Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/24/22
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
922 PM CST Wed Feb 23 2022
.UPDATE...
Issued at 916 PM CST Wed Feb 23 2022
Flurries and lake effect snow are the main focus the rest of the
evening and overnight. While LES parameters are marginal (at
best) with lake-induced ELs generally under 4500 feet, a more
appreciable near full-lake fetch and modestly enhanced low-level
convergence may help supplement things a bit. Seeing pockets of
25-30 dBZ returns off of Milwaukee`s terminal radar and these will
be spreading onshore through about 10-1030 pm or so. Going
message is in good shape of scattered coatings (up to perhaps
three tenths of an inch or so) across mainly parts of Cook and
Lake (IL) counties through the overnight/early Thursday morning.
This could result in some patchy slick travel for the early-
morning commute on Thursday. Additionally, expanded the flurry
mention inland for locales north of I-80 through the rest of the
night, and it`s possible flurries persist through all of Thursday
morning.
Across central Illinois, multiple disorganized/transient
frontogenetic bands are in place and forecast to meander northward
with time. While this forcing is pretty unimpressive overall,
there are signs in evening guidance that the right entrance of a
broadly anticyclonically-arcing jet streak late tonight may
provide enough "push" to expand precipitation farther into parts
of Ford, Iroquois, Newton, and Jasper counties. Have nudged PoPs
northward and up a bit in this area as a result, but will note
guidance is about 50-50 split on whether we`ll even manage to get
precipitation into our area. The main issue if precip does expand
a bit farther north is p-type, as forecast soundings universally
indicate marked drying above 700 mb, with a 10,000 foot thick
layer of dry air aloft just way too deep for any seeder-feeder
assistance. As a result, have introduced a mention a mix of snow
and freezing drizzle for our far southern tier of counties.
Going forecast for tomorrow afternoon and evening looks to be in
good shape overall. Potential for a front-end burst of heavier
snow coincident with the afternoon/evening rush is still apparent
in early evening guidance as large scale forcing for ascent
intercepts a region of convectively unstable lapse rates in the
600-450 mb layer. Quick transition to "poorer-quality" snow,
drizzle, and sleet through the evening hours looks on track as
well, especially south and east of I-55.
Carlaw
&&
.SHORT TERM...
Issued at 318 PM CST Wed Feb 23 2022
Through Friday...
[Bottom Line Up Front]
We issued a Winter Weather Advisory for the entire CWA starting
Thursday afternoon and ending early Friday for a long duration of
accumulating snow and associated travel impacts (slippery, snow
covered roads), mainly to the Thursday evening commute, but
possibly to the earlier part of the Friday AM commute for
northeast Illinois and far northwest Indiana. Forecast
accumulations for most of the area are 2-5".
For southern sections, particularly near and south of US-24,
after a burst of snow (possibly mixed with sleet) Thursday
afternoon, much of the remainder of the precip. starting Thursday
evening could be freezing rain/freezing drizzle, mixed with poor
quality snow. The snow (sleet) followed by icy glaze combo will
lead to hazardous travel conditions.
[Meteorological Details]
The rest of our Wednesday will be quiet with thickening cloud cover
and temperatures falling into the teens out west while hanging onto
the 20`s across the metro and further south. NE winds this evening
set us up for a good chance of lake-effect snow near the IL shore.
While we expect notable lift in the mixed layer, steep low-level
lapse rates, and a couple of hundred joules of lake-induced CAPE,
none of these lake-effect parameters are overwhelming and enough
to compensate/overcome sub marginal inversion heights (below 5kft)
and therefore should result in nothing more than some light snow
showers. Mid evening through just prior to daybreak Thursday
appears to be the most favorable timeframe for lake-effect.
Additionally, a plume light snow is pushing through central IL
this afternoon. This could possibly push northward into the
southern CWA this evening and overnight though these should have
little to no travel impacts and shouldn`t result in any accumulation.
