will transition to snow east of the Cascades
later this afternoon and evening as freezing levels lower to around
3000 feet MSL. -BPN/Spilde

&&

.MARINE...Updated 200 PM Saturday, May 4, 2024...Showers will
dissipate through this evening, with a very low chance for a
thunderstorm before sunset. Moderate west winds and steep fresh
short period west swell will continue through tonight, then
southwest winds increase Sunday ahead of another front that will
move through late Sunday night into Monday. Seas are likely to
remain elevated Monday night into Tuesday with building west-
northwest swell. After that, we expect high pressure to build in mid-
late next week with a thermal trough strengthening along the coast.
This will bring a return of stronger north winds and steep seas,
highest south of Cape Blanco. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 11 PM PDT this evening above 4000
     feet for ORZ027-028.

CA...Freeze Warning from 2 AM to 8 AM PDT Sunday for CAZ080-081.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Monday
     for PZZ350-356-370-376.

&&

$$

TAD/MCB/BPN