Wildfire in Washington, July 9 to 12, 2018

Area Forecast Discussion
National Weather Service Pendleton OR
728 PM PDT Mon Jul 9 2018

.UPDATE...An upper trough is moving into western Oregon/Washington
at this time with clouds ahead of it already reaching the Cascade
east slopes. There is a southwest flow ahead of this front with
increasing winds from now until the front passes. Instability is
marginal, but there is a slight chance of thunderstorms late tonight
over the Lower Columbia Basin of Washington. Then winds will
diminish by early Tuesday morning. There will be some increase in
winds again Tuesday afternoon due to mixing, but the frontal winds
will have moved off to the east. Tuesday will be about 10 degrees
cooler than today with the lower elevation readings in the in the
mid 80s...with mostly upper 60s to mid 70s in the mountains...
warmest in the eastern mountain valleys where the cooler marine air
doesn't penetrate very well to. Warming will take place again
beginning Wednesday and continue through the rest of the week under
a mostly zonal flow pattern. Conditions will also remain dry. There
may be a possible need for heat related highlights at the end of the
week due to temperatures being around or over 100 degrees in the
lower elevations. 88

&&

.AVIATION...06Z TAFs...VFR conditions will persist through the next
24 hours. The winds will increase this evening ahead of a dry cold
front. Then clouds will increase from west to east overnight with
CIGs around 7K-10K feet MSL. 88

&&

.PREV DISCUSSION... /issued 210 PM PDT Mon Jul 9 2018/

SHORT TERM...Tonight through Thursday...Continue to watch the
closed upper level low pressure system off the Pacific Northwest
coast that will open into a wave pushing a dry cool front up against
the Cascades late this afternoon and then passing over the forecast
area overnight. Main impact will be increasing westerly winds along
the eastern slopes of the Cascades this afternoon then spreading out
into the Columbia Basin in the evening and continuing overnight. The
potential for any precipitation associated with this system will
mainly be limited to the central Washington Cascade crest and
perhaps central Washington north of Pasco late tonight with a slight
chance of some thunderstorms. The system will exit the forecast area
early Tuesday leaving behind a cooler breezy day. A flat ridge of
high pressure will build over the western U.S. Wednesday and
Thursday which will provide a warming trend for the later half of
the work week to the forecast area.

LONG TERM...Thursday Night through Monday...Thursday night a dry
westerly flow will be over the area and expect fair weather with
clear skies and light winds. Friday through Saturday low pressure
over the southwest will try and circulate monsoon moisture into the
southern portion of the area though an approaching trough out of the
Gulf of Alaska will suppress moisture southward. Models differ as to
how far north the moisture will get but generally agree in having
little if any showers over our area. Have kept a dry forecast with
mostly clear to partly cloudy skies. Friday afternoon and evening
the trough will tighten pressure gradients and there will be 15 to
25 mph winds in the Columbia Gorge and Kittitas Valley with 10 to 20
mph winds elsewhere. By Saturday the trough will be off to the east
with a cooler northwest flow moving over the region. Sunday and
Monday will keep a dry west to northwest flow over the area for
continued dry weather, clear skies and light winds. Models keep
monsoon moisture generally to the south and east of us. Temperatures
will be above normal through the long term period. Friday will be
hot with highs in the mid 90s to lower 100s in the Columbia Basin
and in the mid 80s to mid 90s elsewhere. On Saturday the trough will
drop temperatures to the lower to mid 90s with 80s and lower 90s
elsewhere. Sunday will be similar to Saturday and Monday will be a
degree or two warmer. Perry

FIRE WEATHER...A cold front will be sweeping across the region late
this afternoon and evening, bringing breezy winds to many areas in
and around the Columbia Basin down to Central Oregon.  Wind gusts to
35 mph will occur in the eastern Columbia River Gorge. The grasses
and shrubs are dry, and wind-driven fires are always a possibility
this time of year. The one negating factor will be RHs, as values
will not be critically low. Two areas that have the best potential
for winds and low humidity and marginal red flag conditions will be
near Goldendale and north central Oregon.

After a closer look at the upcoming shortwave trough, we decided to
include a slight chance of thunderstorms late this evening for the
Hanford District.  The lightning activity...if any...will be limited
and not enough to warrant Red Flag Warnings.

The hot and dry conditions will return by the end of the week. Not
only will daytime RHs be critically low, but the overnight
recoveries could be poor in many areas.  Wister

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  61  84  57  88 /   0   0   0   0
ALW  63  85  59  90 /  10   0   0   0
PSC  66  87  58  91 /  10   0   0   0
YKM  59  85  55  90 /  10   0   0   0
HRI  65  87  58  92 /  10   0   0   0
ELN  59  81  54  90 /  10   0   0   0
RDM  50  83  49  89 /   0   0   0   0
LGD  56  80  51  86 /   0   0   0   0
GCD  55  81  53  88 /   0   0   0   0
DLS  63  84  60  92 /  10   0   0   0

&&

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

&&

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