Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
100 PM PDT Friday Aug 22 2014
Discussion...22/12z NAM/GFS in.
Stratus has burned off...leaving scattered stratocumulus behind.
Cumulus clouds are starting to pop on the ridges from the Cascades
east. There is also lots of smoke aloft emanating from several
fires in western Siskiyou County.
A long wave upper level trough remains over the Pacific northwest
this morning...with the trough axis running from British
Columbia...through eastern Washington and eastern Oregon...and
into extreme western Nevada. The Medford County Warning Area remains under west to
northwest flow aloft.
The trough will move east...but this will be a slow process due to
short waves diving down the backside of the trough. One such wave
will move through this afternoon and evening. It will be dry due
to its mostly overland trajectory and the main effect will be to
enhance offshore low level flow tonight.
Heights will rise Saturday as the trough moves out and onshore
flow will return Saturday night into Sunday. However...one more
strong short wave will dive down Sunday night...which will dig out
another trough over the Pacific northwest.
Once that trough moves out Monday the offshore long wave ridge
will build in in earnest...and this will kick off another heat
wave for the inland portions of the Medford County Warning Area. Offshore low
level flow will peak Monday night.
Expect continued dry conditions into the middle of the week. The
thermal trough will move inland Wednesday...and this will bring
the hottest temperatures of the week to the west side valleys. Medford
highs will flirt with the century mark Wednesday.
The upper ridge will slowly weaken around the middle of the week...and
the axis will break to the east of the area Wednesday. The medium
range models did diverge after Wednesday...but the latest 22/12z
run of the GFS is now in line with the 22/00z ec solution.
So...will go with continued weak ridging with the axis well to the
east of the County Warning Area and southwest flow aloft. Expect continued dry
weather with a slow cooling trend inland from Thursday on.
Temperatures will remain above normal though.
Aviation...based on the 22/18z taf cycle...
smoke from wildfires in Siskiyou County will continue to result
in IFR to MVFR visibilities from the crest of the Marble Mountains
eastward across the Shasta Valley through early afternoon. Expect
visibilities to improve to MVFR or better there later this
afternoon and early evening before smokes settles into mainly the
valleys and midslopes later this evening through Saturday morning.
Northeast winds are expected to push the marine layer west tonight
through Saturday morning, such that only the Coos coast should see
IFR conditions between 02z and 17z. Elsewhere, VFR conditions will
persist for the next 24 hours. Btl
Marine...updated 100 PM PDT Friday 22 Aug 2014... winds and seas
will begin to build this evening as a thermal trough pattern
develops. This will result in a return of gusty north winds and
wind driven seas, lasting at least through Tuesday. Strongest
winds and steepest seas will be over the southern outer waters
south of Gold Beach during the afternoons and evenings each day.
There is some uncertainty regarding wind strength through the
weekend, but winds are expected to remain below gale. With north
winds continuing for several days, have opted to issue a hazardous
seas watch for the southern outer waters beginning Saturday
afternoon, but much will depend on the strength and the extent of
the affected area as to how steep the seas may become. Confidence
should increase over the next several forecast cycles. /Fb
Pacific coastal waters...Small Craft Advisory for winds from 2 PM
Saturday to 11 PM PDT Tuesday for pzz356-370.
Hazardous seas watch from Saturday afternoon through Tuesday
evening for pzz356-376.
Small Craft Advisory for hazardous seas until 11 PM PDT Tuesday
Small Craft Advisory for winds from 5 PM this afternoon to 11 PM
PDT Tuesday for pzz376.