821
FXUS66 KMFR 121141
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
441 AM PDT Wed Mar 12 2025

.DISCUSSION...Updated Aviation Section...

&&

.AVIATION...12/12Z TAFs...Along the coast and just offshore. Marine
stratus remains locked in with low VFR/MVFR ceilings as warm moist
air pushes in ahead of the cold front. Look for these lower ceilings
to persist through the day. The strong winds and turbulence should
prevent any IFR or LIFR ceilings to develop. Wind shear will be a
concern during frontal passage around 12z to ~16z today.

Inland west of the Cascades, VFR ceilings will continue through the
TAF period, although scattered MVFR ceilings are possible early this
morning. As the cold front approaches, there is a low chance of low
level wind shear over Roseburg this morning.

Farther south, Medford will remain VFR through the TAF period with
strong southeast winds in the southern end of the Rogue valley.
Those south winds should eventually break into MFR by the afternoon
hours.

East of the Cascades, VFR conditions will continue through the TAF
period with southwest winds increasing this afternoon with winds
remaining elevated and shifting south this evening. Winds could peak
out close to 35 kts towards daybreak Wednesday as KLMT always seems
to over perform with wind gust strength during south flow.

Overall areas west of the Cascades will see more shower activity
this morning with the rain moving to more areas east of the Cascades
into the afternoon. -Smith/Hermansen

&&

.PREV DISCUSSION... /Issued 257 AM PDT Wed Mar 12 2025/

DISCUSSION...The cold front lies just offshore, and will pass
through the area today and tonight, producing wind and
precipitation across the region. Active weather then continues
with additional systems expected over the next several days.

Wind will be a concern today in our usual trouble spots: the
Shasta Valley, the East Side, and over high terrain, but will not
be overly strong, as MSLP gradients are on the weaker side, and
700mb winds are not expected to exceed more than 55 kt. This sets
the area up for mostly advisory level winds. Meanwhile, snow
levels of 5000 to 6000 feet this evening will lower to around 4000
feet with the passage of the front, with the exception of the
Mount Shasta area where upslope precipitation generation will be
strong, and precipitation rates (snowfall between 1 and 2 inches
per hour is almost certain above 4000 ft) will drag snow levels
down to as low as 3500 feet. As a result, several Warnings and
Advisories are in effect for late Tuesday night into Wednesday. A
winter Storm Warning covers much of Siskiyou County, where 12 to
18 inches of snow is possible above 4000 feet, and several inches
are expected in Mount Shasta City, McCloud, and Dunsmuir. Official
amounts along I-5 through southern Siskiyou County are around 1-2
inches, but some uncertainty exist here for the interstate as
snowfall rates could reduce snow levels further than anticipated.
Ultimately, any snowfall will make hazardous driving conditions a
reality, so travel should be conducted with caution today through
Thursday morning.

A winter Weather Advisory is in effect for the Cascades north of
Lake of the Woods, and for portions of the East Side, for a
combination of several inches of snow and gusty winds. Meanwhile,
a Wind Advisory is in effect for the Shasta Valley. Details on
the winter headlines can be found at PDXWSWMFR, and wind advisory
details can be found at PDXNPWMFR.

Showers will then 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 mass returns 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 as showers finally taper off. This means that low
elevation snow is possible for the morning commutes, although
amounts should be light, and may not stick at all given the past
couple of weeks of warm temperatures.

The upper trough finally passes to the east Thursday night, then
the next trough arrives quickly on its heels Friday. This will be
a more compact trough embedded within the swift northwest flow
aloft, and will take on a negative tilt as it passes overhead.
These types of systems are typically more prolific wind makers
than others, and this is no exception if forecast pressure
gradients are any indication. Wind headlines will likely be
needed for many areas, especially the Shasta Valley and the Eats
Side, but also may be needed at the coast.

As mentioned earlier, snow levels Friday morning could easily be
down to the valley floors as showers taper off, but will rise
rapidly to around 3000 feet as the trough arrives Friday afternoon
and the next round of moderate to heavy precipitation arrives.
Some more sheltered areas could hold on to lower snow levels, and
once again, the Mount Shasta area will see lower snow levels as
strong southerly flow ahead of the front produces heavier
precipitation rates that would then drag snow levels down. Another
round of winter weather headlines are likely for Siskiyou County
and the Cascades.

The front exits to the east by Friday night, then once again,
onshore flow will keep ongoing showers in the area through
Saturday. Then the active pattern continues as a potentially
stronger system arrives Sunday, which has the potential to produce
more rain, snow, and wind impacts as we head into early next
week. -BPN

MARINE...Updated 245 AM PST Wednesday, March 12, 2025...Low end
gales are possible through this morning as a front moves in. South
winds will diminish and shift from south to southwest as the front
moves eastward today. However, a westerly swell will increase late
this afternoon into Thursday evening, and seas will remain elevated
for Small Craft conditions to resume and continue through Thursday
night once the Gale Warning headline ends later this morning.

The pattern will remain active for the reminder of the week with a
series of systems moving through. There`s good agreement the first
could bring strong south winds Friday, followed by another round of
strong winds Saturday night, timing of when winds will be strongest
will likely vary this far out into the forecast period, this we`ll
keep a close watch on this. If nothing else, the combination of
winds and seas will likely result in at least Hazardous Seas Warning
conditions Friday into this weekend. -Petrucelli/Hermansen

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 5 AM PDT Thursday for ORZ027-028-
     030-031.

CA...Winter Storm Warning until 5 AM PDT Thursday for CAZ080-082-083.

     Wind Advisory until 2 PM PDT this afternoon for CAZ081.

     Winter Weather Advisory until 5 AM PDT Thursday for CAZ085.

PACIFIC COASTAL WATERS...Gale Warning until 11 AM PDT this morning
     for PZZ350-356-370-376.

     Small Craft Advisory from 11 AM this morning to 5 AM PDT Friday
     for PZZ350-356-370-376.

&&

$$