The focus remains to be this approaching storm system threatening
widespread accumulating snowfall and possibly some sleet and
likely freezing drizzle in the southern CWA tomorrow-tomorrow
night. A hefty superimposed jet max sits on the lee side of a
positively tilted trough hanging over the desert southwest this
afternoon. This jet streak will push into Midwest by early
tomorrow morning quickly reeling in plenty of moisture, especially
in the sfc-700mb layer, and providing noteworthy synoptic-scale
dynamics. This includes a good vorticity signature and plenty of
synoptic-scale lift, especially near the left exit region of the
jet max.
Snow is expected to begin moving in from the south in the
late morning and quickly fill in across the CWA through the early
afternoon which is when we anticipate the aforementioned left
exit region to propagate through the area. A rather narrow DGZ
during this time may keep from prime dendrites and very efficient
snow rates. However, the favorable jet dynamics and the area
being in favorable location for these, along with steep lapse
rates in the DGZ could still support a burst of at times heavy
snowfall rates. The afternoon timeframe has been uncertain with
northward extent due to questions on how long top down saturation
occurs, but starting to see signs that snow onset won`t be delayed
too much except perhaps far north (where we started advisory at
3pm).
The far southern CWA could be an exception with some guidance,
namely the NAM, insisting upon the presence of a warm nose melting
precipitation aloft from the late morning through mid afternoon.
If this warm nose comes to fruition, it should be elevated enough
(~750mb) to result in sleet during this period due to a deep re-
freezing layer at the low levels. If it does not and the entire
profile remains below freezing, then this area will join the rest
of the CWA and experience a 2-4 hour burst of snow (likely what
the more aggressive GFS solutions have been keying on). Meanwhile,
continued northeasterly winds and a sfc-850 delta-T of near or
just over 10 degrees will likely provide some very modest lake-
enhancement across IL`s lakeside counties through the afternoon
and evening.
Heading into the evening, potent dry air advection aloft in the
700-500 mb layer will quickly dry out the mid and upper levels.
The majority of the CWA should be cold enough to keep snow
developing through the saturated low levels with a much more
favorable presence in a portion of the DGZ, though probably a
lower quality/lower snow ratio snow for a time. However, a lack
of ice concentration in the cloud layer further south where
temperatures will be a bit warmer will likely result in freezing
rain or freezing drizzle from the evening into the overnight. This
is primarily a concern for the southernmost counties of the CWA,
which we are messaging as near and south of US-24.
As a stout mid-level short-wave and associated vort max pivot
overhead late evening and after midnight Thursday night, the DGZ
is forecast to deepen to upwards of 6-7kft and be fully saturated
for the northern half or two thirds of the CWA. During this time,
expecting ratios to increase to 15-20:1. The good synoptic lift,
expected higher ratio/higher efficiency fluffy snow should cause
hourly snow rates of up to 1/2", possibly briefly over 1/2" per
hour. Highest concern for that would be closer to the lake where
improved lake induced thermodynamics, good convergence, and long
north- northeasterly fetch should result in a corridor of higher
totals (4-5", locally a touch more) into the northeast 1/4 of the
CWA (Chicago and north-northwestward across the northern burbs.
Finally, with weak, albeit notable, cold air advection taking
place overnight, the precipitation should wrap up in the form of
snow for southern sections in the predawn hours of Friday morning.
All in all, a few to several inches of snow are expected across
most of the CWA with locally higher amounts expected in Cook and
Lake IL counties and possibly as far inland as eastern DuPage and
McHenry counties due to lake enhancement. Lower snow totals,
upwards of a couple of inches, are anticipated further south.
However, this rides heavily on precipitation types through the
event which, as previously noted, is still rather uncertain. The
Thursday evening commute is expected to be heavily impacted with
travel delays also possible through the earlier half of the Friday
morning commute.
Doom/Castro
&&
.LONG TERM...
Issued at 348 PM CST Wed Feb 23 2022
Friday through Wednesday...
