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FXUS66 KPQR 290245 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
745 PM PDT Thu May 28 2020

Updated aviation discussion

.SYNOPSIS...High pressure on Friday brings temperatures into the low
to mid 80s inland and, into the low to upper 60s along the coast. Low
pressure will move northeast towards the area Friday afternoon. This
will bring a more active pattern, including a slight chance for
thunderstorms and, cooler temperatures across the area through
Saturday. Sunday a return to a more seasonal late May/early June
pattern develops.

&&

.SHORT TERM...Tonight through Saturday night...The ridge which has
been the dominant synoptic feature anchored across the Pacific NW,
will slowly move eastward tonight. At the same time a vertically
stacked low, which has been mentioned in previous discussions starts
to move into the area Saturday. Deterministic and ensemble models are
showing this low maintaining a northeastward track. As a result this
will lead to a more active pattern across the area from Friday
afternoon through at least Saturday afternoon. Model soundings are
signaling that upper level convection will develop in the easterly
flow. What this means is that any cells that develop along the
Cascades will push inland into the Willamette Valley. Specific timing
is still questionable as models are not in exact step with each
other. Therefore storms could start slightly earlier than Friday
afternoon or linger after Saturday afternoon. However, models do have
the low pushing further northeast throughout Saturday, this will
cause the easterly winds to turn southerly and impede storm
development. Saturday will be cooler because of clouds and
precipitation. /42

.LONG TERM...Sunday through Friday...Sunday a return to a more
seasonal late May/ early June pattern returns as and upper level
trough maintains an onshore flow pattern through the early part of
next week. Tuesday and Wednesday look to be rather dry, but models
start to diverge on Wednesday. The GFS has a low has a surface low
developing west of 130W on Wednesday and moving east towards Puget
Sound by Thursday. The cold front associated with this low would
bring the next round of precipitation to the area from Thursday
through Friday. The ECWMF on the other hand has a more zonal flow
pattern developing through the middle of the week, with an upper
level trough and surface low developing in between 130W and 140W but
north of 40N, moving eastward and being just offshore on Friday. With
this in mind have kept moderate PoPs in the forecast for most of the
area from Wednesday through Friday. /42

&&

.AVIATION...Expect mainly VFR conditions through Friday, except for
areas of IFR stratus along the coast overnight into Friday morning.
Guidance continues to hint at some coastal stratus filtering locally
inland later tonight, with IFR conditions possible along the south
Washington coast and lowlands and far north Oregon coast, generally
north of KTMK, between 12Z-18Z. KEUG may see a scattered layer of
IFR clouds near sunrise, but the chance of IFR cigs are low. Expect
increasing mid and high clouds Friday afternoon, with isolated
thunderstorms possible along the Cascade Crest after 21Z. There is a
chance that some of these storms may drift into the valley Friday
night

KPDX AND APPROACHES...VFR the next 24 hours with weak northwesterly
flow. Expect increasing mid and high clouds Friday afternoon.
/64/Weishaar

&&

.MARINE...North wind 15-20 kt will continue through late evening.
Gusts to 25 kt have been noted at buoy 46029 earlier today, but
the gusts have eased a little into the early afternoon.
Contemplated putting out an advisory, but it appears these 20-25
kt gusts have been localized and infrequent. The 12Z models
continue to advertise stronger wind Fri afternoon and evening.
Will issue a small craft advisory for all waters 18Z Fri through
12Z Sat. The wind becomes west at 15 kt or less Sat afternoon
and continues through Sun morning. A return to the typical
northwesterly pattern occurs Sun afternoon and prevails through
at least the middle of next week. It is likely small craft
advisory level gusts transpire in the afternoons and evening
early next week.

A northwest swell continues to build in the waters this afternoon
and evening peaking at or just under 10 ft at 14 seconds early
Friday and subsiding to around 7 feet early Saturday. Another
shorter duration NW swell will build seas to around 9 feet
Saturday afternoon. The NW swell will slowly subside through mid
next week. Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 11 AM Friday to 5 AM PDT Saturday for
coastal waters from Cape Shoalwater WA 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 nm offshore. This area is commonly
referred to as the forecast area.
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