Freeze Warning 1, NWS Chicago, IL

Boone County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, McHenry County, IL, Ogle County, IL, Will County, IL, Winnebago County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN

983 
WWUS73 KLOT 200158
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
858 PM CDT Mon Apr 19 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-201000-
/O.CON.KLOT.FZ.W.0001.210421T0500Z-210421T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
858 PM CDT Mon Apr 19 2021 /958 PM EDT Mon Apr 19 2021/

...FREEZE WARNING REMAINS IN EFFECT FROM MIDNIGHT CDT /1 AM EDT/
TUESDAY NIGHT TO 9 AM CDT /10 AM EDT/ WEDNESDAY...

* WHAT...Sub-freezing temperatures in the upper 20s expected.

* WHERE...Portions of northwest Indiana and northern and central 
  Illinois.

* WHEN...From midnight CDT /1 AM EDT/ Tuesday night to 9 AM CDT 
  /10 AM EDT/ Wednesday.

* IMPACTS...Frost and freeze conditions will kill crops, other 
  sensitive vegetation and possibly damage unprotected outdoor 
  plumbing.

* ADDITIONAL DETAILS...Sub-freezing temperatures in the upper 
  20s and lower 30s are again possible Wednesday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Exposed
outdoor water pipes and hoses should be wrapped, drained, or
allowed to drip slowly. Those that have in-ground sprinkler
systems should cover above-ground pipes to protect them from
freezing.

&&

$$

965 
WWUS73 KLOT 200732
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
232 AM CDT Tue Apr 20 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-202030-
/O.CON.KLOT.FZ.W.0001.210421T0500Z-210421T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
232 AM CDT Tue Apr 20 2021 /332 AM EDT Tue Apr 20 2021/

...FREEZE WARNING REMAINS IN EFFECT FROM MIDNIGHT CDT /1 AM EDT/
TONIGHT TO 9 AM CDT /10 AM EDT/ WEDNESDAY...

* WHAT...Sub-freezing temperatures in the upper 20s and lower 30s
  expected.

* WHERE...Portions of northwest Indiana and northern and central
  Illinois.

* WHEN...From midnight CDT /1 AM EDT/ tonight to 9 AM CDT /10 AM 
  EDT/ Wednesday.

* IMPACTS...Frost and freeze conditions will kill crops and other
  sensitive vegetation, and possibly damage unprotected outdoor 
  plumbing.

* ADDITIONAL DETAILS...Sub-freezing temperatures in the upper 
  20s and lower 30s are again possible Wednesday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Exposed 
outdoor water lines and hoses should be wrapped, drained, or 
allowed to drip slowly. Those that have in-ground sprinkler 
systems should cover above-ground pipes to protect them from 
freezing.

&&

$$

810 
WWUS73 KLOT 201556
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
1056 AM CDT Tue Apr 20 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-210000-
/O.CON.KLOT.FZ.W.0001.210421T0500Z-210421T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
1056 AM CDT Tue Apr 20 2021 /1156 AM EDT Tue Apr 20 2021/

...FREEZE WARNING REMAINS IN EFFECT FROM MIDNIGHT CDT /1 AM EDT/
TONIGHT TO 9 AM CDT /10 AM EDT/ WEDNESDAY...

* WHAT...Sub-freezing temperatures in the upper 20s and lower 
  30s expected.

* WHERE...Portions of northwest Indiana and northern and central 
  Illinois.

* WHEN...From midnight CDT /1 AM EDT/ tonight to 9 AM CDT /10 AM 
  EDT/ Wednesday.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation, and possibly damage unprotected 
  outdoor plumbing.

* ADDITIONAL DETAILS...Sub-freezing temperatures in the upper 
  20s and lower 30s are again possible Wednesday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Exposed
outdoor water lines and hoses should be wrapped, drained, or
allowed to drip slowly. Those that have in-ground sprinkler
systems should cover above-ground pipes to protect them from
freezing.

&&

$$

724 
WWUS73 KLOT 201932
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
232 PM CDT Tue Apr 20 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-210345-
/O.CON.KLOT.FZ.W.0001.210421T0500Z-210421T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
232 PM CDT Tue Apr 20 2021 /332 PM EDT Tue Apr 20 2021/

...FREEZE WARNING REMAINS IN EFFECT FROM MIDNIGHT CDT /1 AM EDT/
TONIGHT TO 9 AM CDT /10 AM EDT/ WEDNESDAY...

* WHAT...Sub-freezing temperatures in the upper 20s and lower 
  30s expected.

* WHERE...All of northern Illinois and northwest Indiana.

