356
FXUS66 KPDT 092359
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
459 PM PDT Mon Mar 9 2026


.UPDATED AVIATION DISCUSSION...


.KEY MESSAGES...

1. Moderate snow continuing into Tuesday
 WINTER WEATHER ADVISORY IN EFFECT 5 AM MONDAY THROUGH 8 AM
TUESDAY

2. Heavy snow Tuesday night into Friday morning
 WINTER STORM WARNING IN EFFECT 5 PM TUESDAY NIGHT THROUGH 5 AM
 FRIDAY MORNING

3. Breezy winds will persist through the week

&&

.DISCUSSION...
Current radar shows returns moving across the Cascades over
Snoqualmie Pass through Hyak and into Easton. Current webcams shows
snow build up along the shoulder and in the trees with ground
observations reporting 3 inches of snow so far.  Snowfall is
expected to continue through the remainder of the day today and
through 5 AM Tuesday morning. The Winter Weather Advisory remains in
effect with an additional 2 to 6 inches of snow accumulations (70-
90% confidence).

Models show northwest flow aloft to continue to bring in bands of
precipitation through the week. The strongest band will begin
Tuesday night and an atmospheric river gets caught up in the flow
around the Pacific high and flows directly into the PacNW. CW3E
ensembles show a 90% probability of 250 kg/(ms) making its way
across the Cascades bringing with it increased chances of heavy
mountain snow. Models are in form agreement with the upper level
system and WPC cluster are only showing the main variance to be is
with the amplitude of the system. EFI also shows abnormally high
amounts of snow and QPF in comparison to the seasonal averages with
an EFI of 0.97 and a shift of tails of -5. This shows how abnormally
strong and wet this system is for this time of year. Due to this, a
Winter Storm Warning has been issued for the event with 70-90%
confidence the event will bring 2 to 4 feet of snow to the WA
Cascades. There will be a lull in heavy precipitation as the AR will
bring in some slightly warmer air allowing the snow levels to
increase and precipitation to turn to a wintery mix between 11 AM
Wednesday and 5 AM Thursday. However, Thursday shows another cold
air mass moving in bringing the snow levels back down to near 1500
feet and temperatures back to freezing.

Lastly, models show relatively tight pressure gradients to be
associated with this system so breezy conditions are expected
through the week. NBM raw ensembles show 50-70% probabilities of
winds gusts 30-35 mph gusts across the area with localized areas
seeing 20-25 mph such as the lower Columbia Basin, the Gorge, and
central OR. 90

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...VFR conditions prevail
for all sites. An embedded disturbance in mid-level zonal flow will
continue bringing snow showers across the East Slopes of WA Cascades
and portions of the Blue mountains. With that, KDLS may see light
rain showers this early evening, but with a 30% probability. In
addition to the zonal flow, breezy winds (20-30 kts) will linger
through the evening hours for KPDT, KRDM, KYKM, and KPSC. However,
winds may pick up again around Tuesday morning for KPDT, KALW, and
KPSC. Feaster/97

&&

.Preliminary Point Temps/PoPs...
PDT  29  47  33  57 /  20  20  20  40
ALW  31  47  36  56 /  40  30  40  60
PSC  31  52  36  60 /  10   0  10  20
YKM  26  48  29  54 /  10  10  50  60
HRI  31  51  36  60 /  10  10  10  20
ELN  24  42  28  46 /  20  20  60  70
RDM  23  42  28  54 /  10  10  10  30
LGD  26  42  28  49 /  50  40  40  70
GCD  23  41  27  53 /  10  30  10  40
DLS  31  49  36  54 /  40  50  70  80

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 8 AM PDT Tuesday for WAZ522.
     Winter Storm Warning from 5 PM Tuesday to 5 AM PDT Friday for
     WAZ522.
OR...None.

&&

$$

DISCUSSION...90
AVIATION...97