Winter Storm Warning 8, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
1034 AM PDT Mon Mar 10 2025

.Updated Marine and Aviation Discussion.

.DISCUSSION...High level clouds are streaming southwest to
northeast across the region this morning, and are associated with
a very slow moving front that lies right along the southern
Oregon coast and crosses inland into the Willamette Valley. This
front will gradually dissipate as it slowly moves across the area
to the southeast today. Aside from some very light rain or drizzle
along the coast and into the Umpqua Basin, the frontal passage
will be dry, with breezy winds this afternoon, especially in
northern California and across the East Side. Dry conditions then
continue into Tuesday morning.

The next front will arrive late Tuesday into Wednesday. Models
still depict the possibility of a deepening low offshore, but now
track the low farther to the northwest with a much higher central
pressure than previous runs. What this means is that rather than a
stronger wind event that was previously forecast, this event now
looks to be more of a run-of-the-mill wet season event.

As such, there is high confidence for advisory level winds in the
Shasta Valley and over the East Side with winter impacts during
the day Wednesday over the mountains (Cascades/Siskiyous) above
4000 feet. The main frontal band and upslope precipitation will
shift through southwest Oregon and NorCal Wednesday into Wednesday
evening maintaining snow above about 3500-4000 feet, though snow
levels could lower to around 3000 feet Wednesday morning near Mt.
Shasta City. The main thrust of precipitation shifts east of the
area Wednesday night into Thursday, but post-frontal showers
continue in onshore flow behind it. Storm total snow accumulations
of 8-16 inches are likely above 3000 feet in the MOunt Shasta Area
and across the Klamath and Siskiyou mountains, with 12-20 inches
above 5000 feet. Additionally, snow will be moderate to heavy and
wet, with snowfall rates getting close to an inch or more per hour
Wednesday into Wednesday evening. This will bring winter impacts
to I-5 near Siskiyou Summit and around Mt. Shasta City. Given the
increasing confidence of significant snow impacts in and around
Mount Shasta, a Winter Storm Watch has been issued. Please see
WSWMFR for more details.

Showers continue for much of the week as the upper level trough
slowly makes its way across the area and onshore flow persists. IT
should be noted that much colder air dies return to the region
with the trough, and as showers continue, snow levels may drop as
low as 1500 feet Thursday morning, and 1000 feet by Friday
morning. This means that low elevations snow is possible for the
morning commutes, although amounts should be light.

A warm front will then move across the region Friday/Friday night
with another round of potentially impactful south winds and
rain/mountain snow. Models are then showing a deep low pressure
forming offshore Saturday and moving into the PacNW Saturday night
into Sunday. -BPN/Petrucelli

&&

.AVIATION...10/12Z TAFs...Along the coast and just offshore, VFR
conditions are expected through this evening. The cloud deck at
North Bend will lift north with a clear to scattered deck withing
the hour. Marine stratus will return north of Cape Blanco with MVFR
and local IFR ceilings later this evening until the end of the TAF
period. MVFR ceilings cannot be ruled out along the south coast, but
confidence on that is not high. Clouds will develop, but ceilings
should remain VFR.

Inland, VFR conditions will continue through the TAF period. The
exception will be in portions of the Umpqua Basin where marine
stratus could result in MVFR ceilings towards 9z. -Petrucelli

&&

.MARINE...Updated 345 AM PST Monday, March 10, 2025...A weak frontal
boundary orientated from southwest to northeast has resulted in
light to moderate north winds over the northern and northwest part
of the southern outer waters. Elsewhere light south winds are bring
observed. This weak front will dissipate, but winds will shift from
south to north in the inner waters this afternoon. Calmer conditions
are expected tonight into Tuesday afternoon. Then, south winds will
increase later Tuesday evening and night as a stronger cold front
approaches the waters. High end Small Craft conditions are likely
and it's even possible low end gales could be reached Tuesday night
into Wednesday morning. We'll look at this in more detail and if any
upgrade to the current headlines will be issued for this afternoon.

The front will move inland later Wednesday morning with south winds
diminishing and shifting from south to southwest. However, a
westerly swell will increase Wednesday afternoon which could result
in Small Craft conditions. The pattern will remain active for the
reminder of the week with a series of systems moving through. -
Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...Winter Storm Watch from late Tuesday night through Wednesday
     evening for CAZ080-082-083.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT this
     morning for PZZ350-356-370-376.

&&