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000 
FXUS66 KPQR 222238
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
337 PM PDT Thu Jun 22 2017

.SYNOPSIS...High pressure aloft over the forecast area will
strengthen through the weekend. A thermally-induced surface trough
and resultant offshore low-level flow will result in hot temperatures
Friday through the weekend. A southwest marine surge occurs along the
central coast Saturday night and Sunday. A deeper marine push occurs
Monday for cooler temperatures inland. Strong onshore flow
continues Tuesday through mid-week, potentially followed by a gradual
warming trend late in the week. 

&&

.SHORT TERM...Thursday Night through Sunday...Skies are clear across
the CWA this afternoon. Temps over the interior have warmed into the
low 80s, with highs at the coast limited to the 60s due to an onshore
component to the flow. We are also seeing breezy northerly winds
develop through the interior lowlands in response to a thermal trough
developing over southern Oregon. Expected gusts 20 to 25 mph to
continue into this evening.

The pleasant weather we have had the past few days will give way to
the first significant heat wave of the season starting Fri and
continuing through the weekend. A strong upper level ridge over the
NE Pac will shift toward the Pac NW on Fri, then strengthen over the
region this weekend. This will lead to a gradually warming air mass.
850 mb temps are in the 14 to 16 C range today, and are modeled to
reach 17 to 20 C tomorrow. This would support high temps in the low
to mid 90s for the interior, and we have bumped up fcst temps for
tomorrow accordingly. Meanwhile, the coast will remain cooler,
generally in the 70s as the flow keeps the onshore component.

The air mass then warms to around 22 to 24 C at 850 mb over the
weekend. Mixing these temps down to the surface would support high
temps in the upper 90s or even just above 100 degrees. Offshore flow
is modeled to develop Fri night, then strengthen on Sat. So we
shouldn't have a problem mixing, and in fact, we may even overachieve
temps based on mixing down the 850 mb temps due to compressional
warming with the downsloping easterly flow. The offshore flow is also
expected to reach the coast Sat, which should allow temps there to
climb into the mid 80s to near 90 degrees.

The fcst models continue to suggest that a southerly flow reversal
will begin along the central OR coast late Sat, then progress
northward Sat night into Sun morning. This will bring marine stratus
and fog to the coast and effectively end the heat wave west of the
Coast Range crest. It also appears that there will be some marine air
seepage into the southern Willamette Valley Sun, which will likely
limit high temps somewhat compared to the northern valley locations,
which can expect highs on Sunday just as high if not a couple of
degrees higher than on Saturday.  

The only thing we have going for us with this heat wave is that dew
points remain generally on the lower side, in the 40s to start, then
into the mid 50s by Sunday as the marine air slowly starts to seep
in. Overnight lows, although much warmer than normal, will not be
oppressive and should drop into the upper 50s to mid 60s across the
region. We have issued a Heat Advisory for all zones expect the coast
for Fri and Fri night. Then an Excessive Heat Watch is in effect for
the weekend, with a Heat Advisory for the coast Saturday. Pyle
    
.LONG TERM...Sunday night through Friday...By all indications, an
approaching upper level trough will nudge the strong ridge axis east
of the Cascades late Sunday into Monday. The associated surface
trough is also modeled to push east of the Cascades late Sunday. This
should open the door for much cooler marine air to pour into the
region and cool temps off considerably for Mon. However, we have seen
marine surges move in more slowly than the models suggest time after
time, so we have not cooled things off quite as much as guidance is
suggesting at this time. Still, our current fcst of highs in the low
to mid 80s across the interior would feel pretty good compared to the
temps we will see over the weekend. There is also a slight chance for
thunderstorms over the Lane County Cascades at some point Mon as the
trough comes through. Decided to add a slight chance to the fcst,
although the best chances remain east of the Cascades. Then by Tue,
confidence is high that we will in a more cooler and more seasonal
pattern. Onshore flow should bring plenty of marine stratus into the
region Tue morning, with clouds clearing back to the coast in the
afternoon. The same general pattern holds through the rest of the
week, but inland marine intrusion may be less widespread each
morning. Highs should generally remain in the 70s over the interior
from Tue through Fri, with 60s at the coast due to the onshore flow.
Pyle

&&


.AVIATION...VFR conditions through the period. North winds have
started to pick up this afternoon and will remain gusty into the
evening. The strongest winds will be along the coast and in the
south Willamette Valley.

