177
FXUS66 KPDT 250502
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1002 PM PDT Mon Jun 24 2024

.Updated for Aviation...


.AVIATION...
06Z TAFS...VFR conditions and winds 10 kts or less are generally expected
through the period. However BDN and RDM could see gusts to around
20 kts Tuesday afternoon/early evening before decreasing.

&&

.PREV DISCUSSION... /issued 418 PM PDT Mon Jun 24 2024/

Updated for Aviation...

AVIATION...
00Z TAFS...VFR conditions are expected through the period. Some
gusty winds to around 20 kts at DLS/BDN and RDM will decrease
early this evening and then all sites will be 10 kts or less.

&&

.SHORT TERM...Tonight through Wednesday...A ridge of high pressure
will continue building over the Pacific Northwest through Tuesday as
an upper level trough in the Gulf of Alaska drops down towards the
Pacific Northwest coast. This will boost Tuesdays high temperatures
into the lower to mid 90s across the lower elevations and increase
heatrisk to moderate.

The upper level trough will begin moving inland Wednesday. Models
are in good agreement that a shortwave rotating around the bottom of
the trough will pass over the forecast area early Wednesday
increasing instability leading to a low chance (15%) of showers and
thunderstorms across most of the forecast area. Following the
passage of the shortwave there will be increasing westerly winds of
15 to 25 mph through the day decreasing instability for some
portions of the forecast area. Exception will be over the east
slopes of the Washington Cascades and the eastern mountains. These
areas will continue to see enough instability for convective showers
and thunderstorm through the afternoon and into the evening. Some
showers will persist along the Cascade crest Wednesday night as well
as over the eastern mountains mainly east of Meacham as the overall
upper level trough continues moving into the Pacific Northwest.

The breezy conditions Wednesday will be in conjunction with minimum
relative humidities dropping into the low to mid 20s. Combine this
will the slight chance of thunderstorms early in the day across the
Columbia Basin there is an elevated potential for increased rate of
spread in fine fuel fires.

.LONG TERM...Thursday through Monday...

Bottom Line Up Front

1. Breezy conditions return Thursday.

2. Thunderstorms along the eastern mountains.

3. Below normal to near normal temperatures.

Models are in decent agreement with an upper level low over the
PacNW.  The axis of energy is directly over the region with the
center just to the north of the CWA. This will bring strong
northwest flow across the Cascades. Looking at the surface guidance,
gradients tighten to between 9 to 10 mb along the Cascades which
will lead to an increase in winds, especially through the Gaps. The
EFI is also picking up on the abnormally breezy conditions mainly
along the Blue Mountains and into Wallowa County. However, winds
along the northern Blues and Wallowa County be below 25 mph with no
ensembles showing otherwise and only 10% probabilities for the
Northern Blues. 65+% of the NBM ensembles show the two main areas
that will see sustained winds of 25 mph and higher with gusts to 35
mph (70%) will be along the Simcoe Highlands and through the
Kittitas Valley with 30-40% showing the Southern Blues to see the
same with gusts at 70% for 35 mph as well. Once the upper level low
moves to the east Thursday night, winds will return to near normal.

With the upper low moving into the region bringing with it mid level
moisture and some instability parameters. Looking at model derived
soundings for Thursday afternoon, they show MUCAPE values between
350-500 J/kg, lifted index between -2 to -4, PWATs of 0.50-0.60
inches, lapse rates of 8.3 C/km and bulk shear nearing 40 kts. With
all these parameters we cannot rule out some high based
thunderstorms along the Northern Blues and Wallowa mountains
Thursday afternoon and into the early evening. With that said, there
are 15-30% probabilities of thunderstorms over the Blue and Wallowa
mountains with the higher probabilities over the Wallowas.

Lastly, the upper level low will bring with it some cooler
temperatures to start the term with. However, EFI is showing
temperatures to be at or just below normal. However, once the upper
level low exits the CWA, a transient ridge will move back in
overhead warming temperatures up again.  Thursday is the coolest day
of the period with over 60% of the raw ensembles having the
temperatures for Pendleton in the mid 60s to low 70s, 60% shows the
Gorge and central OR to be in the mid to upper 70s while the Basin
and adjacent valleys will see temperatures in the upper 70s to low
80s. As the ridge slowly pushes over the area, temperatures will
increase gradually each day until it maxes out on Sunday. However,
confidence in the max temperatures of high 80s to low 90s so far out
is low/moderate with on 30-40% of the ensembles in agreement for any
portion of the CWA. Bennese/90


&&

.AVIATION...18Z TAFs...VFR conditions expected over the next 24
hours. Breezy winds possible for DLS with a few breezes around 10-12
knots possible at DLS, with winds 10 knots or less all other sites.
Bennese/90


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  92  58  84 /   0   0   0  20
ALW  54  95  59  88 /   0   0   0  20
PSC  57  96  63  90 /   0   0   0  20
YKM  53  92  60  87 /   0   0   0  20
HRI  54  96  62  88 /   0   0   0  20
ELN  51  90  57  82 /   0   0   0  20
RDM  47  91  57  81 /   0   0  10  20
LGD  51  90  58  85 /   0   0   0  20
GCD  52  95  56  89 /   0   0  10  20
DLS  55  94  61  80 /   0   0   0  20

&&

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

$$

SHORT TERM...91
LONG TERM....90
AVIATION...90


.PRELIMINARY POINT TEMPS/POPS...
PDT  51  92  58  84 /   0   0   0  20
ALW  54  95  59  88 /   0   0   0  20
PSC  57  96  63  90 /   0   0   0  20
YKM  53  92  60  87 /   0   0   0  20
HRI  54  96  62  88 /   0   0   0  20
ELN  51  90  57  82 /   0   0   0  20
RDM  47  91  57  81 /   0   0  10  20
LGD  51  90  58  85 /   0   0   0  20
GCD  52  95  56  89 /   0   0  10  20
DLS  55  94  61  80 /   0   0   0  20

&&

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

$$

SHORT TERM...91
LONG TERM....90
AVIATION...77