FXUS66 KPDT 242228 AAA

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
328 PM PDT Thu May 24 2018

Updated Aviation Discussion

.SHORT TERM...Tonight through Sunday. Upper low approaching the
California coast has turned the flow aloft southerly across the
forecast area. Water vapor imagery shows a weak short wave moving
through. This feature combined with some instability will result
in scattered showers and isolated thunderstorms over central and
northeast Oregon this afternoon into the evening. Activity should
dissipate a few hours after sunset. Models develop a large area of
convection over the Sierra and advect this into southern and
central Oregon later tonight and Friday morning. Forecast will
indicate the potential for some heavier rain in this area toward
morning. By Fri afternoon the center of the upper low is moving
into central California with a deep southerly flow over the
forecast area. Expect showers and thunderstorms over much of
central and northeast Oregon in the afternoon and evening. Will
likely have some stronger storms as well. The Columbia basin
northward into Yakima valley and Ellensburg will have little to no
activity tonight and Friday with partly cloudy skies. Based on the
position of the upper low could see showers continue into Friday
night over the eastern portion of the forecast area. By Saturday
the low is moving eastward into Nevada. Lingering clouds and
showers over the eastern mountains otherwise skies becoming partly
cloudy. Upper level ridge builds over the region Sat night and
Sunday with fair weather. 94

.LONG TERM...Sunday night through Thursday...An upper level low over
the Great Basin will drift slowly east Sunday night and Monday.
Wraparound moisture and instability from the low may trigger a few
showers and thunderstorms in Wallowa County Monday and Tuesday
afternoon and evening. Transitory ridging will develop behind the
low and keep most of eastern WA and OR dry Sunday night and Monday.
An upper level trough from the Gulf of Alaska will drop down into WA
and OR Tuesday night and Wednesday. The associated cold front will
bring much cooler temperatures Wednesday and Thursday. The moist
flow ahead of the system will trigger some showers along the
southern border of the CWA Tuesday night and Wednesday. Orographic
effects, daytime heating, and lift from the trough will enhance
instability and trigger a few thunderstorms from Grant to Wallowa
County Wednesday afternoon. Coonfield


.AVIATION...0Z TAFs...A moist and unstable southwest flow will keep
a chance of showers and thunderstorms near TAF sites KRDM and KBDN
tonight. There may be brief periods of MVFR conditions associated
with TS. Decreasing winds after sunset tonight, then increasing again
at KDLS KPDT and KALW tomorrow afternoon. 76


PDT 56 77 54 71 / 10 20 30 30
ALW 59 81 55 73 / 10 20 40 30
PSC 59 84 55 79 / 10 10 10 10
YKM 55 82 51 77 / 10 10 10 10
HRI 58 81 56 76 / 10 10 20 10
ELN 53 78 50 72 / 10 10 10 10
RDM 52 67 43 65 / 40 80 30 20
LGD 51 74 52 64 / 40 50 70 40
GCD 52 72 48 62 / 40 70 70 40
DLS 56 76 52 71 / 10 20 20 10




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