* WHEN...From midnight CDT tonight to 9 AM CDT Wednesday.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation, and possibly damage unprotected 
  outdoor plumbing.

* ADDITIONAL DETAILS...Sub-freezing temperatures in the upper 
  20s and lower 30s are again possible Wednesday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Exposed
outdoor water lines and hoses should be wrapped, drained, or
allowed to drip slowly. Those that have in-ground sprinkler
systems should cover above-ground pipes to protect them from
freezing.

&&

$$

436 
WWUS73 KLOT 210209
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
909 PM CDT Tue Apr 20 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-211015-
/O.CON.KLOT.FZ.W.0001.210421T0500Z-210421T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
909 PM CDT Tue Apr 20 2021 /1009 PM EDT Tue Apr 20 2021/

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM CDT /10 AM EDT/
WEDNESDAY...

* WHAT...Sub-freezing temperatures in the upper 20s and lower 
  30s.

* WHERE...All of northern Illinois and northwest Indiana.

* WHEN...From midnight CDT tonight to 9 AM CDT Wednesday.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation, and possibly damage unprotected 
  outdoor plumbing.

* ADDITIONAL DETAILS...Sub-freezing temperatures in the upper 
  20s and lower 30s are again possible Wednesday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Exposed
outdoor water lines and hoses should be wrapped, drained, or
allowed to drip slowly. Those that have in-ground sprinkler
systems should cover above-ground pipes to protect them from
freezing.

&&

$$

684 
WWUS73 KLOT 210822
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
322 AM CDT Wed Apr 21 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-211630-
/O.NEW.KLOT.FZ.W.0002.210422T0500Z-210422T1400Z/
/O.CON.KLOT.FZ.W.0001.000000T0000Z-210421T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
322 AM CDT Wed Apr 21 2021 /422 AM EDT Wed Apr 21 2021/

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM CDT /10 AM EDT/
THIS MORNING...
...FREEZE WARNING IN EFFECT FROM MIDNIGHT CDT /1 AM EDT/ TONIGHT
TO 9 AM CDT /10 AM EDT/ THURSDAY...

* WHAT...Sub-freezing temperatures from the mid 20s to the lower 
  30s.

* WHERE...All of northern Illinois and northwest Indiana.

* WHEN...From midnight CDT tonight to 9 AM CDT Thursday.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation, and possibly damage unprotected 
  outdoor plumbing.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Exposed 
outdoor water lines and hoses should be wrapped, drained, or 
allowed to drip slowly. Those that have in-ground sprinkler 
systems should cover above-ground pipes to protect them from 
freezing.

&&

$$

770 
WWUS73 KLOT 211344
NPWLOT

URGENT - WEATHER MESSAGE
National Weather Service Chicago IL
844 AM CDT Wed Apr 21 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-212145-
/O.EXP.KLOT.FZ.W.0001.000000T0000Z-210421T1400Z/
/O.CON.KLOT.FZ.W.0002.210422T0500Z-210422T1400Z/
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
Including the cities of Rockford, Belvidere, Crystal Lake, 
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove, 
Mundelein, Gurnee, Rochelle, Oregon, Byron, Dixon, DeKalb, 
Sycamore, Aurora, Elgin, Naperville, Wheaton, Downers Grove, 
Lombard, Carol Stream, Ottawa, Streator, La Salle, Mendota, 
Marseilles, Oswego, Yorkville, Plano, Morris, Coal City, Minooka,
Kankakee, Bourbonnais, Bradley, Pontiac, Dwight, Fairbury, 
Watseka, Gilman, Paxton, Gibson City, Evanston, Des Plaines, 
Schaumburg, Palatine, Northbrook, Chicago, Cicero, Oak Lawn, 
Oak Park, La Grange, Calumet City, Oak Forest, Lemont, 
Orland Park, Park Forest, Joliet, Bolingbrook, Plainfield, 
Mokena, Channahon, Manhattan, Wilmington, Crete, Peotone, 
Beecher, Gary, Hammond, Merrillville, Portage, Valparaiso, 
Chesterton, Roselawn, Kentland, Morocco, Rensselaer, DeMotte, 
Fowler, and Oxford
844 AM CDT Wed Apr 21 2021 /944 AM EDT Wed Apr 21 2021/

...FREEZE WARNING REMAINS IN EFFECT FROM MIDNIGHT CDT /1 AM EDT/
TONIGHT TO 9 AM CDT /10 AM EDT/ THURSDAY...

* WHAT...Sub-freezing temperatures in the mid 20s expected. 

* WHERE...All of northern Illinois and northwest Indiana.

* WHEN...From midnight CDT tonight to 9 AM CDT Thursday.

