Wildfire in Washington, August 24, 2017

Area Forecast Discussion...Update
National Weather Service Pendleton OR
1057 AM PDT Thu Aug 24 2017

Updated Aviation Discussion

.SHORT TERM...Today and tonight...A dry cold front will be passing
through the forecast area today but then stall from western Montana
back towards south central Oregon. This will place the front over
Wallowa county back to southern Crook County. Enough instability
will be lingering along the front to keep a mention of showers and
possible thunderstorms for this afternoon and evening. The front
will finally leave the forecast area by midnight. Behind the front
temperatures will be 5 to 10 degrees cooler and some locally breezy
conditions. Smokey and hazy conditions will decrease across the
northern portion of the forecast area due to the winds but will
persist from Deschutes county east to Grant county.

&&

.AVIATION...18Z TAFs...VFR conditions will mainly prevail during
the next 24 hours. Smoke and haze due to wildfires over the Cascades
will continue to affect visibilities at KRDM and KBDN at times
through this period. Elsewhere, a smoke layer aloft continues to
shift east due to a cold front gradually moving east and southeast
across the region. This smoke layer has moved east of KDLS, KYKM and
KPSC, but will linger over KPDT and KALW for 2 or 3 more hours.
Otherwise, will see a few cumulus and cirrus clouds. Winds will run
10-20 kts and gusty from the west and northwest at all sites this
afternoon and evening. The strongest winds are expected at KDLS and
KPDT. Winds will decrease overnight, becoming mainly drainage. 90

&&

.PREV DISCUSSION... /issued 228 AM PDT Thu Aug 24 2017/

SHORT TERM...Today through Saturday. Upper level trough and cold
front moving across the Pacific northwest today. Current satellite
and radar trends indicate showers will be exiting the northeast
Oregon mountains this morning. Otherwise skies will be partly to
mostly cloudy. The frontal boundary combined with a short wave and
jet segment may be the focus for scattered thunderstorms this
afternoon over the southeastern portion of the forecast area. Best
chance would be John Day highlands northeast to the Wallowa
mountains. Remainder of the area should be mostly sunny by
afternoon. Temperatures today will be cooler with highs in the
upper 70s and 80s. Surface gradients will create breezy westerly
winds. Dry westerly flow aloft Friday with mostly sunny skies and
lighter winds. Strong upper level ridge building into the region
Saturday. This will start a warming trend that will continue into
early next week as highs get into the 90s. 94

LONG TERM...Saturday night through Friday...The medium to long
range models are in good agreement with an upper ridge over the
forecast area for the beginning of the extended forecast period
(until around Monday). This will result in a hot and dry period with
temperatures in the lower elevations rising to the mid 90s to lower
100s. The atmosphere will be dry, so during this time period am not
expecting any thunderstorm activity and just only perhaps a few
afternoon cumulus buildups during the afternoon Sunday and Monday.
Then by Tuesday an upper trough will swing into the Pacific
Northwest with increasing moisture from the southwest. This may
result in isolated afternoon thunderstorms over southern areas of
the CWA Tuesday and Wednesday. As such have introduced a slight
chance of thunderstorms both Tuesday and Wednesday afternoons and
evenings. At this time any storms that develop looks to be weak. The
longer range models by this time begin to diverge, but all show this
trough moving into the region. The Canadian model is the strongest
with almost a closed low while the ECMWF and GFS only show a broad
upper trough off the coast and a southwest flow over the CWA.
Decided to go with the consensus of the GFS/ECMWF as this seems most
likely for this time of year. Conditions will become dry and stable
again as another high pressure ridge builds into the region on
Thursday and Friday. Winds are expected to remain light through the
extended period. 88

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  83  50  83  49 /   0   0   0   0
ALW  85  53  84  54 /   0   0   0   0
PSC  86  52  85  49 /   0   0   0   0
YKM  85  48  84  49 /   0   0   0   0
HRI  87  52  85  49 /   0   0   0   0
ELN  77  51  82  48 /   0   0   0   0
RDM  80  39  83  42 /   0   0   0   0
LGD  81  46  82  44 /  10  10   0   0
GCD  83  49  85  48 /  20  20   0   0
DLS  82  55  85  54 /   0   0   0   0

&&

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

91/90/90