Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
100 am PDT Wednesday Oct 22 2014
Discussion...22/00z NAM/GFS in.
Currently there is light precipitation over the area from the
Cascades west and Siskiyous north. Amounts in the past six hours
have been 0.10 inches or less...except for The Bald mountain RAWS
with 0.12 inches. Winds are gusting to 35 miles per hour along the South
Coast and Cape Blanco reported a peak wind of 51 miles per hour. Inland...the
highest gust is 48 miles per hour at Squaw Peak...which is by far the
windiest inland location at this time.
The progressive wet pattern continues for the Medford County Warning Area with
multiple fronts moving onshore over the next week.
An offshore long wave trough will slowly approach the coast...
bringing increasing southwest flow aloft. Short waves ejecting
from the trough will push a front onshore Wednesday...but this
front will stall as it becomes parallel to the upper level flow.
Waves will develop along the boundary and move from southwest to
northeast in response to the short waves moving through aloft.
Therefore...the front will remain active but it will be very slow
to progress. It will finally make some significant progress inland
Thursday...but it will weaken as it does so as the best upper
level support will remain offshore.
Rainfall amounts expected with this frontal system are around 3
to 4 inches along the coast through Thursday morning. Amounts west
of the Cascades will be around 0.5 to 2 inches...with the greatest
amounts in the mountains and the Umpqua valley. East of the
Cascades...amounts will be 0.10 to 0.75 inches...with the highest
amounts in northern Klamath County and lowest amounts over Modoc
and Eastern Lake counties. Snow levels will remain Above All but
the highest peaks.
As far as winds go...moderate to strong winds are likely ahead of
the front Wednesday and Wednesday evening...especially east of
the Cascades around Summer Lake and in the Shasta valleys. Wind
advisories are in effect for those areas.
The front will lift back north as a warm front Thursday night into
Friday. This will provide a relative break in the precipitation at
The models last night put the long wave trough onshore Friday
night. The more recent runs keep it offshore until Saturday with a
split flow pattern setting up. This will delay the next cold front
until Friday night. Saturday will be cooler with lots of showers.
Long term discussion from the Tuesday afternoon afd...Saturday,
October 25th through Tuesday, October 29th. Near to slightly above
average temperatures are expected during this time period along
with above normal precipitation.
More specifically, an active southwest flow storm track will persist
over the the forecast are through the period. Friday night surface
low pressure around 990 millibars is expected to move inside of 130
west longitude and then will make landfall over the olympic
peninsula in western Washington or Vancouver Island, British
Columbia. Precipitable water values will be near 1.25 inches as this
system arrives at our coastline. With the low centered well north of
the area, the low level wind trajectory with this frontal system
will be predominately from the south. This means that coastal
mountains westward and northern California stand to see the most
precipitation from this frontal system, but it does appear the cold
front from it will remain intact into at least the Cascades.
Sunday into Monday looks to be a mild reprieve in the wet weather as
transient high pressure briefly builds across the area and then
departs. The next frontal system, which will contain the remnants of
Hurricane Ana, which recently affected Hawaii, is due in with more
wind and rain late Monday into Tuesday. Btl
Aviation...22/06z taf cycle...a frontal system will gradually push
towards the coast this morning with increasing southerly flow
just above the surface. This will result in the potential for low-
level wind shear at koth where the surface winds will be
comparatively weak during the morning. The low level wind shear risk extends
through about 18z today. Then winds are expected to increase at
the surface front moves onshore. Meanwhile, ceilings along the coast
are expected to become widespread MVFR with local IFR this morning
with terrain obscurations over the Coast Ranges. Rain will become
widespread along the coastal areas and become moderate at times by
sunrise...rain will increase further during the afternoon and
continuing into the evening with moderate to locally heavy rain.
Inland, VFR will prevail at the taf sites through much of today,
though ceilings will lower along and west of the Cascades leading to
partial terrain obscuration and isolated MVFR ceilings in the Umpqua
valley. Steadier rain is expected to begin in afternoon at krbg
and around early evening at kmfr. Gusty southeast winds will
develop in the Shasta Valley Wednesday. Also expect some breezy
and gusty south winds east of the Cascades. -Spilde/cirrocumulus
Marine...updated 1045 PM PDT Tuesday 21 Oct 2014...a strong frontal
system will gradually push onshore this afternoon into this
evening. Gale force winds are expected over most the waters this
morning. Winds will gradually lower below gales from northwest to
southeast late this afternoon through late this evening as the
front pushes inland. Heavy west swell will combine with increasing
wind waves today and this evening resulting in chaotic and
dangerous seas. Sea conditions will gradually improve a little
from northwest to southeast late this afternoon into tonight as
the front moves onshore and wind waves lower. Seas will be
dominated by westerly swell Thursday into Friday. Confidence is
increasing that we'll see yet another strong storm system move
through the coastal waters Friday night into Saturday with strong
winds and very hazardous seas. -Spilde/cirrocumulus
or...Wind Advisory from 1 PM to 11 PM PDT Wednesday for orz031.
California...Wind Advisory from 1 PM to 11 PM PDT Wednesday for caz081.
Pacific coastal waters...Small Craft Advisory for winds until 11 PM
PDT Wednesday for pzz356.
Hazardous seas warning until 11 PM PDT Wednesday for pzz356-376.
Gale Warning from 2 am to 11 PM PDT Wednesday for pzz356.
Small Craft Advisory for hazardous seas until 5 PM PDT Thursday
Small Craft Advisory for winds until 8 PM PDT Wednesday for
Hazardous seas warning until 8 PM PDT Wednesday for pzz350-370.
Gale Warning from 2 am to 8 PM PDT Wednesday for pzz350.
Small Craft Advisory for winds until 2 am PDT Wednesday for
Small Craft Advisory for winds from 2 PM to 8 PM PDT Wednesday
Small Craft Advisory for hazardous seas from 2 PM Wednesday to 5
PM PDT Thursday for pzz370-376.
Gale Warning until 8 PM PDT Wednesday for pzz370.
Small Craft Advisory for winds until 8 am PDT Wednesday for
Small Craft Advisory for winds from 2 PM to 11 PM PDT Wednesday
Gale Warning until 11 PM PDT Wednesday for pzz376.