FXUS66 KPDT 171707

Area Forecast Discussion
National Weather Service Pendleton OR
1007 AM PDT Tue Jul 17 2018

Updated Aviation Discussion

.UPDATE...Satellite images show a few clouds lingering in
southeastern WA. Drier air will continue to move into eastern WA
and OR this afternoon. There is enough lingering moisture that a
few fair weather CU may develop over the mountains along the
southern border of the CWA this afternoon. High temperatures will
be in the 90s to 105. Heat advisories remain in effect. Weak
marine push and strong cross Cascade pressure gradients will bring
breezy to windy conditions in the Columbia Basin and adjacent
areas this afternoon. The strongest winds will be in the Columbia
River Gorge and Kittitas Valley. Red Flag Warnings for wind and
low RHs have been issued for these areas. Coonfield

.AVIATION...18Z TAFs...VFR conditions are expected for the next 24
hours under clear skies. Winds will increase to 10 to 20 mph with
gusts to 25 to 30 mph this afternoon and evening before dropping to
5 to 15 kts overnight.


.FIRE WEATHER...Red Flag are in effect for gusty winds and low
humidity this afternoon through Wednesday evening covering the
Eastern Columbia River Gorge, Simcoe Highlands, the southern
Kittitas Valley and Hanford District, the Oregon Columbia
Basin, the east slopes of the Oregon Cascades, and central and
north central Oregon. Although winds today will only increase to
around 10-20 mph (15-25 through the Columbia River Gorge), the RH
values will be critically low at 5-15 percent. A strengthening
onshore flow will allow cool marine air to spread through the
Columbia River Gorge this afternoon then through the Cascade gaps
this evening as the marine layer deepens. Winds will decrease
tonight. The marine push will be stronger on Wednesday. The humidity
will increase on Wednesday but not enough to make a big improvement
in the overall fire weather conditions. Wister


.PREV DISCUSSION... /issued 253 AM PDT Tue Jul 17 2018/

SHORT TERM...Today through Thursday. Water vapor imagery shows
upper low moving out of the forecast area into Idaho. Some
lingering clouds that will be dissipating later this morning.
Otherwise another sunny hot day with highs in the 90s to 105. Heat
advisories remain in effect. RH cross sections show the airmass
becoming very dry by afternoon. Westerly winds will be increasing
and red flag warnings also remain in effect. A dry westerly flow
aloft over the region Wednesday and Thursday with mainly clear
skies. Temperatures will be gradually cooling over the next few
days. Highs Wed mostly in the 90s and for Thu upper 80s and 90s.
Surface gradients and westerly flow aloft will favor continued
breezy conditions each day. 94

LONG TERM...Thursday Night through Tuesday...Thursday Night the
area will be under a westerly flow with high pressure over the
southwestern states and a upper low and trough approaching the
northern British Columbia coast. It should be a fair and dry night
with clear skies. Breezy winds are expected in the Columbia Gorge
and Kittitas Valley in the evening. Friday through Sunday the trough
will cross through British Columbia and into Alberta. A more
southwesterly flow will develop but the air mass will be so dry that
I do not see much in the way of clouds let alone showers or
thunderstorms. Temperatures Friday through Sunday will be fairly
consistent in the lower to mid 90s in the lower elevations and
mainly in 80s elsewhere. Pressure gradients along the Cascades will
be tight Friday and breezy winds will develop in the Kittitas
Valley, Columbia Gorge and Central Oregon and with low humidities,
fire weather concerns may be heightened. Sunday night through
Tuesday the trough will move off to the east and a generally
westerly flow will resume over the area. Models show any moisture
circulating around the high pressure will remain to our south, so
continued dry and fair weather with mostly clear skies is
anticipated. High pressure will build northward slightly Monday and
Tuesday so temperatures will be increasing a degree or two each day
ending up in the mid 90s in the lower elevations and in the mid 80s
to lower 90s elsewhere. Perry


PDT 100 64 95 60 / 0 0 0 0
ALW 102 65 96 62 / 0 0 0 0
PSC 104 64 98 61 / 0 0 0 0
YKM 102 61 96 58 / 0 0 0 0
HRI 104 65 98 62 / 0 0 0 0
ELN 99 60 91 58 / 0 0 0 0
RDM 98 51 92 50 / 0 0 0 0
LGD 97 55 90 52 / 0 0 0 0
GCD 96 57 91 54 / 0 0 0 0
DLS 98 63 91 59 / 0 0 0 0


OR...Red Flag Warning from 1 PM this afternoon to 8 PM PDT Wednesday
for ORZ639.

Red Flag Warning from 4 PM this afternoon to 8 PM PDT Wednesday
for ORZ610-640-641.

Heat Advisory until 9 PM PDT this evening for ORZ044-507.

WA...Red Flag Warning from 1 PM this afternoon to 8 PM PDT Wednesday
for WAZ639.

Red Flag Warning from 4 PM this afternoon to 8 PM PDT Wednesday
for WAZ675.

Heat Advisory until 9 PM PDT this evening for WAZ026>029.



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