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

.SHORT TERM...Today and tonight...Pattern remains persistent with a
ridge of high pressure over the eastern Pacific and an upper trough
over the northern Rockies. This places the forecast area under a dry
northerly flow in which we will see some occasional high clouds.
Winds will be light today and temperatures near normal. Changes are
underway in which a weather system coming over the top of the ridge
will drop into western Canada on Saturday. This will sweep a dry
cool front across the Pacific Northwest resulting in breezy
conditions Saturday afternoon and evening. This will lead to fire
weather concerns discussed in the fire weather section 

&&

.FIRE WEATHER...After a few days of relatively quiet fire weather on
this side of the Cascades...a cold frontal passage on Saturday will
ramp up concerns due to gusty winds and low humidity.  The cold
front will not be as strong 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 have been issued for the Lower Columbia Basin,
Yakima Valley, areas in and around the Eastern Columbia River Gorge,
and the Blue Mountain Foothills (fire zones WA/OR 639, WA/OR 641,
and WA 675).  The next fire weather concerns will focus on the
thunderstorm potential as early as Wednesday morning when an upper
level shortwave embedded in a southwest flow aloft tracks across
eastern Oregon and southeast Washington.  This obviously will bring
on the threat of new fire starts due to lightning. Wister


&&

.PREV DISCUSSION... /issued 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


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  88  57  89  59 /   0   0   0   0 
ALW  89  63  90  66 /   0   0   0   0 
PSC  91  55  93  62 /   0   0   0   0 
YKM  93  59  92  58 /   0   0   0   0 
HRI  91  56  92  61 /   0   0   0   0 
ELN  92  57  86  56 /   0   0  10  10 
RDM  88  47  88  48 /   0   0   0   0 
LGD  85  51  88  52 /   0   0   0   0 
GCD  86  50  88  53 /   0   0   0   0 
DLS  96  59  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.

&&

$$

91/99/99

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