Area Forecast Discussion

from: NWS Pendleton, OR

FXUS66 KPDT 241714 CCA

Area Forecast Discussion
National Weather Service Pendleton OR
1013 AM PDT Mon Jun 24 2024

.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.


.Update...Minor changes made to the forecast for today and tonight.
Main change was made for Wednesday when the next weather system will
arrive. Expect a shortwave to pass over the forecast area early in
the day with enough forcing and instability to trigger some showers
and possible thunderstorms. By afternoon and evening the main focus
of instability shifts to northeast Oregon and southeast Washington
where the potential for showers and thunderstorms will continue.

.SHORT TERM...Today through Wednesday night...There are a few
weather concerns and forecast challenges in the short term, but
nothing significant to require highlights at this time. The
weather will be quiet over the next 24 hours, and Tuesday will be
hot and dry. There is a slight chance (20%) of early morning
thunderstorms on Wednesday over the northern Blues and an
increasing chance (20-30%) of thunderstorms over northeast Oregon
Wednesday afternoon and evening. The Cascades will have a 40-60%
chance of showers Wednesday and Wednesday night, mainly near the
crest. Unfortunately, the two large wildfires-- Slide Ranch near
White Swan and the RV Long Bend near Maupin-- will have less than
10% chance of observing any precipitation during the short term.

Winds have decreased behind yesterday`s cold front, and winds
through Tuesday night will be relatively light. The westerly flow
aloft today will keep pressure heights down and afternoon
temperatures similar to yesterday. High pressure aloft centered
over the four corner states will strengthen tonight and Tuesday,
and the inverted surface thermal trough will make its appearance
Tuesday afternoon and allow temperatures to climb into the 80s to
mid 90s. The HeatRisk category will be minor to moderate. There
are hints of elevated instability in eastern Oregon on Tuesday,
but little to no moisture. However, as an upper level trough off
the eastern Pacific nudges towards the coast and the upper flow
shifts to the southwest Tuesday night, there will be increasing
moisture combined with elevated instability that will bring a
slight chance of early morning thunderstorms over the northern
Blues (20%).

The chance of thunderstorms increases over far northeast Oregon
on Wednesday to around 20-30% as the offshore trough moves inland,
and the upper flow increases from the southwest with embedded
disturbances. CAPES are weak...less than 200 J/kg...but shear is
very strong. 0-H5 bulk shear is as strong as 60 kts over most of
eastern Oregon but 45 kts over Wallowa County. A 60-kt shear may
result in cumulus tops being sheared off and cutting off any
updrafts. But, Wallowa County will have the best chance for
thunderstorms. NBM indicates 20% but the forecast will show 30% in
the Wallowa Mountains where my confidence is a little higher. A
tight pressure gradient will set up as the thermal trough is forced
eastward towards the ID border and it will be breezy (locally
windy). The afternoon RHs will not be critically low with the
exception of southern OR, mainly south of John Day and Prineville,
where forecast RHs are in the teens for Wednesday. This area has the
best chance for elevated fire concerns but confidence that red flag
conditions will be met is fairly low. Wister/85

.LONG TERM...Thursday through Monday...A semi-progressive pattern
is on tap for the long term, beginning with a passing low
pressure system that will stay just to our north, followed by
transient ridging that will give way to another shortwave by the
end of the period. This will keep our temperatures just below
normal on Thursday, becoming closer to normal then through
(mostly) the end of the forecast with periods of breezy winds and
some showers and possible thunderstorms that should be primarily
relegated to the high terrain of the region.

The period begins with a deep upper low situated along the
borders of Washington and Canada, quickly moving eastwards and
exiting our area by Friday morning. Unfortunately this should
equate to a lack of significant moisture making it into our
region, keeping the bulk of any noteworthy precipitation along the
mountains and in Northern Washington. The NBM only shows a 50%
chance of QPF totals greater than or equal to a tenth of an inch
for the Cascades in Kittitas County - anywhere else along the
mountains including into the Blues has a 10% chance or less, with
zeros for our lower elevation zones. Even our winds will be
breezy but not at significantly impactful levels, with only a
30-80% chance of seeing gusts around or in excess of 35 mph for
the lower Columbia Basin/Foothills of the Blues, Kittitas Valley,
and Simcoe Highlands, hardly a strong for around here and not
nearly enough to trigger a wind advisory. Noteworthy however will
be temperatures, with highs descending into the 70`s for our
population centers outside of the Columbia Basin where low 80`s
are expected. This places us around 2-6 degrees below normal.

Conditions are expected to be mostly benign for Friday and
Saturday under transient ridging, with temperatures warming
around 5 degrees each day. Sunday a quick moving shortwave will
bring us back down around 3-5 degrees while winds breeze similarly
to Thursday. Another round of mountain precipitation could occur,
but this time with a bit more moisture and instability values
around 500-800 J/kg in the Eastern Mountains of Oregon, a few
thunderstorms can`t be ruled out. And with PWAT anomalies around
125-150% of normal, if any lightning does occur, hopefully there
will be accompanying rain to help preclude a dry lightning risk as
we continue to delve deeper into fire weather season. Into Monday
the bulk of the precipitation exits as we should see similar
temperatures to Sunday under westerly to northwesterly flow.


PDT  82  52  92  59 /   0   0   0   0
ALW  85  55  95  62 /   0   0   0   0
PSC  86  56  95  63 /   0   0   0   0
YKM  85  53  92  59 /   0   0   0   0
HRI  86  55  96  64 /   0   0   0   0
ELN  82  52  91  59 /   0   0   0   0
RDM  84  49  92  54 /   0   0   0   0
LGD  82  53  91  58 /   0   0   0   0
GCD  88  54  96  57 /   0   0   0  10
DLS  85  56  94  62 /   0   0   0   0





NWS PDT Office Area Forecast Discussion