Hermiston, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

589
FXUS66 KPDT 231800
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1000 AM PST Sat Nov 23 2024

.MORNING UPDATE...Patchy dense fog persists in the Columbia Basin
and adjoining lowlands this morning, especially where low stratus
intersects terrain. Have included a mention of fog only through
10AM for the bulk of the region, with more targeted areas along
heavily traveled corridors for 10AM-1PM. Otherwise, expanded a
chance of showers across south-central Washington where radar
returns are present. Plunkett/86

&&

.AVIATION...18Z TAFs...Lingering moisture and high humidity from
the precipitation the past 24 hours have resulted in areas of
fog and low clouds across the Lower Columbia Basin, including the
Kittitas Valley. Although PDT is currently VFR, confidence is high
that it will deteriorate to IFR/LIFR as winds shift to the WNW
and fog spreads across the airport. The fluctuating conditions
across the Basin have made for a challenging forecast. The stratus
is shallow and may easily burn off by the afternoon sun. VFR
conditions have been observed and will continue at RDM and BDN
with base between 5-15 kft. Winds will be 10 kts or less at all
sites the next 24 hours. Wister/85

&&

.PREV DISCUSSION... /issued 258 AM PST Sat Nov 23 2024/

SHORT TERM...Today through Monday...Forecast area continues under
a moist southwest flow and a slow moving cold frontal boundary
over the eastern mountains. This is all due to the closed upper
level low pressure system off the coast which more or less stays
there until it weakens and finally moves inland late Monday into
Tuesday.

The frontal boundary will slowly continue moving east through the
morning and then exit into Idaho. Eastern mountains will continue
to see a steady precipitation through the morning then changing
over to showers in the afternoon. Snow levels are slowly lowering
and will be around 4000 feet through the day. Snow accumulations
are expected to remain low and below any advisory criteria.
Tonight the showers over the eastern mountains are expected to
come to an end.

With the closed low remaining off the coast Sunday most of the
precipitation threat will be confined to the Cascade region and
areas westward. Then another shortwave coming out of the low will
move across the forecast area Sunday night and Monday bringing
another round of showers across the forecast area with snow levels
down around 3000 feet. Again, precipitation amounts are expected
to remain light so snow accumulations will remain below advisory
levels.

&&

LONG TERM...Tuesday through Saturday...Guidance continues to point
toward a benign, cold pattern for much of Thanksgiving week. After
an open low moves through the forecast area to start off the
period, north to northwesterly flow aloft prevails over the PacNW,
making for a relatively dry forecast, as the oncoming airmass
lacks moisture, but with cold temperatures that struggle to climb
into the 40s by next weekend. Without the presence of high
pressure and subsidence aloft, light mountain precip remains
possible, albeit with limited PoPs (15-25%) given the lack of
moisture advection. Most guidance suggest that this upper-level
flow won`t be amplified enough to cause many precip concerns, but
will have to keep an eye on how the forecast evolves given that
some deterministic guidance (such as the GFS) do try to embed a
shortwave into the prevailing flow pattern towards the end of the
period.

Light precip impacting primarily our high mountain zones is most
likely on Tuesday what with the low overhead, but QPF again looks
to be limited given the lack of sufficient moisture transport.
Other than that, beyond the colder temperatures coming in by
Thanksgiving, only other real concern would be valley and Basin
fog, which can form under these otherwise quiet patterns. Still
opting to keep mention out of the forecast, as the oncoming
airmass is pretty dry and the synoptic pattern doesn`t quite
produce ridging, which is the most ideal set-up for low elevation
fog, but given how wet we`ve been recently, could certainly see
the atmosphere being primed enough for some patchy early morning
fog later in the week. Will pin forecast confidence at the low end
for now (20-30%) for fog chances. Evans/74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  48  29  49  33 /  30  20  10  20
ALW  50  34  50  37 /  50  40  10  30
PSC  51  35  48  37 /  20  10  10  20
YKM  48  28  43  33 /  30  10  30  30
HRI  51  32  50  36 /  20  10  10  20
ELN  47  26  41  32 /  30  10  40  30
RDM  44  26  45  32 /  20  20  10  30
LGD  45  26  41  32 /  90  70  10  20
GCD  45  26  44  30 /  60  40  10  40
DLS  49  33  49  38 /  20  20  30  60

&&

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

$$

MORNING UPDATE...86
SHORT TERM...91
LONG TERM....74
AVIATION...85