952
FXUS66 KPQR 200328 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
823 PM PDT Fri Jul 19 2024

Updated Aviation and Marine Discussions

.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

&&

.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

&&

.AVIATION...High pressure remains over the region, along with
mild southwest flow aloft. LIFR/IFR conditions along the coast as
marine stratus will persist along the coast through at least
17Z-19Z Saturday. Around 18Z-20Z Saturday, northwesterly winds
will increase along the coast, with gusts up to 25 kt.

For inland areas, VFR under clear skies are expected to develop into
IFR/MVFR conditions around 10Z-12Z Saturday within the Willamette
Valley as the aforementioned marine stratus will likely push through
the gaps/flows of the coast range. Around 17Z-19Z Saturday expect
VFR conditions to return along with northerly winds.

PDX AND APPROACHES...VFR conditions will give way to IFR/MVFR
conditions around 12Z Saturday. Around 17Z Saturday expect VFR
conditions to return along with northerly winds. /42


&&

.MARINE...High pressure offshore will gradually strengthen into
this weekend, and with thermal low pressure on south Oregon coast,
will see return of northerly winds . As pressure gradients
tighten on Saturday, will see gusts up to 25 kt across all waters
for Saturday and Sunday. As a result have issued a Small Craft
Advisory for all waters starting late Saturday morning. Seas
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.

Cold water and shallow marine stratus will result in patchy,
dense fog for near shore waters. As a result there is a Dense Fog
Advisory for zones PZZ252 and PZZ253. This fog could spread to
PZZ251 and the Columbia River Bar, so will keep an eye on
observations and expand the advisory as needed. /42

&&

.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.

     Dense Fog Advisory until 9 AM PDT Saturday for PZZ252-253.

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

$$

www.weather.gov/portland

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