Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/25/22
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
651 PM CST Thu Feb 24 2022
.UPDATE...
Issued at 647 PM CST Thu Feb 24 2022
Quick update to expand the mention of freezing drizzle in the
grids farther northward this evening. Cloud top temperatures are
analyzed in the -7 to -10 C range, although the coldest
temperatures in the layer appear to be closer to the surface based
on recent AMDAR soundings. Still, a recent rash of moderate low-
level icing PIREPs suggest a general loss of cloud ice is
occurring, and indeed we`ve seen more observations with "unknown
precipitation", rain, or 2-3 SM BR, all of which are likely
indicative of freezing drizzle mixing in, or entirely taking over
as the dominant p-type. This is especially true south of the
Kankakee River, with more of a snow and occasional freezing
drizzle mix farther north.
The atmospheric column will cool later this evening as the core of
the parent upper wave approaches. Forecast soundings show the DGZ
deepening markedly and, as a result, expect overall snow quality
to increase sharply after about 9-10 PM near I-39, and towards 11
pm to midnight across northeast Illinois. Steadier snow, with
hourly rates increasing to closer to a half inch per hour or maybe
a little higher appear probable through the early overnight hours
before the deformation precip finally exist to the east.
Carlaw
&&
.SHORT TERM...
Issued at 330 PM CST Thu Feb 24 2022
Through Friday night...
A low pressure system and associated upper-level wave continues to
advance towards northeastern Illinois and northwest Indiana where
snow has began to initiate on the north end of the low. The snow
will continue through the remainder of the afternoon and
throughout the night before gradually tapering off heading into
Friday morning.
An area of mixed precipitation can also be expected for areas south
of I-80 where forecast soundings continue to show a dry layer
developing in the snow growth region. Below the snow growth region
the soundings remain saturated which will allow supercooled
liquid water droplets to exist and lead to areas of freezing
rain/drizzle mixed with some poor quality snow this evening. A
glazing of ice can be expected during the period of freezing
rain/drizzle which will generate slippery road conditions for the
evening commute. Guidance suggests that moisture should return to
the snow growth region and allow for the mixed precipitation to
transition back over to all snow after midnight. Snowfall rates
are expected to be the highest during this time with accumulations
on the order of 0.5 inches per hour in the heaviest showers.
While most of the area will see the snow coming to an end shortly
after daybreak, a band of lake effect snow is expected to develop
and push eastward across the Illinois lake shore and into
northwest Indiana through the morning on Friday. The lake effect
snow is expected to gradually taper off by Friday afternoon, but a
few showers could persist into the early part of Friday evening
for portions of Porter County Indiana. Snowfall totals of 2 to 4
inches can be expected across northeastern Illinois and northwest
Indiana with upwards of 5 inches possible along the lake shore.
Yack
&&
.LONG TERM...
Issued at 330 PM CST Thu Feb 24 2022
Saturday through Thursday...
The long term continues to look incredibly quiet. This weekend will
be dry with gradually warming temperatures thanks to a large high to
our south bringing mild, southerly winds to the area. Highs just
above freezing on Saturday will be followed by upper 30`s and lower
40`s Sunday afternoon. A very dry profile will provide lots of
sunshine over the weekend, especially on Saturday. A bit more
moisture gets reeled in Sunday as the base of a moist upper level
trough passes just to our north. This should be just enough to throw
up some scattered clouds for the latter half of Sunday.
The only really notable precip signature in the long term arrives on
Monday. A midlevel shortwave trough is slated to pass over the area
and provide a shallow saturated layer roughly between 850 and 925mb.
The mid and upper levels will remain dry with a ridge axis passing
over. With weak, albeit noteworthy, forcing tied to this shortwave,
we just might be able to squeeze out some light sprinkles.
Otherwise, we`ll likely just see some broken to overcast skies for
the start of the work week. Continued weak warm air advection will
pull highs into the lower to middle 40`s on Monday and again on
Tuesday. A broad high pressure system tied to the lee side of an
approaching ridge will push in from the northwest on Wednesday.
Resulting cold air advection will drop highs just a couple of
degrees for Wednesday and Thursday and dry air advection will keep
us precipitation-free through the end of Thursday.
Doom
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns for this TAF period include:
* Snow continuing this evening and into the overnight hours
* Low probability of a period of freezing drizzle occurring at the
terminals this evening
* IFR visibilities likely later tonight with periods of LIFR
visibility possible
* MVFR ceilings continuing through most of the TAF period with
some IFR ceilings possible as well
Steady snowfall arrived at the terminals earlier this afternoon,
and while a general lull in snow recently occurred, we`re now beginning
to see an uptick in precipitation echoes once again on local
radar which should continue to blossom into this evening. Expect
the steadiest snowfall to occur towards the mid-late evening with
"poor quality" snowflakes likely producing IFR visibility with
perhaps some intermittent periods of LIFR visibility as well. With
dry air attempting to meddle with saturation in the Dendritic
Growth Zone, there is also some concern that freezing drizzle
could briefly mix in at the terminals this evening. During the
late afternoon, there were a few isolated reports of freezing
drizzle mixed with snow at ground level in northern Illinois,
though this has generally been the exception and not the rule.
Given the very isolated nature of the FZDZ, did not include a
mention of this in the going TAFs, but will continue to monitor
precipitation type trends closely. The synoptic snow shield will
begin to depart the area from west to east between roughly 08Z and
12Z, though lake effect snow/flurries is/are likely to continue
over or in the vicinity of the Chicago metro terminals through at
least Friday afternoon.
Ceilings are expected to remain MVFR through most of the TAF
period with a few exceptions. Periods of IFR ceilings will be
possible later tonight as the steadier snowfall pivots through the
area, and while the MVFR ceilings may continue well after the
system snow has ended, it`s possible that cloud cover may become
more SCT than BKN after daybreak Friday away from Lake Michigan
towards RFD and DPA. By Friday evening, think that most of any
lingering MVFR should scatter out and/or lift across the area. Winds
will back from northeasterly towards a more westerly direction by
the end of the TAF period.
Ogorek
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-
ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-
ILZ108 until 6 AM Friday.
IN...Winter Weather Advisory...INZ001-INZ002-INZ010-INZ011-INZ019
until 6 AM Friday.
LM...Small Craft Advisory...IL nearshore waters until noon Friday.
&&
$$
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