Gale Warning 10, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
811 PM PDT Sat Mar 28 2020

.UPDATE...

No changes to the forecast this evening as showers continue across
the forecast area. The chances for rain increase tonight,
especially along the coast, as the trough moves onshore.

Read the discussion below for more information on the weather
beyond tonight.

-Smith

&&

.SHORT TERM.../Issued 249 PM PDT Sat Mar 28 2020/
The next 48-72 hours (through Tuesday) will continue to be active
with several disturbances moving through the area. This will
bring unsettled weather with showers/periods of rain and some
mountain snow. The strongest system will move through late Sunday
night through Monday night. Since we have been so dry through most
of the winter and into the early part of spring, precipitation
with these systems will be mostly beneficial and welcome.

An upper level trough offshore will continue to move southeastward
tonight and into northern California on Sunday. Moist southwest
flow aloft in advance of this trough is bringing some rain
showers to the area this afternoon and will continue to do so
through tonight, but precipitation amounts will be generally
light. Another "kicker" trough is following closely behind this
system and will send a cold front onshore into Washington and
Oregon on Sunday with more showers. Precipitation with this front
may be a little heavier, but still primarily on the light side.
Snow levels will waver between 4000 and 5000 feet during this time
frame, but with accumulating snow mainly staying above the higher
passes. Tonight through Sunday evening, amounts of 2-5 inches are
forecast in the Cascades above 5000 feet, but road accumulation
even there will probably only occur during the late night and
morning hours; otherwise, it should melt due to higher sun angle
and warm ground during the day. Showers should taper off at least
for a while Sunday evening.

The next fast-moving disturbance will bring precipitation back to
coastal areas overnight Sunday with the cold front moving onshore
on Monday. Since the flow will be primarily WSW, we expect a
period of moderate to heavy precipitation along the coast and
also the adjacent Coast Ranges/Cascades with common liquid amounts
of 0.50-2.00 inches. The heaviest amounts will be where
orographic enhancement is maximized (Coast Ranges/Cascades north
of Hwy 140). We are currently forecasting around 0.25 of an inch
here in Medford. Some precipitation is also expected east of the
Cascades, but with much lighter amounts. Advisory level west to
southwest winds are a good bet east of the Cascades, especially in
the Summer Lake area along Highway 31, on Monday/Monday evening
ahead of the front (models indicate 700 mb winds close to 55 kt).
Snow levels once again look to be mostly above 4500 feet, keeping
the best snow above the main passes. Accumulating snow will again
be mostly for elevations above 5000 feet, with several inches
possible up around Crater and Diamond Lakes. Since much of the
precipitation will be coming during the day up there, road snow
will be mitigated somewhat, but with precipitation lingering
Monday night, an advisory could be necessary for portions of zone
27.

The parent upper low will move across southern British Columbia on
Tuesday, but this will keep showers going in moist onshore flow.
Showers will be focused from the Cascades westward with snow
levels remaining mostly 4000-5000 feet. Showers gradually diminish
in coverage Tuesday night. -Spilde

.LONG TERM.../Issued 249 PM PDT Sat Mar 28 2020/

Wednesday through Saturday...The area
will still be on the southern periphery of the upper level trough
centered over central Canada Wednesday morning. Energy riding
around the base of this low will maintain at least a slight chance
of showers for the far northern and western portions of the
forecast area through Wednesday afternoon. As the energy moves out
of the area, showers will come to an end by late Wednesday and
dry conditions will persist into the weekend.

Upper level ridging attempts to establish itself over the area
Thursday, but shortwaves moving through the ridge will keep it from
really strengthening. The models are in fairly good agreement up
until this point. The GFS strengthens the ridge Friday while the EC
maintains a flat ridge and brings a weak front with precipitation
into the area. The GFS shows some precipitation with the shortwave
as well, but is further north and less robust for our area compared
to the EC. The majority of the ensembles for both models maintain
dry weather during this period, so have opted to keep the forecast
dry through the start of the weekend. Although conditions should be
dry, there could be periods of increased cloudiness as shortwaves
move through the area. A warming trend will commence Wednesday into
the weekend with afternoon temperatures around 5 to 10 degrees above
seasonal norms. /BR-y

&&

.AVIATION...For the 29/00Z TAF Cycle...A showery pattern will bring
a mix of mainly VFR and MVFR ceilings through tonight with areas of
obscured terrain. Freezing levels will be 4500 to 5000 feet with
showers most numerous near the coast and secondarily, over the
higher terrain this evening into tonight. Showers will increase from
the Cascades west Sunday morning. Conditions will lower to MVFR/IFR
tonight into Sunday morning as another wave of precipitation moves
into the area. Expect MVFR cigs to continue into Sunday afternoon.
-CC

&&

.MARINE...Updated 800 PM PDT Saturday 28 March 2020...Active weather
will bringing periods of increased southerly winds. Winds will reach
low end advisory levels and seas will be wind driven and steep,
especially north of Gold Beach through tonight. Conditions will
subside below advisory levels Sunday afternoon.

Swell will begin increasing Sunday night and another front will move
onshore Sunday night into Monday. This front may be strong enough to
create gale conditions in coastal waters north of Cape Blanco as the
front is trapped along the coast. Current thinking is for winds to
remain just below gales but, hi-res model guidance is trending winds
stronger. So if this trend holds, the current hazardous seas watch
could be upgraded to a gale watch in coming updates.

High pressure will build offshore Monday night into Tuesday.
Northwest swell will peak Tuesday. -miles/CC

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 AM PDT Sunday for
     PZZ350-356-370-376.
     Small Craft Advisory from 8 PM Sunday to 11 AM PDT Monday for
     PZZ350-356-370-376.
     Hazardous Seas Watch from Sunday evening through Monday morning
     for PZZ350-370.