587
FXUS66 KPDT 180953
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
253 AM PDT Sat May 18 2024

.SHORT TERM...Today through Monday...A broad upper-level low
centered over western Canada continues to influence our weather in
the form of mountain showers and gusty winds, as a jet associated
with the southern flank of this system remains situated over the
forecast area. If there`s any solace from these prolonged windy
conditions, it`s that we`re not quite expecting advisory-level winds
anywhere in our area, however some localized areas could come close
at times this afternoon.

Guidance has generally trended downward as far as wind gusts are
concerned for Saturday afternoon, with even the bullish HREF
suggesting that wind gusts will largely remain in the 30-35 mph
range across our typical wind-prone areas, including the Cascades
Gaps and Oregon Basin. NBM probabilistic guidance is oddly pretty
aggressive on the Oregon Basin and Simcoe Highlands achieving
advisory level gusts, with values as high as 80% in some pockets.
That being said, the lack of a strong signal in the deterministic
NBM, as well as the HREF, and with 850 mb winds hovering right
around 35 mph, just don`t think the ingredients are quite there to
pull the trigger on any headlines.

Precip will remain primarily over our mountain zones, as the airmass
overhead is still dry with PWATs in the 0.3 to 0.5 range, leaving
upslope flow as the primary mechanism for showers. 00z HREF does
suggest a few isolated showers may form over the Basin, likely due
to upper-level support with the jet overhead, but rain will struggle
to reach the surface outside of the mountains with how dry the
boundary layer is. NBM did also paint some thunder potential over
the central WA Cascades, but with how cool temps are expected today,
opted to leave out any mention for thunderstorms.

Sunday looks to be dry as NNW flow prevails aloft, allowing for
cool, below normal temps to settle in, with highs struggling to
eclipse 70 degrees even in the lower Basin. Winds will remain breezy
in spots, albeit much less so than today. Monday also looks dry for
most of the forecast area, however an area of amplified northerly
flow aloft on the back end of the departing Canadian low could
trigger some isolated shower and thunderstorm activity across
Wallowa County. Evans/74

.LONG TERM...Tuesday through Friday...Several lows/troughs move
through the region during the extended period. The first will be
on Tuesday. There is already disagreement with the deterministic
models, with the GFS having a much stronger low moving across the
Pacific Northwest on Tuesday than the GFS. However, regardless of
which solution is correct, there will be a trough over the area
through Wednesday which will bring unsettled conditions. Rain,
mainly over the mountains and possibly some thunderstorms over
eastern areas are expected on Wednesday. However, there could even
be some light QPF, generally a few hundredths, over lower
elevation locations as well. THursday night should see decreasing
precipitation as the trough moves eastward and then there is more
uncertainty into Friday with the ECMWF having a flatter/drier
solution and the GFS being stronger/wetter with the next system
moving onshore. Obviously, a lot can change in a week, but the
parade of systems will continue and timing ans strength will
affect the upcoming holiday weekend.

Only about 32% of the ensemble clusters support the deeper GFS
solution on Day 4/Wednesday and about 22% support it on Day
5/Friday.  Additionally the ECMWF is ensemble mean is more in
agreement with its deterministic run than the GFS leading to more
support for the ECMWF solution as well.

High temperatures will be close to or slightly below normal through
the extended generally from the upper 60s to the mid 70s.

&&

.AVIATION...12Z TAFS...High confidence (80-100%) in VFR conditions as
the next upper low/trough moves across the area later today
though Sunday. Winds will increase during the afternoon hours with
gusts 25 to 30 kts at DLS, PDT, RDM and BDN and 20 to 25 kts
elsewhere (90-100% confidence). Winds should decrease towards the
end of the TAF period.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  66  39  63  39 /   0  20   0   0
ALW  69  42  65  43 /   0  20   0   0
PSC  72  46  71  46 /  10  10   0   0
YKM  68  39  68  41 /  10  10   0   0
HRI  71  44  70  43 /   0  10   0   0
ELN  62  38  63  39 /  10  10   0   0
RDM  65  33  57  31 /   0   0   0   0
LGD  65  38  58  36 /   0  10   0   0
GCD  67  36  58  34 /   0   0   0   0
DLS  66  45  66  44 /   0   0   0   0

&&

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

$$

SHORT TERM...74
LONG TERM....77
AVIATION...77