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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Saturday
• 
• High: 61 °
• Low: 45 °
• Rain

• Sunday
• 
• High: 59 °
• Low: 45 °
• Rain

• Monday
• 
• High: 59 °
• Low: 43 °
• Rain

• Tuesday
• 
• High: 57 °
• Low: 39 °
• Chance of Rain

• Wednesday
• 
• High: 59 °
• Low: 39 °
• Chance of Rain

Area forecast discussion 
National Weather Service Portland or 
322 am PDT Sat may 25 2013 


Synopsis...it appears cool and wet conditions will linger across 
southwest Washington and northwest Oregon for much of the Memorial 
Day weekend. Broad upper level low pressure will linger across 
southwestern Canada and the northwestern United States for the next 
several days...with a series of disturbances bringing occasional rain 
to the forecast area. The next weak low pressure system will bring an 
increasing chance for rain as today progresses...with steady rain 
likely throughout the district tonight and early Sunday before 
tapering to showers later Sunday afternoon. A stronger system should 
spread more rain across the district Monday...possibly along with a 
brief period of breezy conditions along the coast. Brisk westerly 
flow will keep things unsettled with rain at times into midweek. 


&& 


Short term...most of the forecast area is starting out the day 
cloudy but dry for a change...aside from a few showers mainly across 
portions of Clark County and the S Washington coast. There are some breaks in 
the clouds across the Willamette Valley Salem southward...where there 
may be some sunshine this morning. However weak isentropic lift out 
ahead of an approaching weak low pressure system will cause clouds to 
increase throughout the day. Rain chances will increase along the 
coast by afternoon and inland by this evening. Today may be the 
warmest of the next few...especially near Eugene where some sunshine 
may warm temperatures into the middle to upper 60s. 


The weak low will move onshore overnight tonight. Weak flow pattern 
will result in minimal orographics...and little to no rainshadowing 
for the Willamette Valley. So again there could be a good bit of 
steady rain in The Lowlands tonight into Sunday morning. Not 
expecting the same kind of totals we experienced around Portland the 
last few days...but this will probably be a heavier event for Salem 
and Eugene who received less precipitation from the last couple of systems. 


There is a bit of question as to whether rain will be steady or more 
showery Sunday afternoon as the associated upper low moves onshore. 
NAM bufr soundings show a very moist air mass but little in the way 
of instability. Regardless we are starting to suspect temperatures may again 
have a hard time getting out of the 50s Sunday in a very cloudy and 
wet day. 


Precipitation will taper off as this system moves east sun evening... 
just in time for a more organized Pacific frontal system to move 
onshore later Sunday night or Monday/Memorial Day morning. Depending 
on the track of this system it may have a brief punch of modest 
coastal wind with it...but this appears more likely for southern 
Oregon or northern California where the best jet dynamics will be. As 
a result this system may try to split somewhat as it moves onshore... 
but still should hold together enough for a decent rain Memorial Day. 
The good news is that snow levels will probably remain above the 
passes through the Holiday weekend. Weagle 


Long term...made very few changes for the extended period. General 
model trend remains wet midweek followed by more seasonable weather 
later in the week. Previous discussion follows...models start out in 
good agreement during the extended period Monday night and Tuesday...with a 
trough pushing inland over the West Coast. Most of the energy appears 
headed S of the forecast area towards California. As the northern stream 
appears to remain an open wave...will boost probability of precipitation into likely 
category. Models diverge some later in the week...but keep a common 
theme of shortwaves pushing in in a westerly flow aloft. Will keep 
probability of precipitation relatively high for a system on Wednesday...but then will drop probability of precipitation 
off later in the week as upper heights rise. 


&& 


Aviation...predominant MVFR or better across the area although 
weak low-level convective elements have brought brief MVFR ceilings 
under showers. Will see this pattern continue through early 
daylight hours but with showers primarily confined to the northern 
coastal areas. Will thereafter see middle-level rain develop toward 
afternoon with ceilings again closing up but likely staying MVFR or 
better. Should see rain continue before easing late overnight at 
the coast and early Sunday morning inland. 


Kpdx and approaches...occasional weak showers continue to form 
near the field then move north. Predictability and confidence 
is rather low for any specific timing so will keep monitoring for 
consistent IFR but don't want to force any hands for IFR planning 
by including a broken deck at this point. Should see the threat 
ease with time today. A more solid deck around 4 to 6 kft should 
develop by middle afternoon along with more persistent rain by 00z 
this afternoon. Expect to see rain and MVFR ceilings continue until 
after 26/12z. /Jbonk 


&& 


Marine...will see a weak surface low sit just offshore bringing 
wind gusts knocking on the 21 knots small craft threshold. Will 
follow the when in doubt leave it out philosophy as models show 
disagreement regard wind strength. Seas will stay around 6ft today 
then ease back a bit overnight tonight. The waters will then stay 
somewhat benign until Memorial Day when another Pacific front will 
approach. It appears that solid small craft winds and possible 
seas will arrive. One model does show gale gusts but it appears to 
be an outlier at this time. Using a more conservative approach 
yields seas in the 6 to 8 feet range and even then primarily wind 
wave/fresh swell driven. As such will see a rapid easing once winds 
drop off Monday night. 


Still looking for rather Large Bar swell during the very strong 
Ebb this morning and keep the rough bar advisory in play for this 
mornings Ebb. Winds are weaker today and cameras did not show any 
breaks yesterday morning. Thus...will mention breaks only as a 
possibility due to the stronger flow. /Jbonk 


&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for rough Columbia River bar until 8 am PDT 
this morning. 


&& 


$$ 


More weather information online at... 
http://weather.Gov/Portland 


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.