High Wind in Oregon, March 12, 2024

Area Forecast Discussion
National Weather Service Portland OR
1039 AM PDT Tue Mar 12 2024

.SYNOPSIS...
Showers and perhaps a thunderstorm or two today, with snow at times
across the Cascades. Mix of sun and clouds with decreasing showers on
Wed. Then, high pressure builds, bringing warmer temperatures and dry
weather for Thu, lasting into early next week.
&&

.SHORT TERM...(Today through Thursday)...
Broad upper trough will gradually shift across the region over the
next 24 hours. As such, will maintain cooler westerly flow aloft,
with showers today into tonight. With the cooler air aloft, will see
favorable lapse rates to support enough instability to have a few
thunderstorms around the region today into this evening. No big
changes to overall forecasts with current trends.

Snow levels lowering back to 2000 to 2500 feet today. As such, expect
accumulations at times with the showers. Generally, 4 to 8 inches of
new snow expected through this evening, with 8 to 14 inches for areas
above 3000 ft. Will extend current Winter Weather Advisory out
through 8 pm today.

Showers gradually decreasing tonight, with most of the showers
favoring the higher terrain. But, will take until Wed for shower end.
Air mass aloft gradually stabilizing on Wed, with showers ending in
the afternoon.

High pressure builds further on Thursday. After a chilly start with
areas of frost, will see mild day with plenty of sunshine. Will be
warmer, with highs in the middle to upper 50s along the coast as well
as most of the interior lowlands.		/Rockey

.LONG TERM...(FRIDAY THROUGH MONDAY)...High pressure intensifies
on Friday with southerly winds aloft and offshore winds at the
surface. 850 mb temperatures Friday afternoon are reaching
around 13 degrees Celsius which is quite warm for mid-March.
Climatologically the average March maximum temperature in
Astoria is near 53 degrees. On Friday though, ensembles are
showing highs ranging from 62-68 degrees Fahrenheit, and 66-71
degrees on Saturday. Inland sites around Salem, OR average a
high of 55.5 degrees. Forecasts though are showing a 90%
probability that temperatures will be greater than that. Have
trended slightly warmer in the long term forecast for Friday and
Saturday using the 50th-75th percentile of the NBM for max
temperatures. This is due to the shoulder season phenomena. This
is where the models struggle to handle the rapid shifts in
temperatures. Will have to continue to monitor as we receive
more hi-resolution guidance in the coming days.

The ridge will remain nearly stationary through Monday but it
will begin to erode as a weak long wave trough drops down from
British Columbia. It's quite the messy pattern so cannot rule on
any significant weather, but based on what models are currently
showing, will be a mild start to next week.	   /Muessle

&&

.AVIATION...Showers continue throughout the area, though these will
diminish in intensity over the rest of Tuesday and Wednesday. While
conditions are predominantly VFR at all terminals, there remains at
least a 30-40% chance of brief showers deteriorating conditions
temporarily to MVFR at times for almost all terminals, for at least
until 22z Tue. Afterwards, while showers continue, chances of MVFR
conditions drop to 10-20%. Later in the night, some clearing will
allow for the possibility of fog (20% chance of LIFR conditions) or
a low cloud deck (40-50% chance MVFR ceilings) developing after
around 12z Wed in the Willamette Valley. Highest probabilities for
fog look to be in the western Willamette Valley.

*Note: The observations out of KONP are generally limited to wind
and pressure at this time. Periodically cloud cover, vis, and
present wx are reported but are unreliable.

PDX AND APPROACHES...Generally VFR conditions are expected through
12z Wed, though there is around a 30-40% chance of showers
temporarily dropping conditions into MVFR thresholds. After around
12z Wed, with enhanced clearing, surface fog may develop, reducing
visibility. This currently looks to be about a 20% chance of LIFR
conditions.
/JLiu

&&

.MARINE...Strong westerly breezes are present across the coastal
waters this morning in the wake of yesterday's front, with recent
observations showing winds gusting to 30 kt. Steep and hazardous
seas also persist across the waters as available buoy data shows
short period seas lingering around 10 feet while a westerly swell
of 10 to 13 feet produces combined seas of 15 to 17 ft as of early
Tuesday morning. Expect gusty west winds and showery conditions to
persist through today as a trough of low pressure remains centered
near Vancouver Island. Short period, wind driven seas will
gradually subside, but the westerly swell will build back to
around 15 ft this afternoon and maintain the existing Hazardous
Seas Warnings through tonight. Have extended the Hazardous Seas
Warning for the Columbia River Bar out through mid Wednesday
morning to account for steeper, choppier seas produced by the
ongoing strong ebb cycle across the bar.

Conditions will begin to improve on Wednesday as the trough
shifts inland and is replaced by strong high pressure building
over the NE Pacific. This will yield lighter winds on Wednesday,
with seas likely continuing to warrant Small Craft Advisories as
the swell remains in the 10 to 12 ft range. A northerly wind
regime will develop during the latter half of the week as high
pressure continues to strengthen offshore, with seas trending down
below 10 ft as the swell continues to decay. /CB

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory until 8 PM PDT this evening for
     ORZ126>128.

WA...Winter Weather Advisory until 8 PM PDT this evening for WAZ211.

PZ...Hazardous Seas Warning until 9 AM PDT Wednesday for PZZ210.

     Hazardous Seas Warning until 3 AM PDT Wednesday for PZZ251>253-
     271>273.
&&

www.weather.gov/portland

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