Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
100 am PDT Monday Sep 1 2014
Discussion...01/00z NAM/GFS in...and September has arrived.
Mostly clear skies prevail across the Medford County Warning Area this
morning...except for some low clouds along the coast north of Cape
Blanco. Fires in western Siskiyou County continue to produce a lot
A broad long wave ridge continues to build into the area from the
southwest with dry northwest flow aloft. 500 mb heights will rise into
Monday then level off. The upper level flow will back to zonal
Monday night into Tuesday as a short wave rides over the top of
the ridge...flattening it a bit. Expect a thermal trough near the
coast to gradually strengthen during this interval...with weak
to moderate offshore low level flow developing tonight. This will
make for mostly clear skies and slightly above normal temperatures...
especially near Brookings where it will be quite warm Monday.
That short wave will dig a trough as it moves onshore Tuesday.
Most of the associated energy will remain north of the Medford County Warning Area
and no precipitation is expected. It will cool a bit along the
coast and in the Umpqua basin as the thermal trough moves inland
and the marine layer returns. Highs over the rest of the Oregon
west side will remain about the same as Monday. Meanwhile...it
will warm up over northern California and the east side as the
thermal trough moves over that area.
The main trough will move out to the east Wednesday...leaving a
weak residual trough over the area Wednesday night into Thursday.
As it does so...a cold front will push through the area. Inland
highs will drop around 5 degrees west of the Cascades...and 5 to
10 degrees east of the Cascades. It will still be dry.
North to northeast flow aloft will develop over the area Wednesday
into Wednesday night. This pattern usually dictates that there
will be a low level offshore event and that will be the case here.
Expect clear skies everywhere Wednesday night into Thursday with
gusty winds and poor recoveries over the ridges from the Cascades
west. Inland highs Thursday will generally be 1-5 degrees warmer
than the Wednesday highs...except in the Umpqua...where highs will
be 5-10 degrees warmer.
Extended discussion from the Sunday afternoon afd...Friday through
Sunday. Models push the thermal trough north from California
towards the Willamette Valley. The forecast area can therefore
expect continuing warm temperatures and low humidity to continue
through the remainder of the forecast term. There may be some
relief by early next week, as models are producing a stronger, and
more importantly, wetter system entering the Pacific northwest.
Uncertainty is very high, so have left mention of probability of precipitation out of the
forecast at this time.
Aviation...based on the 01/06z taf cycle...MVFR ceilings have
returned to the coast from Cape Blanco northward, including North
Bend/koth. This coastal stratus will lower overnight into the
early morning and spread into the Coquille Valley with areas of
IFR ceilings and visibilities developing. Coastal conditions will improve
after 15z Monday morning. Northerly low level winds along the
coast will increase during the day.
Elsewhere, clear skies will prevail for the next 24 hours with the
exception of reduced visibility in Siskiyou County due to smoke
from wildfires in the western portion of Siskiyou County.
Marine...updated 1030 PM PDT sun 31 Aug 2014...northerly winds will
increase from early Monday morning into Wednesday afternoon with the
strongest winds in the area south of Cape Blanco and beyond 5 nm
from shore. A thermal trough will persist along the coast with
moderate northerly winds and steep seas developing on Monday then
moderate to strong northerly winds and steep to very steep wind wave
dominated seas expected from Tuesday through Thursday. -Dw
Pacific coastal waters...Small Craft Advisory for winds from 11 am
Monday to 11 am PDT Wednesday for pzz356-376.
Small Craft Advisory for hazardous seas from 11 am Monday to 11
am PDT Wednesday for pzz356.
Small Craft Advisory for hazardous seas until 11 am PDT
Wednesday for pzz376.