Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 210548 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1040 PM PDT Fri Oct 20 2017

updated the aviation discussion

.UPDATE...The latest radar was showing some showers along the
wa/or cascades and this will expand in coverage while moving
further inland with the approaching storm system now over the
epac. The storm system will spread clouds and showers into central
oregon overnight and this will migrate into interior Oregon and
Washington toward morning. Snow levels will hover between 3500
and 4k feet where snow advisories remain in place tomorrow
morning in and near the Ochocos and Blue mountains and later in
the Wallowas. In addition the rain may become heavy at times and a
Flash Flood Watch is in place along the east slopes of the WA
cascades where previous fires stripped the terrain of vegetation
increasing the potential for rapid runoff. As the storm system
moves inland pressure gradients will tighten creating breezy to
windy conditions tomorrow especially in the Grande Ronde Valley
where a wind advisory is in effect. Otherwise pops and weather
were adjusted and expanded to include central oregon later tonight
and over and near the gorge. Thus the present short term forecast
appears on track for now as low temps fall into the 40s except in
the 30s across the higher elevations.

.AVIATION...vfr conditions will give way to areas of mvfr after
10z as clouds lower and showers move into the region especially at
taf sites krdm and kbdn and kdls. The areas of mvfr conditions will
effect the remainder of the taf sites after 15z such as kalw and
kpdt and kpsc. Also the winds will increase after 18z with gusts
over 30 kts. The gusts may approach 40 kts after 01z.

&&

.PREV DISCUSSION... /issued 205 PM PDT Fri Oct 20 2017/

SHORT TERM...Tonight through Monday...Weather pattern will be very
active and complex over the coming days. An upper level trough over
the region will be pushing off to the east overnight with showers
associated with it coming to an end. This will be followed quickly by
a warm front moving into the forecast area on Saturday. It will
arrive in central Oregon before sunrise and then spread
precipitation north and east across the forecast area through the
morning. Snow levels will begin around 4000 feet Saturday and then
rise through the day and overnight. Accumulating snow above 4000
feet has warranted the issuance of winter weather advisories through
the day and into the evening. Will also see increasing southerly
winds associated with the warm front through the day and the become
southwesterly overnight. Wind advisories will be issued when the
afternoon forecast goes out.

A moist westerly flow will continue into Sunday mainly impacting the
Cascades and eastern Mountains with some continuing precipitation
but snow levels will be around 7000 feet. A flash flood watch has
been issued for the Jolly mountain and Norse Peak fire burn areas as
two to four inches of rainfall is expected by Sunday. A ridge of
high pressure will begin to build into the region from the west
which will bring precipitation to an end Sunday night.

LONG TERM...Monday night through Friday.  High pressure will be
building into the region Monday and Tuesday with drier northwest
flow. Under the ridge, there may be some fog development in the
lower basin areas along the rivers during the early morning hours. A
frontal system will be moving through the area Wednesday with some
rain for the Cascades and a slight chance over the mountains of
northeast Oregon. Behind this system, the models are coming into
agreement on stronger northerly flow and cooler air spreading into
the area from the north as high pressure builds offshore.
Temperatures will be above seasonal averages Tuesday and Wednesday
and then cool to below normal through the rest of the week. 93

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  59  53  68 /  10 100  70  40
ALW  44  56  53  69 /  20 100 100  50
PSC  43  58  53  69 /  10  90  60  20
YKM  37  53  48  65 /  10 100  70  20
HRI  42  60  53  69 /  10  90  40  20
ELN  36  49  44  60 /  10 100  90  20
RDM  36  60  46  63 /  70  90  20  20
LGD  38  50  44  56 /  30 100  90  70
GCD  36  51  47  58 /  30 100  50  40
DLS  43  59  54  67 /  40 100  70  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 5 PM Saturday to 8 AM PDT Sunday for ORZ507-
     508-510-511.

     Winter Weather Advisory from 8 AM to 11 PM PDT Saturday for
     ORZ050.

     Winter Weather Advisory from 5 AM to 11 PM PDT Saturday for
     ORZ502.

     Winter Weather Advisory from 5 AM to 5 PM PDT Saturday for
     ORZ503-506.

     Wind Advisory from 1 PM to 11 PM PDT Saturday for ORZ049.

WA...Wind Advisory from 5 PM Saturday to 8 AM PDT Sunday for WAZ521.

     Winter Weather Advisory from 5 AM to 11 PM PDT Saturday for
     WAZ030.

     Flash Flood Watch from 7 AM PDT Saturday through Sunday morning
     for WAZ520.

&&

$$

97/



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