Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 300922
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
222 AM PDT Tue May 30 2017

.SHORT TERM...Today through Thursday Night...Upper level ridging
continues to push to the east of the region early this morning.
An initial weak shortwave that crossed Central Oregon to the
Columbia Basin last evening continues to weaken as it exits to the
north/northeast. A trough offshore the WA/OR coast will move
onshore this afternoon, with a marine push entering areas east of
the Cascade crest early this afternoon, and a surface cold front
sweeping across the area this evening into the overnight. Winds
will increase this afternoon as surface pressure gradients
tighten, with breezy/windy conditions felt first in the Columbia
Gorge this afternoon, spreading east into the Kittitas/Yakima
Valleys and the Columbia Basin this evening. Forecast pressure
gradient magnitudes point to winds remaining under advisory
levels, with 20-30 mph winds gusting to 40 mph at times late this
afternoon and evening before decreasing overnight. The approaching
front and a mid level shortwave will provide enough forcing with
increasing mid level moisture to generate showers and
thunderstorms this afternoon/evening. Initial isolated activity
will likely develop early this afternoon, increasing to scattered
for late this afternoon and evening. Rainfall looks to be rather
limited, with most areas receiving less than one tenth inch of
rainfall. With deep layer shear of 45-55 knots some of the storms
will be capable of producing gusty winds. High temperatures today
will range from the lower/mid 90s across the Columbia Basin, with
cooler 80s further west due to the earlier marine push. Expect
mainly upper 70s/lower 80s for the eastern mountains. Lows tonight
will range from the 50s lowlands to the 40s mountains.

Upper level troughing will persist across the interior Pacific
Northwest Wednesday through Thursday Night. Cooler highs in the
mid 70s to around 80 can be expected for the lower elevations,
with mainly 60s for the mountains. Chances of showers will
persist across the eastern mountains, with slight chances of
afternoon thunderstorms. The lower elevations will remain
mainly dry.

.LONG TERM...Friday through Tuesday...A broad upper trough will
move through the region on Friday and then it will be replaced by
a broad upper ridge Friday night and early Saturday. This will
bring a break in any showery conditions with dry and stable air.
Then another trough will move into the Pacific Northwest Saturday
night and on Sunday. This will combine with some increase in
moisture and instability to cause some isolated to scattered
showers with a slight chance of an afternoon thunderstorm Saturday
afternoon through Tuesday. Showers and thunderstorms will be
mostly over the eastern mountains...central oregon highlands and
along the Cascade east slopes. Elsewhere it will remain dry.
Temperatures will be near normal temperatures through the period
with no significant cold or hot spells. The medium to long range
models are in fair agreement at the start of the extended period
but then they diverge from each other some after Saturday. However
all are still showing some kind of upper trough/low which will
keep the unsettled weather in place Saturday afternoon through
Tuesday. Winds will be mostly light...except for the period Sunday
afternoon through Sunday night as the upper trough/low moves into
the region. The winds will become moistly light again by Monday
and will remain light through Tuesday.

&&

.AVIATION...12Z TAFs...A strong cold front will move across the area
today and move off to the east tonight. This frontal system will
bring a chance of showers and a slight chance of thunderstorms at
all TAF sites this afternoon and/or evening. Some storms could cause
MVFR conditions for brief periods due to heavy rain, hail or blowing
dust due to gusty winds. The winds will become mainly westerly
behind the front by this afternoon and this evening. They will
increase in speed to at least 15 to 25 kts at KDLS and KPDT.
Elsewhere winds will also become west to northwest but will remain
below 15-20 kts.

&&

.FIRE WEATHER...Will continue the Fire Weather Watch for
Central Oregon northward to the Columbia Basin for this afternoon
and evening for scattered thunderstorms capable of producing
abundant lightning. In addition, most of the storms will produce
limited rainfall increasing the threat. Will allow the day shift
to make the final call on any warnings that may be needed. Gusty
winds are also expected in this area late this afternoon and
evening which could contribute to escaped fires that may develop.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  89  57  74  53 /  10  40  10  20
ALW  95  60  77  56 /  10  30  20  20
PSC  94  58  79  55 /  10  30  10  10
YKM  92  57  81  54 /  10  40  10  10
HRI  92  58  78  55 /  10  40  10  10
ELN  89  54  75  51 /  10  40  10  10
RDM  80  46  74  46 /  30  20  20  10
LGD  88  57  74  50 /  10  20  30  40
GCD  90  56  75  50 /  10  30  30  40
DLS  78  57  79  56 /  20  20  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Fire Weather Watch from noon PDT today through this evening for
     ORZ640-641.

WA...Fire Weather Watch from noon PDT today through this evening for
     WAZ641-675.

&&

$$

80/88



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