Rip Current in Washington, May 31, 2021

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
920 AM PDT Mon May 31 2021

Updated aviation discussion

.SYNOPSIS...A warming and drying trend will continue for the next
couple of days, peaking on Tuesday with inland valley temperatures in
the upper 80s to mid 90s. The second half of the week will feature
more seasonable temperatures and increasing chances for rain, but at
this point it appears the rain will not amount to much for the
majority of our forecast area.

&&

.SHORT TERM...Today through Wednesday...Early morning satellite
imagery is quite similar to the last couple mornings, but so far
without the fog and low clouds that were along Oregon's central coast
Sunday morning. As of 3 AM the closest marine stratus was well
offshore and there is no sign of it approaching the coast. Cannot
rule out a few patches of fog this morning in the coastal valleys,
otherwise today looks like another mix of sun and mainly thin high
clouds which will filter the sunshine from time to time.

Meanwhile, a strong upper level ridge will continue to build into the
Pac NW from the southwest, with models agreeing on 500 mb heights in
the mid to upper 580s decameter range. This should push most of the
high cloudiness north and west of the forecast area, resulting in
stronger solar energy reaching the ground today and Tuesday. Along
with a progressively warmer air mass aloft, this should result in
further warming today and Tuesday. The 850 mb temperature from Sunday
afternoon's Salem sounding was +13.4 deg C; the 00z ECMWF
deterministic run warms these 850 mb temps to around +16 deg C this
afternoon and to around +20 deg C by Tuesday afternoon. Meanwhile,
the strong upper ridge will keep the marine layer compressed to the
point of having little impact on temperatures outside of the
immediate coast and perhaps a few miles into the coastal valleys.
With minimal marine influence except near the beaches and high
cloudiness decreasing enough for nearly full sunshine, these 850 mb
temps can be considered reflective of the temperature trends
for our forecast area in general.

With all this in mind, we expect afternoon temperatures to warm
further into the 80s for the inland valleys today, with 70s and lower
80s for the mountains and coastal valleys. It is not out of the
question that some of our hotter inland valley locations reach 90
degrees today; NBM gives Salem a 50/50 chance of doing so (but only a
10% chance for Portland and Eugene). With a reasonably dry air mass
in place, overnight temperatures should cool to fairly comfortable
levels tonight outside of the urban cores. Temperatures continue to
heat up inland Tuesday, with it now seeming highly likely that most
of our interior lowlands reach the lower 90s during the afternoon.
There is even the possibility a couple spots could push into the mid
90s, which is getting into the territory where we would consider a
Heat Advisory. That said, our heat risk algorithm does not suggest
issuing an advisory, which seems to be a good call considering the
ability to cool off at night. While outlying rural or suburban
valleys should able to cool into the 50s each night, urban areas will
struggle to fall below the lower 60s. While we may actually end up
breaking record warm minimum temperatures each tonight and again Tue
night, these kind of overnight temps are not all that uncommon
during the summer, and therefore are not particularly alarming from
a heat risk standpoint either.

Wednesday will be another hot day inland, but changes will begin as
our upper ridge begins to shift eastward and a Pacific frontal system
approaches. This should serve to deepen the marine layer with
increasing low clouds along the coast, potentially wringing out some
drizzle as early as Wed night. The deepening marine layer and
somewhat stronger onshore flow should also begin a cooling trend
through the coastal valleys. But as mentioned, inland areas will
remain hot as 00z EC ensemble 850 mb temps remain in the upper teens
deg C. As a result, expect Wed afternoon temps to top out within a
few degrees of 90 deg F for our interior lowlands. A few models hint
toward thunderstorms along the central and southern Oregon Cascades
as the upper ridge shifts/breaks down Wed afternoon, but these should
remain east of the crest due to southwesterly flow aloft.  Weagle

.LONG TERM...Thursday through Sunday...Precipitation chances Thursday
continue to look less and less impressive on most models, and only a
handful of 00z ECMWF ensembles show any QPF for Portland Thursday.
Coastal areas and west slopes of the Coast Range stand a better
chance of picking up measurable drizzle or light rain, but
significant rains are not expected. This first, splitty system gets
sheared apart and shoved eastward Thu night and Friday as an
unseasonably strong and zonal Pacific jet stream pushes into the
Pacific Northwest. This should decisively bring an end to the warm to
hot weather, with temperatures possibly even dipping a little below
seasonal norms over the weekend. Unfortunately, most guidance keeps
the moisture field shallow despite all the dynamic support. This may
result in several moisture-starved disturbances swinging through the
forecast area to keep our weather a tad unsettled but without enough
precipitation to make a significant dent in our recent drought
conditions.  Weagle

&&

.AVIATION...18Z TAFS: VFR with high clouds and northerly winds
across the area through 18Z Tue. The 12Z HREF shows a 50-60%
chance of IFR stratus along the coast between 12Z and 15Z
Tuesday, especially near coastal bays and river valleys. IFR
conditions will improve between 15Z to 18Z along the coast but
low cloud cover will likely stay just offshore which may surge
onshore periodically as winds shift ever so slightly onshore.

For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR with high clouds through 18Z Tuesday.
Prevailing northwest wind to 10 kt 22Z through 05Z Tuesday.
Transitioning to calm overnight. -BPhillips

&&

.MARINE...A typical summertime pattern will continue across the
coastal waters for the next few days. High pressure will remain
over the waters with thermally-induced low pressure confined to
the north California and south Oregon waters. The 00Z model
guidance shows tightening northerly surface gradients over
PZZ255 and PZZ275 this afternoon. Several models suggest 20-25
kt boundary layer wind speeds over the south zones beginning mid
to late afternoon. The current advisory looks good. Will need to
monitor PZZ255 for potential advisory conditions. Gradients look
to weaken slightly Tue afternoon, but there is a chance for small
craft advisory conditions again for PZZ275.

Wind speeds diminish Tue night through Wed as the thermally-
induced surface trough dissipates and wind direction shifts more
to the west.

Seas remain dominated by fresh swell. Longer range guidance
indicates seas building to 7 to 9 feet late in the week. Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
     Tuesday for Waters from Cascade Head to Florence OR from
     10 to 60 NM.

&&

&&

&&

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland