Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 230448

Area Forecast Discussion
National Weather Service Pendleton OR
948 PM PDT Thu Oct 22 2020

06Z TAFS...Tonight and most of Friday will be VFR, however,
conditions will begin to deteriorate late Friday afternoon or
Friday evening across the region as a storm approaches from the
north and west. MVFR CIGS will develop in RA during the late
afternoon or early evening hours at all TAF sites except RDM and
BDN which will be too far south. Conditions could worsen beyond
the end of the period, and IFR is possible at some point,
especially going into later Friday night and early Saturday
morning. Winds are expected to be fairly light, mainly less than
10 kts through the period.


.PREV DISCUSSION... /issued 846 PM PDT Thu Oct 22 2020/

A clear and quiet and another cold night is in store with light
winds. Not much to change in the update, so just adjusted temps
where needed.

PREV DISCUSSION... /issued 206 PM PDT Thu Oct 22 2020/

SHORT TERM...Tonight through Saturday night...A dry northwest flow
will continue through the night with some increasing clouds late in
advance of the next weather system arriving early Friday. Mostly
clear skies and light winds overnight will allow for another night
of freezing temperatures so have reissued the freeze warning for
another night.

The next weather system will arrive early Friday and bring some rain
and snow to the east slopes of the Washington Cascades and then
spread east into the Blue Mountains in the afternoon. This system
will begin to pull colder air over northern Washington southward
Friday night and Saturday which will begin to significantly lower
snow levels so that some light snow will be possible even in the
Lower Columbia Basin with some possible accumulations up to an inch.
More significant snow is expected near the crest of the Washington
Cascades and over the northern Blue Mountains where Winter Weather
Advisories have been issued. This system will begin to depart the
forecast area Saturday afternoon and night resulting in some very .
cold overnight low temperatures dropping into the teens to lower
20s with some single digits lows possible in the higher elevations.

LONG TERM...Sunday through Thursday night...Northerly flow aloft
takes on bit of a westward component Sunday and Monday as deep
troughing translates eastward. Conditions at the surface still
expected to be cold, well below normal, with some clouds lingering
Sunday from the departing system. Temps single digits to about 20 in
warmer areas Sunday and Monday morning rising to about freezing to
lower 40s through the day. Tuesday and Wednesday to feature light
northwest flow aloft as a ridge builds off the coast with pleasant,
albeit still cool, conditions at the surface by day. Influence from
the ridge keeps a lid on the atmosphere through this period though,
particularly in the overnight hours which may lead to some spots of
patchy fog or freezing fog as well as slowly deteriorating air
quality. More seasonable temperatures expected Wednesday and
Thursday to even slightly above normal for central OR as ridge axis
passes to our south through California. Models suggest a weak to
moderate strength system may bring some breeziness, clouds, and
higher elevation precip on Friday into Saturday. 76

AVIATION...00Z TAFs...Light winds and VFR conditions continue as
region lies between two systems. Cu field has developed in elevated
areas but very light cirrus only other cloud cover. Light and
somewhat variable sfc winds this afternoon to become drainage winds
and continue to be light tonight. Winds not quite as light tomorrow
and clouds will build and eventually begin to lower through the day
as an early winter system approaches, likely bringing worsening
aviation conditions to terminals Friday night into Saturday.  76


PDT  26  50  30  39 /   0  60 100  80
ALW  30  49  32  39 /   0  70  90  50
PSC  29  48  34  44 /   0  40  70  20
YKM  28  44  32  43 /   0  60  70  20
HRI  28  49  35  44 /   0  40  90  60
ELN  28  41  30  38 /   0  80  80  20
RDM  21  59  35  42 /   0  10  30  20
LGD  23  48  31  35 /   0  60  90  70
GCD  26  56  36  41 /   0  20  70  60
DLS  32  50  39  47 /   0  50  70  60


OR...Freeze Warning until 9 AM PDT Friday for ORZ041-044-505-507-508-

     Winter Weather Advisory from noon Friday to 9 AM PDT Saturday
     for ORZ502.

WA...Freeze Warning until 9 AM PDT Friday for WAZ024-026>029-521.

     Winter Weather Advisory from noon Friday to 9 AM PDT Saturday
     for WAZ030.

     Winter Weather Advisory from 8 AM Friday to 1 AM PDT Saturday
     for WAZ520.



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