Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 291127 AAA

Area Forecast Discussion...Update
National Weather Service Pendleton OR
425 AM PDT SUN MAY 29 2016

Updated Aviation Discussion

.SHORT TERM...Today through Tuesday...Another upper trough and
vorticity maximum will move across the CWA today...though it is a
weak system. The flow will be from the southwest which will
transport some moisture and instability into the northeast mountain
today. There will also be some moisture from the west spilling over
the crest of the Washington Cascades onto the east slopes. These
areas can expect a chance of afternoon showers and a slight chance
of afternoon thunderstorms. Any thunderstorms that develop will be
mostly weak...though a couple could become strong but not severe.
Showers and thunderstorms will end by late this evening and then a
strong upper ridge will begin to build over the CWA on Monday and
Tuesday. Temperatures will be near normal today and Monday but then
they will quickly warm to above normal on Tuesday. Tuesday will be
the beginning of an extended warm spell with lower elevation highs
Tuesday in the lower to mid 80s. Winds will pickup today becoming
breezy to windy...mainly in the Lower Columbia Basin and adjacent
valleys and Blue Mountain foothills. Winds will diminish by late
this evening and then winds will be light for the remainder of the
short term forecast period. 88

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...The extended period will
start off with a large upper level ridge firmly in place over the
forecast area Tuesday night and Wednesday AM. As the ridge axis
slides just east a return southerly flow may be just enough to see a
slight chance of an afternoon thunderstorm in Deschutes and Crook
Counties Wednesday PM. Otherwise the remainder of the CWA should
remain dry with warming temperatures (mid-80s to lower 90s). A
trough then moves by well to our north on Weds night and will act to
lower heights as it suppresses the ridge. How much the ridge is
suppressed remains to be seen as our forecast area is caught in the
middle (between the ridge over NV/UT and the advancing trough over
Northern WA / BC). Later Thursday into Thursday night the latest
guidance is in good agreement that yet another upper level ridge
will rebuild over our CWA from the south. There will be a slight
chance of thunderstorms...mainly in the mountains in the developing
southerly flow around this ridge. As heights continue to rise
believe Friday ends up being generally dry and warm for much of the
area. The ridge continues to build over the intermountain west for
Saturday...putting our area on the NW side of it...this means a
slight chance for afternoon/evening thunderstorms yet again as
moisture continues to increase from the south. Saturday will be
downright hot...with highs reaching at least the lower to mid-90s in
the valleys/basins and 80s in the mountains. This is 15-20 degrees
above average for this time of year and could even be close to a
record for some locations. Model uncertainty increases for Sunday as
the latest GFS/CMC bring a trough into the area with increasing
chances for showers and thunderstorms. The increasing clouds would
also mean temperatures lowering at least a few degrees. The latest
ECMWF does not have the well defined trough...but instead only very
slowly moves the upper ridge east...allowing for diurnal
showers/storms to develop. For now took a blend of the latest
available guidance until a viable...clear solution emerges. 77


.AVIATION...12Z TAFS...VFR conditions forecast at all terminals
through the TAF period. A Weak system moving across the region will
bring SCT to BKN clouds between 6k to 12k FT AGL through much of the
day Sunday. Look for a gradual clearing trend at most terminals
after 30/06z.

Winds AOB 12 kts through 29/15z. Then westerly winds quickly
increase to between 15-25 kts region wide during the afternoon and
early evening hours. Winds should gradually decrease after 30/06z
back under 12 kts. 77


PDT  75  44  75  45 /  10  10   0   0
ALW  76  48  76  46 /  10  10   0   0
PSC  79  51  79  49 /  10   0   0   0
YKM  75  47  79  47 /  10   0   0   0
HRI  78  49  78  46 /  10   0   0   0
ELN  67  46  76  47 /  10  10   0   0
RDM  71  39  74  39 /  10   0   0   0
LGD  70  44  70  41 /  30  20   0   0
GCD  72  43  73  41 /  10  10   0   0
DLS  73  48  80  48 /  10  10   0   0


.PDT Watches/Warnings/Advisories...


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