NWS Portland, OR wrote its last area forecast discussion before the first event at Oct 25, 8:33 PM PST, 57 minutes earlier.
Area forecast discussion, Oct 25, 8:33 PM PST, 57 minutes before
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
933 PM PDT Fri Oct 25 2024
Aviation Discussion Updated...
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.SYNOPSIS...A slow moving front shifts inland tonight, with
another front arriving later Sat night. Cooler, with showers for
Sunday into early next week, with snow in the Cascades. Another
strong front looks to arrive next Wed, with more rain and
mountain snow.
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.SHORT TERM...(Today through Sunday)...Gusty east winds
continue through the western Columbia River Gorge and into the
eastern Portland/Vancouver metro. The pressure difference
between TTD- DLS remains around -10 mb, producing winds gusts
between 25-30 mph at TTD and between 40-50 mph farther east up
the Columbia River. Gusty winds are expected to continue into
the evening but will relax as low pressure approaches from the
west, weakening the pressure gradient through the Columbia River
Gorge. Elsewhere, light easterly winds will shift to the south
through the evening as a strong area of low pressure passes
offshore and toward the northern Washington coast. Winds along
the north Oregon and south Washington coast will approach High
Wind Warning criteria for gusts along the beaches and headlands
from 7pm this evening to around 2am. Given this is also the
first stronger system of the year, could see some power outages
and minor damage.
Rain chances enter the coast after 00Z this evening and into the
Willamette Valley after midnight. This first round of rain from this
evening through Saturday will be showery and lighter with totals
ranging from 0.50-1.00 inches along the Coast Range and west while
totals from 0.25-0.50 inches are more likely inland. The second
round of rain will come as a fast moving front arrives later
Saturday night, with rain increasing overnight. This front will be
more robust, with decent shot of rain late Sat night into very early
Sunday. At this time, looks like solid 0.50 to 1.25 inch across much
of the region, with the heavier rainfall over the Coast
Range/Willapa Hills and Cascades. Front being pushed by much strong
jet aloft (120-130 kt), so front will push across the region at
fairly good clip. As such, think front will push to the Cascades by
8 am. Then, cooler unstable air aloft arrives, maintaining showers
and even a chance of a thunderstorm to two through the day. Snow
levels will drop from 8000 ft early in the day, falling to near 5000
ft by late afternoon. -Batz/Rockey
.LONG TERM...(Monday through Thursday)...Will maintain showery and
cooler air mass for Monday into Tuesday, with showers decreasing or
nearly ending Tuesday night. Snow levels will be lower, running 3500
to 4500 feet. So, high Cascades and even the passes will run moderate
to high chance of getting minor accumulations from the snow showers.
Too early to say, but seems reasonable that high elevations (above
4500 ft) could see 3 to 8 inches of new snow on Mon into Tue.
On Wednesday, will see another strong cold front pushing out of
the Gulf of Alaska and into the Pac NW, with more rain, and
snow across the Cascades. Then, cool with showers for Halloween.
&&
.AVIATION...Currently, widespread VFR conditions throughout the
airspace, with rain spreading into most of the region. Inland
will continue to see VFR conditions until 12Z Saturday, then
deteriorate to a mix of VFR/MVFR for most terminals through the
rest of the TAF period (30-60% chance of MVFR). Could see
conditions lower to IFR for a few terminals between 14-18Z
Saturday, specifically KPDX and KHIO. Between these times, KHIO
looks to have a 30-50% chance of IFR and a 20-30% chance of LIFR,
while KPDX only has a 10-20% chance of IFR. Beyond 18-19Z
Saturday, most inland terminals will have a 20-30% of MVFR CIGs
through the remainder of the TAF period, so expect a few terminals
to improve to VFR at times. Otherwise, expect inland winds to
increase and gust up to 20-25 kt until 12-13Z Saturday.
Along the coast, terminals will see a mix of MVFR/IFR conditions
through the TAF period, with KONP likely to see occasional LIFR
CIGs. Probabilistically, there is a 40-70% chance of MVFR
conditions through the TAF period beginning on 07-08Z Saturday.
Chances for IFR conditions increase to 10-20% between 12-17Z
Saturday. Around 18Z Saturday, KONP will see a 20-40% chance of
LIFR CIGs that will persist through the rest of the TAF period. As
for other coastal terminals beyond 18Z Saturday, MVFR CIGs with
infrequent breaks of VFR through the rest of the TAF period.
Otherwise, overall gusty winds for most of the TAF period.
Southerly winds of 15-20 kt with gusts up to 35 kt will last
until 12Z Saturday, then become 10-15 kt with gusts up to 20-25 kt
through the rest of the TAF period.
LLWS possible until 10Z Saturday due to higher wind speeds just
above the surface.
PDX APPROACHES...VFR conditions, becoming a mix of VFR/MVFR
between 12-18Z Saturday as heavier rain moves overhead.
Southeasterly winds with gusts up to 25 kt expected to decrease to
winds under 10 kt by 12Z Saturday. Due to higher winds just above
the surface, a period of LLWS concerns still exist until 10Z
Saturday.
~Hall
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.MARINE...Gale Force winds across the waters this evening as the
low center progresses to near 127W off the WA coast and heads to
Vancouver Island/Western British Columbia overnight. Given little
change in the guidance will continue with the high end Gale
Warning in place, but there is around a 20-40% chance for Storm
Force winds, especially around and north of Cape Foulweather and
over the outer waters. Latest models do continue show a pronounced
low-level jet just above the surface from roughly 2000 this
evening to 0100 Saturday morning as this disturbance moves in
leaving a possibility for the isolated gusts near 55 knots to mix
down to the surface and the main driver of Storm Force wind
potential. In addition to the strong southerly gusts, seas will
also build toward 14 to 16 ft tonight into Saturday morning as
conditions become heavily wind wave dominant. Since wave periods
will only be around 9-11 seconds expect a fairly steep wave
environment.
As the aforementioned system progresses into Western Canada,
model guidance remains in good agreement showing a rather broad
upper-level trough in place across western CONUS. This will
transition winds back to westerly for Monday then briefly
north/northwesterly winds on Tuesday; back to west to southwest
wind afterward. Through this period winds will remain breezy but
are not likely to result in Gale Force conditions with gusts of
15-25 knots at times. Seas will slowly subside by the middle of
next week, however expect seas to remain in the 13 to 18 ft range
at 13-15 seconds through Monday. We'll need to watch the arrival
of another swell on Thursday into Friday that would push wave
heights back towards 15 feet. -Schuldt/mh
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 2 AM PDT Saturday for ORZ101-102.
WA...High Wind Warning until 2 AM PDT Saturday for WAZ201.
PZ...Gale Warning until 5 AM PDT Saturday for PZZ210-251>253-271>273.
Hazardous Seas Warning from 5 AM to 11 AM PDT Saturday for
PZZ210-251>253-271>273.
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