FXUS66 KPDT 172225

Area Forecast Discussion
National Weather Service Pendleton OR
224 PM PST Sat Nov 17 2018

.SHORT TERM...Tonight through Tuesday...High pressure will dominate
area weather for the next few days. The ridge is currently centered
offshore but will move to the coastline by tomorrow afternoon and
then overhead Monday and Monday night. This will be a quiet and dry
weather period with light and variable winds. The big concern will
be low clouds and fog over the Columbia Basin and its effects on
temperatures. Low clouds and fog tonight should be a little more
widespread than last night and primarily near the larger rivers.
Have patchy fog and freezing fog in the forecast for the Columbia
Basin, Yakima Valley and from Ellensburg up to Snoqualmie Pass. The
fog should burn off in the late morning which will keep temperatures
down several degrees from today while the rest of the area will be a
few degrees warmer as the ridge influence strengthens over the area.
Sunday night the fog will increase and spread down south as far as
Madras and then into Redmond and Bend by Monday night. During the
day Monday the fog and clouds will only partially burn off and only
around the edges on Tuesday morning. By Tuesday afternoon, the ridge
will be moving off to the east as a system approaches the coast and
this will help mix out the low clouds and fog and bring some mid
level clouds across the Cascades. The clouds and fog will keep
temperatures Monday and Tuesday in the fog affected areas in the
upper 30s to around 40 while the rest of the area will be in the mid
40s to lower 50s. Low temperatures through the next few nights will
be quite cool with upper teens to mid 20s in the lower elevations
and in the upper 20s to around 30 on some of the higher mountain
ridges though the mountain valleys will be in the teens. Perry

.LONG TERM...Tuesday Night through Saturday...A rather abrupt
pattern change will take hold into the extended period. Large scale
upper ridging will shift eastward into the northern and central
Great Plains as a series of storm systems line up over the northern
Pacific. This will bring a period of unsettled weather, and with any
luck, beneficial rains/mountain snow beginning late Wednesday and
continuing through the Thanksgiving holiday weekend.

We will continue to experience expansive fog and low clouds Tuesday
night into Wednesday, but as the first upper level storm system
moves into the region Wednesday afternoon, increased winds and
precipitation should allow fog to lift/diminish from west to east
through the Columbia Gorge and Basin. Models have generally come
into much better agreement on timing with precipitation chances
increasing markedly by Wednesday evening, especially for higher
elevations. Thereafter, several troughs will move west across the
region, making for a damp cloudy holiday weekend. Nonetheless, this
should mean beneficial precipitation. Snow levels generally look to
remain 4000+ feet with high elevation/mountain snow a good
possibility and rain elsewhere. Long range models diverge
substantially late in the weekend into early next week in handling
another storm system shifting southeastward into the Pacific
Northwest. Either way, it appears a fairly active and progressive
pattern may linger beyond the 7 day period. 79


.AVIATION...00z TAFs...VFR conditions will prevail through the
early evening hours. Thereafter, as a strong inversion sets in,
expansive fog and low stratus should develop after 06z. This will
likely lead to prolonged IFR visibilities with brief LIFR possible
from 12z on. Some improvement in visibility will likely occur beyond
20z Sun, but low stratus looks to persist. 79


PDT 45 24 42 24 / 0 0 0 0
ALW 43 23 42 24 / 0 0 0 0
PSC 49 21 42 21 / 0 0 0 0
YKM 52 21 42 20 / 0 0 0 0
HRI 48 23 43 22 / 0 0 0 0
ELN 48 20 46 21 / 0 0 0 0
RDM 48 11 53 15 / 0 0 0 0
LGD 47 22 48 24 / 0 0 0 0
GCD 46 24 50 25 / 0 0 0 0
DLS 51 26 46 25 / 0 0 0 0


OR...Air Stagnation Advisory from 7 AM Sunday to 1 PM PST Wednesday
for ORZ041-044-507-508-510-511.

WA...Air Stagnation Advisory from 7 AM Sunday to 1 PM PST Wednesday
for WAZ024-026>029.



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