NWS Portland, OR wrote its last area forecast discussion before the first event at Jan 6, 4:37 AM PST, 2 hours 3 minutes earlier.
Area forecast discussion, Jan 6, 4:37 AM PST, 2 hours 3 minutes before
Area Forecast Discussion
National Weather Service Portland OR
437 AM PST Thu Jan 6 2022
.SYNOPSIS...Steady rain continues today with the axis of heavier rain
over western Washington. Will see snow level above the passes today,
then lower Friday. A strong low pressure area well offshore will
push into northwest Oregon early Friday, bringing windy conditions to
the coast and parts of the interior. As this low pushes inland, will
see heavy rain shift south and east Friday. High pressure will bring
dry but cool weather for Saturday and Sunday, that could last into
early next week.
&&
.SHORT TERM...Today through Saturday...A warm front took a little
longer to lift north of the area overnight with the rise in snow
level delayed as well. Snow levels are now above pass levels with in
the north Oregon Cascades so will end the winter weather advisory
there. Snow level over the south WA Cascades are mostly over the
highest peaks, but the eastern half of the zones still near freezing.
Radar indicating probably a mix of snow, sleet, freezing rain
occurring there, so will keep the winter weather advisory going
through midday (though conditions will probably warm sooner.) The
central Gorge and upper Hood River valley likely also in the
transition from snow to freezing rain and sleet this morning. Will
extend the winter weather advisory through noon. By then stronger
westerly flow across the mountains should develop a lee side surface
low on the east slopes to finally pull the cold air out of the area.
Latest model trends brings a deepening low pres off the Pacific and
into western Oregon later tonight into Fri. Appears that gusty south
winds of 55 to 65 mph are likely along the coast and coast range
later tonight and Friday morning. A little more uncertain is winds
for the interior valley, but looks like south winds gusting 40 to 50
mph is possible Friday morning, especially Salem southward.
As the low shifts inland, it will pull a cold front onshore. This
will bring the heavier rain (over far nw Oregon/sw Washington) back
southward late Thu night into Fri am. So, not only will it breezy,
but also rather wet. Once front pushes across region, rain will ease.
Snow levels tumble in the afternoon behind the front, from 5000 to
6000 feet early down to 2000 to 2500 ft by late Fri afternoon.
Orographics remain favorable for the Cascades Fri and Fri night so
may need a winter weather advisory there.
High pressure builds across later Fri night into Sat, with drying
trend. Snow levels stay in the 1500 to 2500 feet range, but not much
more in accumulations likely. After a few showers, should be rather
nice day on Saturday though on cool side. A welcome break after a
very wet week. /mh /Rockey
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...Models in good
agreement of drying trend this weekend. Deterministic models show an
upper level ridge building over the Pacific Northwest through Sunday.
WPC cluster analysis also shows a strong signal of this upper level
ridge extending northward into western Canada, then shifting east
across the intermountain west on Monday. With high pressure building
east of the Cascades and low pressure well offshore, expect offshore
flow into early next week. Partly cloudy skies Saturday night and
overnight temperatures falling, expect a chilly Sunday morning with
temperatures near freezing. Daytime temps on Sunday should warm into
the mid to upper 40s and provide another day to dry out. Areas where
the sun is able to shine will likely see warmer temps, while fog or
some low stratus in the valley may keep temps slightly cooler.
Models show an upper shortwave trough lifting northeast across the
NE Pacific on Monday. The main difference between long range models
is how far north the shortwave moves that will determine if the dry
weather continues next week or if some light rain returns during
parts of next week. The GFS and its ensemble indicate better chances
for dry weather to persist, while many of the ECMWF Ensemble members
suggest better chances for wet weather, but not heavy rain. Will
keep a chance of rain over much of the forecast area per the NBM for
Monday through Wednesday. Temperatures will generally be normal for
this time of year with snow levels around 4000 feet on Monday
gradually lifting to over 5000 ft by the middle of next week. /DH
&&
.HYDROLOGIC...The axis of heavier rain will stay nearly stationary
across southwestern Washington back over far northwest Oregon.
Current QPF guidance indicates this morning will see the heavier rain
across the Willapa Hills into the south WA Cascades with some bleed
over to the north Oregon coast. IVT values from ECS & GEFS support
this with IVT values peaking around 750 kg/m/s this morning. Rain
rates taper some this afternoon and this evening a the focus shifts
further north over western WA. Rain amounts taper off quickly south
of Salem.
So, we have a FLOOD WATCH and a FLOOD ADVISORY up. What are these?
First, the FLOOD WATCH. This is mainly for all the larger rivers,
indicating that there is potential for some rivers to reach flood
stage. It is not a given this will happen, but bears watching - hence
FLOOD WATCH. All in all, this rain, combined with the snowmelt from
the coastal mtns and to some degree, the lower slopes of the
Cascades, will push many rivers upward, some potentially reaching
near flood stage. Highest potential of flooding will be those rivers
over southwest Washington, as well as those draining the north Coast
Range of Oregon. This includes the Grays, Naselle, Willapa, Wilson,
Nehalem, Trask and the Tualatin River.
Other rivers such as the Cowlitz could reach close to flood stage by
Friday morning. So, will maintain current Flood Watch for all of the
region through Friday.
