Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 200551 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
951 PM PST Sun Feb 19 2017

Updated Aviation Discussion

.SHORT TERM...Evening Update...A few showers continue to drift
northeast across the region, but overall the area is currently
experiencing a lull in the active weather. Another disturbance
approaching the southwest Oregon coast at the moment will cause
showers to increase across the area overnight into Monday morning.
Overall the forecast package handles the main trends for tonight
through Monday. Did make some adjustments to snow levels for tonight
into Monday morning. For the most part snow accumulation looks to
remain below advisory levels. How things develop in Wallowa county
will have to be watched late tonight into Monday morning. Snow
levels should rise late tonight into Monday morning, though they
will rise slowly over Yakima and Kittitas counties. Added some fog
to the Oregon Lower Basin and the lower Yakima valleys based on road
camera information. Will have to monitor the conditions in the
Oregon Lower Basin for a potential dense fog advisory. Also adjusted
some overnight low temps and wind directions. 90

.LONG TERM...Previous Discussion...Upper trough moves to coast
on Wednesday and spreads precipitation east of the Cascades with the
snow level 1000-2000 feet. Lower Columbia Basin should remain dry
through Wednesday afternoon while PoPs increase through the day at
higher elevations. Precipitation amounts will be light and snow
accumulations will be less than an inch even in the higher
mountains. Wednesday night through Thursday night the trough will
remain over the region for unsettled weather. An influx of colder
air from the north will lower snow levels to below 1000 feet during
the day on Thursday. This will yield a chance of light snow showers
and afternoon rain showers at lower elevations. Friday and Friday
night models show another influx of colder air spilling westward
across the Canadian Rockies and entering forecast area thus keeping
snow levels around 1000 feet during the day on Friday with snow
levels lowering to near the floor of the Columbia Basin Friday
night. This results in a chance of snow showers in the mountains and
a slight chance of rain showers and snow showers in the lower
elevations. Next weekend a strong impulse dives south through the
western flank of the aforementioned upper trough, which results in
strong dynamic deepening of the trough with the main energy
developing just offshore and evolving into a strong closed mid/upper
level low that digs south into California. This track for the low
means that the main dynamic lift associated with this system will
miss eastern sections of WA/OR and thus result in only a slight
chance of snow in the mountains of central and NE Oregon. Next
upstream mi/upper level shortwave moves SE along coastal British
Columbia on Saturday/Saturday night and moves into interior Pacific
Northwest by daybreak Sunday spreading moisture east of the Cascades
for a chance of mainly snow from sunup to sundown on Sunday.

&&

.AVIATION...06Z TAFS...Another Pacific disturbance will swing across
the region and affect all TAF sites during the next 24 hours. Expect
precip to be mainly rain, though some snow may mix in at KBDN and
KRDM between 20/09 and 20/14 UTC. Steadier precip at KBDN, KRDM,
KDLS and KYKM should produce periods of MVFR cigs/vis. Expect KPSC,
KALW and KPDT to remain VFR, though brief lower cig/vis conditions
can not be ruled out during heavier showers. Expect winds to
increase to 15 to 20 kts sustained at KRDM and KBDN by late morning
Monday, and at KPSC, KALW and KPDT during the afternoon. Winds will
be lighter at KYKM and KDLS. 90

&&

.HYDROLOGY...Previous Discussion...Significant rain will fall Monday
and Tuesday with these warm fronts. Rising snow levels from the warm
air aloft will add snowmelt to the runoff. Rainfall up to three
quarters of an inch in the Simcoe Highlands and up to one half an
inch in the Yakima and Kittitas Valleys may create localized
flooding. A flood watch has been issued for these areas Monday
through Tuesday afternoon. Lesser amounts of rain will fall in the
Lower Columbia Basin and Foothills of the Blue Mountains. A
Hydrological Outlook - product PDXESFPDT - has been issued for these
areas. 76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  36  52  38  49 /  40  90  60  50
ALW  36  53  40  49 /  30  90  80  60
PSC  35  50  37  49 /  20  70  50  70
YKM  33  44  32  45 /  20  80  50  60
HRI  34  52  36  49 /  40  80  50  50
ELN  31  39  31  42 /  20  90  50  50
RDM  34  49  33  47 /  40 100  50  30
LGD  36  48  40  47 /  50 100  60  50
GCD  36  52  38  49 /  60 100  50  50
DLS  34  44  35  45 /  60  90  50  40

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Flood Watch from 4 AM PST Monday through Tuesday afternoon for
     WAZ026-027-521.

&&

$$

90/99/90



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