242
FXUS66 KPQR 151006
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
306 AM PDT Wed May 15 2024

.SYNOPSIS...High pressure lingers through Wednesday as a weak
trough begins to ascend from the Gulf of Alaska on Thursday.
While a pattern shift is in store, precipitation will be
minimal. Zonal flow follows which will keep the weather mild and
dry.

&&

.SHORT TERM...Now through Thursday Night...High pressure
continues to build over the next 24 hours and will reach it`s
peak intensity this afternoon. Have seen a return of the marine
stratus which, as of 2 AM is sitting just offshore. However,
over the next few hours it will push inland filling the north
Oregon and south Washington Coasts, and moving through the Coast
Range Valleys. High resolution models are showing increasing
clouds once again around the Portland-Metro including Vancouver,
Camas and Troutdale. However, the inland clouds will burn off
fairly quickly as the sun rises and conditions begin to warm.

Overnight temperatures are trending nearly ten degrees warmer
than the previous night, so a persistence forecast for daytime
highs will be skewed. Decided to incorporate the 90th percentile
to the interior lowlands as the warmer temperatures overnight
will act as a springboard for daytime highs. Conditions will
see minimal change from what occurred on Tuesday - clear skies,
warm temperatures, and northerly winds.

Thursday on the other hand will see a pattern shift as a
shortwave trough tracks southeastward from the Gulf of Alaska.
At 500 mb, there are some isolated bands of absolutely
vorticity, but most of the activity is to the north. This is
coupled at the jet stream as a band of 115 kt winds moves over
the forecast area Thursday. This support, along with the cold
frontal band, will initiate precipitation. A majority of the
precipitation will fall north of Marion County in Oregon. The
orographic lift over the Cascades will enhance the precipitation
and keep it going a bit longer. Ultimately though, the amount of
precipitation is non-impactful, and will be fairly benign.
-Muessle

.LONG TERM...Friday through Tuesday...As the cooler front exits
the region, zonal flow will take over. Temperatures will settle
out and stay fairly consistent through Saturday. Another low
pressure system will move over Canada extending a trough over
the west. This trough will bring another round of precipitation
and a gradual cool down. The ridging to the east though will
cause winds to amplify. Through the Columbia River Gorge we
could see some gustier winds on Saturday.

The pattern gets pretty messy on Sunday. Looking at the 500 mb
heights cluster analysis, there are a few that are showing a
ridge redeveloping, others a trough, and others maintain the
zonal flow. The outcome leads to a low confidence forecast in
regards to temperature and wind. NBM temperatures have quite the
spread on Sunday through Tuesday with the 90th percentile
reaching 80 degrees. However, deterministic models are
suggesting temperatures in the mid-60s, with westerly winds.
-Muessle

&&

.AVIATION...High pressure will bring mainly VFR flight conditions
today as mostly clear skies remain in place over the region. The
exception is along the coast where an LIFR to IFR marine stratus
deck is currently expanding southward from KAST down towards KONP.
Still expecting this stratus deck to move into KONP by 12z
Wednesday, but possibly as early at 10z. Gusty north winds will
redevelop along the coast Wednesday afternoon and linger through
the evening hours, strongest at KONP where gusts should peak
around 25 kt.

Although skies were mainly clear over inland areas as of 09z
Wednesday, there is a 55-85% chance of MVFR cigs developing over
and near KTTD between 12-18z (best chance around 15z). Will
maintain MVFR cigs in the KTTD TAF as this still appears to be the
most likely outcome.

PDX AND APPROACHES...VFR flight conditions are likely to continue
over the next 24 hours under mostly clear skies. That being said,
there is a 40-50% chance for a brief period of MVFR cigs between
13-17z Wednesday at the KPDX terminal. The most likely outcome
will be for MVFR cigs to stay confined to the east of KPDX,
impacting KTTD. -TK

&&

.MARINE...High pressure continues over the waters today, resulting
in a typical summertime northerly wind regime. Similar to
yesterday, northerly winds will peak in strength during the
afternoon and evening hours with gusts to around 25 kt to the
north of Cape Foulweather and gusts to 30 kt to the south.
Therefore, have extended the Small Craft Advisory for all marine
zones to continue through the afternoon for the northern waters,
through the evening for the central waters, and through Wednesday
night for the southern waters. Winds should temporarily fall
below small craft criteria on Thursday as a weak cold front moves
inland, but should increase behind the front Thursday evening with
gusts to around 25 kt.

Seas will generally remain between 5 to 9 feet over the next few
days as a primary northwest swell continues along with northerly
wind waves. -TK

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for PZZ251-
     271.
     Small Craft Advisory until 11 PM PDT this evening for PZZ252-
     272.
     Small Craft Advisory until 5 AM PDT Thursday for PZZ253-273.
&&

$$

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