High Wind in Oregon, December 19 to 20, 2019

Area Forecast Discussion
National Weather Service Portland OR
1023 AM PST Thu Dec 19 2019

.SYNOPSIS...A warm front will lift north into Washington this
afternoon, bringing a continuation of rain, while snow in the
Cascades switches over to rain at the late today. A front stalled
over the region tonight through Friday night will bring a prolonged
period of rain and a threat for flooding, before the front moves
through to the east Saturday and Saturday night. In addition, the
beaches can expect strong winds and a potentially dangerous surf
zone tonight and Friday. Showers will decrease on Sunday followed by
a dry start for next week.

&&

.UPDATE...As the next round of rain moves back into the region this
morning and is likely to continue into the afternoon, temperatures
in the central Columbia River Gorge and Upper Hood River Valley have
only crept slowly upward this morning, lingering just a little below
freezing below 2500 ft. Until the warm front lifts north, which most
models suggest is around mid afternoon, a light easterly drift
appears likely to limit the potential for temperatures to rise much
through the first half of the afternoon. As such, the rain moving in
looks likely to continue as freezing rain until temperatures climb
above freezing later in the afternoon.

.SHORT TERM...Originally from 418 AM...Today through Sunday...An
occluded front is producing rain and Cascade snow this morning. Light
east winds has maintained freezing temperatures in the Central
Columbia Gorge where there is a mix of snow and freezing rain.
Temperatures are slowly moderating in the Gorge, but think the
potential for mixed precipitation continues through at least 7 AM,
and have maintained the current timing of the winter weather advisory
for the Gorge. Colder temperatures are holding in the Upper Hood
River Valley where the Ice Storm Warning holds. The temperatures will
be slower to moderate in this somewhat protected valley. Snow levels
have risen to 4000-4500 feet this morning.

Precipitation rates have let up a bit early this morning, but they
will increase again later this morning as a shortwave trough will
move over NW Oregon. Heavy rain and Cascade snow will then persist
through late this afternoon. The snow levels will be rising
throughout the day and are expected to be around 6500 feet late this
afternoon. The precipitation rates lighten up across Lane County this
evening as the front lifts north. However, heavy rain will remain
across SW Washington and the north Oregon coast tonight through
Friday morning as a very moist front stalls over western Washington.

This front will shift a little south on Friday with the axis of heavy
rain extending from the central Oregon coast and coast range to the
south Washington Cascades. The front will then lift north Friday
afternoon as it pivots to a more northerly orientation over the coast
by Friday evening. The latest models suggest that the inland areas of
Lane county may be spared from the heavy rain on Friday, but the
Oregon coast and coast range and parts of SW Washington will continue
to have periods of heavy rain. The rain becomes more widespread
across the region on Saturday as the front begins moving inland, but
the heaviest rain will move into SW Oregon at this point, and the
rain rates across the Portland forecast area will lighten up.

This front will support strong winds this afternoon through Friday
afternoon, especially along the coast where a High Wind Warning has
been issued for the beaches and headlands. Winds will be gusty at the
higher elevations of the coast range and the Cascades tonight through
Friday morning, but are not expected to reach warning criteria. Gusts
of 35 to 40 mph are possible in the Willamette Valley as well.
Saturated soils from all of the rain may make it easier for weakened
trees to fall with these winds.

The front moves east of the Cascades Saturday night. Colder air
behind the front will allow snow levels to lower down to the Cascade
passes Saturday night and Sunday. Diffluent flow aloft ahead of an
approaching low will support rain and Cascade snow showers across the
area on Sunday. Models do not have a great handle on this low yet,
but there is some potential for convection and breezy winds in some
of the model solutions. Have not bit off on these stronger solutions
yet, as there is still a lot that needs to be figured out with the
shortwaves moving along the current frontal system first.

Rain totals expected from this morning through Sunday are: 5 to 7
inches for the coast, 5 to 10 inches for the coast range, and the SW
Washington Cascades, 2 to 4 inches for the Willamette Valley and the
Oregon Cascade foothills. Mainstem River flooding, small stream
flooding, urban flooding, and land debris slides are all possible
hydrological impacts from this prolonged period of heavy rain. A
Flood Watch is in effect for much of the Portland forecast area.

