Flood in Washington, January 11 to 12, 2022

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
924 PM PST Tue Jan 11 2022

.SYNOPSIS...Still have plenty of clouds streaming across region, as
warm front lifts northward today. Most of the rain will be focus over
western Washington, and far northwest corner of Oregon. Not much
change for Wed, with rain over western Washington and mostly dry over
western Oregon. Cold front will push onshore later Wed night and Thu,
with return of rain. High pressure builds over the region Friday into
the weekend, with dry weather.
&&

.SHORT TERM...Tonight through Friday...UPDATE: The main body of the
front has shifted northward, but a few shortwave troughs remain
passing along the frontal boundary. Each shortwave is enhancing the
already rainy front which has kept it nearly stationary over the
northern portions of the forecast area this evening. Even though it
is still raining, accumulations have been less with most locations
within the SW Washington counties seeing anywhere from 0.10-0.30
inches of rain. Some locations, especially those at higher
elevations of the Coast Range are seeing a bit more rain with closer
to 0.50 inches in the last three hours. However it appears that the
forecast area is on the downward trend in regards to rainfall
accumulations. The flood watch that was in place earlier this
afternoon has been cancelled due to rainfall diminishing and less
response from local area rivers. May still see some rises, however
rivers, like the Gray's River, are not forecast to reach flood stage
any longer. Previous discussion follows.                -Muessle

Not much change this afternoon, as warm front continues to lift
slowly northward across the region. Mostly dry to south of Portland,
with rain to the north. Rain mostly over western Washington, and
clipping far northwest corner of Oregon. This moisture plume,
atmospheric river, is becoming entrained into a baroclinic zone
ahead of a broad area of low pressure over the NE Pacific. While
heaviest rain will be focused on the Olympics, do have occasional
heavy rain over the Willapa Hills. Likely to see another 1 to 3
inches of rain through tonight before the axis of heavy rain lifts
bit more to the north. Will maintain Flood Watch for Pacific and
Wahkiakum counties for this rainfall and rising rivers.

Otherwise, looks like mostly dry conditions farther to the south over
northwest Oregon. Will hold onto modest PoPs (50-70 pct) for areas as
far south as a Tillamook-to-Portland line, with PoPs dropping
dramatically as move to the south. Will trend such that only have
some occasional sprinkles as move farther south, such as Eugene, into
this evening, but otherwise, dry for most of the region south of a
Newport to Salem line later tonight, there with patchy fog overnight.

Models continue to show a break across the region for Wed into Wed
night, as warm front sits well to the north of the area and the
approaching cold front is well offshore. With variable clouds, and
light south to southeast winds, overall MOS guidance with Wed high
temperatures in the lower to middle 50s looks reasonable.

Then, the low pres offshore will push into the Pac NW later Wed night
and Thu, with cold front pushing onshore late Wed night into very
early Thu am. System is moving fast enough that, even with decent
shot of rain, would not expect enough to create flooding issues. Some
indication system will have tight enough pressure gradient to pop 35
to 50 mph wind gusts along the coast, mainly south of Astoria. But,
some question on that, as GFS and ECMWF differ on where the low comes
onshore, and subsequent gradients. Will keep with blend, showing
breezy conditions along coast, mainly in the morning to early
afternoon. Otherwise, seems like typical January front. Snow levels
will tumble, from 7000 feet today to 4500 feet on Thu. Favorable
orographic flow will likely result in locally enhanced snowfall over
the Cascades. For now, seems 8 to 12 inches of snow looks reasonable
for later Wed night and Thu.

High pressure will build across region Thu night into Friday, with
drier weather and seasonable temperatures.	      /Rockey

.LONG TERM...SATURDAY THROUGH MONDAY...No changes. High pres will
remain over the region through the coming weekend, keeping region
dry. Warmer daytime temperatures are in store but with clearing skies
during the day, low temperatures likely will dip down quite a bit
lower than what occurred earlier in the week. Low temperatures
will sit in the mid 30s within the Willamette Valley with cooler
lows to the east. There is a chance though that temperatures could be
impacted within the southern Willamette Valley as there is always a
chance for denser fog to form in this high following a low pressure
scenarios. Far too far into the future to determine this specific
feature though. 			     /Muessle

&&

.AVIATION...06Z TAFs: Heavier rain continues to impact sites
further north into western WA, although AST still receiving plenty
of rain as well as gusty winds. Light spotty rain may still occur
down to Newport, but it's looking far less widespread and long
lasting at this time. Will limit it as prevailing in the forecast
package, as well as improve the ceilings, improving ti VFR by early
morning. Southerly winds will be slow to recede as the gradient will
remain tight, but overall expect a downward trend in speeds through
the forecast period. For inland sites, expect VFR conditions, except
for a brief period of MVFR ceilings possible around 12Z. Still
looking at fog or low stratus potential to be found in the central
to southern Willamette Valley, however the potential is decreasing.
Looking upstream, the high clouds do seem like they may remain thick
enough, and latest HREF guidance shows the high and mid layer clouds
thick enough with no low layer clouds expected. There is even zero
percent chance of a cloud deck lower than 2000ft AGL, but a 10-20%
chance of less than 3000 feet. With no signs of fog on the RAP or
HRRR, but some hints of lower ceilings still remaining on the latest
MOS guidance, will keep some lower ceilings, but no fog or BR.

For detailed regional Pac NW aviation weather information, go online
to: https://weather.gov/zse

KPDX AND APPROACHES...VFR conditions expected to prevail next 24
hours, however there may be a brief period of ceilings down to near
2500 ft AGL near 12Z. East wind 10 to 15 kt in the area, but local
gusts to 25 kt possible KTTD into the Gorge. Skies should break up
to scattered tomorrow afternoon. /Kriederman

&&

.MARINE...Winds over the outer northern waters, and most of the
coastal waters have dropped below Gale strength, however just along
the coast, they are remaining in the 35-40 kt range, mainly near the
mouth of the Columbia River. Viewing high resolution guidance, seems
like these higher speeds will last another 2 to 3 hours in this
area, so will extend the Gale Warning until 1 AM PST. Otherwise, the
weakening but present pressure gradient will support Small Craft
Advisory winds through Thursday. Winds may reach gale force on
Thursday as a low approaches the waters Thursday morning, but model
ensembles are showing weaker winds for Thursday compared to today's
Gale event, so forecast confidence still is not very high for gales
at this time. Seas 14-17 feet this evening, but will subside late
tonight to around 12-14 feet Wednesday.

High pressure is expected to build over the coastal and offshore
waters on Thursday before strengthening on Friday. This will bring a
period of quieter conditions heading into the weekend.
-TK/Kriederman

BEACH HAZARDS...Westerly swell arriving at the coast with a dominant
period around 15 to 16 seconds. This is enough for a threat of
sneaker waves along our beaches through tonight. The chances for
sneaker waves diminish Wednesday.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 4 PM PST Thursday for Coastal waters
     from Cascade Head to Florence OR out 10 nm-coastal waters from
     Cape Shoalwater WA to Florence OR from 10 to 60 nm.

     Gale Warning until 1 AM PST Wednesday for Coastal waters from
     Cape Shoalwater WA to Cascade Head OR out 10 nm.

     Small Craft Advisory until 4 AM PST Thursday for Columbia River
     Bar.

&&

www.weather.gov/portland

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