Wildfire in Oregon, September 1 to 30, 2020

Area Forecast Discussion
National Weather Service Pendleton OR
950 PM PDT Mon Aug 31 2020

.SHORT TERM...Water vapor imagery showing a weak short wave moving
across the region this evening. Mostly high level clouds and some
increased winds. The cirrus will continue to move south with clear
skies overnight. Winds will diminish. Upper ridge builds in Tue
with sunny and much warmer conditions. Ridge will dominate the
weather pattern for the week. Mainly clear skies and warm temps.

.AVIATION...06z tafs. Clear skies tonight into Tuesday. Winds 5-10kt
tonight and 10-20kt Tue.

&&

.PREV DISCUSSION... /issued 500 PM PDT Mon Aug 31 2020/

SHORT TERM...Rest of today into tonight...Cool northwest flow
aloft is prevailing with mostly clear to partly cloudy skies...
decent Cu field persists, especially in Blue Mtn and Wallowa areas
with some passing high cirrus. Another cool night expected with
lows near 60 Basin, 40s mid elevations and near freezing on
volcanic peaks and elevated valleys such as Seneca region.

Tomorrow...much advertised warming and drying pattern commences as
a NW to SE oriented ridge begins to encroach into the area with
rising heights and weakening flow aloft pulling westward. Temps in
the 90s for much of the Basin, quite a bit above climatology. Some
breeziness may still exist in Kittitas Valley and along I-90 where
winds aloft will be a bit more pronounced than in OR closer to
ridge center. Temps again fall considerably in the evening under
mostly clear skies and a dry airmass.

Wednesday...as the warm, dry days continue, so does our fire
weather risk as fuel moisture metrics become more critical. See
fire weather discussion for more. Day two of warm pattern expected
to feature temps a few degrees warmer with warmest spots of Basin
entering upper 90s and a larger footprint of 90 or more temps
swallowing lower elevations as ridge axis approaches. A trough
axis will impinge on the NW-SE oriented ridge from the NW. This
presents precious little precip chances in our dry airmass and
entrenched high pressure/associated ridging. But it will bring
enough momentum southward to elevate surface winds in the
afternoon, particularly through Columbia Basin and the Gorge.
Currently not anticipating wind highlights but fire highlights may
be needed for this timeframe. Winds ease late overnight and early
into Tuesday. 76

LONG TERM....
Thursday through Monday...The region will be under the control of a
large upper level ridge and expect hot temperatures through the
holiday weekend, with no precipitation and very few clouds.  It is
possible, depending on how things set up that it could be marginally
cooler toward Sunday and Monday, but not by much.  The peak of the
heat looks to be Friday.  High temperatures on Thursday look to be
in the lower to mid 90s....increasing to the mid to upper 90s by
Friday and Saturday.  It is certainly possible that triple digit
readings are realized on Friday, Saturday or both especially in the
Columbia Basin.  The ridge does flatten a bit for Sunday and Monday,
so temperatures could be in the low to mid 90s again.

FIRE WEATHER...The ridge/associated high surface pressure
mentioned is a high confidence feature with moderate confidence
some type of warm, dry pattern persists into next week. Today and
tomorrow, some light breeziness (10-15mph) through Cascade gaps
with warm, dry conditions on Tue. Winds on Wed (15-20g30
in/around Gorge and parts of Basin) are expected, though models
still show some spread on how gusty winds will get Wed evening.
Monitoring this situation on Wed for local RFW conditions in the
western Basin, eastern Gorge, and eastern Cascade slopes of OR. By
late week, each warm dry day will continue to wring what little
moisture may be left in fuels but confidence wanes on identifying
windy periods for weekend timeframe. Thursday seems to be a lull
after Wednesday's event but as we look to the holiday weekend,
we're currently confident in continued warmth and low RH but
waiting for confidence to increase on what winds will be like, if
any. 76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  50  90  55  92 /   0   0   0   0
ALW  54  91  59  94 /   0   0   0   0
PSC  54  93  57  96 /   0   0   0   0
YKM  53  92  54  95 /   0   0   0   0
HRI  52  94  57  96 /   0   0   0   0
ELN  54  86  56  87 /   0   0   0   0
RDM  43  91  48  94 /   0   0   0   0
LGD  44  86  49  90 /   0   0   0   0
GCD  43  88  52  94 /   0   0   0   0
DLS  55  93  59  95 /   0   0   0   0

&&

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

SHORT TERM...94