397 
FXUS66 KPQR 301302 AAB
AFDPQR

Area Forecast Discussion...Corrected
National Weather Service Portland OR
602 AM PDT Fri Jun 30 2023

Updated WWA headlines

.SYNOPSIS...Onshore flow is expected to continue over the next 
week with mainly dry weather and above average temperatures. 
Patchy drizzle and fog along the north coast possible through 
this morning. Warm temperatures are expected through the 
weekend. However, a more substantial warming trend is likely 
early to mid next week, which could cause impacts around the 
upcoming holiday.

&&

.SHORT TERM...Friday through Sunday...Ensemble guidance 
remains in good agreement that the upper level trough currently 
moving toward the British Columbia coast will nudge farther 
south today, lowering heights over the PacNW and producing 
mainly zonal flow through Saturday as the low moves through 
central British Columbia. By Sunday, ensemble guidance shows 
high pressure beginning to build over the NE Pacific into the 
Gulf of Alaska with weak shortwave troughing extending over the 
PacNW as the upper trough slides into Central Canada. At the 
surface, high pressure is expected to remain situated over the 
eastern Pacific with low pressure east of the Cascades. Onshore 
flow will increase under this pattern with strengthening surface
pressure gradients, leading to breezy north to northwest winds.
Gusts up to 20-25 mph are possible in the late afternoon and 
evening hours each day for inland locations and up to 30 mph 
along the coast. Additionally, patchy drizzle and dense fog 
remain possible along the coast this morning.

Above normal temperatures continue through the weekend with 
lowland highs generally in the mid to upper 80s. Probabilities 
of temperatures reaching or exceeding 90 degrees Friday range 
from 30-50% across the central and southern Willamette Valley
and 10-20% for the northern Willamette Valley. For the weekend,
these probabilities are only 10-25% across the lowlands due to
troughing. Along the coast, temperatures will remain more mild 
due to the onshore flow influence with temperatures in the mid 
60s to low 70s. -HEC/DH

.LONG TERM...Monday through Thursday...There is little change to
the extended forecast as hot and dry weather will be the main
impacts leading into the holiday week. WPC 500 mb cluster
analysis indicates ensembles are in good agreement that on
Monday the upper ridging over the NE Pacific will continue to 
build into the Gulf of Alaska, beginning to spread east to the 
PacNW coast and the lower heights will begin to shift into
eastern Washington/Oregon. At the surface, high pressure will 
remain situated over the eastern Pacific with a thermal trough
beginning to push north into Oregon. The warming trend is
forecast to begin today with NBM deterministic guidance
indicating high temperatures mainly in the low 90s across the
lowlands. Probabilities of temperatures reaching or exceeding 
90 degrees are around 50-75%.

Tuesday and Wednesday are still slated to be the hottest days of
the week. ECMWF Extreme Forecast Index (EFI) continues to 
suggest anomalously hot temperatures for these dates. WPC 500 
mb clusters indicate the majority of ensemble members suggest 
heights continuing to build over the PacNW Tuesday into 
Wednesday, with only 20% of solutions indicating heights 
slightly lowering on Wednesday. At the surface, the thermal 
trough is expected to extend north over western Oregon. This 
will allow temperatures to rise to the mid to upper 90s across 
the lowlands. Even if the 20% of the ensemble solution occurs, 
temperatures would likely remain in the 90s. NBM probabilities 
of temperatures reaching or exceeding 90 degrees continues to 
remain high for the lowlands at 85-95% each day. Additionally, 
there is a 10-45% probability of temperatures reaching or 
exceeding 100 degrees. These temperatures will create a moderate
risk of heat related illness, especially for those planning on 
spending extended time outdoors around the holiday. 

Thursday into late next week, ensemble guidance indicates the 
upper ridge will slowly retrograde west with heights beginning 
to lower over the PacNW. 500 mb cluster analysis shows there is 
some uncertainty on the timing of this as well as how much
heights will lower. Because of this, temperatures could remain
in the 90s Thursday and possibly longer with NBM probabilities 
of temperatures reaching or exceeding 90 degrees at 40-60%.
NBM deterministic guidance has temperatures dropping to the
upper 80s to low 90s for Thursday.