An upper level shortwave and associated sfc low will lift out of
the Ohio River Valley towards the eastern Great Lakes Friday
morning. Behind it, any lingering LES should be swept eastward out
of the CWA as winds gradually veer more westerly. A much drier
air mass will advect into the midwest along with ~1030mb surface
high pressure. Light southwest winds will offer a sunny albeit
still chilly Saturday with highs still lingering in the low to mid
30s.
The polar front jet takes a dip south late Saturday into Sunday,
driving a sub 1000mb surface low across Quebec underneath a 150kt
jet streak. WPC day 4 surface analysis has its associated cold
frontal boundary push through the CWA Sunday morning/afternoon.
Though some previous long range guidance had shown some snow
showers with its passage, the main forcing looks to remain east
underneath the stronger synoptic ascent. Ensembles are signaling a
shortwave traversing the midwest Tuesday into Wednesday, though
agreement on timing and placement of various features remains in
low confidence. In response to broad mid-level ridging sliding
eastward and troughing focusing into northeast CONUS, temps look
to climb into the 40s by Tuesday-Wednesday. This is near to a bit
above normal for the start of March and meteorological Spring (!).
Quiet weather will likely prevail through day 7 and at least a few
days beyond.
BW/Castro
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns for this TAF period include:
* Flurries continuing tonight with potential for a band of
steadier snow to move near or over ORD, MDW, and GYY
* More concentrated snowfall tomorrow afternoon and evening
* MVFR ceilings continuing through most of the current TAF period
* IFR visibilities probable with tomorrow`s snow
Despite very poor saturation depths being indicated on recent
AMDAR soundings originating from the Chicago terminals, this
saturation within the overhead MVFR deck is within the Dendritic
Growth Zone and has been sufficiently deep for a few flurries to
be wrung out and observed at our TAF sites. Very light radar
returns emanating from over Lake Michigan seem to suggest that
flurries will at least intermittently continue through much of the
night. There`s also a band of steadier snowfall currently out
over lake that should progress inland a bit and possibly produce a
period of MVFR visibility at ORD, MDW, and GYY before fading as
it moves farther away from the lake and the fetch over the lake
becomes shorter with winds turning easterly.
A period of more concentrated snowfall is then expected to come
Thursday afternoon and evening with an incoming wintry system.
There is still some disagreement amongst forecast guidance over
the exact onset time of snow, so the 21Z start time in the current
TAFs may need further refinement, but once the snow gets going,
anticipate visibilities falling to MVFR soon after precipitation
onset. IFR visibility is then likely to prevail throughout much of
the evening as the quality of the snowflakes becomes poorer with
time, but may be reached even earlier during the mid-late
afternoon as a result of the more intense snow rates being more
intense towards the beginning of the event. However, confidence
in IFR visibility materializing soon after the onset of precipitation
during the afternoon isn`t very high at this point.
As for ceilings, look for them to remain MVFR for the most part.
Most guidance suggests that there will be a period late Thursday
morning and afternoon where the lower clouds scatter out or lift
above 3000 ft, which would result in VFR conditions being
realized for a few hours before MVFR ceilings trickle back in late
Thursday afternoon with the incoming snow system. Ceilings may
ultimately get as low as IFR at some point Thursday night, but
confidence in this is currently low.
Ogorek
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory...ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-
ILZ104-ILZ105-ILZ106-ILZ107-ILZ108...noon Thursday to 6 AM
Friday.
Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006...3 PM
Thursday to 6 AM Friday.
IN...Winter Weather Advisory...INZ001-INZ002-INZ010-INZ011-
INZ019...noon Thursday to 6 AM Friday.
LM...Small Craft Advisory...Gary to Michigan City IN until 9 PM
Wednesday.
&&
$$
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Area Forecast Discussion
National Weather Service Memphis TN
907 PM CST Wed Feb 23 2022
.UPDATE...
