Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 251718
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1017 AM PDT Tue Apr 25 2017

.SYNOPSIS...A brief break in the rain early this morning will come to
an end as the leading round of rain will spread onshore and across
ther region this morning. and into the early afternoon. 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 and mild
day on tap for Saturday. However, the next disturbance will bring a
renewed threat of rain on Sunday.

&&

SHORT TERM...(Today through Thursday)...Plenty of clouds remain in
place acrossj the forecast area this morning, with some light
moisture also begining to spread across the region. Outside of some
light showers that developed inland ahead of the warm front near
Scappoose and north into Cowlitz and Skamania counties, no real sign
of measurable rainfall has been somewhat sparse thus far this
morning. 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 morning into early afternoon. Most areas in the
interior may only see one to three tenths of an inch today through
evening, but somewhat larger amounts are more likely across the
higher terrain of the Cascades and also the coastal mountains.
Remainder of previous discussion follows.   Cullen

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
showers.     Rockey.

.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.
/Neuman

&&

.AVIATION...VFR conditions most areas as a warm front lifts
north. Exceptions are KONP where dew point spread remains low
and KHIO there MVFR likely to become more widespread with the
cold front later today and this evening. Cigs appear to remain
MVFR 020-030 at best following the cold front and more likely in
the 015-020 range. Cigs will remain low, especially for areas
south of a KTMK-KSLE line, through Wednesday morning as another
frontal disturbance is aimed at southern Oregon and arrives after
26/09z. WOuld also expect Vsbys to remain MVFR at best per
guidance, but have a feeling heavy rains will drop Vsbys into an
IFR range for several hours during the morning.

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. If they do improve, then expect another drop
overnight with Cigs at or below 020 and about a 20% chance of
below 010 through 26/18z. /JBonk

&&

.MARINE...SCA wind gusts have arrived at buoy 50 and will
gradually increase with gusts primarily around 30 kt today.
Models have backed off on the threat of gales today but have not
completely eliminated them. Thus, have still included a mention
of brief 35 kt gusts for today in the products.

A weak surface low passes south of the waters Wednesday while
broader high pressure builds over the NEPac keeping a relative
lull in winds through Friday. Seas may 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 Panhandle. /JBonk

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 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 5 AM PDT Wednesday for Coastal Waters from
     Cape Shoalwater WA to Florence OR out 60 nm.

     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.


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