This pattern is expected to create elevated fire weather 
concerns due to prolonged drying of fuels. Onshore flow is 
expected to continue through the forecast period with periods of
breezy northwesterly winds with gusts up to 20-25 mph in the 
afternoon and evening hours. These winds could exacerbate fire 
weather concerns, especially with holiday activities, though the
overall pattern does not suggest high fire weather concerns. 
Those spending time outdoors should practice heat safety as well
as fire safety. -HEC

&&

.AVIATION...IFR to MVFR stratus has pushed onto the coast and 
will spread eastward through the Coast Range gaps overnight. 
Pressure gradients are remarkably similar to 24 hours ago. As 
such, have leaned into persistence. Nonetheless, high resolution 
model guidance suggests a 70-80% chance that IFR conditions make 
an appearance at KTTD around 15-16z Friday, but only a 30-40% 
chance that similar conditions develop at KPDX and KUAO. For now 
will continue to keep high IFR to low end MVFR ceilings only in 
the forecast at KTTD. Given stronger north to northwesterly winds 
are expected across the waters on Friday, latest high resolution 
model guidance suggests a 70-80% chance that conditions should 
return to VFR conditions along the coast after 21z Friday. 

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

KPDX AND APPROACHES...Northwesterly onshore flow will lead
predominantly VFR conditions through 06z Saturday. The latest high
resolution model guidance suggests a 30-40% chance that high end
IFR conditions could develop between 13-16z Friday. Given 
pressure gradients are remarkably similar to last night and 
stratus along the coast is shallower, have kept the forecast VFR.

&&

.MARINE...Expect a persistent pattern through the weekend and 
into next week; high pressure over the NE Pacific with a diurnally
driven thermal low over the OR/CA border will bring a rise in 
winds and seas each afternoon with a slight weakening during the 
overnight hours. 

The synoptic scale ridge of high pressure over southern California
will strengthen today and into Saturday. This will enhance the 
thermal low over the OR/CA border during the afternoon and evening
hours. High resolution model guidance continues to show chances 
for Gale Force wind gusts across the southern parts of PZZ253 
around Florence this evening. But because the spatial extent of 
the hazard is so small, will not issue a Gale Warning but mariners
should take extra precaution in this area. 

Moving into Saturday gradients across the waters will tighten 
further as the thermal strengthens and the NE Pacific high ridge 
axis shifts east towards the coastal waters. Chances for Gale 
Force wind gusts are again high during the late afternoon hours 
and into the early parts of the night. The forecast currently has 
wind gusts up to 34 kt for areas south of Waldport roughly between
5-30 nm offshore for about a 6 hour period. Will not issue a Gale
Watch, again, because of the relatively small spatial extent of 
the marginal wind gusts and the relatively brief period in which 
they will be occurring Saturday evening.

Winds will weaken slightly going into Sunday but expect advisory
level northerly winds and periodically, steep wind driven seas 
through much of next week. 

Latest guidance suggests about a 70% chance of visibility of 1 NM
or less across the inner waters south of roughly Tillamook 
tonight, then these chances decrease Friday morning. Will maintain
the Dense Fog Advisory through 5 AM for the inner waters.
-BMuhlestein

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Saturday for Coastal waters 
     from Cape Shoalwater WA to Cape Falcon OR out 60 NM.

     Small Craft Advisory until 8 AM PDT Sunday for Coastal waters 
     from Cape Foulweather OR to Florence OR out 10 NM.Coastal 
     waters from Cape Foulweather OR to Florence OR from 10 to 
     60 NM.

     Small Craft Advisory from 8 PM Saturday to 8 AM PDT Sunday for 
     Waters from Cape Shoalwater WA to Cape Falcon OR from 10 to 
     60 NM.
&&


&&

$$

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