810
FXUS66 KPDT 172104
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
204 PM PDT Mon Jun 17 2024

.SHORT TERM...Tonight through Wednesday...Water vapor satellite
imagery this afternoon shows an upper shortwave trough exiting
into the northern Rockies. Shower activity associated with the
trough passage has begun to increase this afternoon across far
eastern WA/OR, while surface heating has provided enough
instability for a few isolated thunderstorms to develop in
northern Wallowa county and further east and north along the ID
border.

Shower activity will linger early into this evening across the
northern Blues, but as the shortwave trough continues east, this
activity will diminish and be mainly confined to the mountainous
terrain of Wallowa county overnight. With the trough further east,
winds will also weaken through the Cascade gaps and the lower
Columbia Basin overnight.

By tomorrow morning, the PacNW will be under a broad upper level
troughing pattern with mostly light winds at the surface and dry
conditions across much of the forecast area. That said, a weak
shortwave impulse will move across the PacNW tomorrow afternoon,
producing chances of light showers across the WA Cascades,
northern Blues, and Wallowa county. Lingering surface instability
with modest low-level lapse rates will also allow for an isolated
thunderstorm or two to develop across Wallowa county Tuesday
afternoon. With ridging developing across western Canada and
troughing across the western US, a split flow will develop along
the US/Canadian border Wednesday. This will continue to promote
dry conditions and light winds at the surface.

While the region is expected to be under a broad troughing pattern
through the mid week, an inverted thermal trough developing
through the Great Basin will lead to warming temperatures. By
Wednesday afternoon temperatures will have warmed back into the
80s across the lower elevations, with 60s to 70s in the
mountainous zones. Lawhorn/82

.LONG TERM...Thursday through Monday...Models continue to be in
fairly good agreement through the end of the week but some timing
and placement issues remain on Sunday and Monday.

The Pacific Northwest will be under the influence of a weak and
decaying upper level trough Thursday. The trough will dissipate
allowing the flow to become westerly Friday and then amplify into an
upper level ridge centered over the northern Rockies on Saturday as
the next upper level trough approaches the coast. This will produce
a warming trend with generally light winds through the end of the
week. Hottest temperatures of the week will be Friday into Saturday
with Saturday being the peak day. The probability of temperatures
greater than 90 degrees these 2 days across the Lower Columbia Basin
is 60-90% but the probability of greater than 100 degrees remains
less than 10%. So, primarily expecting high temperatures Friday and
Saturday across the Lower Columbia Basin in the lower to mid 90s and
80s in the higher elevations then cooling Sunday and Monday.

The arrival of the upper level trough into the region Saturday night
and Sunday is in better agreement than yesterday. This will lead to
then onset of a weak marine push Saturday evening becoming a full
blown push on Sunday with breezy to windy conditions and winds 15 to
30 mph with higher gusts. This poses an elevated risked of fire
spread in existing or new fire starts on Sunday. Temperatures will
begin to cool Sunday with the arrival of the trough and then even
cooler on Monday. Precipitation threat looks to remain focused along
the crest of the Washington Cascades with some showers Saturday
night through Monday.

As of now there are no thunderstorms in the forecast as
probabilities are below 10%. However, as the flow aloft becomes more
southwesterly on Saturday due to the building ridge this could
become an issue over the eastern mountains as probabilities begin to
increase above 10%.


&&

.AVIATION...Previous Discussion...18z TAFs...Main aviation
concerns with be the breezy to windy conditions today followed by
some shower this afternoon through evening but overall expecting
VFR conditions. Will see sustained winds 10-20kts with gusts
30-35kts this afternoon through evening before decreasing
overnight becoming less than 10kts. Showers will produce some
local CIGS 040-080 into this evening before showers dissipate and
clouds decrease.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  44  73  45  82 /  30   0   0   0
ALW  48  75  48  85 /  40  10   0   0
PSC  49  79  49  87 /  30   0   0   0
YKM  45  77  46  83 /  10  10   0   0
HRI  48  79  48  87 /  20   0   0   0
ELN  45  74  46  82 /  10  10   0   0
RDM  35  74  39  81 /   0   0   0   0
LGD  40  68  41  77 /  40  20   0   0
GCD  37  71  41  79 /  20  10   0   0
DLS  48  78  51  87 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

SHORT TERM...82
LONG TERM....91
AVIATION...91