Yakima, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

442
FXUS66 KPDT 040530
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
930 PM PST Tue Dec 3 2024

Updated aviation discussion

.Update...Forecast was updated to include the John Day Valley in the
Freezing Fog Advisory.

.SHORT TERM...Today through Thursday...The Freezing Fog Advisory
remains in effect through 11 AM PST tomorrow for portions of the
Foothills of the Southern Blues, north central and central OR due
to visibility falling to one mile or less from the freezing fog.

Based on current radar and satellite imagery, the low stratus
layer remains over the Columbia Basin, valley zones extending down
to central OR. Freezing fog will continue over north central and
central OR with patchy fog at portions of the Foothills of the
Southern Blues. Visibilities may still drop to one mile or less
for the aforementioned areas. Thursday morning, an approaching
shortwave trough will bring showers at the WA/OR Cascades and
continue lingering over mainly WA Cascades Thursday night (<25%
chance). And with the upper ridge returning, patchy fog will then
redevelop into Friday morning.

High temperatures will range between mid 30s and 40s at the Columbia
Basin and 40s and 50s across the Blues. The low stratus layer will
keep the temps cooler for the Columbia Basin, but not much for the
Blues with cloud coverage decreasing thus allowing more radiation
to warm the temps. Feaster/97

.LONG TERM...Friday through Tuesday...Models are still trying to
refine some details in the long term forecast, but the overall
picture looks to be that of widespread rain and high mountain snow
over the weekend, followed by a colder pattern moving in for next
week. Ensembles diverge a bit Monday and beyond, but confidence in
the forecast this weekend is starting to become relatively high (60-
70%).

On Friday, we get some transitory ridging overhead after the passage
of a weak shortwave. This ridge may be a bit dirty in nature, as
models depict PoPs in the 30-40% range across the central WA
Cascades as this ridge picks up on some SW moisture. Not expecting
any meaningful moisture on Friday, however, as a more organized
system in the form of a broad low pressure system sweeps through the
forecast area over the weekend, with its associated moisture
occurring primarily between late Saturday morning and early Sunday
morning. This system is broad enough in scope to produce rain across
much of the forecast area, with snow occurring mainly in elevations
above 4000-5000 feet. Snow levels will drop steadily over the
weekend, decreasing down around the 3000-4000 feet range by Sunday
afternoon, but by then, cold, drier air will start to filter in, and
only light orographic precip looks to occur after the passage of the
low.

One complicating factor in the forecast is the ongoing stratus deck
across the lower elevations. Am wondering if models are being a bit
overzealous with snow levels Friday into the weekend across the
lower elevations, as Thursday`s system has trended weaker and
weaker, so am not expecting widespread mixing out of the stratus
deck until the weekend, when winds pick up with the passage of the
low. How much this will impact precip type over the weekend is
uncertain, but will hold off on messaging these complications too
much until higher-res guidance comes in. Still, something to keep in
mind in the coming days.

Guidance seems to trend toward that of dry, northerly flow Monday
onward next week, which may bring about a cold air outbreak, however
ensemble clustering does show model discrepancies that come in the
form of where the flow aloft is oriented after the weekend low
passes through, and whether or not it is more due north,
northwesterly, or if ridging moves in over the PacNW. Either way,
the biggest precip concerns look to occur over the weekend, but with
snow levels expected to climb across the mountains, expectation is
that the mountain passes will see only light snowfall at best over
the period. Evans/74

&&

.AVIATION...06z TAFs...Low stratus and fog continue to plague all
TAF sites, with little change in the forecast expected over the next
24 hours with MVFR conditions mainly due to low ceilings. The only
sites expected to see variable conditions are BDN and RDM. Both
sites are expected to see LIFR conditions through Wednesday morning
then some improvement during the day.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  28  32  27  37 /   0   0   0   0
ALW  30  33  29  38 /   0   0   0   0
PSC  33  35  32  35 /   0   0   0   0
YKM  28  32  26  36 /   0   0   0   0
HRI  33  37  30  36 /   0   0   0   0
ELN  25  32  25  38 /   0   0   0   0
RDM  16  40  19  43 /   0   0   0   0
LGD  27  44  25  47 /   0   0   0   0
GCD  29  47  26  50 /   0   0   0   0
DLS  33  35  31  42 /   0   0  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freezing Fog Advisory until 11 AM PST Wednesday for ORZ508-510-
     511.

WA...None.
&&

$$

SHORT TERM...97
LONG TERM....74
AVIATION...74