Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 270357 CCA

Area Forecast Discussion
National Weather Service Medford OR
815 PM PDT WED OCT 26 2016

.SHORT TERM...A cold front located near the coast will move inland
across the area on Thursday. Ahead of this front, models continue
to show gusty south winds over eastern and southern portions of
the area tonight into Thursday afternoon. Strong gusty south
winds are expected overnight into Thursday in the higher mountains
from the Cascades east. Also expect strong gusty winds in the
southern Shasta Valley this evening...gradually decreasing tonight
and early Thursday. The area near Summer Lake will also see
periods of strong gusty winds through Thursday as well. A wind
advisory is in effect for strong winds in the mountains, Summer
Lake and Weed areas. See the NPWMFR for details. During the day on
Thursday, also expect south winds to increase and become gusty in
some eastern valleys, mainly in eastern Siskiyou, Modoc and Lake

Models continue to show that precipitation will gradually spread
inland from the coast to the Cascades tonight. With the slow
movement of the front inland expect moderate to heavy rainfall
along the coast through Thursday morning. Current observations
indicate around 0.3 to 0.7 inches of rainfall has fallen along the
Coos Coast in the last three hours with 0.5 to 1.25 inches along
the Curry Coast in the last three hours . Another 0.5 inches of
rain is expected over Coos tonight into early Thursday morning
with an additional 0.5 to 1.5 inches over Curry. By late Thursday
morning expect decreasing rain along the coast with widespread
moderate precipitation over inland areas from the Cascades west.
Areas of light to moderate rain will also spread into areas east
of the Cascades by late Thursday morning, mainly Klamath and
eastern Siskiyou counties. In the afternoon expect most inland
areas to see light to moderate precipitation. Meanwhile, along
the coast, behind the front models support continued shower
activity. As the front shifts eastward, valleys west of the
Cascades may see some brief breaks as the rain transitions to a
showery pattern.

By Thursday evening, expect the front to shift just southeast of
the area, with scattered to numerous showers continuing east of
the Cascades and in the Mount Shasta area and isolated activity
over southwest Oregon and western and central Siskiyou county.


.AVIATION...27/00Z TAF cycle...A cold front will slowly move
inland the next 24 hours, producing light to moderate precipitation
and generally a mix of MVFR and VFR ceilings and gusty south to
southwest winds ahead of it. Confidence is lowest at the coast where
IFR ceilings are expected to lift to MVFR this evening behind the
front. Winds will diminish some overnight then increase again east
of the Cascades during the day Thursday. Turbulence is expected to
be widespread, especially in and around highest terrain.

Mountain obscuration will affect mainly areas from the Cascades
west tonight and then spread east of the Cascades tomorrow.

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 250 PM PDT Wednesday, October 26, 2016...
Gales have subsided as the front moves inland, but seas will remain
steep to very steep through tonight. Winds and seas will continue to
gradually subside Thursday though small craft advisory conditions
for seas aren`t expected to end over all the coastal waters until
early Thursday night. Latest models bring another round of
increasing south winds early Friday morning followed by building
long period west swell Friday night. There is low confidence on the
evolution of the forecast next week because of significant model
differences. The possibilities include a deep low just offshore on
Tuesday, but we are favoring the model with less active weather at
this time.


.PREV DISCUSSION... /Issued 538 PM PDT WED OCT 26 2016/

Aviation discussion updated.

SHORT TERM...While inland areas of southern Oregon is a short
reprieve from wet weather, we will ease back into the wet pattern
tonight. An occluded low pressure is located off Astoria Oregon
with a cold front about to come ashore this afternoon. Earlier in
the day the warm front lifted of our forecast area, and warm air
has moved into the Rogue Valley. Medford warmed to around 72 this
afternoon and downslope winds kept rain out of the valley. We had
thought that the front would move a little faster but it is now
starting to move east. SE winds continue to be breezy in the
Shasta Valley and we will continue with the wind advisory there.
Short term model indicates wind should come below advisory level
around 10pm this evening. The higher terrain east of the Cascades
could see gusty winds continuing through the night and traffic
along Hwy 140 in Klamath and Lake Counties could be impacted
especially at the passes.

Rain is not expected in the Rogue Valley until closer to midnight
tonight when the front approaches and the SE winds turns more
toward the SW. During the second half of tonight, rain could
spread into the Klamath and Tulelake Basin but should stay out of
Lakeview/Alturas area until Thursday morning. Expect widespread
rain across southern Oregon and northern California on Thursday as
onshore flow increases.

Thursday night a closed low pressure approaches central California
coast. This low will bring another round of rain to the Mount
Shasta area and rain is expected to spread into southern Oregon as
well but at a much lighter amount. Friday could be a dry day for
southern Oregon as the low moved east into Nevada but northern
California counties are expected to remain showery. Friday will
also be an in-between day for southern Oregon as the next deep
trough moves toward the coast and southerly flow develops over our

Saturday could see a return to wet weather as an occluded front
moves across southern Oregon. Confidence however is only moderate
at this point as the low could deepen offshore and delay the
eastward progression. /FB

LONG TERM...Sunday through Wednesday night.
There is still general model agreement on an active weather pattern
for next week with a series of frontal systems to move into the west
coast. However, as was the case yesterday, the model differences in
the timing, track, and strength of these systems quickly increase
and increase with time. The forecast utilizes a model blend while
incorporating typical climatology and topographic influences
associated with a west to southwest flow aloft. The GFS solution
remains generally faster and stronger/colder/wetter with these
disturbances than the ECMWF or DGEX.

The long term begins on Sunday with better though still not great
model agreement that the southern branch of a split flow aloft will
send an occluded front into southern Oregon and northern California
with the highest probability of precipitation into Curry, Josephine,
and Siskiyou Counties with a snow level around 6000 feet. The ECMWF
is still slower than the GFS but has sped up a bit. Both of the
models bring a broad closed low into our area by Sunday evening with
a transition to showers and a modest decrease in snow levels to
around 5500 feet.

Another colder trough is expected to follow from the west on Monday.
The GFS remains notably stronger and faster with this system. The
earlier in the day and the farther to the east that one goes, the
higher the possibility that the weather will be dry/between systems
for Halloween activities. There is a decrease in forecast confidence
beyond the day-time on Monday as model differences increase
regarding the evolution of the upper low and associated front.

By Wednesday, the next broad cold trough is expected to move into
the Gulf of Alaska. A new series of disturbances moving through the
base of the trough into the Pacific Northwest are expected to be our
dominant weather producers during the second half of the week. -DW


OR...Wind Advisory until 2 PM PDT Thursday for ORZ029>031.

CA...Wind Advisory until 11 PM PDT Wednesday for CAZ081.
     Wind Advisory until 2 PM PDT Thursday for CAZ083-085.

Pacific Coastal Waters...Small Craft Advisory for hazardous seas from
       2 AM to 11 PM PDT Thursday for PZZ350-356-370-376.
     Small Craft Advisory from 11 PM Thursday to 5 AM PDT
       Friday for PZZ350-370.
     Hazardous Seas Warning until 2 AM PDT Thursday for


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