Finally, a high energy ocean swell will enhance the threat for
sneaker waves Friday night through Saturday posing another
potential beach hazard. Anyone planning on visiting the beach on this
rainy Saturday should remain far from the tidal edge as water could
suddenly rush further up the beach than expected. ~TJ

.LONG TERM...Sunday night through Wednesday...No changes. Previous
discussion follows. As the upper low possibly closes off and shifts
south into California Sunday night, we'll likely see some ridging
Monday and Tuesday for a possible break from the wet weather. The
overall weather pattern will remain progressive though, and there
will be threats for rain at times next week.

&&

.AVIATION...Moist west to southwest flow aloft through Thursday.
Widespread MVFR conditions through Thursday morning. There is
also patchy IFR/LIFR conditions within the central Willamette
Valley. A warm front will lift north across the region bringing
precipitation to the area, which can be heavy at times from early
Thursday morning through the afternoon. Expect widespread MVFR
through Thursday, with pockets of IFR in heavier rain and
clouds.

Expect increasing southerly winds behind the front. Winds will be
highest along the coast and higher terrain, gusts of 35 to 45
kt are possible. With temperatures below freezing, expect
freezing rain and snow in Hood River Valley through Thursday
morning, and even possibly close to Columbia River.

KPDX AND APPROACHES...MVFR conditions through tonight and
Thursday,with rain at times. East winds will continue at 10 to
14 kt through Thursday. Brief IFR conditions are possible
Thursday if heavier rain moves over the terminal. /42

&&

.MARINE...No changes. Previous discussion follows. Southerly winds
10 to 20 kt on the waters through Thursday, with seas running around
11 to 14 feet, with higher seas beyond 30nm. Currently, a Small
Craft Advisory is in effect through Thursday morning.

A Gale Warning has been issued for all of our waters starting
midday Thursday, as a developing low pressure well offshore
pulls a warm front north across the region. As a result expect
southerly winds to pick up rather quickly as the front moves from
south to north. Winds generally 15 to 20 kt Thursday morning,
but behind the front, winds are expected to increase to 30 to 35
kt with gusts 40 to 50 kt through the afternoon. Expect choppy
wind waves to build quickly, with overall seas around 17 to 20
feet towards late Thursday afternoon, and seas building to above
20 feet by Thursday night then starting to subside below 20 feet
by Friday morning.

A trailing cold front will slowly approach the coast Thursday
night, and looks to become almost stationary over the coastal
waters Friday into early Saturday. A moderately strong gradient
will still remain over most of our waters, therefore have
extended the Gale Warning for zones PZZ275 and PZZ255 through
Friday night, with gusts 40 to 45 kt expected. Model guidance is
suggesting that zones PZZ270 and PZZ250 might have a period of
non Gale winds, but expect seas to remain around 15 to 17 feet
during this time. Seas will continue to pick up, as a westerly
swell from the Gulf of Alaska will reach the coast during this
time. Which will cause the seas in zones PZZ275 and PZZ255, to
build towards 20 to 25 ft Thursday night and Friday.

May have enhanced sneaker wave conditions Friday and Saturday,
owing to the longer period westerly swell.

The cold front finally shifts south of the area late Friday and
Saturday, with south to southwest winds running 20 to 25 kt. But,
still have seas in 15 to 20 ft range. More tranquil weather is
expected for early next week, with seas subsiding back closer to
10 ft, and winds mostly 10 to 15 kt. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Ice Storm Warning until 10 AM PST this morning for Upper Hood
     River Valley.

     Flood Watch from this evening through Sunday morning for
     Central Coast Range of Western Oregon-Central Oregon Coast-
     Central Willamette Valley-Coast Range of Northwest Oregon-
     Greater Portland Metro Area-Lower Columbia-North Oregon
     Coast-Northern Oregon Cascade Foothills-South Willamette
     Valley-Western Columbia River Gorge.

