Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 302148
Area Forecast Discussion
National Weather Service Medford OR
248 PM PDT Thu Mar 30 2017
.SHORT TERM...Moist, onshore flow continues to produce lots of
orographically enhanced cumulus, a few showers, and gusty
northwest winds this afternoon. This will continue into the
evening hours, and then all of the above will diminish overnight.
With a cool airmass in place, temperatures will be chilly tonight,
and frost is possible in west side valleys depending on the
degree of clearing we get tonight.
An upper ridge builds in tomorrow, which will bring dry and warmer
weather to our area. The ridge flattens a bit on Saturday as a
weak disturbance goes over the top. This may produce some light
rain over northern sections, but mostly it will bring increased
high cloud to the area. This may limit temperatures on Saturday,
but the airmass should be mild enough to drive temperatures above
normal everywhere save for the coast and Umpqua Basin.
The models have come into better agreement regarding an upper
trough on Sunday. This trough will be moving quickly through the
westerly upper flow, and it will remain positively tilted as it
moves through here. The net result of this is that some convective
showers should break out on the east side Sunday afternoon, but
west side areas should remain dry. -Wright
.LONG TERM...Monday through Thursday...The ECMWF and GFS
are in pretty good agreement through forecast period. Shortwave
ridging will build over the area Monday bringing dry and milder
weather. The ridge will remain in place as a large upper trough
deepens near 150 W Monday night into Tuesday. In fact 500mb heights
will rise some on Tuesday. The GFS shows a front dissipating as it
approaches the coast which makes sense given the above mentioned
reasoning. The ECMWF keeps it flat out dry and suspect dry weather
will continue on Tuesday. THE ECMWF and GFS show the ridge hanging
tough (although the ridge axis does shift east) on Wednesday with
the precipitation remaining offshore. It may not be until Thursday
morning when precipitation reaches the coast, then inland Thursday
afternoon. The ECMWF and GFS suggest precipitation will be
convective east of the Cascades Thursday afternoon, but it`s still a
ways out and this could change. Of note: The Canadian solution is
similar to what the ECMWF and GFS were showing yesterday indicating
a wetter solution from Tuesday afternoon through Thursday. Suspect
this may be an outlier and the forecast in the extended will lean
towards the ECMWF/GFS solution. -Petrucelli
.AVIATION...30/18Z TAF CYCLE...The main concern will be moderate
to strong winds east of the Cascades, including Klamath Falls
into early this evening.
VFR conditions are expected to be the predominate condition
through this evening. However cannot rule out MVFR CIGS in
showers this morning in the Umpqua Basin, including Roseburg and
kept them as the prevailing condition in the TAF until 21z. Also
partial mountain obscuration is possible into this afternoon.
VFR conditions will continue tonight into Saturday morning. There
is a chance for MVFR cigs to develop in the Umpqua Basin,
including Roseburg around 8z, but confidence on the timing and
these conditions developing are low to medium so watch for updates
on this. -Petrucelli
.MARINE...Updated 300 AM PDT Thursday 30 March 2017...Seas will
remain steep this morning due to west swell around 10 feet at 14
seconds. Westerly swell will diminish early this afternoon. High
pressure will build west of the waters today and persist on Friday.
This will bring increasing north winds today into tonight. An area
of small craft advisory level winds and seas is expected to develop
late this afternoon and this evening for locations south of
Brookings within 25 nm of shore. North winds are expected to lower
below small craft levels tonight and Friday. A disturbance will move
across the area late Saturday and Sunday. High and very long period
west swell is expected to arrive late Saturday into Sunday. This may
bring dangerous bar crossings and possible high surf to the coast.
OR...Beach Hazards Statement from Saturday afternoon through Sunday
morning for ORZ021-022.
Wind Advisory until 11 PM PDT this evening for ORZ031.
CA...Wind Advisory until 11 PM PDT this evening for CAZ085.
Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT this
evening for PZZ356-376.
Small Craft Advisory from 2 PM Friday to 2 AM PDT Saturday for