Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 142130
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
230 PM PDT Thu Mar 14 2024

.SHORT TERM...Today through Saturday...Current radar and visible
satellite imagery is showing dry conditions as a few thin veils
of high level cirrus clouds stream in from the northeast. These
clear skies attributed to a chilly start to the day this morning,
as low temperatures dropped into the mid-20s to low 30s across the
area. However, today is the start of a warming trend that will
extend into next week, as above normal high temperatures are
anticipated to occur on Friday with values breaking into the low
to mid-60s across our higher population centers in the Basin.
High temperatures will continue to increase on Saturday, with
highs in the Eastern Gorge, Tri-Cities area, and the
Yakima/Kittitas Valleys nearing 70 degrees. Confidence in these
areas reaching high temperatures of 70 degrees or higher on
Saturday is currently low to moderate (30-50%) as the NBM shows a
42% chance at the Dalles, 34% chance at Yakima, 27% chance at
Ellensburg, 23% chance at La Grande, 21% chance at Redmond, and
19% chance in the Tri-Cities. ECMWF ensemble members are also
keeping high temperatures in the mid-60s at Pasco and Yakima on
Saturday, with GFS ensemble members 2 to 3 degrees lower.

These dry, calm, and warming conditions are a result of a building
upper level ridge and area of high pressure moving in from the
west today, before centering over the Pacific Northwest and
developing into a Rex Block pattern into the weekend. This
synoptic feature will continue to provide sunny skies, calm winds,
and warming temperatures through the period. Flow aloft has
shifting from out of the north this morning to more out of the
northeast this afternoon/evening, which has allowed high
temperatures to be near or slightly above normal today. The flow
aloft will incur more of an easterly component tomorrow and
Saturday as the Rex Block sets up, to further allow warming that
will persist into the extended period. 75


.LONG TERM...Sunday through Thursday...Models are in excellent
agreement about having a Rex Block pattern over the western states
with a ridge of high pressure over the Pacific Northwest and a
closed low over Arizona Sunday and Monday. This will give us fair
and dry weather with unseasonably warm temperatures 10 to 15 degrees
above normal. The forecast becomes more uncertain on Tuesday as an
upper low and trough approaches offshore and the Rex Block begins to
break down. Models are mostly keeping the ridge overhead on Tuesday
though about 15% of the model ensemble members (mainly from the
GFS) have the trough nearer to the coast and the ridge axis over
Montana and eastern Idaho, which would be cooler than the other
ensemble members. By Wednesday, clusters show significant
differences as there are several different camps. About 55% still
have a ridge though it is split as to whether the ridge axis is over
Idaho (two thirds) or if it is overhead (one third), 25 percent have
a very flat ridge with a zonal westerly flow and 20 percent (mainly
GFS) have the trough near the coast. This will start cooling over
the area and introduce the possibility of light rain in the
mountains. Thursday doesn`t change much as 60 percent continue to
have a ridge over the west while 40 percent have a trough over the
area.

Confidence is high that weather on Sunday and Monday will be dry and
sunny with light winds. There is some uncertainty with temperatures
as the probabilistic NBM temperatures are 3-5 degrees warmer than
the NBM deterministic temperatures on Sunday and 2-4 degrees warmer
on Monday. The GFS and ECMWF temperatures are a degree or so cooler
than the NBM deterministic. Have used the NBM deterministic
temperatures as the best middle ground though they could end up
being a little too cool. This yields highs in the mid to upper 60s
in the lower elevations and in the mid 50s to mid 60s in the
mountains. Sunday will be a few degrees warmer with widespread lower
70s in the Columbia Basin. Clear skies and a drier air mass will
allow temperatures to drop to the mid 30s to lower 40s Monday
morning.

For Tuesday, have favored the ridge solution and have another day of
sunny and warm temperatures similar to Monday. However, with the
possibility of the trough arrival, have a slight chance of rain late
Tuesday night along the Oregon Cascade crest. Wednesday cools about
3 to 5 degrees and a chance of very light mountain rain develops
with snow levels at 5000-6000 feet. The lower elevations are
expected to remain dry though as we get into Wednesday night and
Thursday, a slight chance of rain is possible in the Blue Mountain
Foothills while the mountains have a chance of more light rain with
light snow above 4000-5000 feet. Temperatures on Thursday drop a few
more degrees to the upper 50s to mid 60s in the lower elevations and
in the upper 40s to mid 50s in the mountains. Both Wednesday and
Thursday afternoons will be breezy with 10 to 20 mph winds expected.
Perry/83


&&

.AVIATION...18Z TAFs...VFR conditions are expected through the next
24 hours with just occasional FEW cirrus around 25k feet AGL. Winds
will be mostly N-NE 5-10 kts this afternoon, becoming light terrain
driven tonight. 83


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  31  57  35  62 /   0   0   0   0
ALW  34  59  37  64 /   0   0   0   0
PSC  34  64  37  67 /   0   0   0   0
YKM  34  62  38  69 /   0   0   0   0
HRI  32  62  36  66 /   0   0   0   0
ELN  33  61  37  68 /   0   0   0   0
RDM  26  55  28  64 /   0   0   0   0
LGD  29  58  32  65 /   0   0   0   0
GCD  28  58  32  67 /   0   0   0   0
DLS  36  63  40  69 /   0   0   0   0

&&

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

$$

SHORT TERM...75
LONG TERM....83
AVIATION...83


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