Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
205 PM PDT Wednesday Aug 27 2014
Discussion...27/12z NAM/GFS in.
Mostly clear over most of the Medford County Warning Area this afternoon...except for
areas of marine stratus along parts of the coast. Other than
that...the Siskiyou County and Cascades fires continue to crank
out a lot of smoke.
A long wave ridge will continue to build into the Pacific
northwest today...and it will be hot and dry over inland
locations. Medford will flirt with a high of 100 degrees.
A short wave will ride over the ridge tonight into
Thursday...flattening the ridge out a bit. Overall it won't make
much of a difference this far south...but inland locations may be
a degree or two cooler. The other concern is the possibility of
isolated afternoon and evening thunderstorms east of the
Cascades...as model lifted indices show some instability there.
However...lifted indices and available moisture are both
marginal...so will go with a dry forecast.
On Friday a long wave trough will approach the coast. The models
have been generally weakening this feature from run-to-run.
However...there are still several concerns. It will push a weak
front onshore Friday and it will be breezy east of the
Cascades...and once again there is the possibility of isolated
afternoon and evening thunderstorms east of the Cascades. It will
be cooler though...and there may be some light precipitation along
the coast. At this time am going with a slight chance along the
coast and no mention of inland convection.
The trough will move through the area Saturday...and another long
wave ridge will begin building in from the west. Saturday will
likely be the coolest day of the week over inland portions of the
Medford County Warning Area...and a warming trend will commence Sunday. Low level
flow will turn offshore Saturday night...but it will be a weak
The ridge will continue to build through Monday before flattening
a bit Tuesday due to short wave activity to the north. Expect the
warming trend to continue into Tuesday with continued dry weather.
The 27/12z GFS solution shows another trough approaching
Wednesday. If this verifies...this will bring in some cooler
temperatures...but the trough looks to weak to bring any
precipitation to the area. It will make for another breezy day
east of the Cascades. On the other hand...the 27/12z ec holds on
to a ridge Tuesday but digs a trough near the West Coast
Wednesday. If that verifies...it will continue to be dry with a
weaker cooling trend. Have opted to go with the dry forecast and a
slight bit of cooling from Tuesday to Wednesday.
Aviation...based on the 27/18z taf cycle...areas of LIFR and IFR
stratus and fog near the north coast will return to the coast and
Coquille Valley between 00z-03z and persist overnight.
Inland...the IFR stratus is expected to intrude into the northern
portion of the Umpqua valley late tonight...perhaps bringing a
couple of hours of stratus as far south as Roseburg around 13z-
15z. Otherwise, VFR conditions will prevail with clear skies,
except for areas of wildfire smoke producing MVFR/IFR visibilities
in western Siskiyou County. /Dw
Marine...updated 200 PM PDT Wednesday 26 Aug 2014...as the thermal
slowly strengthens, small craft conditions for hazardous seas and
winds are expected to develop late this evening. Winds and
seas are expected to lower on Friday but some small craft conditions
may persist for areas south of Cape Blanco. Then as a low pressure
system to the north moves inland, expect increasing northwest swell
late Saturday into Sunday. Behind this system, there is a chance for
moderate north winds to develop early next week. -Sven
Pacific coastal waters...Small Craft Advisory for winds until 11 PM
PDT Thursday for pzz356-376.
Small Craft Advisory for hazardous seas until 11 PM PDT Thursday
Small Craft Advisory for winds from 11 am to 11 PM PDT Thursday