943
FXUS66 KPDT 072341
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
441 PM PDT Fri Jun 7 2024

Updated Aviation Discussion

.AVIATION...00z TAFs...VFR conditions expected across all sites as
skies remain clear and winds remain light to moderate out of the
north and east. Only potential impacts this evening would be
around BDN and RDM, where showers and thunderstorms have developed
across southern Deschutes County. Not expecting too much northward
extent for these showers, but did include a mention of it as a
tempo group for BDN at least. Evans/74

&&

.PREV DISCUSSION... /issued 211 PM PDT Fri Jun 7 2024/

SHORT TERM...Today through Sunday...

Bottom Line Up Front (BLUF)

1. Thunderstorms over south central OR and along the eastern
mountains Saturday and Sunday.

2. Warmer than average temperatures through the short term with
hottest day Saturday.

3. Winds increase again Sunday.

Hi-res models are in decent agreement with the upper level synoptic
patter through Saturday. An upper level ridge is in place over the
region and will begin to flatten slightly as the leading edge of an
upper level trough makes its way towards the PacNW. Mid level
moisture will enhance as the southwesterly flow intensifies ahead of
the the upper level trough. This synoptic set up will lead to
thunderstorm probabilities across the eastern mountain steadily
increasing in probabilities each day. The SPC has a general
thunderstorm outlook over the southern portion of the CWA both today
and Saturday then it switches to along the eastern mountains on
Sunday. Model derived soundings across the eastern mountains, MUCAPE
values will be 200-300 J/kg through Deschutes county  with lapse
rates of 7.9 C/km, lifted index of -2, PWATs of 07 inches and bulk
shear neat 20 kts. While these ingredients are present, confidence
in thunderstorm chances are low of Deschutes County with less than
15%. As the upper level trough continues to push onshore,
thunderstorm ingredients are projected to increase as well as begin
to move along the Ochoco-John Day Highlands. Model derives sounding
again show MUCAPE of 250-350 J/kg, lapse rates of 8 C/km, lifted
index of -2 to -3, PWATs of 0.85 inches and bulk shear nearing 25-
35kts. This increases thunderstorm probabilities to 20% Saturday.
Lastly, thunderstorm probabilities increase Sunday to 25-30% and
shift along the entire eastern mountains and highlands as well as
the WA Cascade crests. MUCAPE increase to 400 J/kg and even higher
values of 600 J/kg through the Wallowa mountains with lapse rates
cresting 9 C/km, lifted index of -4, PWATs nearing 0.9 inches and
bulk shear of 35 kts. Confidence in these storms becoming severe is
low, less than 5%.

With the upper level ridge in place over the region through Saturday
and the incoming frontal boundary and upper level trough,
temperatures are going to remain above average through the short
term period. Models show the upper level trough to be mostly dry and
cooler, only dropping the temperatures as few degrees Sunday. EFI is
signaling above average temperatures for much of OR today increasing
across portions of WA Saturday and leveling back to near normal on
Sunday. Over 50% of the raw ensembles show that today much of the
region will be in the upper 80s with some isolated 90s in the
Basins, mid elevations like central and north central OR will be in
the upper 80s and the higher terrains will be in the mid 60s.
Saturday, the hottest day of the period, 80% of the raw ensembles
are showing the majority of the region to be in the upper 80s to low
90s, mid level terrains in the mid to upper 80s and the higher
terrains in the upper 60s. Models then show the trough  axis to be
onshore Sunday which will push a frontal boundary across the
Cascades allowing some cooler air to rush into the area.
Temperatures will only cool by a few degrees with over 60% of the
raw ensembles showing temperatures in the mid to upper 80s through
the Basins, upper 70s to low 80s along the lower and mid elevations
and low 60s along the higher elevation. There is an enhanced heat
risk on Saturday of portions of the Basin where HeatRisk guidance is
signaling moderate risk, so be mindful if outside and remember to
drink plenty of fluids.

Lastly, with the upper level trough pushing across the Cascades,
model derived pressure gradient tool shows that there is a slight
tightening of the surface gradients along the Cascades. Due to this,
ensembles are picking up on increased winds, especially through our
wind prone areas. There is over a 55% chance the Simcoe Highlands
and portions of the Gorge seeing winds of 25 mph or greater, 50-70%
through the lower Kittitas Valley and less than 25% along the
foothills of the Blues. Bennese/90

LONG TERM...Monday 12Z(Monday) to Saturday 06Z(Friday
night)...

Key Messages:

1. Cooling period during this week.

2. Breezy to locally windy conditions throughout this week.

As the transient ridge exits eastward Monday, the PacNW enters a
zonal pattern Tuesday through Wednesday. A short-lived ridge will
build in Thursday followed on Friday by a trough moving into the
PacNW. This trough is driven by the upper low centered over the BC
coast, bringing a cooling period across the region this week. This
would result in seasonable temperatures through the weekend (>60%
confidence). Precip could occur along the crest of Cascades Friday
once the trough moves over the PacNW (20-30% confidence). Otherwise,
there will be no significant weather impacts for the extended
period.

There is a high chance for windy conditions at Yakima Valley, Simcoe
Highlands, and Kittitas Valley during this period at 25-35 mph
(>70%). The wind gusts could exceed up to 40 mph mainly in the
Kittitas Valley and Simcoe Highlands, but confidence is low (<20%).
The surface pressure gradient remains strong as this progressive
pattern persists. Breezy winds will be across for the remaining
PacNW at around 17-25 mph (>50% confidence). Feaster/97

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  56  87  59  82 /   0   0   0  20
ALW  57  90  61  84 /   0   0   0  20
PSC  57  92  63  88 /   0   0   0  10
YKM  56  89  59  86 /   0   0   0  10
HRI  57  92  62  88 /   0   0   0  10
ELN  55  88  60  82 /   0   0   0  10
RDM  53  85  56  80 /   0   0  20  10
LGD  54  84  58  77 /   0   0  10  30
GCD  56  89  57  80 /   0  10  30  50
DLS  62  89  63  84 /   0   0   0  10

&&

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

$$

SHORT TERM...90
LONG TERM....97
AVIATION...74