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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 181720 AAA

Area Forecast Discussion
National Weather Service Pendleton OR
1020  AM PDT Sun Aug 18 2019

Updated Aviation Discussion

.SHORT TERM...Through Tonight...No significant changes planned.
Dry northwest flow will result in mainly clear skies. Winds will
increase to breezy levels this afternoon across the Cascade gaps,
but with RHs remaining at or above 25 percent in the breezy areas,
red flag conditions not expected. Seasonably warm conditions will
prevail, with highs today in the mid 80s to around 90 for the 
lower elevations, and 70s for the mountains.


.PREV DISCUSSION... /issued 140 AM PDT Sun Aug 18 2019/ 

SHORT TERM...Today through Tuesday night...A northwest flow will 
persist this morning and then the flow will become more westerly and 
then southwesterly this afternoon and tonight. The atmosphere is dry 
and stable and there is very little if any moisture or instability 
available in the short term period that would be enough to cause the 
development of showers or thunderstorms. Models are all in good 
agreement with this scenario in the short term forecast period. High 
temperatures today will be about 7-10 degrees warmer than Saturday 
due to the flow turning to the southwest which will pull in warmer 
air from the south. Highs today and Monday will be in the upper 80s 
to lower 90s in the lower elevations and in the 70s to mid 80s 
mountains. This is above normal of about 2-4 degrees. The southwest 
flow will become more southerly on Tuesday which will bring in 
hotter air into the region and forecast area. By Tuesday afternoon 
highs will be in the lower to mid 90s in the lower elevations and in 
the 80s to near 90 in the mountains. The hot temperatures will 
continue into the extended period. These temperatures are not all 
that unusual for mid August even though they will be above normal. 
Winds in most areas will be diurnally terrain driven, but there will 
be locally to breezy conditions in the afternoons and early evenings 
in the usual locations along the Cascade gaps and passes, such as 
the Kittitas Valley and north central Oregon, as well as the eastern 
Columbia River Gorge. 88 

LONG TERM...Wednesday through Sunday...A shortwave trough will move 
across the area Wednesday/Wednesday evening. The westerly flow 
associated with it will limit the moisture and instability so expect 
just a few light rain showers along the Cascade crest and dry 
elsewhere. As a cold front crosses the area late in the afternoon 
and evening Wednesday...westerly winds could pick up to at least 20-
25 kt across the lower elevations. With Humidities of 20-25 percent 
its possible that there will be some fire weather concerns. 
Additional surges of westerly winds are expected on Friday, 
Saturday, and Sunday afternoons and evenings especially in the 
Cascade gaps. Otherwise the weather will be dry for the remainder of 
the forecast period with variable amounts of clouds. Temperatures 
will be above normal for this time of year but not abnormally hot 
after Wednesday. 78

AVIATION...18Z TAFS...VFR conditions through the period. A few high 
level cirrus clouds becoming clear overnight.  Winds will be 5-15 kt 
this afternoon and early evening but 15-25 kt at KDLS before 
diminishing overnight. 93 


PDT  87  56  86  54 /   0   0   0   0 
ALW  91  60  90  59 /   0   0   0   0 
PSC  90  61  90  60 /   0   0   0   0 
YKM  89  55  89  56 /   0   0   0   0 
HRI  91  59  91  57 /   0   0   0   0 
ELN  86  55  85  55 /   0   0   0   0 
RDM  89  50  87  52 /   0   0   0   0 
LGD  89  55  86  55 /   0   0   0   0 
GCD  93  54  91  55 /   0   0   0   0 
DLS  87  60  88  61 /   0   0   0   0