366 
FXUS66 KPQR 030314
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
813 PM PDT Wed May 2 2018

.SYNOPSIS...A ridge of high pressure aloft will bring dry and warm 
weather to the region through Thursday. Mild weather continues 
into the weekend, but chances for showers also return over the 
weekend as an upper level trough moves into the area. Dry weather
returns for the start of next week.

&&

.SHORT TERM...Tonight through Saturday...Just cosmetic changes to the
tonight and Thursday periods. Evening water vapor imagery showed an
500 mb ridge axis just inside 130W. High-level moisture continues to
stream over the top of the ridge. This 500 mb ridge axis reaches the
coastline around 12Z Thu and then shifts east of the Cascades in the
afternoon. The 00Z Thu Hi-RES ARW run shows less boundary layer
moisture compared to 24 hours ago. Thus, not expecting much, if any,
morning stratus. The model does suggest the potential for some along
the coastline, mainly KTMK southward, in the 12Z to 15Z time frame.
The model also hints at localized stratus along the SW Washington I-5
corridor near KKLS. Included some patchy late night and morning fog
in the south Willamette Valley. 

The Hi-RES ARW also shows the boundary layer wind becoming more W to
NW along the coast by 18Z Thu, then shifting to SW to W in the
afternoon. There is the potential for marine stratus to either hover
near the coast through the morning then gradually spread inland
during the afternoon as the onshore flow strengthens. Or, any marine
stratus that is present along the coast in the morning could simply
move inland sooner. Either way, max temp forecast for the west slopes
of the Oregon Coast Range will be tricky. Inland areas from the east
slopes of the Coast Range to the Cascades should see max temps
similar to today, or a degree or two warmer. Weishaar

Rest of the short term discussion unchanged...Moisture continues to
increase Friday as onshore flow strengthens. Models even show some
light rain or drizzle over the northern coastal areas and adjacent
waters, so maintained slight chance PoPs for those areas into Friday
morning. The next upper low makes its initial approach to the west
coast Saturday off northern California, putting the local area in
southerly to southeasterly flow, which could be favorable for Cascade
thunderstorms. Have introduced a slight chance of thunder Saturday
afternoon south of Mt. Hood. However, models are not in perfect
agreement about the track of the low and a more southerly track would
likely keep convection farther south. Bowen 

&&

.LONG TERM...Saturday night through Tuesday...A negatively tilted 
upper level trough approaches the coast late Sat/ early Sun. This 
feature will nudge the ridge that has been over the area to the east 
and over the Cascades. This process will cause a short period of 
time where S/SE mid level flow to develop, which may bring a chance 
for thunderstorms into the area. The best chance for thunderstorms 
will be along the Oregon Cascades. As the trough moves out of the 
area, the next upper level ridge moves into the area late Sun, and 
continues to set up though Mon and Tue. /42

&&

.AVIATION...Conditions are VFR with generally clear skies this
afternoon. The models suggest the flow will turn a bit more
onshore later tonight and Thu with a mixture of IFR/low MVFR
conditions along the coast later tonight continuing through the
day Thursday with little or no clearing Thu afternoon. There
could be some patchy fog or low stratus inland around sunrise
otherwise conditions inland will remain VFR through Thu. We will
probably start to see some higher clouds developing Thu afternoon
ahead of the next system.

KPDX AND APPROACHES...VFR conditions prevailing tonight and Thu.
Could see some patchy clouds around 1000 ft near sunrise.
Otherwise some increasing higher clouds Thu afternoon. pt

&&

.MARINE...There will be a little N wind along the coast but it
should stay below Small Craft Advisory thresholds as the pressure
gradient is not strong enough or oriented quite right for
anything stronger. Pressures briefly weaken or lower along the 
Washington coast later tonight and Thursday which turns the winds
more southwesterly but speeds will be modest. The models say the
winds turn back to more northerly this weekend, possibly 
approaching 20 kt.

Seas look to stay around 4 or 5 ft into the weekend per the most
recent wave models. pt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.

&&

$$

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland

This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the CWA or forecast area.