Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 251715 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
915 AM PDT Mon Sep 25 2017

Updated Aviation Discussion

.SHORT TERM...Morning Update...An upper level ridge, currently along
135 west longitude, will continue to build during the next 24 hours.
This ridge will also begin to slowly shift east late tonight. This
ridge will keep the Pacific Northwest under a northwesterly upper
level into this evening. The upper level flow will shift to
northerly overnight. There is a weak disturbance moving southeast
within the upper flow at the moment. This disturbance will mainly
bring partly to mostly cloudy conditions to the region. Conditions
will also be dry except for a few showers over the Washington
Cascade east slopes and the higher elevations of the Blue and
Wallowa mountains. Updates this morning focused on adjustments to
the shower locations and high temperature forecasts. 90

.LONG TERM...Previous Discussion...Thursday through Monday...A large
upper level ridge of high pressure will be over the CWA for Thursday
and Thursday night. This will bring mostly clear skies, light winds
and above normal temperatures. The ridge axis shifts east by Friday,
with a weak trough/front moving in from the west late in the day.
Skies start off mostly sunny Friday morning, but then give way to
increasing clouds by afternoon. From late Friday afternoon into
Friday night there will also be a slight chance of rain showers over
the mountains...but any precip amounts are forecast to be very
light. There could be some lingering clouds and light showers on
Saturday morning...mainly in the eastern mountains. Otherwise, the
trough axis move east into Idaho by Saturday afternoon...with mostly
sunny skies and westerly winds of 8-15 mph in its wake. Temperatures
will remain mild Saturday afternoon, with highs reaching 75-80 in
the valleys/basins and mid-60s to lower 70s in the mountains. The
latest model guidance is in strong agreement that a flat upper level
ridge builds over the region Saturday night into Sunday...with a
shot of very dry mid-level air moving through during this time. A
system well to the north over the Gulf of Alaska could bring a weak
warm front through the forecast area on Sunday. This would allow for
a few more clouds...especially in Washington. There is a general
consensus from the latest model guidance that the aforementioned
flat ridge will be replaced by a broad upper level trough, which
will approach the Pacific Northwest coast sometime late next Monday
or Tuesday. The exact timing and details remain uncertain at this
time. However, did bring increasing clouds and a slight chance of
mainly mountain showers into the forecast toward the end of the
extended forecast period...especially day 8 (next Tuesday).
Temperatures look to remain generally above average through the
extended period...with daytime highs in the 70s to lower 80s and
overnight lows in the 40s to low 50s...except some 30s in the colder
mountain valleys.

&&

.AVIATION...18Z TAFS...VFR conditions will prevail through the
period. Sct to bkn mid/high clouds are moving through the region.
Decreasing clouds tonight except KPDT and KALW where clouds will
linger into Tuesday morning. Winds will remain generally under 10
kts through the period. 76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  73  48  73  48 /   0  10   0   0
ALW  74  51  74  50 /   0  10   0   0
PSC  76  50  77  50 /   0  10   0   0
YKM  76  48  76  49 /  10  10   0   0
HRI  76  50  78  48 /   0  10   0   0
ELN  74  46  75  47 /  10  10   0   0
RDM  70  41  73  42 /   0  10   0   0
LGD  70  42  70  42 /  10  10  10   0
GCD  70  40  73  42 /  10  10  10   0
DLS  77  52  79  52 /  10  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

90/77/76



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