Mount Shasta, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

870
FXUS66 KMFR 062143
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
243 PM PDT Mon Apr 6 2026

.DISCUSSION...Warm temperatures continue today across the area,
especially in valleys west of the Cascades. With a generally zonal
flow pattern in place, little activity is expected today. SPC
guidance shows some isolated thunderstorms are possible over
northern Lake and Klamath counties this evening. Cumulus development
over elevated terrain shows that the moisture is present. Model CAPE
values for these areas are in the 150-200 J/kg range, which is
enough to support some development but not entirely threatening.
Chances for thunderstorms drop quickly into the evening.

Temperatures cool slightly on Tuesday and Wednesday but remain 10 to
15 degrees above seasonal levels. A low pressure system passing to
the northeast will allow for some higher winds over elevated terrain
on Tuesday afternoon and evening. Terrain east of the Cascades may
see gusts of 15 to 25 mph, which is safely below Advisory levels but
is still work acknowledging. Otherwise, Tuesday looks to be an
uneventful day. The upper pattern starts to change on Wednesday as a
low pressure system approaches the west coast. Southerly flow around
the periphery of the system will allow for some slight thunderstorm
chances in southern Lake and Modoc counties on Wednesday evening,
with showers possibly continuing into the night.

Activity on Thursday and Friday will be guided by the position and
approach of the Pacific low. The low itself looks to drift south and
move inland over California. Stronger southerly flow is forecast to
push more moisture up to the area, bringing moderate shower chances
to most areas. Most areas have a 30-40% chance of showers through
Thursday and Friday, with the Siskiyou Mountains and Cascades having
higher 50-60% chances. Snow levels remain high, generally in the
7500-8500 range, minimizing winter concerns. Rainfall amounts are
unimpactful, with Siskiyou County and Cascades peaks currently
forecast to see 0.50 to 0.75 inches of rainfall across the two days.
Lower elevations are expected to see 0.33 inches or less.
Instability may bring some thunderstorm activity to parts of
Siskiyou County, but confidence in these chances are slight.

Activity remains in the forecast past Friday, but long-term
solutions start to diverge for the weekend and into next week.
Most guidance supports further cooling, with daytime highs
approaching seasonal norms. ECMWF guidance brings a low pressure
system from the Gulf of Alaska over the area, while the GFS keeps
this second low to the west then to the south. NBM probabilistic
guidance is leaning towards supporting snowfall, with 40-60%
chances of 1 inch of snowfall along the Cascades for Sunday and
Monday. The ECMWF outcome might also bring stronger winds over
terrain. Long-term meteograms for both models show some agreement
in unimpactful precipitation continuing further into the week, but
the timing and amounts vary. -TAD

&&

.AVIATION...06/18Z TAFs...Mostly clear skies are expected for
inland areas except for cumulus builds ups over the Siskiyous and
along the southern Oregon Cascades and eastward. There is a low
chance (15%) for thunderstorms this afternoon and evening over the
southern oregon Cascades and eastward into northern Klamath and
northern Lake. Over the Siskiyous and western slopes of the
Cascades, there is a very low (5-10%) chance for thunderstorms this
afternoon. Along the coast, there is LIFR ceilings with IFR/MVFR
visibilities in low clouds and fog. Conditions are expected to
worsen late this evening and tonight, with locally dense fog and
widespread LIFR ceilings/visibilities along the coast. These
conditions will persist into Tuesday morning, with gradual lifting
and clearing in the late morning and early afternoon on Tuesday.

&&

.MARINE...Updated 100 PM PDT Monday, April 6, 2026...Relatively
calm conditions are expected through tonight. Fog and low clouds
will persist over the waters today into Tuesday morning. A weak
thermal trough develops on Tuesday, resulting some gusty north winds
that will create borderline advisory level seas Tuesday through
Wednesday. The thermal trough weakens on Thursday as the upper level
pattern transitions. A trough approaches the California coast on
Thursday, then shifts southward over the weekend. This will continue
the pattern of low pressure inland and high pressure offshore,
resulting in periods of increased north winds and steep seas with
borderline advisory conditions possible through the end of the week.


&&

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

CA...None.

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

&&

$$