Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 250952 CCA
Area Forecast Discussion
National Weather Service Portland OR
252 AM PDT Tue Apr 25 2017
.SYNOPSIS...Yes, Virginia, there is more rain coming. Brief break in
the rain early today, but rain will spread across the region this
morning. More rain tonight, especially late tonight into early
Wednesday. Snow levels rise today, but will fall back to pass levels
in the Cascades on Wed as cooler air arrives. Showers decreasing on
Fri, with a dry mild day on tap for Saturday. But, threat of rain
returns on Sunday, although not great threat yet.
SHORT TERM...(Today through Thursday)...Plenty of clouds across the
region this am, but not much in way of moisture. That will change
later this morning, as an occluded front offshore will spread more
clouds and rain to the coast by mid-morning, with rain spreading
across all of the remainder of the interior later this am into early
afternoon. Looks to be a rather wet afternoon and evening. Most areas
generally will get 0.20 to 0.50 inch of rain, with somewhat heavier
amounts over the higher terrain and coastal mtns.
Models insist on bringing another frontal system into the region
later tonight into Wed am. So, with that in mind, will see rain
tonight into Wed am. Now, could see somewhat of a lull in the rain
this evening behind the occluded front. Not a lot of cold air behind
the front, so not not much in way of showers. But, next system
arriving later tonight, so rain will start increasing along the coast
by late evening, quickly spreading inland after midnight. So, even
though may see a lull this evening, may not be last too long.
Cold front will push to the coast Wed am, and then across the
interior Wed afternoon. So, will see rain transition to showers on
Wed. Snow levels will stay up tonight into Wed am, generally 5000 to
6500 feet. But snow levels lower Wed afternoon as colder air spreads
inland. Likely to see down to 3500 to 4500 feet by late Wed
afternoon. Very well could see 3 to 7 inches of new snow in the
showers Wed afternoon and Wed night, as westerly flow aloft will
favor continued decent orographic uplift for the Cascades.
Not much change on Thu, as will maintain cool onshore flow with
.LONG TERM...No Changes. Previous discussion follows...Thursday night
through Monday...The strong jet aimed over the Pacific Northwest
during the middle of the week will slowly become more north-south
oriented and shift east of the region Thursday night and Friday. This
should result in decreasing showers during this period. Models are in
decent agreement that shortwave ridging will push over the Pacific
Northwest Friday night and Saturday and will bring some sunshine and
mild temperatures. This pleasant weather could last into Sunday, but
it could certainly be short lived based on the latest operational and
ensemble model guidance. As a result, trended PoPs into at least
mentionable thresholds and closer to climo for Sunday and Monday.
.AVIATION...A bit of a break in the rain ahead of the next
system. VFR prevailing across the area but there is some breaks
in cloud cover. This will allow a lower cloud layer to form in
the moist near surface layer for a several hours early this
morning, but do not expect it to be widespread. MVFR likely to
become more widespread with the front later today. Coastal areas
to see MVFR cigs/vis beginning after 15Z and inland after 20Z-
22Z or so.
KPDX AND APPROACHES...VFR conditions will remain through about
20Z the chances for MVFR increase as rain increases. MVFR most
probable between 22Z and 03Z Wed, through it may last longer into
the evening. Winds will be from the south through the day and
expected to remain below 15 kt. /mh
.MARINE...Active weather pattern continues as there is another
system today that will likely bring high-end small craft
advisory wind and possibly brief low-end gales. For now will hold
on to the advisory for wind. Seas look to remain around 7 to 9
ft but may spike to 10-11 feet for a couple hours, so will add a
small craft advisory for hazardous seas for today.
Surface high pressure then begins to build offshore shunting the
surface lows mainly north of the waters and keeping a relative
lull in winds through Friday. Seas next reach 10-11 ft Thursday
through early Friday as the southern end of a swell train clips
the northern waters from a surface low crossing the Alaskan
PZ...Small Craft Advisory for winds from 8 AM this morning to 11 PM
PDT this evening for Coastal Waters from Cape Shoalwater
WA to Florence OR out 60 nm.
Small Craft Advisory for hazardous seas from 2 PM this
afternoon to 11 PM PDT this evening for Coastal Waters
from Cape Shoalwater WA to Florence OR out 60 nm.
Small Craft Advisory for Rough Columbia River Bar until 7 AM
PDT this morning.
Small Craft Advisory for Rough Columbia River Bar from 4 PM
this afternoon to 7 PM PDT this evening.
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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.