Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 11/22/22
Area Forecast Discussion
National Weather Service Indianapolis IN
953 PM EST Mon Nov 21 2022
.Forecast Update...
Issued at 952 PM EST Mon Nov 21 2022
Forecast remains on track this evening with only minor adjustments
to cloud cover. Skies have largely cleared this evening, though a
few high clouds remain east of Indianapolis and well to our
northwest. Lows tonight will be dependent on wind, as radiational
cooling conditions will otherwise be optimal under generally clear
skies. High pressure displaced to our east should act to keep light
southerly flow present overnight. A few sheltered locations may go
calm, however, as the low-level inversion deepens. These are the
locations that may see the coldest overnight temperatures, with lows
possibly dipping into the lower 20s, compared to mid 20s elsewhere.
&&
.Short Term...(This evening through Tuesday)
Issued at 233 PM EST Mon Nov 21 2022
* Warming trend continues through midweek
.This evening and tonight...
Current surface analysis shows high pressure stretched from Texas to
the Mid Atlantic states while an area of low pressure around the
Hudson Bay swings a moisture starved front just north of the region.
High pressure will be the dominant weather feature through midweek
as subsidence and dry air keep precipitation away from the region
and skies mainly clear. Main forecast concern for the rest of the
afternoon and evening is the elevated fire threat. 19z IND ACARS
sounding shows a shallow mixed layer near the surface that just
reaches into the lower portion of a 30-40kt low level jet. Wind
gusts of 20-30 mph have already been reported around the region
today and will persist through around sunset when a low level
inversion redevelops. Dry air has also been mixed down to the
surface with RH values dipping into the upper teens in some spots;
therefore an SPS has been issued through the evening for an elevated
fire threat.
Nudged high temperatures for the rest of the afternoon above NBM
95th percentile as mixing has really helped bring down relatively
warmer air aloft. Indianapolis hit 50 degrees for the first time in
10 days!
After sunset expect winds to die down and temperatures to plummet
once again. While winds do not fully go calm, they will be low
enough for radiational cooling to take place resulting in low
temperatures by sunrise to fall into the mid 20s regionwide.
.Tuesday...
High pressure remains south and east of the region tomorrow making
for another dry and mild November day. The area of high pressure is
oriented in such a way that much of the Gulf moisture is blocked
form surging northward; however southwesterly return flow will very
slowly work to increase moisture in the area through the week.
Observations already show an increase in RH values to the west,
which should make their way east into the state by Tuesday. Dew
points yesterday dropped down to -4F and have risen into the teens
today... and by Tuesday expect them to rise further into the 20s. So
while it still is very dry, it has been much drier over the past few
days! Fortunately, the weak moisture return will help limit the fire
threat through the week. Forecast soundings still show another
shallow mixing layer setting up tomorrow, under 2,000 feet; which
should work to increase afternoon gusts again and keep RH values
low. Went above guidance for winds and gusts once again Tuesday,
nudging them toward the NBM 90th percentile with gusts 15-20 kts
during peak heating of the afternoon. This correlates nicely with
the weather pattern setting up for tomorrow. As for min RH values,
nudged them the opposite way toward the far lower end of most
guidance. Fire threat still appears lower tomorrow since min RH
values look to only drop down into the 30s to low 40s during the
afternoon and gusts are not expected increase as much as today.
Temperatures tomorrow will be a few degrees warmer than Monday with
highs in most locations reaching the low to mid 50s. Southwest flow
aloft will continue to advect in a relatively warmer airmass over
the next few days. Due to on the mixing and dry conditions mentioned
above, nudged temperatures above guidance towards the NBM 90th
percentile for highs which is reasonable considering the pattern and
observations from Monday.
&&
.Long Term...(Tuesday night through Monday)
Issued at 233 PM EST Mon Nov 21 2022
* Mild through the long term.
* Chances for rain Thursday night through the weekend. Confidence in
rainfall timing this weekend is low
A quasizonal upper level flow pattern is expected to continue
through mid week across the region, with surface high pressure well
in control over the Ohio Valley eastern CONUS. This should prevent
any substantial moisture return but will allow for high temperatures
to moderate back into the 50s.
The end of the week has much more variability with a deep trough
progressing through the central CONUS. Latest trends are agreeing on
a deeper push of the trough axis into the Southern Plains. This
should slow east ward progression. There will be some energy brought
northward within moderate WAA Thursday night, providing likely
chances for light rain. This WAA will also buoy temps with highs in
the upper 50s Thursday.
The more impactful rainfall will likely be associated with the
parent trough as it nears over the weekend. As the system matures,
the upper level cold air looks to become detached from the polar
jet. This should also impede progression, but the track of a weakly
forced closed upper low is also creating a wide array in solutions
for low level cyclogenesis and precipitation. For now, PoPs have
been left at a long duration of 30% or less given the uncertainty.
