416
FXUS66 KPDT 030438
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
938 PM PDT Tue Jul 2 2024

.SHORT TERM UPDATE...The forecast area is under a dry northwest
flow aloft, and breezy to windy conditions remain. A shortwave
trough over far NE WA and the ID Panhandle allowed gradients to
strengthen and cooler marine air to surge through the Cascade gaps
and CR Gorge this evening. Nighttime microphysics of GOES West
show stratus clouds banked up along the west slopes of the WA
Cascades. However, the stratus is shallow based on the 00Z UIL
sounding with a marine depth up to 2800 ft MSL. Forecast was
updated to increase winds in some locations as well as extend the
breezy winds through 06Z. Due to the shallow marine layer,
confidence is high (80%) that winds will decrease after midnight.

&&

.AVIATION...06z TAFs...Clear skies will continue through
Wednesday evening. WNW winds 10-20kt gusting to 25-30kt this
evening will diminish overnight, and winds on Wednesday will be
primarily light and terrain driven with the exception of breezy
winds at DLS. Wister/85



&&

.PREV DISCUSSION... /issued 450 PM PDT Tue Jul 2 2024/

Main changes begin to take place on Thursday as the ridge of high
pressure over the eastern Pacific begins pushing into the Pacific
Northwest. This will be the beginning of a long hot dry period
that will persist into next week. High temperatures will climb
into the lower to mid 90s across the lower elevations with
pleasant 80s in the mountains. Skies will be generally clear
through the day providing easy viewing of evening firework
displays. Winds will also be light and generally under 10 mph.
Conditions will be dry with afternoon and evening relative
humidities down to 10-20 percent with fine grass fuels being
extremely dry.

LONG TERM...Friday through Tuesday...No changes in messaging.
Forecast confidence is high (>90%) that we will see the hottest
temperatures of the summer so far as strong, persistent ridging
moves over the PacNW during the day Friday and sticks around for the
foreseeable future. The only thing ensembles really waver on is the
exact positioning of the ridge axis, and the extent to which a
shortwave on Friday riding the ridge to our northeast modulates the
high pressure position at all. This would only serve to delay the
inevitable, however, as guidance exhibits a strong signal on the
region being enveloped by high pressure by Saturday at the latest,
and likely (70-80%) lasting through most of next week.

We have issued an Excessive Heat Watch for most of our non-mountain
zones starting this Friday and lasting through the middle of next
week. NBM probabilistic shows high probabilities (generally 60-80%)
in highs eclipsing the century mark starting on Saturday for the
majority of our population centers. We`ll have to keep an eye on
where this ridge of high pressure ultimately centers itself early
next week, as the NBM may be a bit gun-shy on temps should the high
fall directly overhead as the deterministic GFS and ECMWF currently
suggest.

Otherwise, fire weather concerns will be low, as hot temperatures
will cause RHs to sink well into the teens, but winds are expected
to be weak, outside of the usual cross-Cascade gradient that will
only be exacerbated under this heat wave. Still, the forecast looks
to be very stagnant: hot, dry, and clear. Stay hydrated! Evans/74



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  55  83  55  90 /   0   0   0   0
ALW  57  86  58  93 /   0   0   0   0
PSC  59  89  59  94 /   0   0   0   0
YKM  55  88  56  92 /   0   0   0   0
HRI  58  88  57  95 /   0   0   0   0
ELN  55  83  55  90 /   0   0   0   0
RDM  46  84  49  92 /   0   0   0   0
LGD  50  79  51  87 /   0   0   0   0
GCD  48  83  50  90 /   0   0   0   0
DLS  56  88  59  97 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Watch from Friday afternoon through Tuesday
     evening for ORZ041-044-505-507-508-510-511.

WA...Excessive Heat Watch from Friday afternoon through Tuesday
     evening for WAZ024-026>029-521.

&&

$$

SHORT TERM...91/85
LONG TERM....74
AVIATION...85