462
FXUS66 KPQR 031755
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1055 AM PDT Fri May 3 2024

.UPDATED AVIATION DISCUSSION...

.SYNOPSIS...
Dry start to the morning before the next system
brings heavier rain this afternoon into Saturday. No widespread
hydrological concerns expected. Snow levels will rise above
7000 feet today, then fall back down to Cascade pass-level
tomorrow. Expect another round of advisory-level snowfall above
3500 ft this weekend. Cool, wet, unsettled weather likely
continues through early next week. Pattern change into drier and
warmer weather begins Wednesday through late next week.

&&

.SHORT TERM...Today through Sunday night...High clouds
associated with the next low pressure system are filtering
through the Pacific Northwest and will gradually thicken this
afternoon. Expect rain to begin at the coast around 12-1 PM and
spread into the Willamette Valley by 2-5 PM as the system`s
warm front lifts over the area. Rain will continue tonight into
Saturday morning as the trailing cold front pushes through. This
system will have an abundant amount of moisture as IVT values
max out around 300-400 kg/ms this evening. Models still show
precipitable water values around 1 inch, which is about two
standard deviations above normal for this time of year.

There have been minimal changes the total QPF forecast with
this system. Still expect around 1-1.5 inches for the interior
lowlands, and 1.5-2 inches for the coast and mountains from late
morning today to tomorrow (Saturday) afternoon. No impactful
winter weather is expected for the Cascade passes today as snow
levels will rise above 6500 to 7000 feet. Despite the impressive
QPF forecast amounts for early May, no hydro concerns are
expected thanks to the quick-moving nature of this system. HEFS
probabilistic guidance continues to show a less than 5% chance
of reaching action stage for the majority of rivers. Two rivers
with the highest chances of reaching action stage are Marys
River at Philomath (5-10% chance) and Tualatin River near Dilley
(15% chance).

As the low pressure system progresses southward toward California
tomorrow, cold air aloft will return and snow levels will fall
back down to around 3500 to 4000 feet. We`ll still continue to
see precipitation this weekend, so another round of winter weather
will be in store at pass-level. A Winter Weather Advisory has
been issued above 3500 feet for the North Oregon Cascades to the
Lane County Cascades from 5 AM Saturday to 11 AM Sunday morning.
These locations are forecast to receive around 4 to 10 inches
of snow, except up to 16 inches for the highest peaks above
5000 feet. Those traveling through the passes this weekend
should prepare for winter weather conditions. Meanwhile, the
lowlands will continue to see rain showers through the weekend.
                                                    -Alviz


.LONG TERM...Monday through Thursday...The early part of next
week continues to look cool and showery as ensembles from WPC
cluster analyses show upper level troughing across the Pacific
Northwest through Tuesday. Still not seeing any signals for
particularly notable QPF in any one period beyond Saturday, but
area rivers will likely continue to run high for this time of
year as episodic bouts of rain continue across the region.
Temperatures through Tuesday will continue to run below normal,
with daytime highs struggling to get out of the 50s.

On Wednesday, ensemble guidance begins to suggest drier and
warmer conditions as an upper level ridge builds over the NE
Pacific and extends into our area. By Thursday, WPC clusters
suggest that the ridge strengthens further over the Pacific
Northwest, leading to clearing skies and a quick rise in daytime
temperatures. NBM suggests a 30-50% chance that afternoon highs
on Thursday exceed 70 degrees for interior lowlands. This trend
looks to continue going into next weekend.         -Alviz/CB

&&

.AVIATION...High clouds continue to filter into the area ahead of
next frontal system approaching the coastline - VFR conditions
hold through most of the afternoon at inland sites. The front
properly moves ashore around 20z Fri, reaching the Willamette
Valley around 22z Fri to 00z Sat. Model guidance indicates around
a 60-70% chance of high end MVFR conditions at that time at all
terminals. The southern coast (KONP) sees the most precipitation
trained there, and around a 70% chance of IFR conditions is expect
at that time. These probabilities continue through 18Z Sat. With
deep moisture, expect mountains to become obscured.

Winds remain fairly variable and light (<5 kt), but once the
front nears, winds will take on a stronger southerly character.
Winds at coastal terminals will begin to gust to around 20-25 kt
from the south around 19-23z Fri, then gradually veer more
southwesterly and weaken through the rest of the TAF period.

PDX AND APPROACHES...VFR conditions under increasing high clouds
continue going into the afternoon hours today. The front moving
into the region arrives around 00z Sat with around a 50-60%
chance of high end MVFR ceilings develop shortly afterwards
between 03-06z Sat. Chances increase to around 80% after 06Z Sat.
Winds generally east through about 00Z Sat then more south to
southeasterly. Expect periods of rain and MVFR conditions to
continue through at least 18z Sat. -Schuldt/mh

&&

.MARINE...
Weak high pressure over the waters early today gives way
to a cold front associated with a low dropping out of the Gulf of
Alaska.  Winds along the coast will not be as high as the outer
waters as they are not aligned directly to the coastline. Winds
will be in the 15 to 20 kt with gusts to 30 kt range from 10-60
NM. The north Oregon and central Oregon inner waters may still
see isolated gusts up to 25 kt this afternoon. Due to a lack of
widespread increased winds, have decided not to issue a small
craft advisory for the inner waters. However, there remains a
slight probability in the case the low tracks a little further
north than currently project. Winds ease this evening, but expect
to see a period of steep seas (6 to 8 ft at 8 to 9 seconds)
through Saturday morning, possibly longer, so have extended the
Small Craft Advisory until 11 AM Sat. Will have to watch for steep
seas reaching the inner waters on Saturday. /mh

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 5 AM Saturday to 11 AM PDT Sunday
     for ORZ126>128.
WA...None.
PZ...Small Craft Advisory until 11 AM PDT Saturday for PZZ271>273.
&&

$$

www.weather.gov/portland

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