Ensemble disparity should lessen as the aforementioned trough reaches
the western CONUS and models can initialize with proper observations,
of which should result in a more concise forecast.
Nonetheless, temperatures should remain seasonal to even slightly
above with the upper level cold air remaining to the north. Any
cloud cover or prolonged rainfall will limit temperature gains, but
lowest end Probabilistic forecasts still have highs in the mid to
upper 40s over the weekend.
&&
.Aviation...(00Z TAF Issuance)
Issued at 517 PM EST Mon Nov 21 2022
Impacts:
* No noteworthy impacts.
Discussion:
Periods of mid clouds (~15,000 ft) and high clouds (~25,000 ft) may
be observed, however VFR conditions will prevail. Slight variations
in wind gusts up to around 20 degrees either side of the prevailing
direction in the TAFs are expected. Current gusts as of this writing
will decrease shortly after sunset. Gusts tomorrow afternoon should
be less than today.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Update...Eckhoff
Short Term...CM
Long Term...Updike
Aviation...BRB
Area Forecast Discussion
National Weather Service Portland OR
156 PM PST Mon Nov 21 2022
.SYNOPSIS...Winds will increase tonight into Tuesday as a front
crosses the Tuesday, bringing strong winds along the coast and light
rain to most locations. Looking mostly dry mid to late week, with the
pattern becoming more active towards next high travel weekend.
&&
.SHORT TERM...TONIGHT THROUGH THANKSGIVING DAY...Water vapor
satellite shows a shortwave ridge moving over the area while high
clouds from this morning`s dissipating front pushes in. Additional
clouds behind this are moving across the northern Pacific as an
upper trough starts deepening from a 160kt backside jet. At the
surface, a lighter offshore flow pattern exists compared to the last
several days, however east winds will continue to gust as high as 30
mph in Washougal and northern portions of Troutdale, Wood Village,
and Fairview through Tuesday around noon as Astoria to Pendleton
surface gradients remain in the 6 to 8 mb range. Expect gusts as
high as 40-50 mph at Corbett, Crown Point, and Rooster Rock State
Park. Away from the mouth of the Columbia River Gorge, winds are
generally light and will remain fairly light through tonight,
allowing for the Air Stagnation Advisory to continue until 8 AM PST
Tuesday for the Lower Columbia, central and southern Willamette
Valley, Cascade foothills and central OR Coast Range.
Southerly winds will increase rapidly across the waters tomorrow as
the next system quickly moves in. These strong southerly winds will
spread inland tomorrow morning, producing gusts in the 40 to 50 mph
range along beaches and headlands near the frontal passage, expected
around noon. While rain will start spreading into the coasts early in
the morning, brief moderate to heavy rainfall will occur along the
frontal passage, with showery and gusty weather behind it. The strong
frontal winds and rain will spread inland through the day, reversing
the easterly Gorge winds for a brief moment. Westerly flow will help
bring enhanced rainfall amounts to the Coast Range and the Cascades.
With the known overestimate of QPF of the NBM 4.1, and underestimate
of the 4.0, am going in between these two. Currently have amounts of
0.5-0.8 inches over the mountains, and 0.1-0.25 within the valleys.
Snow levels are expected to be near 6500 ft MSL, so above pass
levels. One sticking point is the Upper Hood River Valley, where cold
air trapped in there might not scour out before the rain comes in.
This would lead to a possibility of freezing rain....however at this
time believe the rain will hold off until the wind reaches in to
scour out the cold air, with precipitation falling as liquid rain.
The strong jet will move the system quite quickly across the area,
and will also bring enough dynamical lift and shear to bring a 15-18
percent chance of thunderstorms, mainly to the central waters and
inland south of a line from Pacific City across to Government Camp.
Rain showers will quickly end in the Willamette Valley Tuesday
evening with the rain shadowing effect, with showers will last over
the mountain ranges into early Wednesday morning.
An upper ridge then quickly builds in behind the system, with all
three ensemble means of the EC, GFS and CMC showing height anomalies
of 2 standard deviations over the area Wednesday night into Thursday
night. As a result, low-level offshore flow will return by late
Wednesday with the breezy east winds returning in the western
Columbia River Gorge into far eastern portions of the
Portland/Vancouver metro. As the upper level ridge amplifies over the
region Thursday, expect slightly above normal temperatures and dry
weather over northwestern OR and southwestern WA through the holiday.
