Kennewick, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

935
FXUS66 KPDT 102205
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
205 PM PST Sun Nov 10 2024

.SHORT TERM...Tonight through Tuesday night...The main sensible
weather highlights in the short term include:
- First of consecutive upper troughs arrives overnight tonight
  ushering in light lowland rain and higher elevation mountain
  snow through Tuesday,
- Nuisance to minor impacts from snow confined to the higher
  elevations of the Cascades Monday-Monday night with snow levels
  falling from around 4.5-5 kft early Monday to 3.75-4.5 kft
  Tuesday morning, and
- Breezy winds daily with peak gusts more likely than not above 25
  mph across the lower elevations.

Latest water vapor imagery shows the passing shortwave trough
exiting far eastern OR with local radar depicting lingering
upslope showers across parts of the eastern mountains that has
has been tapering off over the last three hours. Farther
upstream, an upper-level closed low is positioned east of BC
south of the Gulf of Alaska with its attendant AR streaming
poleward into Vancouver Island and the PacNW coast. Latest MIMIC-
total precipitable water shows precipitable waters around 1-1.5
within the broad plume of moisture that is streaming northward.
The initial shortwave trough associated with this closed low will
move onshore overnight with a secondary embedded shortwave moving
into the PacNW late Monday. This upper-level closed low will
evolve and weaken into a longwave trough over the PacNW by Monday
then eject into MT and the Rockies Tuesday.

Overall, the systems northeastward moving moisture plume is quick
hitting with the ECMWF ensemble mean IVT forecast eclipsing the
90th percentile while it passes across eastern OR and south
central WA. The transient nature in tandem with limited residence
time and its pathway limits the potential for decent interior
rainfall and high elevation snow across the eastern mountain.
Meanwhile, the upper slopes of the Cascades and Cascade crests of
OR pose the greatest chance for accumulating snowfall. However,
confidence in snow greater than 6 is 60-70% over the tomorrow-
Tuesday period for the OR Cascades, including Santiam pass.
Confidence in a winter event is stymied given the modest QPF
probabilities of exceeding 1.5 or more over 48-hr at the OR
crest/Santiam pass with chances around 40-60%. Similar lower
chances for exceeding 0.75" and 1" exists over 24-hr periods too.
This discordance between QPF chance of exceedance and the forecast
QPF lowers our overall confidence in advisory-level snow across
the OR cascades, especially considering the nature of the moisture
plume. Elsewhere, chances for lowlands to see a wetting rain over
a tenth of an inch or more ranges 20-50% across the Lower Basin
by late Monday evening/06Z Tuesday. Higher chances for wetting
rain towards the foothills of the Northern Blues, and much higher
in the eastern Gorge (greater than 80%).

Meantime, a modest synoptically imposed pressure gradient will
develop Monday across Grande Ronde and foothills of the Blues.
This will promote light breezes with daily peak gusts peaking 25
mph or so (70-90% chance of exceedance). Continued modest low-
level flow in tandem with sufficiently mixed BL will support
additional potential for winds to mix down Tuesday with gusts more
likely than not peaking 25 mph or more (70-90%). Otherwise,
largely near average highs with readings few degrees above average
in the Lower Basin.

.LONG TERM...Wednesday through Sunday...Another upper low moves
into the region off the BC coast that will push a frontal system
toward the PacNW Wednesday into Thursday morning. This will bring
both precip and gusty winds. Thus another wet, windy period. Over
50% of the raw ensembles on Wednesday-Wednesday night favor total
QPF exceeding up 1" over the upper slopes of the WA/OR Cascades
and 30-50% for the Northern Blues. The lower elevations are
forecast to see about 0.2-0.50" (chance of wetting rain more than
60%). The precipitation amounts for Thursday are expected to
decrease to 0.25-0.50" over the mountain areas as the upper trough
elongates and weakens.

Wednesday`s snow levels will be 5 kft or above until steadily
decreasing Thursday onward to 4 kft, then trending lower in height
onward in time. There is a 40-60% of mountain snowfall
accumulating up to 6-8" over the Cascades Wednesday into Thursday
morning. As the system weakens Friday through Saturday, chances
of snow accumulation will then start dropping as we enter between
system. Sunday is when we will see mountain snow chances
increasing again due to the arrival of another system.

Else, gusty winds will be peaking 25-35 mph Wednesday. These winds
will develop over the foothills, the Gorge and high
terrain/exposed ridges of central OR (>50% prob). This is in part
due to the surface pressure gradients tightening while
southwesterly winds aloft increase as the system`s warm front
lifts north. Confidence in these winds is further increased owing
to the ECMWF extreme forecast index highlighting an unusual event
with values peaking around 0.6-0.8 for sustained winds. Thursday
morning winds will remain breezy but will begin simmering down
gradually Thursday afternoon with light winds then prevailing
through Saturday when the trough moves out of the area. Feaster/97

&&

.AVIATION...18Z TAFs...KPDT, KRDM, KBDN, and KALW will be in VFR
through this period whereas KDLS and KYKM varies between VFR and
MVFR. Right now, KPSC is IFR due to moderate fog/mist but may be
vary between MVFR and VFR as conditions improve. Localized fog will
continue as the frontal system moves across the area overnight,
which will bring more showers and potential breezy winds tonight
(>60% confidence). Though, KALW currently has ongoing rain but
simmers down around afternoon until this evening when the
aforementioned system passes through. Winds will be less than 12 kts
but might increase this evening with the system over the area.
Feaster/97

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  43  56  39  55 /  30  60  20  30
ALW  43  57  42  56 /  30  70  40  50
PSC  43  57  45  59 /  50  60  20  10
YKM  38  56  32  56 /  90  80  20  30
HRI  43  58  42  58 /  40  70  10  10
ELN  38  52  32  51 / 100  80  20  40
RDM  42  51  34  50 /  20  90  20  20
LGD  41  49  35  48 /  20  80  70  70
GCD  41  50  33  48 /  20  80  50  40
DLS  44  56  42  56 /  90 100  60  80

&&

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

$$

SHORT TERM...80
LONG TERM....97
AVIATION...97