     Winter Weather Advisory until 7 AM PST this morning for Central
     Columbia River Gorge.

     Winter Storm Warning until 4 PM PST this afternoon for Cascades
     in Lane County-Northern Oregon Cascades.

     High Wind Warning from 4 PM this afternoon to 4 PM PST Friday
     for Central Oregon Coast-North Oregon Coast.

WA...Flood Watch from this evening through Sunday morning for
     Greater Vancouver Area-I-5 Corridor in Cowlitz County-
     South Washington Cascade Foothills-South Washington Coast-
     Western Columbia River Gorge-Willapa Hills.

     Winter Weather Advisory until 7 AM PST this morning for Central
     Columbia River Gorge.

     High Wind Warning from 4 PM this afternoon to 8 AM PST Friday
     for South Washington Coast.

     Winter Storm Warning until 10 PM PST Friday for South
     Washington Cascades.

PZ...Gale Watch from Friday evening through late Friday night for
     coastal waters from Cape Shoalwater WA to Cascade Head OR
     out 60 NM.

     Small Craft Advisory until noon PST today for coastal waters
     from Cape Shoalwater WA to Florence OR out 60 NM.

     Gale Warning from noon today to noon PST Friday for coastal
     waters from Cape Shoalwater WA to Cascade Head OR out 60
     NM.

     Gale Warning from noon today to 4 AM PST Saturday for coastal
     waters from Cascade Head OR to Florence OR out 60 NM.

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

&&

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This discussion is for Northwest oregon and Southwest Washington
from the Cascade crest to 60 nm offshore. This area is commonly
referred to as the forecast area.

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE PORTLAND OR
937 AM PST THU DEC 19 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0935 AM     SNOW             2 NNW STEVENSON         45.72N 121.90W
12/19/2019  M2.5 INCH        SKAMANIA           WA   TRAINED SPOTTER

            STARTED AROUND 6PM ON THE 18TH. WAS PURE
            SNOW TURNING TO FREEZING RAIN ABOUT 11PM BUT
            WAS NOT MEASURABLE. ABOUT 1000 FT ELEVATION.

0854 AM     SNOW             HOOD RIVER              45.71N 121.51W
12/19/2019  E1.5 INCH        HOOD RIVER         OR   PUBLIC

            200 FT ELEVATION. LIGHT GLAZE OF ICE ON TOP
            OF SNOW.

0808 AM     SNOW             WEST HOOD RIVER         45.70N 121.54W
12/19/2019  E2.0 INCH        HOOD RIVER         OR   PUBLIC

0800 AM     SNOW             CARSON                  45.72N 121.82W
12/19/2019  E1.5 INCH        SKAMANIA           WA   TRAINED SPOTTER

            STARTED SNOWING AROUND 7:30PM. SNOW WAS WET.
            370 FT ELEVATION.

0743 AM     SNOW             W. HOOD RIVER NEAR POST 45.70N 121.57W
12/19/2019  M0.5 INCH        HOOD RIVER         OR   PUBLIC

            AT 500 FT ELEVATION.

0600 AM     SNOW             1 ESE CARSON            45.72N 121.80W
12/19/2019  M2.0 INCH        SKAMANIA           WA   TRAINED SPOTTER

            STARTED AS RAIN IN THE EVENING ON THE 18TH,
            THEN TRANSITIONED OVER TO SNOW AT SOME POINT
            IN THE EVENING. NO ICE ACCUMULATION.

0550 AM     SNOW             HOOD RIVER              45.71N 121.53W
12/19/2019  M1.5 INCH        HOOD RIVER         OR   TRAINED SPOTTER

            LIGHT CRUST ON TOP OF SNOW. 200 FT
            ELEVATION.

1036 PM     SNOW             1 N STEVENSON           45.71N 121.88W
12/18/2019  M6.0 INCH        SKAMANIA           WA   PUBLIC

            NO BLOWING OR DRIFTING, ACCUMULATIONS RANGE
            FROM 5-7 INCHES. 700 FT ELEVATION.

&&