Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 251801 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1101 AM PDT MON JUL 25 2016

Updated AVIATION Discussion

.SHORT TERM...Morning Update...Westerly flow aloft will continue
through tonight. A couple of waves are embedded within this flow.
One very weak wave is currently moving on to the Pacific Northwest
coast. A slightly stronger wave is approaching 135w longitude. This
second wave will move onshore overnight tonight. At this time the
affects of these waves look to be limited. Moisture over the region
is generally limited, though some depth of moisture is expected to
move into the Washington Cascade east slopes today. Daytime heating
and the weak system should create enough instability for convection
over the Washington Cascade east slopes this afternoon. Meanwhile
increasing surface westerly flow should limit convection as it tends
to dry and stabilize the surface air mass. Thus best chances for any
storm development will be over the ridges. Thus will continue to
indicate a slight chance of thunderstorms over some of the ridges of
the WA Cascade east slopes late this afternoon into early evening.
Winds will increase and become breezy late afternoon into the
evening through and near the Cascade gaps. High temps will be hot
today with lower basin temps approaching 100 degrees. Updates
focused on adjusting thunderstorm locations, sky cover and a few
high temps. 90

.AVIATION...18Z TAFS...VFR conditions will continue for the next 24
hours. Skies will be mostly clear with a few mid/high level clouds
at or above 15K feet AGL over most of the area. However, cumulus
buildups are expected this afternoon and evening above 7K feet AGL
over the Washington Cascades. These clouds (FEW090) are expected at
KYKM by 01Z/26th. Sustained winds will remain below 15 kts, except
at KDLS, which will have winds of 10-20 kts with higher gusts after
21Z.  Polan

&&

.LONG TERM...Previous Discussion...High pressure will dominate area
weather through the first half of the long term period. Wednesday
night a weak wave will cross the area but will have little effect on
our area. Any showers will remain well to our north near or above
the Canadian border. After the wave leaves, a ridge of high pressure
over the Western CONUS will strengthen further and fair and dry
weather will continue through Friday night with temperatures
increasing each day. Thursday will be in the 90s with mid 80s to
lower 90s in the mountains. Friday will be in the mid 90s to lower
100s with mid 80s to lower 90s in the mountains. Saturday through
Monday models agree in having a trough move into the area and
flattening the ridge to our south, though the models disagree as to
the details. The GFS is strongest with the trough and hints at some
monsoon moisture from the desert southwest getting pulled into the
southern fringe of our area late Friday night and Saturday morning
and out of the area by the afternoon. The ECMWF and Canadian models
do not show this moisture. Even if the GFS is right, the timing is
bad for the moisture to produce any showers or thunderstorms so have
kept the previous dry forecast. A very dry west to southwest flow
continues through Sunday night so fair and mostly clear weather will
continue. Models disagree further on Monday. The GFS brings a couple
of waves through the trough and strengthens it with some showers
along the Washington Cascades late Sunday night and Monday. The
ECMWF and Canadian have a weaker wave arriving Monday afternoon with
little to no precipitation in the Washington Cascades. Have kept the
current dry forecast for now until models come into better
agreement. Temperatures Saturday will be a couple of degrees cooler
than Friday and will be mainly in the mid to upper 90s with mid 80s
to lower 90s in the mountains. Saturday will drop to the mid 80s to
lower 90s with lower to mid 80s in the mountains and Monday will
drop another couple of degrees to the 80s with 70s and lower 80s in
the mountains.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  96  62  91  60 /   0   0   0   0
ALW  96  68  91  66 /   0   0   0   0
PSC  99  64  95  63 /   0   0   0   0
YKM  99  64  93  62 /   0   0   0   0
HRI  99  65  94  61 /   0   0   0   0
ELN  96  66  89  63 /  10  10   0   0
RDM  93  50  87  47 /   0   0   0   0
LGD  93  57  88  53 /   0   0   0   0
GCD  96  56  91  54 /   0   0   0   0
DLS  94  66  87  64 /   0   0   0   0

&&

.PDT Watches/Warnings/Advisories...
OR...None.
WA...None.
&&

$$

90/99/83



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