112 
FXUS66 KPQR 031012
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
303 AM PDT Mon Sep 3 2018


.SYNOPSIS...Warmer weather will return this week before a frontal
storm system brings a decent chance for light rain and cooler
temperatures late Friday or Saturday.  
   

&&


.SHORT TERM...Tonight through Thursday...Water vapor satellite
imagery early this morning shows a rather distinct shortwave trough
dropping southeastward into the Rocky Mountain states. Models have
been suggesting this storm system would drag a weak front
southeastward into our northern zones later this morning. However,
satellite imagery suggests this feature is almost indiscernible at
low levels given the lack of clouds associated with it. As a result,
trimmed mentionable PoPs for this morning and may further do so in a
couple more hours depending on satellite and radar trends.
Temperatures for this afternoon were nudged upward a degree or two
given the cloud cover may not be extensive as previously anticipated.


Models are in good agreement shortwave ridging will shift eastward
across the Pacific Northwest Tuesday and Wednesday. Thermal low
pressure over northern California will shift northward into northwest
Oregon and southwest Washington Tuesday and Wednesday, which should
lead to warmer temperatures and plenty of sunshine. Would not be
surprised to see a few inland sites flirt with 90F on Wednesday. 

As a shortwave trough slowly moves southeastward into the northeast
Pacific and Pacific Northwest late in the work week, expect
increasing southwesterly flow to overspread the region Wednesday
night and Thursday. This should allow marine clouds to return to the
coast and perhaps even inland. This should cool temperatures for
inland locations a bit when compared to Wednesday, but these
transition days have a tendency to not cool as much as modeled days
in advance. /Neuman 


.LONG TERM...Thursday night through Monday...Models are in general
agreement a shortwave trough over the northeast Pacific will push a
front into the Pacific Northwest late Friday and early Saturday.
This should bring a good chance for some light rain and cooler
temperatures to the region. However, there still remain some notable
differences between the individual operational runs that affect exact
timing, coverage, duration and total rainfall amounts so kept PoPs in
the chance category for now. Overall, it appears the bulk of the
storm system will swing north of the region and rainfall amounts
should remain rather light across our CWA. 

As we move into Sunday and Monday, models continue to diverge
significantly with the latest GFS producing a warmer and dry scenario
while the latest EC suggests a more substantial frontal storm system
could bring wetting rains to a sizable portion of the forecast area.
Given the uncertainty among the models generally kept PoPs near
climatology with the highest PoPs centered across our northern zones
where even northward shift in the EC solution could still result in
some rain Sunday or Monday. /Neuman	


&& 


.AVIATION...Shallow stratus layer mainly over the coastal waters
but ashore north of KTMK bringing IFR cigs. A weak front was to
move into the area this morning to bring more widespread low MVFR
to IFR cigs along with some rain. This front has all but
dissipated so expect less clouds and pcpn. MVFR cigs should fill
in up the Columbia River to the KPDX area shortly after sunrise,
then dissipate by midday. Do not see much in the way cigs in the
valley, but may have MVFR cigs along the Cascade foothills for a
few hours this morning. Otherwise VFR inland and the coast this
afternoon and evening. Stratus should return to the coast 
in the evening but not push very far inland. 

KPDX AND APPROACHES...VFR should give way to MVFR cigs 1000-1500
feet 14Z-18Z, then return to VFR. Breezy NW winds will pick up 
again Mon afternoon and evening. /mh Pyle


&&


.MARINE...A fairly persistent pattern is expected for the next 
several days. High pressure will reside over the NE Pac, with 
thermal low pressure over the northern CA and southern OR coast. 
This will result in periodically gusty N winds over the coastal 
waters, particularly over PZZ255/PZZ275. Gusts of 25 to 30 kt 
are, with the strongest winds during the afternoon and evening 
hours. The current Small Craft Advisory for winds for 
PZZ255/PZZ275 has been extended through Tue night. Will also need
to watch for occasional gusts to 25 kt over PZZ250/PZZ270 this 
afternoon and evening, but at this time do not an advisory is 
warranted. 

Current models show much of PZZ250/PZZ270 should have gusts to 
25 kt Tue and Tue night. The strongest winds should be beyond 
5-10 NM at night and early morning, then reach the coastline in 
the afternoon and evening hours. Winds are expected to gradually 
subside for the latter half of the week. 

Seas are currently around 5 to 6 ft, but they will increase 
another 1 to 2 ft over the next few days in response to the gusty
northerly winds. Seas will occasionally be steep due to the 
gusty northerly winds, but a persistent northwesterly swell 
around 9 to 11 seconds should prevent the need for a Small Craft 
Advisory for square seas. /mh /64


&&


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

&&


$$

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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.