Vancouver, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

225
FXUS66 KPQR 301108
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
308 AM PST Thu Jan 30 2025

&&

.SYNOPSIS...
Cloudy skies begin to move in over the coast and towards inland
as a low pressure system over the NE Pacific approaches,
pushing and weakening the Omega Block that has sat over the
region for many days. This low pressure system will bring
widespread rain and mountain snow late tonight. At the same
time, an incoming Alaskan low will continue to dig south along
the BC coast, eventually absorbing this NE Pacific low by
tomorrow. This Alaskan low will move south over Vancouver Island
BC through the weekend, continuing rain and snow over the
region. The Alaska low is expected to stall southwest of
Vancouver Island BC at the beginning of next week. Low-
elevation snow will be possible late this weekend and into the
start of next week, but there remains a lot of uncertainty as to
the exact timing and total amounts. At this time, if snow does
occur, impacts to roadways will be limited.

&&

.DISCUSSION...The Omega Block which has been the dominate
synoptic system begins to weaken and push eastward as a low
pressure system over the NE Pacific approaches the region.
Furthermore, an incoming cutoff Alaskan low digs southward along
the British Columbia coast, which will absorb this NE Pacific
low by tomorrow. This NE Pacific low will bring widespread
precipitation to the region late tonight into tomorrow, along
with heavy snow in the Cascades (above 3000 ft). Total snow
accumulations from tonight through Saturday afternoon will be
between 6 and 12 inches. For the lowland during this time,
expect widespread rain and possible rain/snow mix at times
during the early morning or late evening time frame. Given the
pattern, a Winter Storm Watch has been issued from Thursday
evening through at least Saturday afternoon. There still remains
some uncertainty in the exact timing and amounts.

Late Saturday/early Sunday, the digging Alaskan low begin to
stall just west of Vancouver Island and bring precipitation and
much cooler air to the region. Snow levels will drop Saturday
night into Sunday, from around 2000 ft to around 500 ft.
Specifically, snow levels will drop below 500 ft at times
through Sunday, except for the southern Willamette Valley which
will see snow levels between 500-1000 ft. With current models
suspecting 850 mb temperatures around -7 to -9 C through Sunday
and onshore flow expected, snow down to the valley floor is
possible. This pattern is generally showery and with temperatures
around -7 to -9 degrees Celsius, significant snowfall in the
lowlands is NOT expected. At most, the lowlands will likely see
wet snow or a rain/snow mix through this event. Looking at
Sunday and beyond, models still do not have much agreement, with
a spread of 5 to 7 degrees Sunday through Tuesday. Specifically,
the 10th-90th percentile spread gives -3 to -8 degrees Celsius
on Sunday and -3 to -10 on Monday and Tuesday. In short, some
models suggest snow at the valley floor and others do not.

Nonetheless, the deterministic NBM reflects the most likely
outcome well, with snow levels dipping to 200-500 feet Sunday
morning over southwest WA, the greater Portland/Vancouver metro,
Columbia River Gorge and Upper Hood River Valley. Deterministic
snow levels are nearly the same Monday morning and Tuesday
morning. However, the NBM 25th percentile for snow levels is
down to the valley floor across all of southwest WA and most of
northwest OR, further reflecting the ongoing uncertainty regarding
temps aloft and exact snow levels. Furthermore, uncertainty
remains for the location of the Alaskan low Sunday through
Tuesday, as it is expected to stall just southwest of Vancouver
Island BC, with variance of location and duration in most
models.

