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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Thursday
• 
• High: 63 °
• Low: 54 °
• Rain Showers

• Friday
• 
• High: 64 °
• Low: 54 °
• Chance of Rain

• Saturday
• 
• High: 68 °
• Low: 55 °
• Chance of Rain

• Sunday
• 
• High: 63 °
• Low: 55 °
• Chance of Rain

• Monday
• 
• High: 66 °
• Low: 55 °
• Overcast

Area forecast discussion 
National Weather Service Portland or 
903 PM PDT Wednesday Jun 19 2013 


Synopsis...persistent upper level low pressure continues to bring 
clouds and showers to southwest Washington and northwest Oregon. 
Temperatures through Thursday will be well below normal. Showers on 
the decrease Thursday and Friday as the upper low pushes east. 
Temperatures will climb back closer to normal Friday and Saturday 
with some relatively drier weather...but it appears an active 
Pacific jet stream will bring more wet weather Sunday into early 
next week. 


&& 


Short term...evening update...main excitement centered around a 
funnel cloud which formed northwest of the Portland Airport around 3 
PM and lasting around 5 minutes. Public photos revealed a very thin 
rope structure. No damage was reported but it certainly made for a 
newsworthy event given recent history around the pacnw. Suspect very 
weak speed shear where 5 to 10 kts near the surface increased to 15 
to 20 kts just a couple thousand feet off the ground created a 
horizontal spinning vortex...very much like pushing a pipe across a 
table by rolling it with your hand. This spinning tube of air 
crossed paths with localized moderate updraft and briefly became 
vertically oriented thus producing The Funnel cloud. Check our 
facebook Page (posts by others) for a picture submitted by the 
public. Further evidence of the strong updrafts became by several 
cells which produced strong shower activity very quickly in their 
short lifetimes. 


Feel the last gasp of moderate shower activity is underway as we 
reach sunset and begin to lose the thermal triggering at this hour. 
Also...models and satellite indicate a shortwave rounding the west 
side of the elongated upper low later tonight but it appears it will 
be heading south of the area. As such...have decided to cut back on 
shower coverage for overnight tonight and tomorrow morning with the 
biggest decrease for the Cascades and foothills. Still expect some 
showers to remain under minimal orographic enhancement...however. No 
further changes made with remaining discussions following. /Jbonk 


Late tonight through Saturday...temperatures begin to warm aloft tonight as 
the core of cold air aloft drifts east of the Cascades. This will be 
another factor cutting the potential for instability. NAM bufr 
soundings suggest that by Thursday morning we should be under the 
influence of a strong capping inversion near 700 mb so any showers 
Thursday should be shallow. With a little more sunshine temperatures may be 
slightly warmer Thursday but still below normal. 


The upper low meanders toward the Idaho Panhandle Friday...but still 
remains close and broad enough to allow wraparound moisture to keep 
the shower threat going for our northern zones. Temperatures will continue 
their slow recovery as the air mass slowly warms up...with the drying 
and warming trend back toward normal continuing into Saturday as the 
upper low finally tries to move across the northern rockies. However 
a strong Pacific jet will be knocking on our door by then...aiming to 
bring a prolonged period of unseasonably wet weather to the Pacific 
northwest for early next week.Weagle 


Long term...Saturday night through Wednesday...the latest medium 
range model runs are showing fairly good agreement in the extended 
portion of the forecast. After a brief period of dry weather Sat...the 
models are now showing a low coming onshore Sat night into Sun 
morning. Although some model runs are keeping the best precipitation to our 
south...the ensembles solutions are showing likely probability of precipitation over much of 
our forecast area during the day sun. Then a deep closed upper level low 
is prognosticated to drop south and stall over the NE Pacific for most if not 
all of next week. The best chance for significant precipitation appears to 
be Monday night into Tuesday...when the models seem to agree that a juicy 
front will bring a slug of heavy precipitation to the region. Otherwise... 
expect that the Pacific northwest will remain in a cloudy and wet pattern 
through most of next week. Temperatures will also likely be running several 
degree below normal. Pyle 


&& 


Aviation...a showery unstable airmass will lead to mainly VFR 
conditions across the area. The lower atmosphere should remain 
modestly unstable even overnight so ceilings should generally remain 
VFR...but MVFR ceiling development will be possible. Confidence in 
timing and location of any such lower ceilings is low so kept MVFR 
conditions limited in the tafs. 


Kpdx and approaches...expect VFR conditions with scattered 
showers through the evening. Conditions should generally remain 
VFR overnight into Thursday...but cannot rule out an occasional 
MVFR ceiling...particularly toward Thursday morning. 


&& 


Marine...expect tranquil winds and seas through Saturday as high 
pressure moves over the northeast Pacific. A series of weak storm 
systems will likely cause winds and seas to increase early next 
week. However...seas should remain below 10 feet and little more 
than small craft advisories for wind gusts of 25-30kt appear 
possible Monday through Wednesday. 


&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...none. 
&& 


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.