FXUS66 KMFR 242250

Area Forecast Discussion
National Weather Service Medford OR
250 PM PST Fri Jan 24 2020

.SHORT TERM...Tonight through Monday night...2:30 PM Satellite
and RADAR are showing several layers of clouds and as well as a
couple light returns across northern California. No precipitation
appears to be falling at this point, but that will change in the
next few hours. A warm front is poised to make its way across
southern Oregon and northern California. This front will bring
some rain and snow along with it. Snow levels will be around 5000
feet this afternoon, and may decrease to 4500 feet this evening
ahead of the front. The main concern with the front is going to be
the wintry mix east of the Cascades. Along with the rain and
snow, some very light freezing rain will be possible in the
northern Klamath Basin along Highway 97 from north of Chiloquin to
Crescent, especially in sheltered areas where winds are not able
to bring in the warmer air at the surface. The best chance for
this freezing rain is between 10 pm and 1 am. The wintry mix,
without the freezing rain, will continue in that area until around
4 am when the switch to rain is expected.

Snow levels will rise to around 7000 feet tomorrow as we get the
first of several Atmospheric River type systems come through.
These systems will bring beneficial rainfall to many of our
abnormally dry areas, but they could also create some ponding of
water on roads near the coast and the Coast Range. In many of the
mountain locations, snow depth will be high enough that we are
expecting most of the rain to be absorbed by the snowpack instead
of it washing all away. Therefore, we are not expecting any sort
of negative impacts from main stem river flooding or debris flows.
That being said, some small streams and creeks could see some
quick rises.

Snow levels will fall back to around 4500 to 5500 feet by Sunday
as the next of these systems arrives in our area. These types of
systems will move through the forecast area in rapid succession
with one or two more coming before Tuesday, and snow levels will
continue to hover around these levels. It is worth noting that we
will not see continuously within the short term period, but we
will see some moderately significant precipitation for good
durations of time. The other note is that no one particular storm
seems stronger than the rest, but as is the case with these
systems, the forecast should continue to be monitored as this area
is no stranger to rapid changes in the forecast. -Schaaf

.LONG TERM...Tuesday through Friday...An upper trough moves through
Tuesday and brings a cooler air mass behind it, but snow levels will
only lower to about 5000 feet and not much precipitation will be
left with the trough. Precipitation chances diminish Tuesday night
and then increase again Wednesday. There`s a good bit of ensemble
members between the ECE and GEFS that paint precipitation moving
back in Wednesday despite drier deterministic solutions, so we
maintain precipitation chances Wednesday. Snow levels will likely
rise to 6000-7000 feet Wednesday into Thursday as overrunning
precipitation affects mostly areas from the Cascades to the coast.
Upper ridging builds overhead again Friday, and precipitation
chances diminish again.

When considering weather impacts in the extended, ponding of water
on roadways, rising creeks and streams, and low visibility in some
morning valley fog is expected. We`re not expecting any prolonged
Atmospheric River (AR) events or any mainstem river flooding. With
that said, snow levels will remain relatively high and models
sometimes don`t resolve AR events in the extended, so we`ll be
keeping an eye on ensemble trends. Snow levels will generally remain
above mountain passes, so we don`t expect any snow impacts to
roadways in the extended. -Keene


.AVIATION...For the 24/18Z TAF Cycle...A stable air mass and plenty
of low level moisture are bringing low clouds to most of the
forecast area this morning. A mix of IFR and MVFR conditions with
mountain obscuration exists this morning, and conditions should
improve to VFR for most places by early this afternoon.

This evening, a warm front will bring low clouds, precipitation, and
mountain obscuration to the coast first. These lower conditions will
progress inland from the coast to areas east of the Cascades late
tonight into Saturday morning.

West Side valleys will likely experience IFR or MVFR conditions
tonight. There is some uncertainty about when or if these lower
conditions will lift some to MVFR or VFR Saturday. BTL/Keene


.MARINE...Updated 200 PM PST Thursday 23 Jan 2020...Steep seas
will persist through much of the forecast period as multiple fronts
and swell trains move through the area. One such swell train is
building into the waters today and a cold front will move through
the waters tonight into Saturday morning. Expect an increase in
southerly winds, approaching gales but likely remaining below
warning criteria. West-northwest swell will peak this afternoon and
evening in the 10 to 15 foot range with a dominant period around 17

Another stronger low and frontal system will move through Saturday
night. Guidance continues to suggest conditions with this frontal
system will remain just below warning level conditions, although
there may a brief period of hazardous seas late Saturday night.
We`ll continue to monitor for changes in the guidance.

The weather pattern remains active through next week with generally
moderate, fairly typical, January frontal system activity. Peak seas
are expected to occur Sunday night into Monday morning around 18
feet at 14 seconds. It should be noted that, at this lead time, the
details of timing and magnitude of winds and seas for next week are
likely to waiver. While advisory level conditions are likely through
much of the week, watch/warning level conditions will be possible.
There have been fluctuations in the details over the last few model
run cycles, and usually one of the storms a series becomes a bit
more significant than the rest. BTL/BR-y




Pacific Coastal Waters...Small Craft Advisory until 4 PM PST Sunday for


NWS MFR Office Area Forecast Discussion