National Weather Service Raw Text Product

827 
FXUS66 KPDT 160457
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
957 PM PDT Tue Mar 15 2022

.AVIATION...06Z TAFs...Currently all TAF sites are VFR and will 
remain as such over the forecast period. Showers and winds have 
decreased across all sites although around 18Z the winds pick up 
slightly across the Gorge and Basin. KDLS will experience some 
locally breezy winds of 13 kts with gusts to 20kts as a cross 
Cascade gradient tightens and moves over the Mts. VIS will remain 
at P6SM and CIGs will lift to 100kft or more overnight into 
tomorrow. Bennese/90 

&&

.PREV DISCUSSION... /issued 742 PM PDT Tue Mar 15 2022/ 

EVENING UPDATE... No real update to the previous forecast. Showers 
have begun to dwindle for the lower elevations as the trough has 
moved off to the east. The leading edge of the incoming ridge has 
begun to move onshore and the axis of the ridge is just off the coast 
of British Columbia. This ridge will continue to move through the 
region relatively quickly Wednesday giving us a quick dry spell 
before the next trough system arrives onshore Thursday. Winds will 
remain breezy through this evening and will begin to decrease by 
tomorrow morning. Bennese/90

&&

SHORT TERM… Tonight through Thursday night… Conditions trend drier 
and calmer across the CWA tonight through Wednesday with lingering 
mountain snow showers providing the primary impacts moving forward. 
After a brief dry break across the region Wednesday night a weak 
trough moves into the Pacific Northwest the second half of Thursday 
into Thursday night bringing another chance for light precipitation, 
mainly to the higher terrain.  

The trough of low pressure that gave us today’s unsettled, breezy, 
and showery conditions continues to progress east overnight while a 
transient ridge approaches off the coast. This will lead to shower 
activity gradually decreasing, retreating closer to the higher 
terrain of the Cascades and Blues Mtns/Wallowas tonight into 
Wednesday. Guidance also has breezy/gusty winds decreasing this 
evening and overnight as well likely in response to the loss of 
daytime heating mixing winds down from aloft and weakening pressure 
gradients. The axis of the transient ridge moves overhead later in 
the day on Wednesday shifting the upper-level flow more northerly 
and bringing an end to any remaining mountain showers later in 
the afternoon. Snow accumulation tonight through Wednesday isn’t
all that impressive over the mountains with the highest totals 
over the Washington Cascades and into the northern Blues; the bulk
of any snowfall impacts occur before noon Wednesday. Otherwise 
models are in good agreement for the rest of the region to remain 
dry. 

Thursday a weak upper-level trough pushes into the Pacific Northwest 
from offshore while the ridge of high pressure vacates to the east. 
There’s been some model disagreement on the exact timing of this 
disturbance however the latest runs of the GFS and ECMWF ensemble 
means and their receptive deterministic counterparts indicate light 
precipitation working into the Cascades Thursday afternoon then 
spreading to the mountains of eastern Oregon in the evening. 
Considering QPF totals with this disturbance stay less than a tenth 
of an inch or two and snow levels remain in the 4-5kft range, 
snowfall impacts appear minimal for the pass areas. The Columbia 
Basin and Deschutes Basin and are likely skipped over entirely; dry 
weather persists. 99

LONG TERM...FRIDAY THROUGH MONDAY...The extended period is 
characterized by an upper level trough that will bring widespread 
rain and mountain snow across our area through the early part of the 
weekend. High temperatures will also be dropping 10 degrees from 
Friday through Sunday, with values from the low-60s Friday into the 
low-50s on Sunday across lower elevations. Southwest winds will also 
be increasing over the weekend as gusts of 20-25 mph are expected 
along the east slopes of the Washington Cascades and through the 
Eastern Gorge. The EFI is also highlighting that some ensembles are 
picking up unclimatologically high rain/snow amounts for this time 
of year over the Oregon Cascades on Saturday. Snow amounts of 4-8 
inches are likely along the Oregon Cascades and 1-3 inches for the 
Washington Cascades and Eastern Mountains. Current forecasted rain 
amounts of 0.60-0.80 inch for the Oregon Cascades, 0.25-0.50 inch 
for the Washington Cascades, 0.15-.0.25 through the Eastern 
Mountains, 0.05-0.15 inch for Central Oregon, and 0.01-0.05 through 
the foothills of the Blue Mountains and the east slopes of the 
Washington Cascades are likely. The Lower Columbia Basin is expected 
to only see a trace of precipitation during this timeframe. 

A transient ridge will pass through our area on Friday, allowing for 
the warmest day in the forecast to occur as highs peak in the upper-
50s to low-60s across lower elevations of the Basin and through 
Central Oregon. Cloud cover will slowly increase through the day as 
the ridge exits our region through the evening and overnight period. 
This is in response to a digging upper level trough that will push 
onshore and into our region during the late morning and afternoon 
hours on Saturday. Rain and mountain snow will begin along the 
Cascade crest late Friday evening before spilling into the Basin and 
causing widespread rain chances throughout our area by early 
Saturday morning. Showers will begin to be more confined to mountain 
regions through the afternoon and early evening as the trough 
continues to dig to our south and east. As this system departs our 
area, an upper level ridge will infiltrate into our area and 
initiate northwest flow aloft. This will drop snow levels from 3000-
4000 feet Saturday to 1500-2500 feet on Sunday. The ridge continues 
to build into Monday, but consistent northwest flow aloft will keep 
the potential for upslope showers over the Washington Cascades and 
Blues to continue. Snow levels will also increase quickly Monday 
into Tuesday, reaching into the 5000-7000 feet range. High 
temperatures will also be steadily increasing by about 5 degrees 
each day from Sunday through Tuesday.

Guidance is in good agreement with the overall synoptic pattern, but 
there are differences that arise relating to trough strength and 
subsequent ridge strength/timing. The GFS incurs a stronger trough 
than the ECMWF, which correlates to stronger winds associated with 
the passing system. The ECMWF provides a slightly wetter outcome on 
Saturday, but dries out quicker due to the upper level ridge 
following closer to the departing trough. 500mb EOF patterns 
highlight these differences in trough strength and subsequent ridge 
timing on Sunday. The cluster 500 mb heights provide more confidence 
in the ECMWF outcome as the majority of its ensembles and the 
Canadian ensembles are more in line with the ECMWF deterministic 
scenario. However, the cluster phase space shows that the ECMWF 
deterministic is not as representative as the ensemble mean 
beginning Monday as associated with the incoming ridge. Thus, there 
is high confidence in the ECMWF when associated with the incoming 
system on Saturday, but confidence wanes when relating to the faster 
speed of the incoming ridge on Monday as determined by the ECMWF.
75 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  35  54  32  58 /  10  10   0   0 
ALW  39  57  36  61 /  10  10   0   0 
PSC  40  61  36  61 /   0   0   0   0 
YKM  32  59  31  56 /  10   0   0  10 
HRI  38  58  35  60 /   0   0   0   0 
ELN  33  54  32  52 /  10   0   0  10 
RDM  29  54  30  58 /  10   0   0  10 
LGD  33  46  28  49 /  40  20   0   0 
GCD  30  49  29  55 /  20  10   0   0 
DLS  40  57  38  58 /  30  10   0  20 

&&

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

$$

SHORT TERM...90
LONG TERM....75
AVIATION...90