Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
300 am PDT Tuesday Oct 25 2016
Discussion...25/00z NAM/GFS/ec in.
The northern hemispheric pattern shows a wave number of five
around the Globe. This is normally a progressive pattern, but with
a deep nearly cutoff trough off the West Coast, progress will be
slow, at least initially.
That trough will remain in roughly the same location through this
week and beyond, as short waves diving down the back side of it
will force it to maintain its position. As long as it remains out
there, the Pacific northwest will remain under southwest and
occasionally south flow aloft, and short waves ejecting from the
trough will push fronts onshore through the period. It will remain
relatively wet, but high temperatures will be 5 to 15 degrees above
normal for the most part. The exception will be the coast and
Umpqua basin, where temperatures will be near normal.
The next short wave will move through the area Tuesday. The
associated front will be weak. It will move onshore Tuesday
morning, but retreat back offshore as an upstream system develops.
It will bring some gusty winds to the area though, and a Wind
Advisory will be issued for the Shasta Valley and some locations
east of the Cascades. Those winds will peak Tuesday night, then
diminish Wednesday afternoon.
The following short wave will move up from the south Wednesday...
but most of the associated energy will remain offshore and to the
north of the Medford County Warning Area. The associated front will move onshore
Wednesday morning and become stationary through Wednesday night.
The coast and Coast Range will get significant rain from this
system, but not much will fall inland.
Yet another wave will move in Thursday. This one will come in from
the west and the energy is directed farther south. This will
reinforce the stationary front and this front will push inland
Thursday. Precipitation will move inland as well, but there won't
be a lot of it.
Another wave will come up from the south Thursday night into
Friday. This system won't be very windy, but it will bring quite a
bit of precipitation to the area beginning Thursday night.
Long term discussion from the Monday afternoon afd...Friday
through Monday. Models start this time frame in fairly good
agreement with a closed 500 mb low at 39 north and 136 west at the same
indicated 544 height. This first system of the extended period
brings rain ahead of a warm front Saturday. The models remain in
good agreement as the upper low moves down to about 100 nm
offshore of northern California. This brings the triple Point of this
system directly over our forecast area Sunday. From there, models
are in broad agreement with a deep upper level trough over the
coastal waters off of the pac NW, and the timing of systems will
be impossible this far out and have broad-brushed chance pops
through the remainder of the extended. -Sven
Aviation...25/06z taf cycle...instability will keep thunderstorms
possible offshore and along the coast (including koth) through
around 25/09z. Inland, conditions are highly variable. Most of the
area will be MVFR or better with occasional lowering to IFR in
showers. An area of clearing has moved over kmfr and fog is forming
and may bring IFR/LIFR conditions to the terminal until at least
25/09z. An area of higher cloud will arrive soon and may reverse the
fog trend at kmfr, but confidence in this is low. Pilots should be
prepared for the possibility of LIFR conditions throughout the night
at kmfr. Similar problems may develop at klmt later if clearing
develops there. -Wright
Note: the ceilometer at FAA site koth is out of service, so there
will be no ceiling observations available generally between the
hours of 04z and 14z.
Marine...updated 245 am PDT Tuesday, October 25, 2016...south gales
and very steep seas this morning, especially north of Gold Beach,
will ease this afternoon and evening. However, conditions will
remain hazardous to small craft. Another storm will arrive from the
southwest tonight into Wednesday with another round of gales and
steep to very steep seas. Expect winds and seas to gradually subside
Wednesday night into Thursday, then remain low through Friday. The
next front will move in with increasing south winds and steep seas
Friday night into Saturday. -Spilde
Pacific coastal waters...Small Craft Advisory until 11 am PDT Tuesday
Gale Warning until 11 am PDT Tuesday for pzz350-356-370-376.
Hazardous seas warning until 11 am PDT Tuesday for