Area Forecast Discussion Issued by NWS Portland, OR
000
FXUS66 KPQR 110341 AAA
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
841 PM PDT Wed Apr 10 2024
Updated aviation discussion
.SYNOPSIS...High pressure maintains warmer and dry conditions
the rest of today until Thursday morning. The next system approaches
Thursday, returning widespread precipitation chances across
northwest Oregon and southwest Washington. Friday into the
weekend, model guidance suggests this system drops down toward
California, directing the bulk of weekend precipitation far
south of us.
&&
.SHORT TERM...Now through Friday night...Warm weather with
clear skies dominate throughout the region for the rest of
Wednesday as high pressure builds in briefly. Temperatures
inland peak around the mid-60s today, closer to the mid-50s at
the coast. The overnight low Wed night should be well into the
40s for all areas, and no frost concerns are expected. The ridge
shifts eastward tonight, and the next system begins building in
near the end of the night/early Thursday morning. Precipitation
begins to fill in throughout Thursday from the northwest,
reaching the coast by mid-morning and the Willamette Valley by
mid-afternoon. QPF amounts look fairly light for most of the
area, with only around a 10-20% chance of rainfall exceeding
0.25" in the Willamette Valley in the first 24 hrs of
precipitation. Precipitation will be stronger at the SW
Washington coast and Willapa Hills, with around a 70% chance of
24-hr rainfall exceeding 0.5" at the Willapa Hills. Snow levels
remain above Cascade Pass levels, though QPF amounts would
render any snowfall low-impact anyway.
Precipitation continues into Friday morning, but the area will
dry off throughout Friday, with the area generally dry by
evening. A low passes south of the area into California, and
some stray bands of moisture may continue south of Salem over
Friday night, but these showers will be light. Snow levels
continue to remain high Friday night, with no impacts expected
at the passes. Low temperatures will be well into the 40s once
again, and no concerns are expected Friday night. /JLiu
.LONG TERM...Saturday through Tuesday...WPC cluster analyses are
in good agreement (80%) that another brief upper level ridge
builds into the area on Saturday. Most areas will be dry, but
the southern half of our CWA could see some very light rain
showers at times due to wrap-around from a low spinning in
California.
Monday sees uncertainty returning as a trough from British
Columbia moves southward, but some ensemble members have it
moreso reaching further east past the Rockies. Currently around
a 60% chance of the trough reaching us on Monday, bringing
showers back into the area, but it`s also possible the ridge
just persists. In this scenario, 850 mb temperatures will drop
to around -3 to -5C later Monday into Tuesday, bringing snow
level down to around 2000 feet so. This would lead to
accumulating snow below Cascade passes and higher peaks of the
coast range. Though with current QPF forecast expect amounts
will be less than 6 inches. Orographics become favorable later
Monday into Tuesday, so depending on how the QPF turns out could
see higher amounts.
&&
.AVIATION...Scattered high clouds continue to stream across the
area within westerly flow aloft tonight. Upper level flow turns
southwest ahead of a weak front that will approach the coast on
Thursday. Expect predominately VFR through Thursday, except at the
coast where there is a 30-40% chance of MVFR to IFR conditions
developing overnight, mainly after 08Z Thu. Additionally, there`s
about a 10-20% probability of patchy fog development around
10-14Z Thursday in the central and southern Willamette Valley,
including KSLE, KCVO, and KEUG terminals. MVFR/IFR conditions
expected to become more widespread along the coast and Coast Range
after 20z Thursday ahead of the incoming weather system.
Northwesterly winds decreasing overnight, becoming south to
southwest by Thursday morning.
PDX AND APPROACHES...VFR conditions expected to persist through
Thursday. Light rain likely after 00Z Friday. Northwest winds
decreasing below 5 kt overnight, shifting south to southwest
after 18Z Thursday. /DH
&&
.MARINE...High pressure persists over the waters Wednesday with
mostly clear skies and northerly winds to presiding over the
coastal waters. Swells through Wednesday hold around 7-9 ft at
12-14 seconds through Wednesday night, diminishing to 5-7 ft
overnight and remaining there through Friday. A weak front will
approach the waters early Tuesday morning, shifting winds
southerly. Local gusts up to 20 kts are expected as the front
moves through the waters Thursday afternoon and evening, mainly
for the central and northern waters (marine zones PZZ251, 252,
271, and 272).
Additionally, another very strong Ebb current is expected around
7AM Thursday for the Columbia River Bar. This combined with seas
around 7-8 ft has prompted a Small Craft Advisory for the Columbia
River Bar from 3AM to 10AM Thursday.
Another stronger frontal system just west of our waters will move
southeast toward the California coast Friday into the weekend.
This will cause winds to shift back northerly and increase over
our waters. There is high confidence (70-90% probability) in Small
Craft Advisory wind gusts (greater than 21 kts) for all of our
waters, though seas aren`t expected to see much of a response,
rising to 7-8 ft. -HEC
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 3 AM to 10 AM PDT Thursday for PZZ210.
&&
$$
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