499
FXUS66 KPQR 242038 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
138 PM PDT Mon Jun 24 2024

.SYNOPSIS...A transient shortwave ridge will bring dry and warm
conditions to the area Monday and Tuesday, warmest on Tuesday. An
upper level trough will then bring relatively cooler temperatures for
Wednesday and Thursday with increasing chances for rain showers. Warm
and dry conditions will return Friday and Saturday with near normal
to slightly above normal temperatures.

&&

.SHORT TERM...MONDAY NIGHT THROUGH THURSDAY...A transient shortwave
ridge will bring warmer temperatures and dry conditions the rest of
Monday and Tuesday. Temperatures today will peak in the upper 70s for
the Willamette Valley, mid 60s at the coast. Tuesday is projected to
be even warmer. For the Willamette Valley, NBM guidance shows a
60-80% chance of highs over 85 deg, and 20-40% chance of highs over
90 deg. The coast should remain cooler, closer to the upper 60s.
Cloud cover will be fairly minimal during these two days.

Tuesday night, the ridge begins to move eastward, accompanied by a
shift to westerly onshore flow, and the following upper level trough
begins to impact us. A few light showers may be possible Tuesday
night and Wed morning, but the weak warm front passes through Wed
afternoon, bringing a 10-20% chance of rain (mostly north of Salem).
Accumulations look little to none. This will be followed by a cold
front Wednesday night, with better chances for rain. PoPs at 40-70%
for northern regions, decreasing south of Salem. Rain continues until
Thursday evening, and chance of 0.25" of accumulation is below 10%
everywhere but the WA Cascades. The northern Willamette Valley and
northern coast can expect somewhere around 0.10-0.15" of rain, and
areas south of Salem should see little accumulation at all except in
the Cascades.

.LONG TERM...FRIDAY THROUGH MONDAY...Friday shows the trough moving
through, and we return to more of a ridge pattern. While uncertainty
still exists as to when the ridge moves out of the area, Friday at
least shows no real chance for rainfall, with a 60% chance of
temperatures in the Willamette Valley above 80. Saturday sees much
more uncertainty;  WPC Cluster analysis shows 60% chance of weak
ridging continuing, but there is the potential for a very weak and
transitory shortwave trough. If this occurs, expect very weak showers
and possibly cooler temperatures back into the low/mid 70s. Sunday
sees better ensemble agreement (70-80%) on stronger ridging beginning
to develop, continuing into early next week. /JLiu

&&

.AVIATION...High pressure remains over the region, with dry mild
southwest flow aloft. This will maintain VFR under mostly clear
skies through Tuesday. Light low level onshore flow over western
WA and far nw Oregon, and will maintain lower VFR clouds in that
area into early this evening.

PDX AND APPROACHES...High pressure with mild dry southwest flow
aloft will maintain VFR under clear skies.

&&

.MARINE...High pressure will remain over the offshore waters
tonight and Tuesday. Meanwhile, thermal low pressure stays over
northwest Calif into far sw Oregon. This will keep the northerly
pressure gradient tight enough to support north winds gusting 20
to 25 kt into this evening far the waters south of Newport. Seas
still running at 6 to 8 ft, but will fall back to 5 to 6 ft later
tonight into Tue.

Otherwise, not much change in the pattern for early this week,
as high pressure remains anchored off the Pac NW. Low pressure
will arrive mid-week, with a weakening front arriving. This will
bring return of unsettled weather, with return of west to
southwest winds, but still mostly 15 kt or less.    /Higockey

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory through Monday evening for
 PZZ252-253- 272-273.

&&

$$

www.weather.gov/portland

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