/Kriederman
.LONG TERM...THURSDAY NIGHT THROUGH SUNDAY NIGHT...WPC`s cluster mean
for 500 mb heights and anomalies depicts the ridge breaking down by
Friday as a trough pushes down from the north. While the CMC ensemble
is the fast outlier, the GEFS and EPS spread rain into the coasts
starting late Thursday night. Have slowed NBM PoPs Thursday night
into Friday, which suggests the highest chance of rain will occur on
Saturday and Sunday. There is potential for the weekend`s systems to
have an impact on holiday travelers, as both the EC and GFS show
colder air being entrained into the lows, lowering snow levels to the
2000-3000 feet level. This would bring snow to the high Cascade and
potentially the Coast Range passes. /Kriederman
&&
.AVIATION...00Z TAFs: Post frontal VFR conds remain today and
should stay that way well into Tuesday. Also, offshore flow
prevails for the rest of today and into Tuesday morning. Gorge
outflow gusts continue to range 25-30 kts and will likely hover
around 25 kts for the rest of the period.
The next front will quickly approach and cross the region on
Tuesday, first bringing rain and MVFR cigs to the coast around
10Z at KAST and then moderately gusty south winds beginning 15Z at
KAST and a couple hours later at KONP. Winds could briefly gust
35-40 kt along the north coast nearer 19-20Z when the front
crosses along with IFR cigs and again a couple hours later for the
central Coast. Inland, the front will not arrive until 22/21-23Z,
but will see cigs lowering to MVFR along with rain arriving in
the 15-17Z timeframe.
For detailed Pac NW aviation weather information, go online to:
http://weather.gov/zse
KPDX AND APPROACHES...VFR today and through at least 22/18Z with
a mix of mid and high level clouds. Gusty easterly Gorge outflow
winds will bring 25-30 kt gusts at KTTD and would expect some of
these winds to be felt by departing aircraft through Tuesday
morning. Cigs will gradually lower to 060 after 09Z Tuesday and
then below 040 around the beginning of the morning push. East flow
will than also increase at KPDX ahead of the aforementioned
incoming front. Cigs then appear to lower below 030 near 22/18-19Z
as the front approaches and rain increases. /JBonk
&&
.MARINE...As expected, today`s front resulted in little change in
the marine conditions. With that, attention quickly turned to the
front arriving tonight and quickly crossing the waters Tuesday
morning. There may be a a few hours of SCA wind gusts later
tonight, but with the quick movement of tomorrow`s front, decided
to maintain a simple lead into the gales arriving to the NW
waters nearer 0800 hrs and then fully exiting to the SE near 1300
hrs. The position of the surface trough and thus the front has
drifted a bit further south over the recent model runs and has
decided to bring in the remaining waters to the Gale Warning. This
will also include the Columbia River Bar where 2-3 hours of gusts
around 40 kts beginning near mid-day seem quite likely. Seas,
especially along the northern inner waters, will build to around
10 feet driven by the frontal wind waves. There may be a brief
break as winds subside, but then a trailing post frontal NW swell
will again push seas to around 10 feet along with SCA wind gusts
around 25-30 kts. Have then issued a SCA through 4 AM Wednesday to
follow the gale warning. Winds and seas may drop a few hours
earlier, however.
High pressure returns Wednesday for lighter winds but next system
is currently forecast to approach from the offshore waters late
Wednesday and Thursday. Current model forecast show the front
stalling well offshore, but coastal waters will see increase in
southerly winds with modest chances for winds exceeding 20 kt.
This front finally moves ashore sometime Friday in a weakened
state but likely with winds in the 20-25 kt range. A more active
pattern sets up for weekend with a faster pace of systems - and
lower confidence on timing and strength. Current GEFS
probabilistic wind speed forecast has a 20% chance for gale force
winds over the weekend.
The new moon phase this week will produce stronger tidal currents
during the afternoon ebb cycle. Those moving in and out of harbors
and crossing coastal bars should use caution and be aware of any
bar restrictions in place. /JBonk
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until 8 AM PST Tuesday for Cascade
Foothills in Lane County-Central Coast Range of Western
Oregon-Central Willamette Valley-Lower Columbia-Northern
Oregon Cascade Foothills-South Willamette Valley.
WA...None.
PZ...Gale Warning from 10 AM to 1 PM PST Tuesday for Columbia River
Bar.
Small Craft Advisory from 1 PM Tuesday to 6 AM PST Wednesday
for Columbia River Bar.
Gale Warning from 7 AM to 1 PM PST Tuesday for coastal waters
from Cape Shoalwater WA to Florence OR out 60 nm.
Small Craft Advisory from 1 PM Tuesday to 4 AM PST Wednesday
for coastal waters from Cape Shoalwater WA to Florence OR out
60 nm.
&&
$$
www.weather.gov/portland
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