283
FXUS66 KPDT 262325
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
425 PM PDT Fri Jul 26 2024

Updated aviation discussion

.SHORT TERM...Tonight through Sunday night...Satellite imagery
reveals widespread smoke and haze across most of eastern Oregon
and eastern Washington, the result of regional wildfires which
continue to burn. Have extended smoke and haze in the forecast
through Sunday morning based primarily on HRRR smoke output.
While smoke and haze will likely linger across the region,
especially in the vicinity of ongoing wildfires, have opted to
exclude mention in the gridded forecast due to uncertainty in the
evolution of fires and smoke output.

Weak troughing over the Pacific Northwest will keep near-normal
temperatures and locally breezy westerly gap winds in place this
weekend. Saturday, a weak disturbance tracking across southeast
Oregon will bring non-zero, but low (<5%) chances of showers or
thunderstorms across the southern Blue Mountains during the
afternoon. A concurrent shortwave tracking across northern
Washington appears mostly dry with the main consequence being the
wind.

.LONG TERM...Monday through Friday...Models continue to be in good
agreement in having a trough over the Pacific Northwest with a
ridge over the central CONUS Monday and Tuesday. Tuesday afternoon
into Wednesday, a front moves through the area and carries the
trough eastward while closed low develops out in the eastern
Pacific. Models show general agreement in having a westerly zonal
flow overhead Wednesday though about 40 percent of model ensemble
cluster members begin having the ridge building into our area.
Thursday and Friday, model ensemble members all have the ridge
building and strengthening over our area with temperatures warming
well above normal to around 100 degrees by Friday.

The Extreme Forecast Index highlights Precipitation amounts along
the Washington Cascades Monday and Tuesday with values of
0.72-0.82 and some shift of tails values indicating a
possibility of heavier rain. It also highlights breezy winds
Monday afternoon in central Oregon and portions of the Columbia
Basin with a value 0.73. Cooler than normal temperatures are
highlighted Monday and especially Tuesday due to cooler air with
the front.

Monday will see the trough coming ashore with a slight chance to
chance of showers developing the Cascades in the late morning and
afternoon then spreading into the rest of the area Monday night.
The Cascade crest could get up to a half of rain but amounts
will be fairly light away from the crest. Models are not showing
enough instability for thunderstorms and the timing may be too
late (evening) for convection in the eastern mountains, so just
have showers. With the front, winds will increase to 10 to 20 mph
over most of the area. Model probabilities show a 25-55 percent
chance of 20 mph sustained winds, but chances of 25 mph sustained
winds drop to below 15 percent and that is just in the Columbia
Gorge and Kittitas Valley. Temperatures Monday will be similar to
Sunday with highs in the mid 80s to around 90 in the lower
elevations.

Tuesday will see the trough overhead and then moving off to the
east Tuesday night. This will be a more favorable day for
showers and a slight chance of thunderstorms in the eastern
mountains though amounts will be just a few hundredths of an inch
for the most part. Showers and thunderstorms will end quickly in
the early evening. The Columbia Basin will again have 10 to 20 mph
winds but winds will be lighter in central Oregon. Temperatures
will drop a few degrees to the lower to mid 80s with 70s in the
mountains.

With ridging beginning to develop Wednesday, foresee dry weather
and light winds with temperatures warming to near normal in the
upper 80s to lower 90s. The ridge will strengthen further Thursday
with temperatures rising to the mid to upper 90s and in the mid
80s to lower 90s in the mountains. NBM probabilities show a 20-35
percent chance of reaching 100 degrees in the Columbia Basin,
central Oregon and in the John Day valley.

On Friday, the cutoff low that has been parked out in the eastern
Pacific moves closer to the coast and our flow turns more
southerly and unstable due to a possible ridge breakdown. There
is some chance that this situation could pull some moisture into
the area and PWATs are over an inch in the GFS, but at this time
models are holding off on any showers or thunderstorms. It looks
more favorable next Saturday but that is past the scope of the
long term forecast. This will have to be watched during the course
of next week. Temperatures will warm further with highs rising to
97-105 in the lower elevations and mainly in the 90s in the
mountains. NBM probabilities give a 40-70 percent chance of
reaching 100 degrees, but the chances of 110 degrees are less than
5 percent even in the warmest locations. Perry/83

&&

.AVIATION...00Z TAFs...VFR conditions with mainly clear skies will
prevail through the night then expect some increasing high clouds on
Saturday. However, there will be considerable haze and smoke aloft
and some reduced visibilities produced near many of the ongoing
fires. Continue to expect YKM to have vsbys down to around 4SM
overnight in HZ and FU with some possible improvement on Saturday.
KBDN could also see a return of some SCT-BKN around 040 overnight
through Saturday morning. Winds will be less than 10 kts overnight.
KDLS will see winds increasing after 15Z tomorrow to 15-20 kts and
gusts around 30kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  86  56  87 /   0   0   0   0
ALW  54  89  60  90 /   0   0   0   0
PSC  56  91  61  91 /   0   0   0   0
YKM  53  89  55  89 /   0   0   0   0
HRI  54  91  60  90 /   0   0   0   0
ELN  56  87  57  86 /   0   0   0   0
RDM  47  86  48  85 /   0   0   0   0
LGD  51  86  51  87 /   0   0   0   0
GCD  51  88  51  88 /   0   0   0   0
DLS  58  86  61  85 /   0   0   0   0

&&

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

$$

SHORT TERM...86
LONG TERM....83
AVIATION...83