Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 272130

Area Forecast Discussion
National Weather Service Medford OR
230 PM PDT Thu Apr 27 2017


.Short Term...Tonight through Sunday Night...Although satellite
imagery doesn`t show it all too well, satellite and surface
observations show numerous light showers moving across the
forecast area this afternoon. These will diminish through the
evening as the jet stream axis and upper level trough slide to the
east. High pressure and upper level ridging will then build in
over the Eastern Pacific, and this will be the primary driver of
our weather for the next several days. Also of note, the clear
skies and residual cool air in the area may produce some isolated
areas of frost in the Rogue, Applegate, and Illinois valleys
overnight tonight into early tomorrow morning.

With the ridge placed to our west, and a general trough over the
central United States, we will reside under swift northwest flow
aloft for the duration of the term. The ridge will deflect most
energy and precipitation producing systems to our north, leaving
the area dry and warmer. However, the trailing edge of a front
passing to our north on Saturday night into Sunday will skirt the
northern half of the forecast area, producing showers and
slightly cooler temperatures, and also disrupt the thermal trough
pattern that will periodically produce much warmer temperatures
over the ridges and along the southwest Oregon coast near
Brookings. The models have not been consistent on the strength of
the front 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.
Otherwise, expect gradually warming temperatures through the week.

.LONG TERM...Monday through Thursday...The area will be under the
influence of an upper ridge Monday through Wednesday with mainly
warm and dry conditions. A weak disturbance is expected to move over
the ridge on Tuesday, and will bring a slight chance for light
precipitation to northern portions of the area.

Wednesday, models and ensembles continue to show the upper ridge
will build inland over the area and bring dry and very warm
conditions to the area. Highs in the upper 70s to low 80s are
expected in western valleys with in the low 70s possible for eastern

Thursday, the upper ridge is forecast to shift eastward while a
shortwave trough moves into the region. This trough combined with
southerly moisture and instablity will bring a slight chance of
showers and thunderstorms to inland locations. -CC


.AVIATION...27/18Z TAF CYCLE...A weak disturbance will produce a few
showers through this evening north of the Umpqua Divide and over the
Southern Oregon Cascades. This will also result in areas of MVFR
cigs, including at KOTH and KRBG. Expect mainly VFR south of the
Umpqua divide and east of the Cascades. Conditions will improve late
this evening to mainly VFR conditions. However, lingering low level
moisture will allow areas of MVFR to develop in the Umpqua valley
tonight and continue into early Friday morning, including at KRBG.


.MARINE....Updated  200 PM PDT Thursday, 27 April 2017...Weak high
pressure will persist over the waters into early Friday with slowly
diminishing moderate seas. The models are in good agreement showing
small craft conditions primarily for the southern waters. However
it`s possible portions of the northern waters south of Bandon could
experience small craft conditions. Confidence was not high enough to
include the southern portion of the northern waters, but later
shifts will need to take another look at this. Gusty north winds
will increase Friday afternoon as high pressure strengthens offshore
while a thermal trough develops along the coast. Winds will be
strongest from 8 to 30 NM from shore in the waters south of Gold
Beach.  The pattern will weaken slightly on Saturday but strengthen
again early next week with advisory strength northerly winds likely
to develop. -Petrucelli




Pacific Coastal Waters...Small Craft Advisory from 11 AM Friday to 5 AM PDT Saturday for


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