Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 210550 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
950 PM PST Mon Feb 20 2017

Updated Aviation Discussion

.SHORT TERM...Evening Update...Generally a quiet evening to this
point. Winds across the area decreased rapidly towards sunset as the
deeper mixing ended. Thus was able to cancel all warnings and
advisories for wind by 6 PM. Updated winds earlier to coincide with
the end of the highlights. The next Pacific system is moving north
into the region, and appears to be a bit faster than previously
expected. Thus have pushed higher pops northward a bit faster than
in the previous forecast for overnight into Tuesday morning. Made
some adjustments to snow levels. Biggest snow level change was
lowering Yakima and Kittitas counties to 2000 ft for overnight and
between 1400 and 1700 ft for Tuesday morning. Snow amounts look to
remain generally light. Also made adjustments to overnight low temps
to match snow level changes. Flood watches to continue as there
remains the possibility of decent rain over melting snow with the
approaching system. 90

.LONG TERM...Previous Discussion...Thursday longwave trough over
region for chance of mountain snow showers and a slight chance of
rain showers at lower elevations. Thursday night forecast area will
be between weather systems for mainly dry conditions through
Thursday night.

Friday and Friday night 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 deepening of the trough with the
main energy developing just offshore and evolving into a strong
mid/upper level closed low that digs south and then moves inland
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. Monday another trough moves south from British
Columbia into interior Pacific Northwest for a chance of mountain
snow and slight chance of valley rain.

&&

.AVIATION...06z TAFS...The next Pacific system is rapidly moving
north into the region. There appears to a leading lighter band of
precip moving through eastern Oregon now, with a heavier band moving
into southwest Oregon. Expect our TAF sites to see a fair amount of
precip through this period, with the precip type mainly rain. All
sites will see periods of MVFR cigs/vis (possibly lower) due to the
precip. Rapid improvement due to a cold front will occur over KYKM
and KDLS early in the afternoon. This improvement will reach KRDM,
KBDN and KPSC by late afternoon, and KALW and KPDT in the early
evening. Winds will gradually become southwest to west and increase
in the afternoon at most sites. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  36  44  30  41 /  80  70  30  20
ALW  39  45  31  41 /  70  80  30  20
PSC  36  45  29  44 /  60  70  20  10
YKM  32  43  25  44 /  30  70  10  10
HRI  36  45  28  41 /  70  70  20  10
ELN  30  39  24  39 /  20  50  10  10
RDM  37  45  25  38 /  70  40  20  30
LGD  36  45  28  38 /  80  70  30  30
GCD  36  46  28  42 /  80  60  40  30
DLS  37  44  31  41 /  70  70  20  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Flood Watch through Tuesday afternoon for WAZ026-027-521.

&&

$$

90/99/90


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