329
FXUS66 KPDT 302305
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
405 PM PDT Sun Jun 30 2024

.Updated for Aviation...


&&

.PREV DISCUSSION... /issued 223 PM PDT Sun Jun 30 2024/

SHORT TERM...Tonight through Tuesday...

Key Points:

1) Breezy each day with gustier conditions possible for our normal
windy spots.

2) Low chance of scattered showers, possibly thunderstorms this
afternoon and tomorrow for Wallowa County.

3) Stabilizing on Tuesday with a dry northwesterly flow setting up
on the front side of a Pacific ridge.

Areas of scattered showers have been noted in and nearby Wallowa
County this afternoon, and are expected to continue to be possible
through the beginning of the evening. There is a low chance (15%
or less) of isolated thunderstorms as well, but the majority of
this activity is expected further to the east in more favorable
environments, and any activity that does occur is not expected to
be particularly strong with lightning and some gusty outflow winds
possible. Meanwhile a few breezes occurring mainly near the
Kittitas Valley and Columbia Gorge, weakening into the nighttime
hours.

For tomorrow, the trough will continue eastwards, but a secondary
shortwave is indicated by models to round this feature and help
to produce another round of precipitation activity in the Wallowas
as well as further breezy winds. Probabilities for any showers
tomorrow are even less than today (30% or lower), and thunderstorm
chances 10% or less as well. The pressure gradient is expected to
remain enhanced and continue to promote breezy winds with tomorrow
expected to bring the gustiest winds of the week. Still,
probabilities as indicated by the NBM remain on the lower side for
any wind advisory level gusts or higher (45+ mph), with the
highest chances near the Kittitas Valley at around 40-80%. This
combined with only modest flow at the 850 mb level leads to
moderate to high confidence (60-80%) that isolated gusts 40-45 mph
will be possible, but widespread and frequent 45+ are unlikely.
Meanwhile more widespread 20-30 mph gusts are expected for most of
the forecast area, but with fair amounts of moisture still
lingering, fire weather concerns will be enhanced but not high,
precluding any need for red flag products with moderate to high
confidence (60-80%).

Tuesday is when conditions calm and we should see a ridging
pattern beginning to build. A thermal trough should promote
another round of breezy winds primarily across the Cascade gaps
with speeds in the 20-30 mph range. Relative humidities will begin
to drop notably however, with portions of the Columbia Basin and
Central Oregon back down into the 20`s and teens for minimum RH`s.
Temperatures through the next couple of days will remain fairly
moderated, with 80`s to right around 90 for our population
centers. Goatley/87

LONG TERM...Wednesday through Sunday...Deterministic models and
ensembles are in good agreement on the 500 mb pattern through much
of the period, though some differences among the clusters exist
particularly on Sunday that could impact the temperature forecast.
The probability of measurable rain during the entire period is very
low at less than 5%.

The ensembles are beginning to settle on a more offshore ridge
solution through at least Saturday with the PACNW in NWLY flow aloft
but with gradually warming temperatures. On Wednesday high
temperatures will be within 2-3 degrees of normal and it will be a
bit breezy in the Cascade gaps in the afternoon and early evening.
NBM 4.2 gives KELN a peak wind gust of 36 mph at 00Z Thursday. The
probability of needing wind highlights on Wednesday is low (10-20%).
On Thursday high temperatures will warm to the lower to mid 90s
across the lower elevations. Friday through Sunday will be hot with
the probability of temperatures exceeding 90 degrees at 90-100% for
the Columbia Basin and adjacent valleys and foothills, with 70-80%
chances for the remaining elevations below 3500 feet MSL. A few low
100s will be possible each day (50-60% chance) in the Columbia
Basin.

The most likely scenario depicted by the ensemble clusters for
Saturday into Sunday (40% of the ensemble members) is for a
shortwave trough to move across the region in the NW flow aloft and
suppress the ridge somewhat. This could act to cool the temperatures
slightly over the weekend making the hottest day of the week on
Friday as depicted in the latest GFS/MEX Guidance. For now went with
the NBM which has the hottest day on Saturday...but Friday through
Sunday will be hot regardless. The experimental HeatRisk product
shows widespread moderate category Friday through Sunday with a few
small patches of major category indicating that the heat may become
a problem for heat sensitive individuals by late in the week. 78

AVIATION...
00Z TAFS...VFR conditions are expected through the week. Breezy
conditions are once again occurring with winds gusting to around
20 kts at most sites and 30 kts at DLS. Expect winds to decrease
later this evening, when all locations will have winds 10 kts or
less. Wind gusts will increase again on Monday afternoon to
between 20 and 25 kts at most sites and around 30 kts at DLS.



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  56  82  54  83 /   0   0   0   0
ALW  59  86  57  86 /   0   0   0   0
PSC  60  89  58  90 /   0   0   0   0
YKM  54  85  51  87 /   0   0   0   0
HRI  59  88  56  88 /   0   0   0   0
ELN  57  79  54  80 /   0   0   0   0
RDM  47  80  45  83 /   0   0   0   0
LGD  51  77  49  80 /   0  10   0   0
GCD  49  80  47  83 /   0   0   0   0
DLS  60  83  56  82 /   0   0   0   0

&&

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

$$

SHORT TERM...87
LONG TERM....78
AVIATION...77