* IMPACTS...Frost and freeze conditions will kill crops, other
  sensitive vegetation and possibly damage unprotected outdoor
  plumbing.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. To prevent
freezing and possible bursting of outdoor water pipes they should
be wrapped, drained, or allowed to drip slowly. Those that have
in-ground sprinkler systems should drain them and cover above-
ground pipes to protect them from freezing.

&&

$$

BORCHARDT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
250 PM CDT Mon Apr 19 2021

.UPDATE...
1053 AM CDT

No major changes to the forecast through this afternoon. The cold
front continues to move southward and is moving across northwest
Indiana and Iroquois and Ford Counties at this time. West-east
corridor of rain continues between the I-88 and I-80 corridors
and will spread southward with time this afternoon. May see some
redevelopment along and just north of the I-88 corridor early
this afternoon as a shortwave is expected to quickly move east
across that area. Otherwise he bulk of the precip will be to the
south. Areas behind the front have seen their highs for the day
while temps of around 60 ahead of the front will fall into the
40s.

MDB

&&

.SHORT TERM...
335 AM CDT

Through Tuesday...

All eyes remain on the potential for a late snowfall across the
area beginning late tonight and continuing into Tuesday night. The
southeast trend noted in guidance 24 hours ago continued with the
00Z guidance, with a bulk of the precipitation across the CWA now
expected to occur during the day Tuesday. These changes have
further diminished the risk of any substantial snowfall in the
forecast area (though any accumulation this late could be
considered substantial) primarily due to lower precip rates and a
more diurnally-unfavorable period for snow to accumulate.

Today and Tonight: The cold front continues to progress
southeastward toward the CWA, stretching from near Green Bay to
Dubuque and into north-central Missouri as of 3am. As guidance has
noted for a couple days, a faster trend in this frontal passage
across especially the northern CWA continues to favor a colder day
today than was anticipated early this past weekend. Temps will
struggle to reach 50F north of I-80 where cloud cover will
dominate through the day. A fairly prominent swath of low-level
f-gen developing along the front will foster a narrow band of rain
late this morning through this afternoon. The initial focus will
be centered from Mendota to Aurora to Chicago around mid-morning,
then translate south to an area centered between I-88 and slightly
south of the Kankakee/Illinois River Valley for much of the
afternoon and into this evening. An overall lull in precip is then
expected late this evening into the overnight hours north of a
Pontiac to Valparaiso line as the favored axis of low-level fgen
drifts farther south. However, increasingly colder low-level
thermo profiles will support a transition over to snow where
precip does continue.

Tuesday: An axis of precip within the moist conveyor belt of a
developing surface low will quickly spread northeast into the area
beginning around daybreak. A neutral to slightly negatively-
tilted trough rotating into the mid-Mississippi River Valley under
the right-entrance of a departing upper jet streak will provide
continued ample forcing for widespread precipitation across much
of the CWA through the day. However, the bulk of the deepening of
the surface low over the Ohio River Valley is now progged to occur
further east, resulting in a broader and lighter precip shield
across the area. Thermo profiles will continue to support mainly
snow mixed with some rain during this time, but accumulations will
be suppressed by lower snowfall rates and the increasingly strong
late April sun providing enough insolation to maintain melting at
the surface. With storm total precip trending toward under 0.5"
and effective SLRs likely staying well below 10:1 for a bulk of
the event, slushy accumulations of 1-2" on primarily non-paved
surfaces appears likely for areas south of I-80 and especially
east of I-55.

Tuesday night: Mid-level moisture will quickly advect northeast
of the area by mid-evening, effectively ending any appreciable
widespread synoptically forced precip. Guidance has continued to
indicate the potential for a secondary piece of mid-level energy
closely following the primary wave across the area Tuesday night.
Decreasing mid-level temps will begin to increase low-level lapse
rates amid residual moisture below 700 hPa. This will support the
potential for lingering snow showers through the night for
portions of northeast/east-central Illinois into northwest
Indiana.

while cloud cover may be more abundant than previous expected due
to the factors noted above, confidence was high enough to prompt
the issuance of a Freeze Watch for the entire area. With temps
starting in the 30s for much of the area in the early evening, it
will not be hard to cool into the low 30s and upper 20s. With the
potential high impact of a hard freeze on budding vegetation after
2+ weeks without sub-freezing temps for most of the area, felt it
was prudent to issue the watch on this shift to provide two full
days notice to complete any necessary preparation. This is
especially the case with the expected snow falling on the
vegetation.

Kluber

&&

.LONG TERM...
248 PM CDT

Wednesday through Monday...

