Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 260959
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
259 AM PDT FRI AUG 26 2016

.SHORT TERM...Friday through Sunday Night...Fair and dry weather
will continue through this weekend. High pressure offshore will keep
a dry northerly flow over the area today before becoming
northwesterly tonight. Skies will be mostly clear though a weak
disturbance will bring a few clouds to Northeast Oregon this morning
before clearing this afternoon. More clouds in advance of a wave
dropping south out of British Columbia will brush the eastern
portion of the area with a few clouds after midnight tonight. Highs
today will be a couple of degrees warmer than yesterday with highs
in the mid 80s to lower 90s in the lower elevations and in the upper
70s to mid 80s in the mountains. Lows tonight will be in the mid 50s
to mid 60s in the lower elevations with 40s and lower 50s in the
mountains. On Saturday, the wave will swing into the Canadian
Rockies and develop a westerly flow over the area. A second wave on
Saturday night and Sunday will flatten the ridge further and develop
a trough over Southern Canada and the Pacific Northwest. Saturday
and Saturday night temperatures will be similar to Friday and Friday
night. Pressure gradients will tighten up on Saturday and a cold
front will bring 15 to 25 mph winds from the Columbia Basin
northward. Combined with continued low humidities, fire danger will
be a concern Saturday and a fire weather watch in out for the
Columbia Basin, the Yakima Valley, the Columbia Gorge and North
Central Oregon. The situation is discussed in more detail in the
fire weather discussion below. Winds will diminish Saturday night.
Skies will turn partly cloudy in the Washington portion of the area
Saturday and Saturday night. On Sunday and Sunday night the trough
will develop further off the British Columbia coast and deepen.
Temperatures will drop 3 to 5 degrees due to the trough bringing in
cooler air. Some moisture will circulate around the low and into
Washington on Sunday night. Most of it will remain north of our
area, but there will be a slight chance of showers along the
Washington Cascade Crest Sunday night. Perry

.LONG TERM...Monday through Thursday...General Overview...A pattern
shift looks to be heading this way.  Increased clouds on Monday and
Tuesday with temperatures peaking on Monday in the upper 80s to
lower 90s across the lower elevations and in  the upper 70s to upper
80s mountains. Temperatures will cool into the 80s, 70s mountains on
Tuesday.  This cooling trend will continue through Thursday, by the
the highs may only be in the 70s, with 60s mountains.  We will stay
pretty dry on Monday and Tuesday, with exception of the east slopes
of the Washington Cascades, that may see a shower or two.  By
Wednesday the mountain areas will have a slight chance of
thunderstorms, and this will spread to the lower elevations as well
on Thursday.  Although winds may be breezy at times, it doesn`t
appear that there is any significant wind event coming in the
extended.

Technical Synopsis...Upper level low pressure system will continue
to work its way down from the Gulf of Alaska.  A fairly warm and dry
southwest flow ahead of the system will persist through Monday
evening.  By Tuesday as the low nears, an increase in moisture is
expected, with showers and thunderstorms possible by Wednesday and
Thursday.  Seems like there is a decent amount of moisture with this
approaching trough, providing a better chance for wetting rain with
these storms.  As the slow moving low continues to move
onshore,cooler air will be in place and expect temperatures to cool
off to near to below normal on Tuesday, with below normal
temperature to follow on Wednesday and Thursday. Weber

&&

.AVIATION...12Z Tafs...VFR conditions expected to prevail over the
next 24 hours.  Winds are expected to be generally less than 10 kts.
A few thin mid and high clouds possible during the TAF period. Weber

&&

.FIRE WEATHER...No major fire weather concerns are expected through
Friday. The inverted surface thermal trough will remain west of the
Cascades...and a northerly flow aloft will keep temperatures and the
relative humidity (RH) from reaching critically hot and dry values.
However...on Saturday...the thermal trough will shift eastward and a
cold front will sweep across northern Washington.  This will cause
breezy conditions over the Columbia Basin and the Eastern Columbia
River Gorge.  I do not expect this system to be as substantial as
the dry cold front last Sunday that brought 20-30G40 mph winds in
the afternoon when the humidity was 5-15 pct.  On Saturday...the RH
will be 15-25 pct and the winds will be 15-25 mph gusting to 30-35
mph. Nevertheless...the winds will be enough to easily carry a fire
through the dry grassy areas and fire weather watches will be
issued.  Wister

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  87  59  89  59 /   0   0   0   0
ALW  89  67  90  66 /   0   0   0   0
PSC  92  62  93  62 /   0   0   0   0
YKM  92  62  92  58 /   0   0   0   0
HRI  91  60  92  61 /   0   0   0   0
ELN  91  60  86  56 /   0   0  10  10
RDM  88  49  88  48 /   0   0   0   0
LGD  86  50  88  52 /   0   0   0   0
GCD  86  53  88  53 /   0   0   0   0
DLS  94  66  89  63 /   0   0   0   0

&&

.PDT Watches/Warnings/Advisories...
OR...Fire Weather Watch from Saturday afternoon through Saturday
     evening for ORZ639-641.

WA...Fire Weather Watch from Saturday afternoon through Saturday
     evening for WAZ639-641-675.

&&

$$

83/89/89



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