785
FXUS66 KPDT 121015
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
315 AM PDT Sat Sep 12 2026

.KEY MESSAGES...

- Dry much of today, then rain developing late this
  afternoon/early this evening. Isolated thunderstorms this
  evening.

- Widespread rain tonight into Sunday.


- Breezy to windy across the Columbia Gorge, Columbia Basin,
  Kittitas Valley and Blue Mountain Foothills this evening
  through Sunday morning.

- Dry Monday through the rest of the upcoming week.

&&

.DISCUSSION...
An area of low pressure off the coast of Oregon and Washington
is moving southeastward, This low move onshore late this
evening/overnight.

As the low moves closer, rain is expected to develop from west
to east during the evening hours. Rain will become widespread
overnight into Sunday morning before decreasing from west to
east during the afternoon and evening on Sunday as the low moves
northeastward towards southern Canada.

The rain should be over by early Monday. Dry weather is then
expected for the remainder of the week, though a second trough
dropping down Tuesday night into Wednesday will have to be
watched, it has little moisture with it.

Model guidance is still not in great agreement with respect to
rainfall amounts. However, there is solid agreement that the
mountains will get the highest amounts, and most, if not all
areas will receive decent rains and should get wetting rains.
It does appear that the higher amounts will be over the
Washington Cascades and nearby areas, but exactly how much the
models are in disagreement over, though there is agreement on 1
inch plus. Over the Blue Mountains, there is a bit more
variability with amounts ranging from 0.50 inch to over an inch.
NBM probabilities of 24 hour rainfall amounts >=0.50 inches are
high across much of the region, generally greater than 60%,
though current QPF amounts across the Basin are less than 0.50
inches. Across the mountain areas they are >80%. NBM
probabilities >=1 inch are highest in the Washington Cascades
(>80 percent), though more variability is shown across the Blue
Mountains and other eastern mountains where percentages vary
from 30 to about 50 percent.

There is also a low (<20%) chance of thunderstorms this evening
and overnight. Depending on thunderstorm development, the
potential exists for flooding over the burn scars associated
with the Paradise and Hagen fires so flood watches are in
effect for these areas.

Winds will also increase this evening and become gusty and
continue through Sunday across the Columbia Gorge, Basin,
Kittitas Valley and Foothills of the Blue Mountains. Winds gusts
will be in the 25 to 30 mph range with gusts possibly as high
as 40 mph. NBM probabilities of wind gusts >=25 mph are 90%
across much of the region. However, wind gusts >=39 mph are 50%
or higher across portions of the Basin and Blue Mountain
Foothills. Wind gusts >=48 mph are 20 to 40 percent.

The combination of the gusty winds and rain will create wind
swept rain at times across portions of the area.

High temperatures today will be a couple of degrees below
normal. However, on Sunday, highs will be 15 to 20 degrees
below normal, and will struggle in the lower 60s...and in some
areas may not get out of the 50s. Highs will slowly warm up
through the week, into the 70s, (but will still be below
normal), but by Friday and Saturday will be close to normal.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
TAFS will start out dry and VFR across the region, but as an
area of low pressure approaches later today and moves across the
region tonight, CIGS will decrease. RA will overspread the area
this evening/overnight and continue through Sunday before ending
from west to east. MVFR CIGS potentially VSBYS are forecast in
any moderate to heavier rain. Additionally, there is a low
(<20%) chance of thunderstorms this evening and tonight, but due
to the low chances, will not include in any individual terminal
at this time. The only TAF sites not likely to see reduced
conditions are BDN and RDM.

Winds will also increase and become gusty. Wind gusts 25 to 35
kts are expected at all sites and 20 to 25 kts at BDN and RDM.


&&

.Preliminary Point Temps/PoPs...
PDT  76  45  61  45 /   0  90  80  50
ALW  79  49  60  50 /   0  90  90  80
PSC  80  47  63  45 /   0  90  90  20
YKM  76  50  63  44 /  10  90 100   0
HRI  79  46  63  45 /   0 100  80  30
ELN  72  44  59  41 /   0 100 100  10
RDM  71  36  60  32 /  10  80  10   0
LGD  81  44  59  42 /   0  90  80  70
GCD  81  43  59  40 /   0 100  40  10
DLS  77  51  66  49 /  20  90  60   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Flash Flood Watch from this afternoon through Sunday evening
     for WAZ030.
OR...Flash Flood Watch from this afternoon through Sunday evening
     for ORZ502.

&&

$$

DISCUSSION...77
AVIATION...77