Surface low pressure will be moving northeast into the Pennsylvania
Wednesday morning with one upper trough axis exiting to our east
with another moving into Iowa. Between the associated ascent
inherent with the upper trough axis and cold air aloft leading to
steep mid level lapse rates and instability, expect isolated to
scattered convective showers. Given the forecast temp profiles,
expect at least a mix of rain and snow/graupel with the more
ominous and unstable soundings suggesting bursts of all snow
possible as mixing would be quite deep into to the 600-700 mb
range. May see a situation where air temps are well above freezing
but wet bulb cooling associated with the showers pulls temps
down. The concern is that this, combined with any more intense
bursts of precip/snow, could lead to a very brief accumulation
along with sharp visibility reductions under any more intense
showers. With early morning temps in the upper 20s, more surfaces
may be below freezing than we will see tomorrow but air temps will
warm above freezing into midday. Still many details to work out
but for now have gone with high temps lower than blended guidance
and raised pops into the chance range for many areas. Expect to
have to raise pops on upcoming shifts and possibly lower high
temps. Will also need to keep an eye out for the need to add a
mention of isolated thunder should instability trends continue or
look more impressive.

By Thursday, upper ridging will approach and surface high pressure
will pass to the south. Another nigh of lows around or below
freezing is expected Wednesday night/Thursday morning so will
likely need a frost or freeze headline. Dry and milder conditions
are then expected during the day Thursday. The upper flow de-
amplifies into Friday with a series of waves traversing the flow
bringing additional rain chances Friday and Saturday. The warming
trend will continue through the weekend with highs into the 50s to
around 60, though flow off the lake to varying degrees will temper
highs along the lakeshore each day. Additional warming is expected
early next week as ensemble guidance shows upper ridging being in
place which would support above normal high temps with a return to
drier weather.

MDB

&&

.AVIATION...
For the 18Z TAFs...

Aviation Forecast Concerns:

* Band of light rain mainly affecting MDW and moreso GYY through
  the afternoon. Intermittent MVFR cigs possible, mainly GYY.

* Snow/rain mix developing early Tuesday morning. MVFR cigs
  expected with some IFR visibility possible with periods of all
  snow, mainly before early Tuesday afternoon.

* Snow/rain showers may linger through Tuesday afternoon.

A cold front continues to sag south of the terminals early this
afternoon with a band of light rain set up in its wake. The bulk
of this band will impact MDW and GYY with some intermittent light
rain still possible at ORD/DPA. GYY should see light rain showers
linger through much of the evening with a lesser chance at
ORD/MDW/DPA. West to northwest winds persist with occasional gusts
to 20 kt in the Chicago area and a bit higher towards RFD. Mainly
VFR cigs are expected through the afternoon but some occasional
MVFR is possible with the rain band.

Another system will move into the area early Tuesday morning with
colder air continuing to spread in. A mix of rain and snow is
expected to develop prior to daybreak and affect the terminals
through midday. Expect that there will be periods of all snow at
times which may bring IFR visibility. Some slushy accumulation is
possible, mainly on grassy and other non-paved surfaces. Still
some questions as to how long precipitation will last into the
afternoon, but latest signals point to some lingering shower
activity with improving ceilings but there is still some chance
that steadier precipitation may continue into at least part of the
afternoon. Winds will turn north and northeasterly Tuesday
morning but be from the northwest inland of Lake Michigan toward
RFD.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Freeze Warning...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-
     ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-
     ILZ108...midnight Wednesday to 9 AM Wednesday.

IN...Freeze Warning...INZ001-INZ002-INZ010-INZ011-INZ019...midnight
     Wednesday to 9 AM Wednesday.

LM...None.
&&

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Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
402 AM CDT Mon Apr 19 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-200915-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
402 AM CDT Mon Apr 19 2021 /502 AM EDT Mon Apr 19 2021/

This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.

.DAY ONE...Today and Tonight.

  No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday and Tuesday evening...
  Limited Snow Risk.
Tuesday night and Wednesday night...
  Significant Freeze Risk.

DISCUSSION:

A late season storm system may bring accumulating wet snow to the
area late tonight into Tuesday evening, with accumulations
primarily on non-paved surfaces. The greatest potential will be
east of I-55, especially into northwest Indiana, late Tuesday
afternoon and evening. Sub-freezing temperatures Tuesday night and
again Wednesday night will result in a significant freeze risk.

.SPOTTER INFORMATION STATEMENT...

  Spotter activation will not be necessary through tonight.

LMZ740>745-200915-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
402 AM CDT Mon Apr 19 2021

This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.

.DAY ONE...Today and Tonight.

  No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

  No hazardous weather is expected at this time.

Kluber

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