Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
352 am PDT sun Oct 23 2016
Short term...a rather quiet weather pattern will become more
active on Monday as low pressure over the Pacific rapidly deepens
late today into Monday. Moderate to strong winds could impact
much of the inland forecast area on Monday.
Today will feature mostly dry conditions with temperatures generally
near normal for this time of year. High clouds will stream over much
of the area in deep southwest flow. Today into tomorrow morning, low
pressure just outside of 130w over the Pacific will deepen
rapidly, "bombing out", with pressure drop of about 24 millibars
in 18 hours. This is supported by most gefs members and by both
the ec and GFS operational models. Given that we expect the low to
remain generally west of 130w and most wind directions aloft will
be just east of south, the greatest wind impacts are expected over
inland locations instead of at the coast. The coast is still
expected to get windy, but High Wind Warning criteria are not
expected to be met at this time. Further inland, the easterly
component to wind direction will favor moderate to strong winds
over the Shasta and rogue valleys as well as portions of the east
side. We have issued a host of wind advisories and high wind
watches to account for this. Models have trended stronger with the
winds for most areas, with the past 4 runs of the sref indicating
higher wind speeds with each run for Medford, Alturas, Lakeview,
and Klamath Falls.
Precipitation is expected to be heaviest at the coast Monday morning
as the front pushes inland and then in The Mount Shasta area Monday
afternoon due to strong upslope flow. Models suggest 70kt 700mb
southerly flow which supports orographically enhanced precipitation.
We analyzed snow levels tonight, and models suggest perhaps a brief
period of snow Monday morning at the snowmans Summit elevation
(~4500 ft), but due to the brief nature of the snow, will let the
day shift examine further to see if an advisory is warranted. Snow
levels will rise and Road temperatures will warm later on Monday as
the heavier precipitation arrives.
Medford precipitation amounts have trended lower in recent model
runs, with strong downsloping and drying southerly flow expected on
Monday. There still may be a period of moderate rain as the front
moves through Monday afternoon.
On Tuesday the front pushes east and stalls over Modoc and lake
counties. Models hint at the idea that an extended period of
moderate rain is possible in these areas as the front slows.
Meanwhile, another low deepens offshore late Tuesday and pushes
northwest of the forecast area, bringing rain to the coast and most
likely breezy to windy conditions inland. The previous
discussion's long-term section follows.
Long term...Wednesday through Saturday...a long-wave upper
trough remains between roughly 130w and 150w throughout the
extended period. A significant spoke of energy rotates around the
base of the trough and up along our coast on Wednesday. The
associated surface cyclone is expected to track south to north
along or just west of 130w. While much depends on the track of
this low, models are in really good agreement that we'll have at
least gales over our outer waters, so winds in our forecast were
raised. It is a little too far out to have enough confidence to
issue any wind headlines for it, so we'll just keep an eye on it.
From Thursday on, there has been a shift in the European model (ecmwf) which
complicates the forecast. Energy feeding into the long wave trough
is expected to form a closed low off California, but the 12z European model (ecmwf)
is now much more progressive with it. The GFS holds the low off
California with rain likely confined to our coast Thursday. The
European model (ecmwf) now moves it northeast much more quickly and would have
widespread rain for US Thursday. The Canadian has a weaker wave as
opposed to a closed low, but its rainfall pattern is much more
like the GFS. Given these complications, we've chosen not make an
major changes from Thursday on. Any solution is likely wet for the
coast, but solutions vary from wet to dry inland. We've kept pops
at or above climo with the highest at the coast. -Wright
Aviation...23/06z taf cycle...broken to overcast high clouds are
expected to keep inland areas VFR. A weakening cold front moving
onto the coast will lead to some MVFR along and near the coast and
in the coastal waters through this morning and partial terrain
obscurations in the coastal mountains. The front will then drift
back northwestward as a warm front today, so conditions are
expected to improve to VFR. South and southeast winds will
increase over land areas this afternoon and evening leading to the
potential for low level turbulence in much of the area. Looking
further ahead, moderate to strong south winds on Monday will bring
widespread and significant turbulence to the forecast area.
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 330 am PDT Sunday, October 23, 2016...
high and steep seas will continue into early this morning as
elevated west swell continues. South winds will increase this
evening into early Monday morning ahead of an approaching cold front
reaching gale force 35 to 40 kt with gusts up to 50 kt. Heavy rain
and decreased visibilities will accompany this front tonight and
early morning morning. Behind the front, a strong low will approach
the area but stay west to northwest of the waters. This strong low
will bring additional south gales of 35 kt to the waters Monday
through early Tuesday morning. Very high, very steep and chaotic
seas will develop Monday evening and night as a high west swell at
11 seconds combines with very steep south winds seas. These
conditions will continue through early Tuesday morning. Winds will
gradually lower Tuesday to Small Craft Advisory levels. Very steep
hazardous seas may continue into Tuesday afternoon then gradually
Another strong storm may bring additional gales and very steep
hazardous seas to the waters on Wednesday.
or...Wind Advisory from 8 am to 11 PM PDT Monday for orz029>031.
High wind watch from Monday morning through Monday evening for
Wind Advisory from 11 PM this evening to 5 PM PDT Monday for
California...Wind Advisory from 8 am to 11 PM PDT Monday for caz085.
High wind watch from Monday morning through Monday evening for
Wind Advisory from 11 PM this evening to 8 PM PDT Monday for
High wind watch from this evening through Monday evening for
Pacific coastal waters...Small Craft Advisory until 5 am PDT early this morning for
Small Craft Advisory from 5 PM this afternoon to 11 PM PDT this
evening for pzz350-356-370-376.
Hazardous seas warning from 11 PM this evening to 8 am PDT
Tuesday for pzz350-356.
Gale Warning from 11 PM this evening to 8 am PDT Tuesday for
Small Craft Advisory for hazardous seas until 5 am PDT early
this morning for pzz350-356-370-376.
Hazardous seas warning from 2 PM Monday to 8 am PDT Tuesday for
Gale Warning from 5 PM this afternoon to 8 am PDT Tuesday for
Hazardous seas warning from 11 PM this evening to 2 PM PDT
Monday for pzz370.