892
FXUS66 KPQR 180402 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
901 PM PDT Fri May 17 2024

Updated Aviation Discussion

.SYNOPSIS...Dry and cool weather for the rest of the day with
pleasant onshore winds easing into tonight. Another shortwave
trough pushes over the area Saturday into Sunday morning, but
precipitation is minimal. Potential for more active weather
starting Tuesday.

&&

.SHORT TERM...Now through Sunday...Maintaining zonal flow
through the rest of today with little to no actionable weather.
Temperatures will be in the mid to upper 60s with winds
decreasing in the Columbia River Gorge and ranges as onshore
winds ease. Winds are expected to stay northwesterly through
this evening. Tonight, temperatures will drop to the low 40s
and winds will become light and northerly.

A shortwave trough will move southeast into the region Saturday
and last through Sunday morning. With the low located north over
central Washington, will experience the southern band of
precipitation, resulting in minimal precipitation mostly in SW
Washington. Guidance suggests a 30-50% chance of measurable
precipitation for Saturday in SW Washington and north of
Tillamook, and only a 10-20% chance from Portland to Salem. With
850mb air mass aloft expected to be around -2 degree C, expect
temperatures to cool a degree or two. As the trough exits the
region Sunday, a ridging pattern will develop and persist
through early next week.

.LONG TERM...Monday through Thursday...Warm conditions in the
low 70s Monday. A potentially robust and organized trough will
drop from the Gulf of Alaska into our region midweek, some time
between Tuesday and Wednesday morning. The 500mb long range
ensemble clusters suggest the trough arriving Wednesday
morning/afternoon while NBM suggests Tuesday morning/afternoon.
This storm has potential to bring more precipitation than we
have seen as of late. Ensemble member guidance suggests around
0.3 inch for 24 hour precipitation for inland valleys, with
chances around 10-20% to exceed this value. Some members do
suggest potential for precipitation accumulation to reach 0.5
inch, however there is not enough convergence to be certain
(20-30% of members suggest 0.50 inch). Overall, there still is
quite a bit of variation in the intensity and the timing. Either
way, expect lingering showers Wednesday and then dry weather
Thursday.
-JH

&&

.AVIATION...VFR conditions prevail across most of the airspace.
Guidance indicates VFR conditions prevail through Saturday for
inland areas, but with a 10-20% chance for MVFR cigs from 10Z-20Z
Sat. Coastal areas expected to remain VFR as well but with a
25-45% chance for MVFR cigs north of KTMK from now through around 20Z
Sat. Will see a gradual increase in precipitation chances across
north Oregon/south WA coastal area and along the Cascades starting
around 18Z Saturday. Precipitation could result in brief periods
of MVFR conditions. Winds will generally remain out of the
northwest sustained between 5-10 kt.

PDX AND APPROACHES...Expect VFR flight conditions through
Saturday. There is around a 15% chance for MVFR from 10Z-20Z
Saturday. Winds will generally remain out of the northwest
sustained between 5-10 kt. /42

&&

.MARINE...North to northwest winds continue over the waters
tonight as high pressure remains over the waters with a thermal
trough along the south Oregon coast. Strongest winds occurring
south of Newport (zones PZZ253,273) where pressure gradient
tightest.  Seas will be rather steep and choppy through tonight
due to a fresh northwest swell around 7 to 9 ft with a dominant
wave period between 7 and 9 seconds. Seas gradually subside and
the periods increases Saturday to reduce choppiness.

High pressure over the upcoming weekend will result in a typical
summertime northerly flow regime with wind gusts peaking in
strength during the afternoon/evening hours each day. The
strongest winds will occur over the southern zones where marginal
small craft advisory level wind gusts to 25 kt are possible
(20-40% chance on Saturday increasing to a 30-70% chance on
Sunday and Monday).

The next frontal passage of any significance is set to arrive
Monday night into Tuesday morning, bringing rain and a shift to
westerly winds. However, wind gusts look to generally stay around
or below 20 kt as the pressure gradient associated with this
frontal passage appears rather weak. The exception to that is
over the northern outer waters where isolated small craft advisory
level gusts to 25 kt are possible (20-50% chance). /mh-TK

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 6 AM PDT Saturday for PZZ251>253-
     271>273.
&&


$$

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