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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

                            
000
FXUS66 KPDT 161529
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
729 AM PST Sat Feb 16 2019

.UPDATE...The latest radar was showing showers across the area as
a low pressure system approaches or/wa. Light snow has been 
falling in the advisory area of central Oregon and web cams showed
some accumulation already south of Bend. Elsewhere patchy 
freezing fog developed over portions of the columbia basin and the
zones were updated accordingly. Expect snow showers to persist 
with some accumulation in the blue mountains as well today. 
Otherwise the present short term forecast appears on track. VP

&&

.PREV DISCUSSION... /issued 300 AM PST Sat Feb 16 2019/ 

SHORT TERM...Today through Sunday night... 
A series of low pressure systems will track across the two state 
area creating snow across most of the region today and tonight. 
The bulk of the snow is expected to fall around central Oregon 
that has prompted a winter weather advisory for the east slopes of
the Oregon cascades into tonight. Meanwhile the main low pressure
system will move across central Oregon tonight and slowly push 
south while bringing even colder temps behind it and into the 
region Sunday. While the western portions of the region could 
experience some drying on Sunday...a low pressure system will near
our eastern zones that will keep snow showers in the forecast 
into Sunday night.

Long Term (Monday through Saturday)...
An active and unseasonably cold weather pattern will continue 
into the end of next week as a series of storm systems dig 
southeastward across the region. In addition to continued cold, at
least two opportunities for additional wintry precipitation are 
apparent...one late Tuesday through Thursday, and the second 
toward the very end of the long range period heading into next 
weekend. As is the case with ALL weather, the forecast is fluid 
and will certainly change. Check back often for updates.

As we start the work week, expect a fresh batch of Arctic air 
will spill southward into the region, resulting in temperatures 
averaging 15 to 20 degrees below normal. A frigid morning appears 
probable Tuesday with some areas falling into the lower teens to 
upper single digits. This is quite cold for the latter half of 
February.

Some slight warming looks to occur late Tuesday night into 
Wednesday as the next upper trough swings across the area. While 
some mixed precipitation may occur in the lower elevations, model 
soundings generally look to favor primarily snow with potentially 
significant accumulations over the Cascades and Blue Mountains. 
Lesser amounts are expected in the Columbia Basin and lower 
valleys, but guidance is fairly consistent in producing at least 
nominal accumulating snow in the 1 to 2 inch range over a fairly 
widespread area, which is all it will take for travel concerns. We
will have to watch this one closely.

A brief respite looks to unfold from early Thursday into Friday 
as the upper system exist to the southeast with weak ridging 
building in aloft. However another Arctic surface high is expected
to shift south into the region, with another dose of frigid 
temperatures Thursday night into Friday morning.

Models are in general agreement depicting another upper trough 
entering the Pacific Northwest late Friday into Saturday, but 
given that is toward the end of the long term period, confidence 
is rather low on exactly what impact this system may have heading 
into next weekend. We will watch it carefully over the coming 
week.

By the end of the week, models differ significantly. The GFS 
indicates a progressive pattern and weak ridging building into the
West Coast, while the European maintains a cold northerly flow 
pattern. Differences in sensible weather would be subtle, though 
the GFS would be several degrees warmer with the depicted ridging.
At this time, confidence is higher in persistence and would tend 
to favor a colder solution.

Aviation (12z TAFs)...
Patches of light rain and/or rain and snow will persist from near
KBDN/KRDM to KYKM/KPSC/KALW this morning, with IFR/LIFR ceiling 
and visibilities possible. These conditions may persist for 
western terminals KYKM/KDLS/KBDN/KRDM with improving conditions 
for remaining terminals later this morning into the afternoon. 
Brief periods of heavy snowfall may occur at KBDN/KRDM as a weak 
system moves over the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  32  23  29  17 /  30  30  20  30 
ALW  35  25  30  18 /  40  30  20  30 
PSC  33  25  30  19 /  30  20  20  10 
YKM  33  22  32  19 /  40  20  20  20 
HRI  33  25  32  19 /  30  30  20  20 
ELN  34  18  31  13 /  40  20  20  20 
RDM  36  21  34  17 /  60  60  20  10 
LGD  35  23  32  17 /  40  40  20  20 
GCD  34  24  35  19 /  50  50  20  20 
DLS  38  27  36  25 /  60  50  20  20 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST Sunday for ORZ509.

WA...None.
&&

$$

97/