000
FXUS66 KPDT 071803
AFDPDT

Area Forecast Discussion...Updated Aviation.
National Weather Service Pendleton OR
1102 AM PDT Fri May 7 2021

.SHORT TERM...TODAY AND TONIGHT...An upper level trough will pass
over the region today and then form a closed low over western
Montana tonight. The trough passage will bring some shallow
instability to the forecast area this afternoon and evening mainly
over the Columbia Basin and eastern mountains. This will lead to
some showers through the afternoon and evening with showers
decreasing and or ending as sunset approaches. Other impact will be
the cooler windy conditions. Temperatures will be around 20 degrees
cooler today with westerly winds 15 to 30 mph. The Kittitas Valley
could see a little stronger winds so have issued a wind advisory
through 9pm this evening. Tonight will also be cold but expect
enough lingering breezy conditions to keep temperatures from getting
down to the critical level of freezing for crops or vegetation
concerns.

&&

.AVIATION...18z TAFs...Latest satellite imagery shows increasing
coverage and development of cu and stratocu with VFR conditions in
place. Lowest cloud bases generally around 5 kft AGL. Aviation
concerns revolve around winds today as an upper trough moves across
with a decent pressure gradient in place and modest flow aloft.
Winds are expected to be strongest in the Kittitas Valley, 40-45
kts, while winds elsewhere peak around 30-35 kts. Of which, may see
some low-end visibility restrictions in parts of the basin owing to
patchy blowing dust. That said, thinking visibilities will remain
VFR given their magnitude. While winds lessen tonight, winds will
remain elevated, notably in the Gorge and parts of the Lower Basin
to northern Blues. There could be an isolated shower in the Lower
Basin and Blues this afternoon-evening, however, confidence in
showers affecting the PSC, PDT, or ALW terminal is low given
coverage. No thunder is expected nonetheless

&&

.PREV DISCUSSION... /issued 201 AM PDT Fri May 7 2021/

SHORT TERM...Today through Sunday night...An upper trough will
move into and across the forecast area today and tonight. This
will bring much cooler temperatures along with continued breezy to
windy conditions. Maximum temperatures will be about 15-20
degrees cooler than Thursday, with highs in the upper 50s to mid
60s lower elevations and 40s to mid 50s mountains. There will be a
slight chance to a chance of mainly mountain showers.
Thunderstorms are not expected, but any precipitation will be
convective in nature due to the colder air aloft within the upper
trough creating steeper temperature lapse rates. Today`s main
concern will be the windy conditions again, which will kick up
some blowing dust in the Lower Columbia Basin, mainly on the WA
side of the Basin. The winds may also cause some control issues on
any new or existing fires in dry grassy areas of the eastern
Columbia Gorge eastward across the Lower Columbia Basin. Tonight
and Saturday the upper trough will move to the east and a cool
northwest flow will move over the forecast area on the back side
of the trough. There may still be some light mountain showers, but
nothing significant. It will continue to be locally breezy to
windy with continued cool temperatures. A slow warming trend will
begin on Sunday with mostly dry conditions and lighter winds under
a northwest flow aloft. There may still be some mountain showers,
caused mainly due to an upslope low level flow into the eastern
mountains, and some spill over the Cascade crest onto the east
slopes. A warming trend will continue into the extended period
with dry conditions. 88

LONG TERM...Monday through Friday...Models in agreement on a trough
developing just to our east beginning Sunday. This system will stall
over the western Great Plains Monday into Tuesday while caught in
the midst of a weak omega block, before it deepens and progresses
eastward by the end of Tuesday. The result of this developing low
will be a persistent NW flow regime over the forecast area for the
start of the work week. Ensembles keep the cold front associated
with this system to our east, leaving only a minimal chance for
precip in Wallowa County. Elsewhere, mild conditions will prevail,
with highs in the 60s and 70s in the valleys before giving way to
warmer conditions as a ridge moves in for Tuesday and Wednesday.

Ensembles in good agreement on quiet weather for the CWA in the long
term, but diverge a bit towards the end of the work week on
depicting the synoptic pattern. Some members favor persistent
ridging through the work week while others introduce weak zonal
flow, which would cap increasing high temperatures a bit. Current
models suggest a warming pattern through most of the week, with
highs peaking Wednesday in the upper 70s/low 80s for the lower
elevations, before zonal flow keeps high temps stagnant in the 70s
valleys and 50s/60s mountains. 74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  61  36  62  39 /  20  20   0  10
ALW  64  39  65  43 /  20  20   0  10
PSC  66  42  69  44 /  20  20   0   0
YKM  63  35  66  38 /  20  10   0   0
HRI  66  37  67  43 /  20  20   0  10
ELN  57  35  61  40 /  20  10   0   0
RDM  56  27  59  35 /  10   0   0   0
LGD  54  34  57  36 /  20  20   0  10
GCD  57  31  59  38 /  10  10   0  10
DLS  61  43  63  46 /  20  10  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory from noon today to 9 PM PDT this evening for
     WAZ026.

&&

$$

SHORT TERM...91
LONG TERM....80
AVIATION...80

NWS PDT Office Area Forecast Discussion