988
FXUS66 KPDT 062312
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
412 PM PDT Thu Jun 6 2024

Updated aviation discussion

.SHORT TERM...Tonight through Saturday night...Temperatures have
climbed into the mid-70s to mid-80s this afternoon and the heat
trend will continue through the short term. Conditions do not
warrant any headlines, but many locations in and around the Lower
Columbia Basin and the John Day Valley will observe the first 90
degrees of the season. Based on the current position of the
inverted surface thermal trough and the models pushing the thermal
trough east of the Cascades over the next several days, confidence
in the 90+ temps is high (90%). However, the probability of 100
degrees is 15% or less. The thermal trough is not anomalously strong
and 850 temps climb to 17-20C on Saturday--the hottest day of the
week. Keep in mind that overnight lows Saturday night will be 60-65F
for many of the lower elevations, therefore there will be little
relief in the unseasonably hot temperatures.

The previous forecast discussion mentioned the slight chance (15%)
of thunderstorms this afternoon and evening for our far southeast
zones. This was based on some morning convection in Malheur County
where there was elevated instability and a weak impulse embedded
in a southwest flow aloft. Latest visible satellite and web cams
are showing very low tops to the cumulus clouds. Will keep the 15%
in the forecast for the next few hours but definitely don`t want
to go higher. Similar conditions are forecast for Friday with only
a 15% chance of afternoon and evening showers and thunderstorms
for our southern zones. I did extend the slight chance to cover
southern Deschutes County where some of the HREF ensembles, mainly
the ARW and FV3, advertise convective activity in the late
afternoon. The westerly flow aloft will keep the isolated showers
and thunderstorms mainly south of the forecast area.

There has been good run-to-run continuity of the models on
Saturday in terms of the potential for showers and thunderstorms.
Current PoPs are around 20-40%, so any storms that develop will be
isolated but cannot rule out scattered coverage in the afternoon
and evening. SPC has general thunderstorms over eastern Oregon.
Models have backed off on the CAPES compared to previous runs and
now show average SBCAPES around 100-150 J/kg so storms are not
looking to be strong or severe at this time. Wister/85


.LONG TERM...Sunday 12Z(Sunday) to Friday 06Z(Thursday
night)...

Key Messages:

1. Potential thunderstorms with mountain showers for Sunday.

2. Breezy winds (25-35 mph) throughout this week.

3. Above normal high temperatures during this week.

A shortwave trough moves over to the PacNW as the transient ridge
exits the area Sunday through Monday late morning. This can bring
potential chances of mountain showers and thunderstorms for John Day
Basin and then eastern mountains. Developing thunderstorms are
likely for Sunday with CAPE values below 500 J/Kg and isolated
pockets around 600 J/Kg or above, including lapse rates of 7-8
C/Km. However, confidence is low due to these parameters showing
marginal instability (20-30%). There is a 15-30% chance of precip at
the Blues and the Cascades and <15% in the Columbia Basin and
central OR before decreasing onward. By Monday late morning,
conditions should improve when the trough exits further east from
the PacNW as another ridge builds in. The models and ensembles are
in great agreement with the shortwave trough moving in Sunday into
Monday morning thus increasing confidence on this week`s forecast.

Chances are high for breezy winds at Yakima Valley, Simcoe
Highlands, and Kittitas Valley during this week within 25-35 mph
(>70%). Confidence is moderate for wind gusts exceeding up to 40 mph
in the Kittitas Valley (50-60%). This is due to the strong surface
pressure gradient from the shortwave trough. However, wind gusts
will decrease to around 17-25 mph later this week (40% confidence).

High temperatures will remain above normal for this week as well in
the upper 80s to low 90s in the Columbia Basin and mid to upper 70s
across the remaining forecast area. High temperatures could briefly
drop a few degrees for Sunday into Monday night as the shortwave
trough moves over the PacNW. Feaster/97


&&

.AVIATION...00Z TAFS...VFR conditions will continue to prevail
under mostly clear skies for this 24hr TAF period with just a few
high clouds. Overall, winds will generally be less than 10kts.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  54  88  57  88 /   0   0   0   0
ALW  57  90  58  91 /   0   0   0   0
PSC  59  93  59  93 /   0   0   0   0
YKM  52  91  58  90 /   0   0   0   0
HRI  57  92  59  93 /   0   0   0   0
ELN  53  89  56  88 /   0   0   0   0
RDM  50  89  55  85 /   0   0   0  10
LGD  52  86  55  85 /   0   0   0  10
GCD  53  91  58  89 /  10  10  20  20
DLS  59  93  63  89 /   0   0   0   0

&&

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

$$

SHORT TERM...85
LONG TERM....97/90
AVIATION...97