363
FXUS66 KPQR 192227
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
327 PM PDT Fri Jul 19 2024

.SYNOPSIS...Above-average temperatures continue as high
pressure strengthens through Saturday. Chance of light showers
and thunderstorms late Saturday night through Sunday afternoon
with best chances along the coast. Then, broad upper level
troughing brings cooling trend early next week, with
temperatures around seasonable normals through next week.

&&

.SHORT TERM...Friday afternoon through Sunday...Visible
satellite imagery Friday afternoon shows mostly clear skies
across NW Oregon and SW Washington with the exception of low
stratus and fog right along the coast north of Newport. Smoke
plumes from wildfires in the central Oregon Cascades are also
visible this afternoon, and haze and smoke from these fires are
expected into the weekend. Inland temperatures are on track to
peak in the upper 80s today with 60s to low 70s along the coast.
Marine stratus and fog will build along the coast again this
evening into Saturday morning under upper level ridging.

The upper level ridge will amplify over the region on Saturday
while 850 mb temperatures warm to around 22- 24 deg C. Inland
highs are expected to reach the mid to upper 90s (60-95%
probability of reaching or exceeding 95 degrees), while highs
near Hood River will push triple digits (50-60% probability).
This will create widespread high-end Moderate HeatRisk across
the inland lowlands to to localized areas of Major HeatRisk
from the Portland metro through the Columbia River Gorge. A Heat
Advisory has been issued for the eastern Willamette Valley,
Portland Metro area, Clark County, Columbia River Gorge, and
Hood River Valley on Saturday.

Upper level ridge begins to shift eastward on Sunday. Models
continue to indicate a negatively tilted shortwave trough
lifting north over the coastal waters Saturday night through
Sunday, albeit rather weak. Chances are increasing for scattered
showers with light rain through Sunday afternoon across most of
the area (15-20%), though best chances are along the coast
(20-30%). Elevated convection potential has increased to around
15%, so have introduced thunderstorm chances to the forecast.
Temperatures Sunday afternoon expected to be around 10 degrees
cooler than Saturday, along with stronger onshore winds. -DH/HEC

.LONG TERM...Monday through Thursday...Temperatures are very
likely to trend cooler near seasonable normals early next week.
Upper level troughing nudges into the Pacific NW on Monday with
strong onshore flow. Marine stratus more likely to push inland
Monday morning with highs topping out around 80 degrees. WPC
cluster analysis remains in good agreement with model ensembles
showing upper level low centered near Haida Gwaii on Tuesday,
slowly shifting east into British Columbia by mid-week. NBM
guidance suggests temps will likely trend closer to the mid-80s
as near seasonal normals and dry weather persists next week. /DH

&&

.AVIATION...High pressure remains over the region, along with
mild southwest flow aloft, will maintain VFR conditions under
clear skies for inland areas.

Currently VFR and clear skies along the coast, but conditions
will return to IFR beginning 00-03Z Saturday, as the stratus will
once again surge back onshore. Conditions will remain at least IFR
until around 20Z Saturday, with chances of conditions lowering to
LIFR around 50-60%. Around 19-20Z Saturday, northwesterly winds
will increase along the coast, with sustained winds around 10-15
kt and gusts up to 20-25 kt.

PDX AND APPROACHES...Little change, with VFR conditions and clear
skies under high pressure and mild southwest flow aloft.
-JH

&&

.MARINE...High pressure offshore will gradually strengthen today
into this weekend, and with thermal low pressure on south Oregon
coast, will see return of north winds on the waters. As pressure
gradients tighten on Saturday, will see gusts to 25 kt at for Sat
and Sun, mainly in the afternoons/evenings from Cascade Head
southward. Seas mostly stay in the 3 to 5 ft range, with a mix of
variable period swell, but with gusty winds, will have locally
choppy steep seas to 6 or 7 ft. Again, this mainly for areas south
of Newport.                                          /Rockey

&&

.FIRE WEATHER...An upper level disturbance moving through NW
Oregon and SW Washington late Saturday night through Sunday will
bring an influx of mid level moisture to the region. This
moisture will produce a 10-15% chance of elevated thunderstorms.
Since the majority of the moisture is in the mid levels,
rainfall at the surface is expected to be limited, less than a
wetting rain. Therefore, a Fire Weather Watch has been issued
for most fire weather zones in the region excluding along the
coast, the northern Oregon Coast Range, and Willapa hills as
fuel conditions are not primed for rapid fire spread potential
in these areas. The main threat will be fires started by
lightning strikes as well as the potential for spread of new and
existing fires due to gusty outflow winds from thunderstorms.
Thunderstorm chances will spread from the south to north with
best chances 11 PM PT Saturday through 5 PM PT Sunday. -HEC

&&


.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Heat Advisory from 11 AM to 11 PM PDT Saturday for ORZ111-112-
     115-117-118-120>122.

WA...Heat Advisory from 11 AM to 11 PM PDT Saturday for WAZ205>207-
     209-210.

PZ...Small Craft Advisory from noon Saturday to midnight PDT Saturday
     night for PZZ251>253.

     Small Craft Advisory from noon Saturday to midnight PDT Sunday
     night for PZZ271>273.
&&

$$

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