Wildfire in Washington, August 16 to 27, 2018

Area Forecast Discussion
National Weather Service Pendleton OR
1045 AM PDT Thu Aug 16 2018

.UPDATE...The latest radar was showing showers starting to gain
some strength and expanding in coverage over the northeast cwa and
this mornings forecast was updated to reflect this. An upper
level low pressure system was nearing the Oregon coast and adding
additional moisture to the region that was aiding in some shower
development. As the low moves closer to the area this will combine
with daytime heating along with the moisture and make the
atmosphere increasingly unstable that could produce isold tsra
this afternoon across any part of the area. The best chance for
tsra and we concur is where spc generated a marginal risk of tsra
mainly south of the state line. Otherwise showers should drift
slowly away from the region later this morning and high temps are
expected to climb into the 90s.

.FIRE WEATHER...watches have been upgraded to red flag warnings for
later today through Friday for abundant lightning and gusty outflow
winds. Upper level trough moving across the region expected to
result in scattered thunderstorms. Many of the storms will have
minimal rainfall.  94

AVIATION...18Z TAFS...Mid to high based showers this morning will
put out little precip but some gusty winds are possible. Best chance
through midday at KPDT...KALW and KYKM. Otherwise expecting a better
chance of showers and thunderstorms later this afternoon into the
overnight hours. Starting out around KRDM and KBDN during the
afternoon and shifting north and east towards KDLS...KPDT...KPSC and
KYKM during the evening hours. Activity should die off from west to
east during the overnight hours and early morning hours. More
showers and storms possible across eastern OR tomorrow. Aside from
localized gusts near showers and storms...winds should generally be
light except near KDLS and the Columbia Gorge where gusts 20-25kts
likely. 84

&&

.PREV DISCUSSION... /issued 232 AM PDT Thu Aug 16 2018/

SHORT TERM...Today through Saturday...A weak upper low will linger
off the Pacific Northwest coast today, then move inland tonight and
Friday. South to southwest flow ahead of the low will persist until
Friday morning bringing mid level moisture and instability into
eastern OR. Radar indicates isolated showers across the CWA but not
much is reaching the ground due to high bases and evaporation in
drier air below. A series of shortwaves will rotate around the low
into OR and WA today through Friday. These waves will trigger a few
thunderstorms from central to northeast OR Thursday afternoon
through Friday. Fire Weather Watches have been issued due to threat
of abundant lightning and gusty outflow winds creating and spreading
wildfires. See Fire Weather discussion below. The thunderstorms
later today may become strong or severe due to gusty winds. SPC has
included central to northwest OR in area of marginal risk of severe
storms today. There will be enough elevated instability Thursday
night to keep a slight chance of thunderstorms even during late
night and morning hours. The upper level low and associated trough
will cross eastern OR into ID Friday afternoon and evening. Enough
instability and moisture from the departing low will linger in the
northern Blues and Wallowa County Friday afternoon and evening for
thunderstorms. An upper level ridge near the coast Friday afternoon
will build as it moves slowly east Friday night and Saturday
bringing fair and dry conditions.

An Air Quality Alert remains in effect for WA counties and an Air
Quality Advisory is in effect for Oregon counties. These are in
effect through at least Friday at noon. West winds will increase
east of the Cascades late Friday eventually allowing for an air mass
change, leading to some improvement to air quality. Coonfield

LONG TERM...Saturday night through Wednesday. Brief upper-level
ridging continues to shift east. Little better overall agreement
between models with overall general trend for a long wave trough to
slowly work into the Pacific Northwest Sunday and work across the
region through early next week. There still is discrepancies between
timing and location between models and run times and overall
ensemble guidance still varies. Either way, moisture looks to be
quite limited at this time, so have kept the dry forecast going for
early next week but do expect increase in mid to high level cloud
cover. The other concerns for the long term are the ongoing haze and
smoke, as well as the hot temps. Areas of haze and smoke are
probable in certain spots during the the long term...but with
difficulty in pinpointing specific locations this far out...have
left out mention of haze and smoke for now. Lowered temps slightly
with the trough overhead and expected increase in cloud cover but
still expecting highs in the upper 80s to upper 90s for the lower
Columbia Basin, which is around 10 degrees above normal for this
time of year.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  96  64  92  57 /  20  20  30   0
ALW  98  64  92  58 /  20  20  30   0
PSC  98  63  94  57 /   0  20  20   0
YKM  97  61  94  55 /   0   0   0   0
HRI  99  65  94  57 /  20  20  10   0
ELN  97  61  90  57 /   0   0   0   0
RDM  92  52  88  43 /  20  40  10   0
LGD  94  58  88  49 /  20  20  40  20
GCD  93  57  89  51 /  20  30  20  10
DLS  96  63  89  58 /   0  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 5 PM this afternoon to 8 PM PDT Friday
     for ORZ643-645.

     Red Flag Warning from 3 PM this afternoon to 5 AM PDT Friday
     for ORZ610-611-640.

     Red Flag Warning from 3 PM this afternoon to 11 AM PDT Friday
     for ORZ642-644.

WA...Red Flag Warning from 5 PM this afternoon to 8 PM PDT Friday
     for WAZ643-645.
&&

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