Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 262139
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
239 PM PDT Wed Apr 26 2017

.DISCUSSION...

.Short Term...Tonight through Saturday Night...Showers continue
to stream across the area this afternoon, but will gradually begin
to confine themselves to the western slopes of the Cascades and
other north to south mountain ranges through this evening and
tonight. Meanwhile, strong west flow in the mid levels is expected
to transfer to the surface across the East Side, producing gusty
winds there. The latest model solutions are depicting weaker winds
than previous shifts, but already observations form the usual
trouble spots have increased to near advisory levels, and will
probably strengthen a bit more before the end of the day. Have
decided to let the wind advisory remain in place, but an early
cancellation is not out of the question a bit later this
afternoon.

The upper level trough and associated surface system responsible
for today`s showers has shifted to the east, and as they lose
influence over us, a broad, high-amplitude ridge will build in
over the Eastern Pacific. This ridge, while not directly overhead,
will dominate our weather for the next several days. With the
ridge placed to our west, and a general trough over the central
United States, we will reside under swift northwest flow aloft.
The ridge will also deflect most energy and precipitation
producing systems to our north, leaving most of the area dry and
warmer. However, the trailing edge of a few fronts passing to our
north may skirt the northern half of the forecast area, producing
showers and slightly cooler temperatures at times. The first of
these will slide by on Thursday afternoon, then another on
Saturday night. The models have not been consistent on the
strength of the fronts as they pass to our north, nor have they
agreed on where the best chances for showers will be. So, have
kept a slight chance to a chance of showers in some areas and
expanded coverage to others in an effort to more closely align
with the latest guidance, but suspect this may change in later
forecast cycles.

.LONG TERM...Sunday through Wednesday...The area will be under the
influence of an upper ridge which is expected to be centered just to
the west Sunday through Tuesday. However, a couple weak disturbances
are expected to move over the ridge and into the area, bringing a
chance for light precipitation. The first of these, a weak cold
front, is expected to move inland on Sunday. Models indicate that
this front will bring a chance for showers from the Southern Oregon
Cascades west and into northern Klamath and Lake counties. The best
chance for light precipitation is expected to be over the Cascades,
in Douglas County and along the Southern Oregon coast. A period of
dry weather is then likely Sunday night in to Monday as this front
shifts east and out of the area. However, models show a shortwave
trough moving over the ridge and into southern Oregon on Tuesday.
This will allow another chance for light precipitation and cloudy
conditions. The chance for precipitation is expected mainly from the
Southern Oregon Cascades west on Tuesday.

By Wednesday, models and ensembles indicate the upper ridge will
build inland over the area and expect dry and warm conditions to
develop. -CC



&&

.AVIATION...26/18Z TAF CYCLE...Areas of MVFR cigs and local IFR cigs
will continue across the area this afternoon into this evening with
light showers. Gusty west to northwest winds will develop east of
the Cascades this afternoon. Wind gusts to 30 kt are expected,
including at KLMT. Showers will taper off for most areas this
evening and tonight with scattered showers continuing in the Douglas
county area and in the Southern Oregon Cascades. Expect widespread
terrain obscurations through this evening...then partial
obscurations east of the Cascades tonight and Wednesday morning with
widespread mountain obscurations continuing from the Cascades west.

Conditions may briefly improve to a mix of VFR/MVFR late this
afternoon and this evening as showers decrease. However, lingering
low level moisture is expected to result in widespread MVFR and
areas of IFR cigs to develop tonight along the coast and in inland
valleys west of the Cascades tonight, continuing into Thursday
morning. East of the Cascades local MFR/IFR conditions are possible
tonight and early Thursday morning. -CC

&&

.MARINE....Updated 200 PM PDT Wednesday, 26 April 2017...Winds
have already turned westerly this afternoon and showers should be
decreasing as the evening progresses. High pressure will build in
from the southwest on Thursday, persisting through the weekend. A
thermal trough pattern sets up on Friday resulting in gusty
northerly winds also persisting through the weekend. Swell
dominated seas will become wind wave dominated over the weekend.
Small craft conditions could return to the waters by Friday
afternoon, with the strongest winds and steepest seas expected
south of Cape Blanco. /BR-y


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 8 PM PDT this evening for ORZ030-031.

CA...Wind Advisory until 8 PM PDT this evening for CAZ085.

Pacific Coastal Waters...None.

$$

BPN/CC/Duncan


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