NWS Portland, OR wrote its last area forecast discussion before the first event at Feb 23, 2:58 PM PST, 1 hour 2 minutes earlier.
Area forecast discussion, Feb 23, 2:58 PM PST, 1 hour 2 minutes before
Area Forecast Discussion
National Weather Service Portland OR
258 PM PST Sat Feb 23 2019
.SYNOPSIS...Cool air mass remains over the region tonight into most
of next week. A series of weather systems will push inland over
Oregon, with continue precipitation at times. Snow levels remain low,
with highest chance of lowland accumulations being later Sun night
into Mon. But, will be a LOT of snow for the the Cascades.
&&
.SHORT TERM...Tonight through Monday...Rather impressive upper trough
now digging into the Pac NW from the northwest today. Orientation at
moment such that has good westerly flow into Oregon tonight into Sun.
This flow such that will maintain showers over much of the region
this evening. An embedded weather disturbance in the flow will push
inland over Oregon later tonight into Sunday. This will allow for
rain to increasing tonight, with snow at/above about 1000 to 1500
feet. Will maintain snow advisories for areas inland above 1500 feet
tonight into Sun am, most of the Hood River Valley, and the Columbia
River Gorge down to river level.
Once that system passes on to the east Sunday morning, precipitation
will decrease over the northern zones. However, front boundary will
still be sitting over southwestern Oregon into central Oregon. This
will be problematic for Sunday night as the next system approaches.
Both GFS and NAM runs from this am seem to be in fair agreement that
the low will be pushing onshore over the south Oregon coast Mon am.
With that in mind, seems bulk of the precipitation will be shunted
bit to the south from what was earlier thought, with much less
precipitation over southwest Washington. In fact, if trend
continues, would not surprise if get any precipitation from Astoria
north.
But, air mass is still quite cool, and still think will have snow
levels lowering to below 500 feet at times later Sun night into Mon
am, especially inland as far south as Salem. So, will see rain
initially, then transition to rain or snow after midnight and
continuing into Mon am. With track of the low, could see rain/snow
line sink a bit farther south, perhaps down to Eugene Mon am. But
for now, and with uncertainty in models, will keep that line near
Albany.
Have eased back a touch on snow accumulations, as this will be
heavier wet snow, with rather high water content. Generally, 1 to 3
inches for interior lowlands later Sun night through Mon am, though
will see bit heavier amounts closer to the Coast Range, and on the
higher hills between Kelso and Salem. Will make no changes to
current winter weather watches and warnings, though may decrease
snow totals a tad. But, as always, this will reflect current
expectations, which could change as we draw closer in time.
Rather messy in the Columbia Gorge and Hood River Valley, where snow
will continue at times into Tue. But, with a touch of warm air aloft
arriving, will see some freezing rain at times later Mon afternoon
through Tue, mainly in the western Columbia Gorge. Have adjusted
forecast to show such, with ice accumulation of less than a quarter
of an inch. This will maintain hazardous travel conditions into Tue.
Front will gradually shift on the east Mon night, with showers on
tap. Showers may decrease later Mon night, but will pick up again on
Tue. But by that time, snow levels will be higher, running around
1000 feet in the north, to around 2000 feet over Lane County.
Winning ticket will still be in the higher terrain, where several
feet of snow will occur across the Cascades and foothills, with 2 to
4 feet of snow likely above 3000 feet. But, with tracking of the
lows bit more to the south, think that so will be the heavier
precipitation. That in mind, any flooding potential will be limited
to ponding of water, and quick rising smaller streams. But, main
rivers will stay well below flood stage. Rockey.
.LONG TERM...Monday night through Friday...No changes...Previous
discussion from Friday afternoon follows...The forecast for the
remainder of the upcoming week remains complicated due to
significant model differences so will continue to use a blend of
models rather than a single deterministic model. The general trend
is for the active weather pattern to continue through the week as
additional disturbances moves approach the region. Will continue to
see a potential for low elevation snow the the middle of the week,
but snow levels look to rise about 2000 feet for the second half of
the week. /64
&&
.AVIATION...Showery pattern continues this afternoon with a mix
of mainly MVFR and VFR conditions. Expect this mix to continue, with
trends more toward MVFR into the evening. A weak low pressure system
is expected to form along the stalled cold frontal boundary offshore
and move onshore along the central Oregon coast tonight, resulting
in steadier rain and even more likely MVFR CIGs from around KSLE
southward. Expect conditions will remain MVFR through the day
Sunday, with occasional drops to IFR.
KPDX AND APPROACHES...MVFR CIG with occasional VFR through the
evening, but trending MVFR overnight and through the day Sunday with
rain becoming more stratiform. Winds turn out of the east Sunday
afternoon. Bowen
&&
.MARINE...Relatively light northwest winds remain across the
waters through the day today. Forecast models suggest that a weak
low will form along the stalled cold frontal boundary, and ride
along the boundary until it pushes onshore somewhere near Florence
late Saturday night. Expect southerly winds to increase on the south
side of this low, reaching gusts of 25 to 35 kt. How far north these
winds impact will depend on the exact track of the low. Winds will
be out of the N-NE and much lighter on the north side of the low.
A stronger low is expected to form along the quasi-stationary
frontal boundary on Sunday into Monday. At this point it looks most
likely make landfall somewhere along the southern Oregon coast,
keeping stronger winds south of the local waters. Areas to the south
of the low look to have a good chance to see gale force winds late
Sunday night into Monday morning, potentially some high end gales.
To the north of the low center, and the most likely scenario for the
local waters, winds will be offshore and will potentially gust to 25
kt. Active weather looks to continue next week, but forecast details
are highly uncertain at this time.
Seas have built to 10 to 11 ft this afternoon, but should lower to
below 10 ft early this evening. Whether or not seas come back up to
10 ft or higher in the next 48 hours will depend on the tracks of
the two aforementioned lows, but overall, the swell looks pretty
small, so it would take a significant wind wave to bring seas back
up that high after tonight. Bowen
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 8 PM tonight to 11 AM Sunday
for... Central Columbia River Gorge
Western Columbia River Gorge
Upper Hood River Valley.
Winter Storm Warning until 10 AM PST Monday
for... Cascades in Lane County.
Winter Storm Warning from tonight through Sun afternoon
for... Northern Oregon Cascade Foothills
Northern Oregon Cascades.
Winter Storm Watch late Sun night through late Mon night
for... Central Columbia River Gorge
Western Columbia River Gorge
Upper Hood River Valley.
Winter Storm Watch Sun night through late Mon night
for... Northern Oregon Cascade Foothills
Northern Oregon Cascades.
Winter Storm Watch late Sun night through Mon afternoon
for... Central Willamette Valley
Coast Range of Northwest Oregon
Greater Portland Metro Area
North Oregon Coast
Lower Columbia.
WA...Winter Weather Advisory from 8 pm tonight to 11 am Sunday
for... Central Columbia River Gorge
Western Columbia River Gorge.
Winter Storm Watch late Sun night through late Mon night
for... Central Columbia River Gorge
Western Columbia River Gorge.
Winter Storm Watch late Sun night through Mon afternoon
for... Greater Vancouver Area
I-5 Corridor in Cowlitz County.
Winter Storm Watch late Sun night through Mon evening
for... South Washington Cascade Foothills
South Washington Cascades.
PZ...Small Craft Advisory for hazardous seas until 6 PM PST this
evening for Coastal Waters from Cape Shoalwater WA to
Florence OR out 60 NM.
Small Craft Advisory for Rough Columbia River Bar from 5 PM
this afternoon to 11 PM PST this evening.
&&
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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the forecast area.