Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 232133
AFDPQR

Area Forecast Discussion
National Service Portland OR
232 PM PDT Tue Jul 23 2019

.SYNOPSIS...Typical summertime weather will continue for the next
several days across southwest Washington and northwest Oregon. An
upper level trough is bringing more clouds and cooler temperatures
today, along with stronger onshore flow. Isolated showers are not out
of the question along the coast and in the higher terrain through
tonight. High pressure builds back into the region for the latter
half of the week, leading to sunnier days and seasonably warm
temperatures.

&&

.SHORT TERM...Tonight through Friday...Expect typical late July
weather to continue across the forecast area, though today will
likely be the coolest of the next several days. An upper level trough
is beginning to move onshore this afternoon, resulting in increased
cloud cover and strengthening onshore flow. This will likely cap
temperatures around 80 degrees for our inland valleys this
afternoon...a few degrees cooler than yesterday. Most of the forecast
area will remain dry this afternoon and evening, but cannot rule out
a couple showers across coastal areas and the higher terrain as the
bulk of the shortwave energy associated with the upper trough moves
through. We removed the mention of thunder along the Cascade crest
this afternoon and evening, as it appears the marine layer has
deepened enough to stabilize areas along and west of the crest.

After the upper trough axis moves through this evening, the rest of
tonight will probably be partly cloudy and cool with temperatures in
the outlying valleys dipping into the 40s. High pressure will build
into the region, turning low-level flow northerly for quick clearing
of any morning cloudiness Wednesday. This should result in a sunny
and seasonably warm afternoon for much of the district, with coastal
temperatures near 70 degrees and inland temperatures pushing back
into the 80s.

With 500 mb heights rebounding into the 585-588 dam range in
shortwave ridging per the 12z ECMWF, the marine layer will probably
be shallow and mostly limited to the coast Thursday. As 850 mb temps
push into the +16 to +18 deg C range, weaker onshore flow and
abundant sunshine will result in much warmer conditions inland
Thursday, with temperatures possibly making a run at 90 degrees.
Similar temperatures and weather are expected for Friday, though some
models suggest lowering heights and strengthening onshore flow
resulting in a slight cooldown.  Weagle

.LONG TERM...Friday night through Tuesday...Longer range forecast
guidance suggests little change in the big-picture weather pattern
for the region through early next week. The region remains in
progressive W-SW flow aloft, with a series of weak disturbances
passing by to our north. This will likely result in a somewhat deeper
marine layer, with the typical summertime pattern of coastal low
clouds extending inland to varying degrees each night and morning. As
usual, morning clouds should clear back to the coast by midday each
day, yielding plenty of sunshine for inland areas. Overall this
pattern seems to suggest temperatures will not stray too far from
late July normals through early next week, and our forecast reflects
this.  Weagle

&&

.AVIATION...VFR conditions have returned to most locations and
should be at all locations by 22Z Tuesday. The passage of the
upper level trough looks to have mixed the area out fairly well
and should keep the marine layer from reforming overnight inland.
Models are suggesting that a SCT/BKN deck could form around 4000
to 5000 foot starting around 05Z Wednesday north of KSLE, have
moderate confidence in this happening.

Coastal areas should see a reformation of MVFR cigs around 2000
to 3000 feet starting around 03Z Wednesday. KONP could see some
brief periods of IFR cigs starting around 09Z Wednesday.
Predominantly VFR conditions expected to return to the coast
starting around 15Z Wednesday.

KPDX AND APPROACHES...VFR conditions are expected through tonight.
Moderately confident that a SCT/BKN 4000 to 5000 foot cig
develop starting around 15Z Wednesday. /42


&&

.MARINE...A northwesterly wind pattern will continue throughout
much of the forecast period. Winds will remain below 15 kt
through Wednesday morning. The NE Pacific high will strengthen
Wednesday through Thursday and will contribute an increased
pressure gradient to a localized thermal trough originating over
southern Oregon. This will result in stronger winds particularly
in the southern inner and outer waters. Gusts of around 25 kt and
choppy seas will prompt the issuance of a Small Craft Advisory
for Wednesday afternoon into Wednesday night. This advisory may
be extended through much of Thursday if the wind pattern holds.
Winds will weaken Friday through Saturday morning.

Seas will remain between 3 to 4 ft today through Wednesday
afternoon. Wave heights in the southern inner and outer waters
will increase to be between 5 to 6 ft and will remain at this
height going into the weekend. -BPhillips

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 1 PM Wednesday to 2 AM PDT Thursday
     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 forecast area.


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