Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 272308 AAA

Area Forecast Discussion...Update
National Weather Service Pendleton OR
408 PM PDT SAT AUG 27 2016

Updated Aviation Discussion

.SHORT TERM...Tonight through Tuesday...A weather system moving
through the upper level trough over western Canada today is sweeping
a cold front across the region. This is resulting in breezy westerly
winds which will continue through the evening with the potential for
some patchy blowing dust before decreasing overnight. The upper
level trough will retrograde west and out over the eastern gulf of
Alaska on Sunday and Monday. This will turn the flow over the region
to southwesterly as an upper level ridge amplifies over the northern
Rockies. Conditions will stay hot and dry through Monday. Then a
shortwave rotating around the bottom of the trough will move into
and through the forecast area late Tuesday. This will lead to a
slight chance of showers and or thunderstorms from central Oregon
to southeast Washington.

period will feature a pattern change...with several upper level
troughs/disturbances moving through the area. This will lead to an
unsettled period of weather with chances for showers... a slight
chance of afternoon thunderstorms, breezy conditions at times and
below average temperatures. Expect high temperatures in the mid-70s
to lower 80s Wednesday through Saturday in the valleys/basins with
60s and lower 70s mountains.

The area will be in a moist south to southwest flow Tuesday night as
an embedded upper level disturbance moves through. This will keep
lingering chances for showers in the forecast through the overnight.
At the same time the next upper level trough will be approaching the
the WA/OR coast which will begin to spread moisture along the East
Slopes of the Cascades and Columbia Gorge by Wednesday morning.
Current guidance spreads this moisture and a chance of showers along
the East Slopes of the Washington Cascades and near the
Yakima/Kittitas Valleys midday Wednesday. There will also be a
slight chance of thunderstorms Wednesday afternoon over Central
Oregon and the eastern mountains as a moisture and marginally
unstable south-south west flow develops once again. The latest
guidance is then in fairly good agreement that this trough will
weaken but be located directly over our CWA Thursday morning. It
moves quickly eastward with some brief low and mid level dry air
filtering into the area Thursday afternoon. Therefore much of the
forecast area is now looking to remain dry on Thursday. The models
are then indicating yet another...potentially stronger disturbance
will approach and move through the forecast area sometime Friday
into Saturday. The latest 12z GFS waits until Saturday to bring the
system through, but has ample moisture associated with it. The 12z
Euro is faster bringing a disturbance through mainly on Friday. For
now leaned the forecast much more toward the GFS as it was more
consistent with the previous forecast. This brings a good chance of
showers and even afternoon thunderstorms to the entire area on
Saturday and Saturday afternoon. 77


.AVIATION...00Z TAFS...VFR conditions will prevail through the
forecast period. SCT to BKN mid and high level clouds(15K to 25K FT
AGL)are expected across the N. Oregon & Washington terminals through
the evening hours. Central Oregon terminals will only see a few high
level clouds near 25K FT AGL overnight.

Gusty west winds will be the primary concern this evening. Winds are
currently 15-30 KT with some higher gusts...these will be
diminishing after 28/03-04z. With the stronger winds there could be
some local BLDU/HZ INVOF KPDT,KALW, KPSC and KYKM mainly through
02z. Winds gradually decrease AOB 10 KTs late tonight and Sunday
morning...before increasing 8 to 15 KTs Sunday afternoon. 77


.FIRE WEATHER...The dry cold front responsible for the gusty winds
will exit the region tonight...and winds will gradually decrease
overnight.  No major fire weather concerns are expected Sunday as
the region will remain under a dry westerly flow aloft.  On
Monday...the upper flow will shift to the southwest.  The air mass
will become increasingly unstable...and the combination of dry and
unstable conditions will result in a HAINES of 5
(moderate)...borderline 6 (high)...over the eastern half of Oregon.
The shortwave on Tuesday will bring isolated showers and
thunderstorms over central and northeast Oregon. This will be
addressed over the next couple of the lightning activity
level may be enough to warrant fire weather highlights.  Wister


PDT  61  87  59  91 /   0   0   0   0
ALW  66  87  65  91 /   0   0   0   0
PSC  60  89  59  93 /   0   0   0   0
YKM  56  88  57  93 /   0   0   0   0
HRI  61  88  59  92 /   0   0   0   0
ELN  56  84  56  90 /   0   0   0   0
RDM  49  90  50  91 /   0   0   0   0
LGD  54  87  53  92 /   0   0   0   0
GCD  54  89  56  92 /   0   0   0   0
DLS  64  90  62  91 /   0   0   0   0


.PDT Watches/Warnings/Advisories...
OR...Red Flag Warning until 9 PM PDT this evening for ORZ639-641.

WA...Red Flag Warning until 9 PM PDT this evening for WAZ639-641-675.



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