Again, there are currently no signs of a high impact snowstorm
as precipitation looks to be somewhat light and showery. The
latest NBM probabilistic guidance backs this up well, showing a
40-60% chance for at least 0.1" of snow each day, but only a
15-30% chance for at least 1" of snow each day, and around a 10%
chance for 2" of snow or more. Will need to monitor how these
probabilities change as we get closer to the event and
uncertainty decreases. Current trends support snowflakes in the
air at times, but with little to no accumulation, mainly on
grassy surfaces and elevated surfaces. In addition, the overall
pattern, as well as forecast LREF soundings, suggest rain, snow,
or a rain/snow mix being the predominant precipitation type
rather than freezing rain and/or sleet. While freezing rain
and/or sleet cannot be completely ruled out just yet, the chance
of these precipitation types occurring is less than 5-10%.
Despite little to potentially no snowfall accumulation on the
valley floor, there will most definitely be accumulating snow in
the Cascades and Coast Range. While snowfall amounts are not
overly significant, this will result in travel impacts for
anyone travelling over the Cascade passes or coastal mountains.
~Hall/TK


&&

.AVIATION...A ridge of high pressure will continue over the
region this morning, however, as it begins to shift eastward it
will allow for the development of light onshore flow. Looking at
satellite and surface observations early this morning, this weak
westerly surge has already translated to ongoing stratus and MVFR
CIGs across the coast, pushing inland through the Coast Range gaps
and up the lower Columbia River Valley. Slightly higher dewpoints
compared to last night may facilitate the development of
freezing fog approaching sunrise for some of more sheltered
sites, particularly KEUG. All in all, expect a period of
widespread sub-VFR conditions come Thursday mid-morning with some
clearing expected in the afternoon although confidence is low on
the exact timing for inland terminals. A system approaching the
region late Thursday into Friday will bring increasing rain
chances and additional sub-VFR conditions. Light rain starts at
the coast around 00-02z Fri.

PDX AND APPROACHES...VFR with clear skies and light winds are
expected through 14z this morning. IFR stratus near the
Kelso/Longview area may push towards the PDX terminal early
Thursday morning around 13-15z. Guidance supports (60-80% chance)
a period of MVFR CIGs Thursday morning before VFR cigs return
around 20z. It`s worth noting there will be around a 20-30%
chance for IFR conditions in this 14-20z time period as well. /DH

&&

.MARINE...Winds remain relatively light this morning but will
shift southerly and gradually increase today ahead of a frontal
system that is expected to move across the coastal waters later
today into Friday. Strongest winds are expected overnight through
early Friday morning, especially near the central Oregon coast
where this is high confidence for winds gusting up to 40 kt. Will
maintain the Gale Warning through Friday morning, though a few
models show gale force wind gusts possibly persisting into Friday
afternoon.

Seas also fairly calm around 4 to 5 ft this morning, continuing
through the afternoon. Then, predominately wind driven seas build
as southerly winds increase with the approaching frontal system
tonight. Steep and choppy seas expected to around 10 to 14 ft
through Friday.

Low pressure near Vancouver Island will maintain westerly onshore
flow Friday night through the weekend, along with a slight chance
for Thunderstorms Saturday morning. A northwesterly swell moves
into the coastal waters Friday night, maintaining elevated seas
through Saturday. Seas expected to gradually fall below 10 feet
by late Sunday. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Storm Watch from this evening through Saturday afternoon
     for ORZ126>128.

WA...Winter Storm Watch from this evening through Saturday afternoon
     for WAZ211.

PZ...Small Craft Advisory from 3 PM this afternoon to 10 PM PST this
     evening for PZZ210.

     Gale Warning from 10 PM this evening to 10 AM PST Friday for
     PZZ210.

     Small Craft Advisory from noon today to 8 PM PST this evening
     for PZZ251-271.

     Gale Warning from 8 PM this evening to 10 AM PST Friday for
     PZZ251-271.

     Small Craft Advisory from noon today to 6 PM PST this evening
     for PZZ252-272.

     Gale Warning from 6 PM this evening to 10 AM PST Friday for
     PZZ252-272.

     Small Craft Advisory from noon today to 4 PM PST this afternoon
     for PZZ253-273.

     Gale Warning from 4 PM this afternoon to 10 AM PST Friday for
     PZZ253-273.
&&

$$

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