Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 240249
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
749 PM PDT Tue May 23 2017

.UPDATE...A cold front has passed over the Washington Cascades
southward to The Dalles and winds have increased along and to the
east of the Cascades to as far south as north central Oregon. Will
need to keep a close eye on the winds at The Dalles as the wind
speeds have been nearing the criteria for a wind advisory. The wind
advisory that is in place for the Kittitas Valley looks good...but
perhaps the winds have increased earlier than expected. Winds have
also increased at YKM, PSC, PDT, and HRI. It is unlikely that these
stations will have wind advisory wind speeds...but will also keep an
eye on these too. Winds have begun to increase over the Oregon
Cascades too...but not as strong. The cold front will continue to
move to the southeast overnight and the winds will help to keep
temperatures up for a while, but cold air advection will eventually
cause cooling to take place overnight and especially on Wednesday.
Wednesday`s highs will be about 20 (+/- 5) degrees cooler on
Wednesday than today. It will remain breezy to windy in many
locations on Wednesday as well. There is very little moisture with
this cold front but there will be scattered to broken mid and high
level clouds overnight and on Wednesday. A weather disturbance will
move down from the north on Thursday and then another on Friday,
with each bringing a slight chance of showers and afternoon
thunderstorms, mainly over eastern areas of the CWA and along the
Washington Cascade east slopes, Thursday and Friday. At this time
Thursday looks to be the better day with the greatest chance of
showers and/or thunderstorms in the CWA. 88

&&

.AVIATION...06Z TAFs...VFR conditions will prevail during the next
24 hours. The main concern will be increasing winds this
evening...especially at KDLS...KPSC...KALW...KPDT and KYKM. Winds in
these locations will increase to at least 10 to 20 mph but more
likely 15 to 25 kts...but likely staying below wind advisory
criteria. Further south KRDM and KBDN will see an increase in wind
as well...but not as much as the stations over the northern two
thirds of the area. 88

&&

.PREV DISCUSSION... /issued 234 PM PDT Tue May 23 2017/

SHORT TERM...Today through Thursday...A short wave and associated
cold front are moving over Vancouver Island this afternoon. Models
show that the mid levels in the atmosphere will remain very dry
with this system so the main effects will be winds and much colder
temperatures. Water vapor satellite shows a strong dry slot that
indicates strong winds in the jet. These winds will mix down to
the surface after the front moves through WA and OR tonight. Tight
surface pressure gradients and higher winds aloft mixing to the
surface will increase the northwesterly winds tonight and
Wednesday over the lower Columbia Basin and adjacent areas. A wind
advisory has been issued for the Kittitas Valley starting at
midnight.

The upper level trough will remain over the area Wednesday with
much colder temperatures. Afternoon high temperatures today
reached the mid 80s to mid 90s. By tomorrow high temperatures will
be 15-20 degrees colder when colder air moves into eastern WA and
OR behind the front. The trickiest part of the forecast will be
low temperatures tonight. Winds will be strong enough to inhibit
nighttime cooling especially in the Columbia Basin.

A pair of short waves moving through the upper trough Wednesday
night and Thursday morning will increase the moisture and
instability over eastern WA and OR. By Thursday morning skies will
be partly to mostly cloudy skies and some showers will develop.
Weak instability and steep lapse rates may trigger a few
thunderstorms Thursday afternoon/evening, mainly over the WA
Cascades and northeast Oregon mountains. Winds will be lighter.

Friday an upper level ridge will build again offshore. Subsidence
from the ridge will start to dry out central and eastern WA and OR
but enough moisture and instability may linger over far eastern OR
to trigger a few showers and thunderstorms in the afternoon.
Coonfield

LONG TERM...Friday night through Tuesday...A ridge of high pressure
will build in from the west late Friday and remain over the region
through the extended period. This will place temperatures at above
normal and winds generally light. Main weather concern will be the
possibility of thunderstorms developing on Monday and Tuesday mainly
over the mountains areas.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  54  68  42  67 /   0   0  10  20
ALW  56  71  48  70 /   0  10  10  20
PSC  57  74  48  75 /   0   0  10  10
YKM  54  73  46  76 /   0   0  10  10
HRI  56  73  47  74 /   0   0  10  10
ELN  54  65  44  73 /   0   0  10  10
RDM  43  69  33  71 /   0   0   0   0
LGD  48  65  42  62 /   0  10  10  20
GCD  46  67  38  66 /   0   0  10  20
DLS  56  69  47  78 /   0  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory from midnight tonight to 10 PM PDT Wednesday for
     WAZ026.

&&

$$

88/91/88


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