940
FXUS66 KPDT 130519
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1020 PM PDT Sun May 12 2024

Updated Aviation Discussion

.SHORT TERM...Tonight through Tuesday...Current visible satellite
imagery shows scattered cumulus fields once again developing
over portions of the eastern mountains and the WA Cascades, with
clear skies elsewhere. Looking over at water vapor imagery, the
upper ridge that has been over the region the past several days
has started to push east into ID, while an upper shortwave trough
approaches the PacNW coast. Ahead of the shortwave trough, the
cross Cascade pressure gradient has begun to tighten, resulting in
breezy winds developing through the Cascade gaps and portions of
the Columbia Basin.

Tonight through Monday, the shortwave trough currently approaching
the region and a secondary shortwave trough behind it will quickly
move across the PacNW. Little precipitation will be associated
with these systems, however the WA Cascades are expected to see
isolated light showers develop in the afternoon. Otherwise, the
main impact from these systems are going to be an increase in
breezy conditions across the lower elevations and through the
Cascade gaps. The strongest winds are expected through the
Kittitas Valley, where sustained northwest winds of 25-35mph and
gusts up to 50 mph are forecast through the afternoon and evening
(confidence 75-85%). In the Eastern Gorge, OR Columbia Basin, and
the Simcoe Highlands westerly winds of 20-30mph with gusts mainly
35-40mph(isolated gusts up to 45mph) will develop by the
afternoon. Elsewhere, winds of 15-25mph with gusts up to 35mph
will develop.

By Tuesday morning, upper level ridging in the northeast Pacific
will build into the PacNW, providing another round of warming
temperatures and dry conditions through the mid-week. Winds will
generally be light through Tuesday, though a weak marine push in
the afternoon will result in breezy northwest winds developing
through the Kittitas valley. Lawhorn/82


.LONG TERM...Wednesday Through Sunday...Deterministic models and
ensembles are in good agreement on the 500 mb pattern for Wednesday
and Thursday depicting NW upper flow over the region. The GEFS
ensemble depicts shortwave energy moving along the Canadian border
Thursday afternoon and evening with lowering heights across the
Pacific Northwest. This is forecast to tighten the pressure gradient
with the latest GFS pressure gradient between PDX and GEG reaching
12 MB from 00Z-06Z Friday. This will favor windy west winds across
the lower elevations Thursday evening. Latest Probabilistic NBM is
indicating a 40-70% chances for winds exceeding 45 mph in gusts for
much of the lower elevations Thursday evening.

Friday through Sunday the confidence in the forecast becomes lower.
There is considerable variability among the ensemble clusters in the
depth/location of the upper troughs and ridges each day. However
there is reasonable confidence (50-60%) that a surface cold front
will cross the region on Friday bringing another bout of gusty
westerly winds across the lower elevations during the afternoon and
evening. Probabilistic NBM is indicating a 30-60% chances for winds
exceeding 45 mph in gusts for the typically windy spots under
westerly wind regimes.

The suite of available guidance is consistent in showing that the
threat for significant precipitation is very low through the entire
forecast period (80% confidence). The NBM introduces 15-25% POPS
along the Cascade East Slopes and northeast mountains on Sunday with
minimal QPF (less than .05 inches). Probabilities of thunderstorms
Sunday afternoon are currently quite low (5-8%). It will be warm on
Wednesday and Thursday with high temperatures in the mid to upper
80s lower elevations. Friday through Sunday high temperatures in the
lower elevations will be in the 70s to lower 80s. 78


&&

.AVIATION...06Z TAFs...There were a few cumulus clouds this
afternoon with bases around 6-8 kft, and there will be more cumulus
with similar bases on Monday.  High level cirrus AOA 18 kft will
also increase across eastern WA and northeast OR during the day.  It
has been breezy for many of the TAF sites today. Winds will decrease
this evening, but winds will be the same or a little stronger on
Monday. Westerly 10-15 kt gusting to 20-30 kt on Monday.  Wister/85


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  74  47  74 /   0   0   0   0
ALW  55  78  50  77 /   0   0   0   0
PSC  57  82  52  82 /   0   0   0   0
YKM  52  77  47  82 /   0   0   0   0
HRI  55  80  50  80 /   0   0   0   0
ELN  50  68  45  77 /   0   0   0   0
RDM  43  71  40  74 /   0   0   0   0
LGD  46  72  43  72 /   0   0   0   0
GCD  44  74  41  74 /   0   0   0   0
DLS  55  74  49  80 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory from 11 AM to 11 PM PDT Monday for WAZ026.

&&

$$

SHORT TERM...82
LONG TERM....78
AVIATION...85