457
FXUS66 KPDT 210910
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
210 AM PDT Fri Jun 21 2024

.SHORT TERM...Today through Sunday night...The forecast area will
be under the influence of a dry westerly flow through Sunday
night. The only precipitation chances in the forecast will be
Sunday night along the east slopes of the WA Cascades in Kittitas
County with a slight chance (20%). There are two main weather
concerns this weekend--the hot temperatures today and Saturday and
a dry cold front brining gusty winds and low humidity on Sunday.
No highlights are planned at this time, but forecasters will be
keeping a close eye on the wind and RH threat on Sunday.

Today will be about 3-7 degrees warmer than yesterday, and
temperatures on Saturday will increase another 3-7 degrees.
Afternoon highs on Saturday will be in the upper 80s to upper 90s
for most of the forecast area--highs that are about 10-15 degrees
above seasonal average. The HeatRisk product has minor to moderate
heat risk. Will there be areas reaching 100 degrees? The NBM
probability for 100+ degrees is around 30-50% in the Lower
Columbia Basin and locally in the John Day Basin, so there is a
chance for isolated locations to reach triple digit temperatures.
The westerly flow aloft will keep the pressure thickness from
rising which will prevent a major warmup. 850mb temps will climb
from around 19-22C today to 22-27C tomorrow, but this would be
considerably higher if not for the westerly flow.

There will be a marine surge of cooler air through the Cascade
gaps late Saturday, and a dry cold front on Sunday will deepen the
marine layer and increase winds across the Columbia Basin down to
central Oregon. It is not a strong cold front, and the only
locations that have the best potential for winds meeting advisory
criteria will be in the Kittitas Valley and the eastern CR Gorge
near Maryhill and east of Biggs. Based on forecaster experience
with pattern recognition, the NBM seems too low on the wind progs
and went closer to the NBM 90th percentile for these two areas.
The forecast will show sustained winds around 30 mph gusting to 45
mph. There will be dry air aloft behind the front, as models
continue to show 700mb RHs less than 10% over south central WA and
north central OR. Surface RHs will be in the teens and 20s.
Confidence in the combination of winds and RHs meeting red flag is
just around 50% for late Sunday so will hold off on any fire
weather watches. Wister/85

.LONG TERM...Monday through Friday...

Bottom Line Up Front

1. Upper level ridge will keep area dry and warm at the beginning of
the period

2. Pattern change midweek bringing cool and moist conditions back to
region

Models are in firm agreement to with regards to the upper level
synoptic pattern. Clusters show little variance between the
ensembles with the upper level flow having a slight westerly
component. This will give way to a brief transient ridge that will
keep the region warm and dry through midweek. EFI shows temperatures
in the OR portion of the CWA to be a bit above normal while the WA
side moderates towards near normal to slightly above normal. Over
60% of the raw ensembles have the Pendleton area and Yakima and
Kittitas Valleys in the upper 70s to low 80s and central OR, the
Gorge and the Basins in the mid 80s. Temperatures will increase
2-5 degrees through Wednesday with Wednesday being the warmest day
of the period with 67% of the raw ensembles having a large
portion of the region in the low to mid 90s and the higher terrain
in the upper 70s.

A pattern shift will occur Wednesday evening when models show an
upper level low begin to push onshore. Clusters do show there will
be some variances in the timing and positioning of this incoming
low. However, this will primarily affect the location of the
precipitation that will come along with it. This upper level low
will not only bring precipitation, but will send a cold front out
ahead bringing with it cooler temperatures. Even with the cooler
temperatures, EFI is showing the region to be under near normal
conditions through the remainder of the period. Much of the
precipitation that will accompany the upper level low will be
along the mountains with nearly 50% of the ensembles in agreement
that the Cascades will see near 0.05 inches of rain and 0.01
inches along the Blue Mountains starting Wednesday steadily
decreasing each day through the remainder of the period.
Bennese/90


AVIATION...12Z TAFs...VFR conditions will prevail through the
period. Mostly SKC with light and variable winds. Bennese/90


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  89  58  93  60 /   0   0   0   0
ALW  92  61  97  64 /   0   0   0   0
PSC  94  62  98  63 /   0   0   0   0
YKM  92  61  95  56 /   0   0   0   0
HRI  95  61  98  63 /   0   0   0   0
ELN  91  60  92  58 /   0   0   0   0
RDM  88  53  91  51 /   0   0   0   0
LGD  85  55  91  56 /   0   0   0   0
GCD  88  56  95  55 /   0   0   0   0
DLS  95  65  93  61 /   0   0   0   0

&&

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

$$

SHORT TERM...85
LONG TERM....90
AVIATION...90