A mix of rain, freezing rain, and sleet continues across the Mid
South. Rain is mainly falling along and south of I-40. Some places
along I-40 have seen some light freezing rain. Areas north and
west of I-40 are seeing more sleet and freezing rain. The winter
headlines will continue through Thursday. We will see temperatures
remain somewhat stable across the area. They may fluctuate a
degree or tow overnight. We expect a warm up Thursday morning
across the area and that will confine the winter weather to
northeast Arkansas and the Missouri boot heel. Precipitation
should end Thursday night. Made a few adjustments to temperatures
and ice accumulations this evening.
&&
.PREV DISCUSSION... /issued 600 PM CST Wed Feb 23 2022/
DISCUSSION...
An extremely messy winter weather regime across the Mid-South
this afternoon. We have already seen thunder snow, thunder sleet,
and thunder freezing rain across eastern Arkansas. There have also
been reports of snow, even though models have indicated the
presence of an elevated warm nose. The thermodynamic mystery is
likely linked to the convective and elevated nature of the sleet
and the combination of dry air from 925mb down to the surface.
Several sleet bursts have already occurred across portions of
eastern Arkansas. We have seen reports up to half an inch of sleet
in 30 minutes, which has accumulated on the bridges. This has led
to big impacts on the roadways, which will continue to
deteriorate over the next 12 to 18 hours.
The biggest change to the forecast was adding accumulations of
sleet up to half an inch or more through sundown. The hope is that
the atmospheric column becomes saturated enough that the warm
nose finally establishes itself. This would reduce the amount of
sleet drastically, but result in freezing rain accumulations
approaching a half an inch by tomorrow morning across the winter
storm warning area.
Ice accumulations will generally be between a quarter of an inch
and half inch of ice in the warning areas, with up to a quarter of
an inch in the advisory areas. The most uncertain part of the
forecast will continue to be sleet accumulations. There is some
concern that sleet totals could exceed an inch, especially across
northeast Arkansas and the Missouri Bootheel.
All winter weather will come to an end by tomorrow afternoon as
precipitation exits the area. A flood watch remains in effect for
portions of west Tennessee through tomorrow evening. QPF totals
could reach two inches or more and most the rivers are at flood or
advisory stage. It won`t take much for areal flooding to occur,
especially near river banks and creeks.
We will see a quick 24 hour period before we see yet another
chance of wintry precipitation moves in. A classic overrunning
pattern will setup on Saturday as a low pressure system lifts out
of east Texas. A wintry mix will be possible across northern
portions of the area and will remain heavily dependent on the
track of the low.
Next week looks dry to start with warming temperatures by midweek.
AC3
AVIATION...
00Z TAFs
Challenging aviation forecast this evening with both some elevated
instability present across the Lower Mississippi Valley and
freezing rain occurring at JBR and MKL. FZRA will be predominant
at JBR tonight and perhaps MKL while MEM may just barely stay
above freezing. Recent ACARS soundings indicate FZRA could
potentially be an issue for a short time tonight at MEM and will
monitor trends very closely this evening. VCTS possible at
MEM/MKL/TUP tonight but confidence in occurrence isn`t high enough
to include in TAFs at this time. Precipitation is anticipated be
in the form of -RA after 24/15Z.
CJC
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Winter Storm Warning until 6 PM CST Thursday for Clay-Craighead-
Cross-Greene-Mississippi-Poinsett.
Winter Weather Advisory until 6 PM CST Thursday for Crittenden-
St. Francis.
MO...Winter Storm Warning until 6 PM CST Thursday for Dunklin-
Pemiscot.
MS...None.
TN...Winter Storm Warning until 6 PM CST Thursday for Dyer-Lake-
Lauderdale-Obion-Weakley.
Winter Weather Advisory until 6 PM CST Thursday for Benton TN-
Carroll-Crockett-Gibson-Haywood-Henry-Shelby-Tipton.
Flood Watch through late Thursday night for Benton TN-Carroll-
Chester-Crockett-Decatur-Fayette-Hardeman-Hardin-Haywood-
Henderson-Madison-McNairy-Shelby.
&&
$$