National Weather Service Raw Text Product

627 
FXUS66 KPQR 250405 AAA
AFDPQR

Area Forecast Discussion...Update
National Weather Service Portland OR
905 PM PDT Thu Jun 24 2021

Updated aviation discussion...

...UNPRECEDENTED HEAT WAVE EXPECTED THIS WEEKEND INTO NEXT WEEK...

.SYNOPSIS...An anomalously strong high pressure system aloft will
move into the Pacific Northwest region over the weekend and into next
week to bring a stretch of hot and dry weather, likely breaking
several temperature records. An upper low will travel northward off
the coast to bring a slow cool down to the region next week, but
temperatures will remain 10 to 20 degrees warmer than average for
late June and early July.

&&

.SHORT TERM...Tonight through Sunday...An area of high pressure
aloft, currently located offshore over the northeast Pacific, will
begin to strengthen and move northeast, arriving over Vancouver
Island by tomorrow afternoon. At the surface, northwesterly flow over
the waters and an overnight weak to moderate marine surge will push
marine stratus back into the coast overnight and patchy coverage into
the Willamette Valley into the morning. This will be the last
moderate push we see for several days though, due to the
aforementioned high pressure building in and a surface thermally
induced trough expanding into the area. 

Subsidence and warm air from the upper high and the high sun angle
part of the year will allow for about 10 degrees in warming tomorrow
over todays readings. This will bring upper 80s to mid-90s for most
of the area, except the far coastal areas who will still see some
onshore flow and remain in the mid 60s to mid 70s. This will start to
increase the possibility of heat stress and heat related issues, but
the real threat will start Saturday, when a Excessive Heat Warning
will go into effect.

The upper high will strengthen and move further inland over the
Pacific Northwest Saturday, allowing for even warmer air to be
generated and transported in northeasterly flow around the high over
the forecast area. Expect another 10 degree spike in temperatures on
Saturday, pushing highs past the century mark over most of the inland
areas. Highs will be likely break June records and may flirt with
all-time records. Winds will generally be light as the thermal trough
is over the Cascades, but will allow the coastal areas to remain cool
still with lighter onshore flow. Lows overnight will remain in the
upper 60s to low 70s, giving little relief, especially since these
aren't reached until early morning. Temperatures at midnight will
likely still be in the 80s. For perspective, the forecast lows are
similar to our average high temperatures this time of year. The upper
high will continue to strengthen for Sunday while the surface thermal
trough pushes west. This will be the hottest day across the area,
including the coastal areas. Dangerously hot readings in the 105 to
110 range will be found over most of the inland areas, and readings
around 80 for the coast. This day will likely have widespread records
broken, monthly and potentially all-time. After seeing models
continue their upward trend in forecast temperatures, we have 109 now
for Portland, beating the current all-time record temperature by 2
degrees, in June (more typical of late July/early August). Good thing
about this hot airmass is that humidity will be low where heat index
values will be very similar to the actual temperature.		     
/Kriederman
	  
.LONG TERM...Sunday night through Thursday...Another hot night is
expected Sunday night, once again with readings close to our average
high this time of year. The one exception will be over the far
southwestern part of the forecast area as a part of the thermal
trough is expected to split off and head out over the ocean, with
onshore flow around the southern end of it to bring cooler
temperatures, and a return to some marine stratus, likely south of
Tillamook. An upper low will be moving north offshore of Oregon
Monday and will shove the upper high to the east slightly, to back
down the highs a few degrees.  So while not as hot as Sunday,
readings will still be over the 100 degree mark and dangerously hot,
so the Excessive Heat Warning will continue through Monday.

The upper high will move slightly more east and become positively
tilted Tuesday through Thursday, with southwesterly flow aloft
expected for the forecast area. The thermal trough is expected to
move into eastern Oregon, allowing for some relief in temperatures,
yet readings will stay 10 to 20 degrees above normal for this time of
year.  Little pieces of energy rotating around the high pressure and
some moisture moving in may be allow for some convection to begin
again over the high terrain for next week.
/Kriederman

&&

.AVIATION...04z Update: Not much change in thinking for 06z
package as stratus has redeveloped at the coastal terminals and
high pressure dominates for the next few days. HREF probs 
suggest a nonzero chance that some low stratus could make it back
into a few valley locations toward daybreak Friday, but opted to
keep all inland terminals VFR given the expected weaker marine 
push tonight. /CB
 
Previous discussion...Building high pressure will result in VFR 
conditions across much of northwest Oregon and southwest 
Washington through 00z Saturday. The main exception to this will 
be along the coast where marine clouds should push back onto the 
coast between 00-03z Friday. This will likely result in a mix of 
MVFR and IFR restrictions that will likely persist until ~16-18z 
Friday. 

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

KPDX AND APPROACHES...Building high pressure over the region will
produce light winds and VFR conditions through 00z Saturday. 
/Neuman


&&

.MARINE...Models have backed off considerably on the northerly
winds expected across the waters off the central coast of Oregon
this afternoon and evening. As a result, opted to drop the Small
Craft Advisory that was in effect because it appears winds and
seas should remain well below criteria. Otherwise, expect 
generally sub-Small Craft Advisory level northerly winds through 
the weekend with seas fluctuating between 4-6 ft as high pressure
remains over the northeast Pacific. There is a chance that the
northerly winds could temporarily strengthen Sunday before a 
southerly wind reversal results in a burst of southerly winds and
fog spreading northward up the waters late Sunday. This burst of
southerly winds may be strong enough to necessitate a Small 
Craft Advisory. Some models suggest southerly wind gusts of 
25-30 kt will lift northward across the waters Sunday night and
this certainly seems plausible given the pattern.

High pressure then appears likely to rebuild across the 
northeast Pacific towards the middle of next week. As thermally 
induced low pressure shifts into the Great Basin, expect 
northwesterly winds to return to the waters towards the middle of
next week. /Neuman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning from 10 AM Saturday to 11 PM PDT Monday 
     for Cascade Foothills in Lane County-Cascades in Lane 
     County-Central Coast Range of Western Oregon-Central 
     Columbia River Gorge-Central Willamette Valley-Coast Range 
     of Northwest Oregon-Greater Portland Metro Area-Lower 
     Columbia-Northern Oregon Cascade Foothills-Northern Oregon 
     Cascades-South Willamette Valley-Upper Hood River Valley-
     Western Columbia River Gorge.

WA...Excessive Heat Warning from 10 AM Saturday to 11 PM PDT Monday 
     for Central Columbia River Gorge-Greater Vancouver Area-I-
     5 Corridor in Cowlitz County-South Washington Cascade 
     Foothills-South Washington Cascades-Western Columbia River 
     Gorge-Willapa Hills.

PZ...None.


&&

$$

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