Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 131749
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1049 AM PDT Tue Apr 13 2021

Updated Aviation Discussion

AVIATION...18z TAFs...Windy conditions and blowing dust will be a
concern for today, as N/NE winds ramp up to around 20 to 25 kts
sustained, gusting as high as 40 kts at times through the early
evening. Areas most vulnerable to blowing dust include
YKM/PSC/PDT/ALW, where vsbys especially in PSC could drop to IFR
at times. Winds expected to decrease starting around 03-05z, but
may remain locally breezy through the overnight hours. Otherwise
clear skies and dry conditions expected through the period. 74

MORNING UPDATE...A strong northeast flow on the north side of a
developing upper low pressure system moving south across the
region today will cause a large area of blowing dust in the Lower
Columbia Basin and adjacent valleys. A Blowing Dust Advisory is in
effect today for these areas from 11 AM PDT - 8 PM PDT. Visibility
will be reduced at times to between a quarter mile to 1 mile,
especially near freshly plowed fields. Winds will diminish tonight
as pressure gradients relax and then an overall northeast wind,
breezy at times in the afternoons, will persist on Wednesday and
then less on Thursday. Beginning Friday will be a more pronounced
warming trend that will persist into early next week with much
above normal temperatures.

PREV DISCUSSION... /issued 431 AM PDT Tue Apr 13 2021/

SHORT TERM...Today through Thursday night...An upper low is
deepening over far eastern Oregon and will develop into a closed
low today. The upper low will dip southward over the Great Basin
tonight and remain over NV Wednesday and Wednesday night. On
Thursday, a series of waves rotating around the closed low will
result in a broad cyclonic circulation over the western half of
the U.S. The low will eventually weaken into an open trough
and will no longer be an influence in our forecast area Thursday
night. By this time, a strengthening high pressure ridge to the
north will make its way across the PacNW.

Despite the large cyclonic circulation over the forecast area the
first 60 hours, PoPs will be less than 15 percent. There may be a
few flurries south of John Day today, but any snow showers will be
south of the forecast area.

The main weather concern during the short term period will be the
winds and the blowing dust today. Winds are already gusting to
25-30 mph from the NE in many areas this morning. Winds as strong
as 56 mph have been observed along the wind exposed Rattlesnake
Hills. Current wind forecast looks good, and one update will be to
include a few more zones in the Blowing Dust Advisory. That is,
the Yakima Valley and the Oregon portion of the Lower Columbia
Basin and Blue Mtn Foothills. Main concern for the Yakima Valley
is the area from Sunnyside to Prosser. The blowing dust advisory
will be in effect from 11 AM to 8 PM. Winds gusts 40-45 mph are
likely for many lower elevation areas which fall just under wind
advisory criteria. One area to watch is central Oregon where
MAV/LAV guidance has sustained winds at 30-35 mph for Redmond and
Bend. This may be overdone, as the HRRR and HREF are showing less
wind, and these models typically do well with gradient driven
winds. Not only blowing dust will be a concern, but wind driven
fires in dry grassy areas. Dewpoints are currently in the teens,
and the RH today will range from about 15-25 pct.

Winds will decrease some tonight and will be breezy from the NNE
on Wednesday. There may be patchy blowing dust on Wednesday but
not as widespread as today. The breezy winds tonight may help
provide just enough mixing to keep overnight lows from plummeting,
but it will be cold with lows in the mid 20s to mid 30s and
dewpoints in the teens. Wister

LONG TERM...Thursday night through Monday. Models in good
agreement through the extended period with a strong ridge over the
area. Airmass is dry and expect mainly clear skies. Temperature
profiles show a gradual warming trend through the weekend with
850mb temps reaching 12-16C. This will put high temperatures into
the 70s which is 10-15 degrees above normal levels. Overnight lows
will remain on the cool side with 30s and 40s. Upper low will
move into the region on Tuesday with a cooling trend and possible
showers.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  58  29  61  33 /   0   0   0   0
ALW  62  34  65  38 /   0   0   0   0
PSC  64  41  69  42 /   0   0   0   0
YKM  62  34  68  39 /   0   0   0   0
HRI  63  36  66  38 /   0   0   0   0
ELN  59  33  67  38 /   0   0   0   0
RDM  54  26  55  29 /   0   0   0   0
LGD  54  29  55  31 /   0   0   0   0
GCD  56  28  56  32 /  10   0   0   0
DLS  63  40  68  43 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Blowing Dust Advisory until 8 PM PDT this evening for ORZ044-507-
     508.

WA...Blowing Dust Advisory until 8 PM PDT this evening for WAZ027>029.

&&

$$

SHORT TERM...88
LONG TERM....94
AVIATION...74


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