Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 241008

Area Forecast Discussion
National Weather Service Pendleton OR
307 AM PDT Thu May 24 2018

.SHORT TERM...Today through Saturday...An upper low that set off
showers and thunderstorms yesterday has moved off into Montana this
morning and weak ridging is developing over the area. However, an
upper low and trough has set up along the California coast and there
is a moist south to southwesterly flow into our area. This should
develop scattered to numerous rain showers with isolated afternoon
and evening thunderstorms in central Oregon and the eastern Oregon
mountains. Further north, north central Oregon over to the Blue
Mountains Foothills will have isolated showers and thunderstorms
with the rest of the area dry. Rain amounts will be 15 to 30
hundredths of an inch. A chance of showers will continue into the
evening in central Oregon and the mountains. Late in the night, the
low will send a wave north into our area and rain will increase into
central Oregon and the Ochoco-John Day Highlands. This will spread
north and east during the day with a chance of showers and
thunderstorms over central Oregon and the eastern Oregon mountains
Friday afternoon and evening. Shear will have increased and storms
will be better organized and stronger. The Storm Prediction Center
has placed the eastern Oregon mountains under a marginal risk for
severe thunderstorms so storms will have to watched carefully that
day for hail, locally heavy rain and gusty winds. Precipitation will
taper off to a chance of showers through the night from central
Oregon northeast to the Blue mountain Foothills and areas south and
east of there. Further north, the Yakima and Kittitas Valleys and
the Columbia Basin will have been mainly dry Friday and Friday
night. Also, Friday afternoon and evening will see a surge of
westerly air through the Columbia Gorge and over the Cascades. The
Columbia Gorge and the Kittitas Valley will reach 20 to 30 mph in
the afternoon and evening while much of the rest of the area will
reach 10 to 20 mph. By Saturday, the low will have moved into Nevada
and stretched northward. Moisture will continue to wrap around the
low and into our area but a chance of showers will be confined to
the eastern Oregon mountains with a slight chance of thunderstorms
over the higher terrain from Grant county northeastward to Wallowa
county. Temperatures today will be in the 80s with mainly 70s in the
mountains. Friday will see upper 70s to lower 80s in the Columbia
Basin but elsewhere with showers and heavier cloud cover
temperatures will be in mid 60s to mid 70s. Saturday will be in the
mid 70s to around 80 with 60s and lower 70s in the mountains. Perry

.LONG TERM...Saturday night through Thursday...An upper low over the
Great Basin will pull more moisture and instability into the
forecast area on Saturday night and Sunday for a continued chance of
showers and afternoon thunderstorms over the eastern mountains
bordering Idaho and in southeast Oregon. Most of the rest of the CWA
will remain dry. This pattern will persist through most of the
extended period, however and upper ridge will try to push eastward
from off the Pacific into Washington and Oregon on Monday and
Tuesday. This ridge will keep western areas dry while there will
still be a chance of showers and afternoon thunderstorms in far
eastern areas. Then by Wednesday a stronger trough will move in from
off the Pacific bringing more showers and afternoon thunderstorms
with greater coverage over the forecast area. It will also bring
cooler air with it, but temperatures will still be near normal.
There may also be locally breezy conditions by mid week next week,
especially in the eastern Columbia River Gorge and the Oregon side
of the Lower Columbia Basin and north central Oregon. Models are in
fair to good agreement early on, but then diverge later in the
extended period. However, they all still indicate an unsettled
weather pattern. Expect cooler weather by Thursday as the Pacific
trough passes over the region along with locally breezy conditions.


.AVIATION...12Z TAFs...A moist and unstable southwest flow will keep
a chance of showers and thunderstorms over southern areas affecting
mainly TAF sites KRDM and KBDN today through this evening. There may
be brief periods of MVFR conditions as a result, otherwise VFR
conditions will prevail during the next 24 hours. It will become
breezy at KDLS and the eastern Columbia River Gorge and the western
Lower Columbia Basin, otherwise winds will be mostly light and under
15 kts through tonight. 88


PDT  82  56  77  52 /  20  10  20  30
ALW  85  58  80  54 /  20  10  20  40
PSC  88  59  83  57 /  10  10  10  10
YKM  86  56  82  52 /  10  10  10  10
HRI  86  58  82  55 /  10  10  10  20
ELN  84  53  79  50 /  10  10  10  10
RDM  79  51  67  41 /  40  40  60  30
LGD  78  52  75  50 /  50  30  60  60
GCD  77  53  73  47 /  60  40  70  60
DLS  82  58  78  53 /  10  10  20  20




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