Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 271030
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
330 AM PDT Wed Mar 27 2024

.SYNOPSIS...A strong front will bring moderate to heavy rain and
gusty south winds to the area today, with numerous showers and a
slight chance of thunderstorms continuing tonight into Thursday
as low pressure spins offshore. Conditions begin to improve on
Friday, with high pressure bringing another period of warm and
dry weather this weekend into early next week.

&&

.SHORT TERM...Through Friday Night...Satellite imagery reveals
an intense, well defined low over the NE Pacific, approximately
600 miles off of the Washington Coast as of 3 AM Wednesday. A
frontal system extends well southeast from the 977 mb low center
towards the Washington and Oregon coastal waters, with light
warm frontal precipitation spreading over the region ahead of a
trailing, gale-force cold front approaching the coast. The front
will push onshore later this morning accompanied by moderate to
heavy rain and gusty south winds, particularly for the beaches
and headlands where gusts may reach 50 mph at times this
morning. Still expect breezy south winds around 15 to 25 mph
with gusts to 35 mph as the front moves inland into the
Willamette Valley later this morning into early this afternoon.
Precipitation amounts are on track from previous forecasts as
guidance has consistently depicted around 1.00-1.50" of rain
for the coast and Coast Range and closer to a half inch in the
interior valleys through this evening. Light snow will remain
limited to the Cascade passes and above as snow levels briefly
climb above 5000 feet this morning before falling back to around
3000 feet behind the front this evening. Will see a transition
to more showery precipitation in the wake of the front this
evening, with a slight chance of thunderstorms for most
locations west of the Casacdes as lapse rates steepen with the
advance of the upper low offshore.

Widespread showery conditions continue tonight through Thursday
as the low makes slow progress towards the coast, with deep
layer southwest flow continuing to focus the bulk of the
precipitation over the coast and Coast Range. QPF guidance
continues to indicate an additional 1.00-1.50" of rain in these
areas through THursday evening, with a few 2 inch bullseyes
likely in orographically favored spots in the terrain. Rainfall
amounts will remain more modest over the valley through
Thursday, but could still see another quarter to half inch with
higher amounts in heavier showers and thunderstorms. Hydro
concerns remain minimal as guidance continue to depict
probabilities of 5 percent or less to reach action stage on area
rivers. Breezy conditions also persist through Thursday
afternoon as the low center nears the coast and maintains a
tight pressure gradient with southerly winds gusting to around
35 mph again on Thursday afternoon.

Conditions will show an improving trend Thursday night into
Friday as the low offshore begins to drop south and is
eventually absorbed into a new dominant low over the California
coastal waters. This will bring more benign conditions for
Friday with a few lingering showers as high temperatures warm
into the 60s during the afternoon. /CB

.LONG TERM...Saturday through Tuesday...Guidance continues to
indicate warm and dry conditions returning this weekend into
early next week as the upper low drops south into southern
California and is replaced by a strong ridge building over the
Pacific Northwest. This is reflected by NBM forecast
temperatures which show high confidence in highs in the mid to
upper 60s Saturday through Monday. WPC cluster analysis depicts
about 85 percent of individual ensemble members keeping the
ridge over the region through Tuesday before temperatures drop
back down towards seasonal normals later in the week. /CB

&&

.AVIATION...A frontal boundary is quickly approaching the region
early this morning with rainfall now being reported at the vast
majority of terminals. Expect a burst of gusty winds to
materialize along the coast before the fast moving front quickly
progresses inland. CIGS likely degrade to MVFR for several hours
this morning as rainfall peaks before a return to VFR conditions
midday into the afternoon. That said, convective showers behind
the front will still possess the capability to temporarily push
vis/cigs back to MVFR at times through the rest of the forecast
period. It`s also worth noting there is around a 20% chance for
thunderstorms mid to late afternoon at all sites before these
chances revert back to the coast. However, have not included in
any TAFs as confidence is still quite low on exact timing and
placement of activity should any develop.

* 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...Rainfall is currently ongoing and while
conditions have held VFR thus far, expect a period of MVFR cigs
between roughly ~1400-1800 ft this morning. Winds will increase
from the SSE between 12-18Z today as well with the gustier
conditions around 2000-3000 ft AGL. A quick transition to
showers occurs ~20z followed by mainly VFR conditions the rest
of the day outside of heavier shower activity. /Schuldt

&&

.MARINE...Active and unsettled conditions continue through the
end of the week thanks to a broad low pressure system now residing
in the northeast Pacific. Early this morning, a frontal boundary
is quickly pushing into the coastal waters with southerly wind
gusts in the 33 to 40 knot range already being observed by several
buoys over the outer waters. Fortunately, this frontal feature is
a quick mover with winds over the waters abruptly weakening mid
to late morning. Still, seas stay elevated around 8-11 feet
through the afternoon hours – anticipate a transition to hazardous
seas for several hours followed by small craft advisory
conditions once the aforementioned front passes eastward. Our
attention then shifts back to the slowly progressing upper-level
low pressure system as it meanders closer to the coastline before
stalling just offshore on Thursday. This will result in another
decent chance(50-80%) for the resurgence of Gale Force wind gusts
focused roughly Cape Falcon southward. Coinciding with the
secondary increase in winds will also be the arrival of a larger
west-southwesterly swell Thursday, helping to push combined
seas into the 15-20 ft range, peaking Thursday evening. A
positively tilted ridge of high pressure then builds across the
region this weekend into early next week resulting in lighter
northerly winds and much improved conditions come Saturday.
/Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Gale Warning until 8 AM PDT this morning for PZZ210-251>253-
     271>273.

     Small Craft Advisory from 8 AM this morning to 11 AM PDT
     Thursday for PZZ210.

     Hazardous Seas Warning from 8 AM this morning to noon PDT today
     for PZZ251>253-271>273.

&&

$$

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