KPDX AND APPROACHES...VFR through the period. Short period of
gusty north winds late this afternoon and evening with 20 to 25 
kt gusts possible through the early evening. Bentley

&&

.MARINE...Persistent high pressure over the NE Pacific and 
thermal low pressure over NW California and S Oregon will
continue gusty north winds through Saturday morning. The winds 
will be strongest south of Cascade Head, with frequent gusts of 
25 to 30 kt. Winds within 10 nm of the coast will weaken during 
the nights, and become offshore through the early mornings. The 
winds will build steep and choppy seas that will reach heights of
8 to 10 feet south of Cascade Head at times. Given the gusty
northerlies continue through the day Friday, extended the small
craft advisory for seas for southern waters through Friday
night. Starting Saturday night, a southerly wind reversal will 
build up the coast as the thermal low actually moves offshore, 
this will likely end the small craft strength winds, but will 
also lead to a complicated wind forecast across OR and WA waters 
with light northerlies in northern waters and southerlies in 
central Oregon waters. Eventually, northerlies return by Monday 
night as a typical summertime pattern develops. /Bentley

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory from noon Friday to noon PDT Saturday for Cascade 
     Foothills in Lane County-Cascades in Lane County-Central 
     Coast Range of Western Oregon-Central Columbia River Gorge-
     Central Willamette Valley-Coast Range of Northwest Oregon-
     Greater Portland Metro Area-Lower Columbia-Northern Oregon 
     Cascade Foothills-Northern Oregon Cascades-South 
     Willamette Valley-Upper Hood River Valley-Western Columbia 
     River Gorge.

     Excessive Heat Watch from Saturday afternoon through Sunday 
     evening for Cascade Foothills in Lane County-Cascades in 
     Lane County-Central Coast Range of Western Oregon-Central 
     Columbia River Gorge-Central Willamette Valley-Coast Range 
     of Northwest Oregon-Greater Portland Metro Area-Lower 
     Columbia-Northern Oregon Cascade Foothills-Northern Oregon 
     Cascades-South Willamette Valley-Upper Hood River Valley-
     Western Columbia River Gorge.

     Heat Advisory from noon to 9 PM PDT Saturday for Central Oregon 
     Coast-North Oregon Coast.

WA...Heat Advisory from noon Friday to noon PDT Saturday for Central 
     Columbia River Gorge-Greater Vancouver Area-I-5 Corridor 
     in Cowlitz County-South Washington Cascade Foothills-South 
     Washington Cascades-Western Columbia River Gorge-Willapa 
     Hills.

     Excessive Heat Watch from Saturday afternoon through Sunday 
     evening for Central Columbia River Gorge-Greater Vancouver 
     Area-I-5 Corridor in Cowlitz County-South Washington 
     Cascade Foothills-South Washington Cascades-Western 
     Columbia River Gorge-Willapa Hills.

     Heat Advisory from noon to 9 PM PDT Saturday for South 
     Washington Coast.

PZ...Small Craft Advisory for winds until 5 AM PDT Saturday for 
     Waters from Cape Shoalwater WA to Florence OR from 10 to 
     60 nm.

     Small Craft Advisory for hazardous seas until midnight PDT 
     tonight for Coastal Waters from Cascade Head OR to 
     Florence OR out 60 nm.

     Small Craft Advisory for winds until 11 PM PDT Friday for 
     Coastal Waters from Cape Shoalwater WA to Florence OR out 
     10 nm.

&&

$$

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