Now, the FLOOD ADVISORY is for all those small streams, creeks,
gullies and ditches, Lots of rain, enough to maintain these will be
running full, with minor flooding expected along these streams and
creeks. This is NOT for the big rivers, rather for small stuff. In
addition, areas with poor drainage will also experience minor
flooding. As such, have issued an Flood Advisory for Small Streams,
in effect for today through Friday. /Rockey
&&
.AVIATION...12Z TAFs: Warm front continues to lift northeastward
across the area, with the gradients changing enough for southerly
winds to overpower the east winds flowing out of the Columbia
Gorge. With southerly winds, the southern and central Willamette
Valley is improving quicker than what model guidance shows, and
terminals will be in the MVFR to VFR with only scattered to
isolated showers. Otherwise, all other terminals will be solidly
in the MVFR conditions, though the coastal sites should remain in
IFR/LIFR, with some improvement later today. The bulk of the
heavier rain is lifting north, but the backside of the system
will swing back down late tonight, which may result in a slight
deterioration of ceilings and visibility, mainly after 09z.
In terms of winds, expect gusts of 40 to 50 kts along the coast
mainly 03-09z, with gusts up to 35 kts possible in the central
Willamette Valley towards 12z and thereafter.
For detailed regional Pac NW aviation weather information, go online
to: https://weather.gov/zse
KPDX AND APPROACHES...Winds should now stay southerly for the
rest of the day, however approaches from TTD may still stay some
easterly direction for the next hour or two. Expect MVFR
conditions to gradually start improving to VFR after about 00z,
though model guidance has been delaying this improvement, so
confidence is still not high on this. Also expect periods of rain all
day, likely increasing late tonight as another system pushes in,
which will increase southerly winds closer to near 12z. /Kriederman
&&
.MARINE...Gale Force winds will spread through the waters this
morning as a frontal system has lifted northeastward. Another
reinforcing low over the northeast Pacific will move towards the
region tonight, to move into the Washington coast around
midnight. This will increase the southerly winds even more, and
with all mean ensemble guidance showing this 50 kts being met,
went ahead and upgraded the Storm Watch to a Storm Warning. Gusts
of near 50 kts are expected to develop in the central waters and
up the inner coastal waters as a coastal jet. This should result
in seas climbing into the low to mid teens today, then increase
possibly to near 20 feet during the peak winds early Friday
morning. The cold front will then push in quickly mid-Friday
morning with decreasing speeds and seas to follow. Seas should
more or less linger in the teens for the rest of Friday, then
decrease even more as an upper ridge moves over the area for the
weekend. Seas to drop below 10 ft early Saturday and may dip
below 5 ft by late Sunday. /Kriederman
BEACH HAZARDS...Higher than normal river levels and high tides
will result in some minor tidal overflow flooding this afternoon
and again early Friday morning. The Astoria and Toke Point
gauges are anticipated to reach near 11 ft during both high
tides, which coupled with rivers likely to be approaching minor
flood stage will result in lots of water backing up in bays,
estuaries in and around Willapa and Tillamook Bay. Other areas
like the lower Necanicum River around Seaside could result in
some flooding of low lying areas as well. The bulk of the waves
with the upcoming storm system will be wind driven and primarily
out of the south so we are not expecting any elevated sneaker
wave threat or the need to issue any High Surf products. /Neuman
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Flood Watch through Friday afternoon for Cascade Foothills in
Lane County-Cascades in Lane County-Central Coast Range of
Western Oregon-Central Columbia River Gorge-Central Oregon
Coast-Central Willamette Valley-Coast Range of Northwest
Oregon-Greater Portland Metro Area-Lower Columbia-North
Oregon Coast-Northern Oregon Cascade Foothills-Northern
Oregon Cascades-South Willamette Valley-Upper Hood River
Valley-Western Columbia River Gorge.
Winter Weather Advisory until noon PST today for Central
Columbia River Gorge-Upper Hood River Valley.
High Wind Warning from 7 PM this evening to 10 AM PST Friday
for Central Coast Range of Western Oregon-Central Oregon
Coast-Coast Range of Northwest Oregon-North Oregon Coast.
Coastal Flood Advisory from 1 PM this afternoon to 7 PM PST
this evening for North Oregon Coast.
Coastal Flood Advisory from 1 AM to 8 AM PST Friday for North
Oregon Coast.
WA...Flood Watch through Friday afternoon for Central Columbia River
Gorge-Greater Vancouver Area-I-5 Corridor in Cowlitz
County-South Washington Cascade Foothills-South Washington
Cascades-South Washington Coast-Western Columbia River
Gorge-Willapa Hills.
Winter Weather Advisory until noon PST today for Central
Columbia River Gorge-South Washington Cascades.
High Wind Warning from 7 PM this evening to 10 AM PST Friday
for South Washington Coast.
Coastal Flood Advisory from 1 PM this afternoon to 7 PM PST
this evening for South Washington Coast.
Coastal Flood Advisory from 1 AM to 8 AM PST Friday for South
Washington Coast.
PZ...Gale Warning until 10 AM PST Friday for Waters from Cape
Shoalwater WA to Cascade Head OR from 10 to 60 nm.
Storm Warning from 9 PM this evening to 7 AM PST Friday for
Coastal waters from Cape Shoalwater WA to Cascade Head OR
out 10 nm-coastal waters from Cascade Head OR to Florence
OR out 60 nm.
Gale Warning until 9 PM PST this evening for Coastal waters
from Cape Shoalwater WA to Cascade Head OR out 10 nm-
coastal waters from Cascade Head OR to Florence OR out 60
nm.
Small Craft Advisory until 10 AM PST Friday for Columbia River
Bar.
&&
www.weather.gov/portland
Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland