803
FXUS66 KPDT 192300
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
300 PM PST Sun Jan 19 2020

Updated Aviation Discussion

SHORT TERM...Tonight through Tuesday Night...An upper ridge is
over the area this afternoon though it is moving east as a system
approaches out in the eastern Pacific. Tonight and tomorrow will
be quiet with no precipitation expected except for a few light
showers near the Washington Cascade crest. Snow cover over much of
the area is cooling temperatures and promoting an inversion and
this will likely lead to low clouds and fog again tonight and
tomorrow morning in the Columbia Basin and Yakima and Kittitas
Valleys with greater coverage than last night. By Monday night,
the ridge will have moved off to the east and a cold front and
upper low will be moving ashore. A chance of rain and snow will
begin in the overnight hours from Yakima and Ellensburg south to
central Oregon. Snow levels in the north will be 1200 to 2000 feet
and 4000 to 4500 feet in central Oregon. Tuesday will see a chance
of rain and mountain snow though by the afternoon the Columbia
Basin will be drying out. Snow levels will be around 1500 to 2000
feet in the Washington Cascades and Yakima and Kittitas Valleys
and 3500 to 4500 feet elsewhere. Tuesday night will continue to
see a chance of snow in the mountains but the lower elevations
will be mainly dry. Tuesday and Tuesday night will see about 1 to
3 inches of snow in the mountains and up to a tenth of an inch of
rain in the lower elevations. The Cascades will have 3 to 8
inches of snow. Pressure gradients will remain tight in the Grande
Ronde Valley and winds there will be southerly at 15 to 25 mph
tonight through Tuesday before decreasing Tuesday night.
Temperatures Monday and Tuesday will be in the mid 30s to mid 40s
though Tuesday will be a couple of degrees warmer than Monday.
Lows will be in the mid 20s to lower 30s tonight and Monday night
then warm a couple of degrees to the mid 20s to mid 30s Tuesday
night. Perry

LONG TERM...Wednesday through Sunday...Currently, some
uncertainty lies in the overall synoptic pattern and series of
systems that will pass over the region between GFS and ECMWF.
Starting Wednesday morning, both advertise a ridge that builds
into the region with a moist warm frontal boundary that starts to
effect the region Wednesday afternoon. However, ECMWF shows a
stronger warm front that infiltrates into WA bringing WA/OR low
elevation light rain and mountain snow, while GFS keeps
precipitation in the WA/OR Cascade crests and central OR. Both
start to evolve into a southwesterly flow into Friday, but GFS
keeps stronger ridge, meaning drier conditions in the basin and
eastern mountains. Meanwhile, ECMWF transports a upper level
shortwave through the flow that brings continued precip chances to
the region. Saturday afternoon into Sunday, both models are
showing a moist/warm southwest flow with a few disturbances
embedded in the flow aloft, bringing the best chances of precip
to the mountains and slight chances in lower elevation areas. For
long term forecast, went with chance/slight chance POPs through
most of the period. Snow levels rise Wednesday night to above
5,500ft across central OR and south central WA, with portions of
eastern OR and central WA below 3,500ft. This warmer airmass
anticipated to stay in place over the region through the weekend,
keeping most precip chances as rain in WA/OR Cascades and lower
elevations. Temps will stay fairly moderate through the long term,
with highs in the mid 40s to lower 50s and lows in the lower 40s
to mid 30s. Lawhorn/82

AVIATION...00Z TAFs...Low stratus has cleared out at several sites
across the region. However, DLS still under MVFR ceilings and ALW
has refused to clear out of VLIFR vsby and ceiling today.
Late overnight, anticipate IFR/LIFR ceilings and vsby to settle
in at DLS/PDT/YKM/PSC, while IFR/VLIFR will persist at ALW through
tomorrow. BDN/RDM expected to stay VFR through the period, with
current southerly breezy conditions to subside by 10Z. Winds will
be light, 3-8Kts, at all other TAF sites through the period.
Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  26  38  30  42 /   0   0  10  40
ALW  28  37  32  41 /   0   0  10  60
PSC  28  36  30  40 /   0   0  10  30
YKM  27  38  29  40 /   0   0  20  50
HRI  28  36  30  41 /   0   0  10  30
ELN  28  37  28  38 /   0  10  20  50
RDM  29  44  32  45 /   0   0  20  50
LGD  30  39  33  41 /   0   0  10  70
GCD  30  44  33  42 /   0  10  10  60
DLS  30  38  32  42 /   0  10  40  70

&&

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

$$

83/82/82

NWS PDT Office Area Forecast Discussion