185
FXUS66 KMFR 200342
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
842 PM PDT Sat Apr 19 2025

.DISCUSSION...Updated Marine Section...

&&

.MARINE...Updated 845 PM Saturday, April 19th...A thermal trough
continues to produce very strong winds in the outer water with gale
force winds at buoy 27. In any case, seas are hazardous to small
crafts with wind driven waves persisting into this evening. These
steep seas will continue through Sunday and early Monday before
winds increase again and come close to gales. We will likely be
issuing a Gale Watch at this time with gale force wind gusts above
40 knots being a realistic threat Monday.

-Smith/Hermansen

&&

.PREV DISCUSSION... /Issued 435 PM PDT Sat Apr 19 2025/

DISCUSSION...Updated Aviation section...

AVIATION...20/00Z TAFs...Gusts of 25 to 30 kt are present at the
coast and will continue through the early evening as the front
weakens. Gusts of 15 to 25 kt are possible inland through the
evening as well. VFR conditions are present and will continue
through the TAF period for all locations inland. The coast will
begin to see MVFR ceilings once again later this evening. Near the
end of the TAF period gusty northerly winds will return, especially
for the coast and east side. -Smith/Hermansen

PREV DISCUSSION... /Issued 245 PM PDT Sat Apr 19 2025/

DISCUSSION...The radar this afternoon shows a well defined line
of very light showers along the weak front currently moving to
the southeast across the East Side. Most of this rain is failing
to make it to the ground, but a few drops have been seen to hit
the ground here and there. Also of note, the radar is showing
several small returns moving south to north against the wind,
especially concentrated around the passes in Siskiyou county and
streaming into much of western Oregon. Given the time of year, the
speed, and the elevation of these returns, it appears that perhaps
a significant number of birds are commencing their migration
north, a sure sign of spring.

Weather-wise, it remains quiet across the region, with high
pressure keeping the area dry and temperatures hovering right
around or just slightly above normal for this time of year.
Another weak front will move through the region tomorrow, much
like today, and again, very little if any rain will be seen across
the forecast area. Some models are showing instability developing
along the far southern portions of Modoc and far southeastern
portions of Siskiyou counties tomorrow afternoon, and given the
pattern, this isn`t out of the realm of possibility. Have
introduced a slight chance of showers and perhaps a thunderstorm
in that area Sunday afternoon, but most likely nothing more than
some cumulus fields and virga will occur. Otherwise, Sunday,,
Monday, and Tuesday will be quiet, with mostly clear skies, cool
mornings and mild afternoons.

Another weak system is forecast to cross the region Tuesday night
into Wednesday. The vast majority of ensemble members depict
another dry frontal passage, but a few (mainly within the EC suite)
are showing an area of convection developing over northern
California Tuesday night into early Wednesday, then spreading
north and east through the morning before dissipating in the
afternoon. As this is an unlikely scenario, have left it out of
the forecast for now, but will keep an eye on it over the next few
days.

A pattern change then arrives Thursday, introducing a period of
cooler and wetter weather for the weekend. A much more robust
trough will pass by the Aleutians and dig to the southeast,
approaching the coast of the Pacific Northwest by Thursday
afternoon before passing overhead Friday, then followed by several
more shortwaves and larger troughs through the weekend. Guidance
agrees on this basic premise, but differs by a great deal
regarding the speed and track of the individual features. The most
likely scenario would be for a mostly dry Thursday morning,
followed by convective development in the afternoon and evening as
the trough edges closer and taps into some southerly moisture and
afternoon heating, essentially resulting in scattered showers and
perhaps a few thunderstorms. Shower chances then overspread the
area Friday and Saturday as the initial trough and the following
impulses pass overhead. The timing of highest shower chances will
have to wait until the models come to better agreement on the
individual features. -BPN

&&

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

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 11 PM PDT this
     evening for PZZ350-356-370-376.

Small Craft Advisory until 11 PM PDT this evening for PZZ350-
     370.

     Gale Warning until 11 PM PDT this evening for PZZ356-376.

     Small Craft Advisory until 11 AM PDT Monday for PZZ356-376.

&&

$$