An upper level storm system tracked east across the eastern Great Plains into northern Missouri and Illinois on from Feb. 8-9, 2018, bringing widespread snow to portions of eastern Iowa and northwest Illinois.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DVN wrote it up.
An upper level storm system tracked east across the eastern Great Plains into northern Missouri and Illinois on from Feb. 8-9, 2018, bringing widespread snow to portions of eastern Iowa and northwest Illinois. The heaviest snowfall fell along the Highway 20 corridor, where amounts of 6 to 8 inches were reported in Independence, Dubuque, and Freeport. To the south, around 2 to 5 inches fell from the Interstate 80 corridor to Highway 30.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Quad Cities, IA wrote its last area forecast discussion before the first event at Feb 7, 5:38 PM CST, 4 hours 22 minutes earlier.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
538 PM CST Wed Feb 7 2018
...00z AVIATION UPDATE...
.SYNOPSIS...
Issued at 321 PM CST Wed Feb 7 2018
18Z surface data has high pressure from the upper Midwest into the
southern Plains. Dew points were in the single digits above and
below zero from the Great Lakes into the central Plains. Dew points
in the teens and higher ran from the Ohio Valley into the southern
Plains and Gulf Coast.
&&
.SHORT TERM...(This Evening through Thursday)
ISSUED AT 321 PM CST Wed Feb 7 2018
Quiet, cold, and dry conditions will be seen from late this
afternoon through the evening hours.
After midnight, a weak upper level disturbance will move through the
area. Moisture is quite limited but it will be moving over a
modified arctic air mass. The forcing supplied by the disturbance
will allow light snow to develop.
Accumulations late tonight will range from a trace to a dusting.
On Thursday, very light snow or flurries will continue during the
morning generally north of I-80 before ending. Attention then turns
to the more significant storm system.
Thursday afternoon, moisture aloft will move into the area. As
forcing from the approaching storm system increases, snow will
develop/move into the area especially north of an Aledo, IL to
Sigourney, IA line. By sunset Thursday snow accumulations
along/north of I-80 will range from a trace to under an inch.
.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 321 PM CST Wed Feb 7 2018
Thursday Evening through Friday
Snow Potential:
Issued a Winter Storm Watch for the counties approximately along and
north of I-80, from Thursday midday afternoon through Friday, for
the potential of 4 to 8 inches of snow.
The favored area for the highest snowfall is in the counties along
the Mississippi River and along/north of highway 30. However, due to
model differences, and since this is 24-36 hours away, there is
still uncertainty regarding exact snowfall amounts and the placement
of the heaviest snow band. As confidence increases with later
forecast updates, expect the Winter Storm Watch to be replaced by
either a Winter Weather Advisory or Winter Storm Warning. Later
forecast shifts will also have to look at the potential for
instability aloft leading to localized higher snowfall amounts than
currently forecast within a narrow zone.
Impacts:
Roads will quickly become snow covered and slippery late Thursday
afternoon and into the evening due to cold pavement temperatures.
Additionally, periods of moderate or heavy snow will reduce
visibilities to under a half mile at times. Light winds should
preclude significant drifting of snow for the majority of the event.
With that said, an increase in NW winds Friday afternoon to between
15-20 mph may result in areas of blowing and drifting snow as the
storm winds down.
Environmental Setup and Model Trends:
Elevated warm air advection and increasing low to mid-level
frontogenetic forcing beneath the right entrance region of an upper-
level jet streak will lead to a band of snow developing across
portions of the forecast area Thursday afternoon and evening. A
closed 850mb low will cause the snow band to spread east initially,
then potentially shift to the north before pivoting back to the
southeast and overspreading the remainder of the CWA.
Overall it should be a dry snow, but not powdery. Forecast soundings
have the lowest 3km layer warmer than the DGZ. This restricts the
saturated DGZ to a depth of only 50-100mb. For this reason, and
incorporating Cobb output, thinking snow ratios near climatology of
12-16:1 are reasonable for an event average.
The ECMWF/NAM/SREF have the heaviest snow across the NE forecast
area which is in line with our current forecast. Other models, like
the CMC/GFS/3km NAM, are further south and focus the heavy snow band
along I-80, keeping the highest amounts in the counties along and
east of the Mississippi River. Current forecast is weighted slightly
more toward the northern models.
Saturday
After a brief break Friday night, yet another round of accumulating
snow is likely Saturday into Saturday night as a mid-level trough
crosses the Midwest and Western Great Lakes area. Several inches are
likely which may require a new set of winter headlines. Right now,
the favored area for the highest amounts are south of I-80.
Sunday On
Fresh snow cover will keep temperatures near or below normal into
early next week. There is a slight chance for light precipitation on
Tuesday as a weak trough passes through.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 538 PM CST Wed Feb 7 2018
VFR conditions are expected through the next 6 hours across the
area before light snow is expected to move in to the area. CID and
DBQ are the sites most likely to see some -sn. MLI and BRL have
low chances for snow so have removed mention in TAF. Late in the
period light snow will overspread the area.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Storm Watch from Thursday afternoon through Friday
afternoon for Benton-Buchanan-Cedar-Clinton-Delaware-
Dubuque-Iowa-Jackson-Johnson-Jones-Linn-Muscatine-Scott.
IL...Winter Storm Watch from Thursday afternoon through Friday
afternoon for Carroll-Jo Daviess-Rock Island-Stephenson-
Whiteside.
Winter Storm Watch from Thursday evening through Friday evening
for Bureau-Henry IL-Putnam.
MO...NONE.
&&
SYNOPSIS...08
SHORT TERM...08
LONG TERM...Uttech
AVIATION...GibbsHazardous Weather Outlook...UPDATED National Weather Service Quad Cities IA IL 620 PM CST Wed Feb 7 2018 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-090030- Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson- Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson- Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll- Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson- Warren-Hancock-McDonough-Scotland-Clark- 620 PM CST Wed Feb 7 2018 This Hazardous Weather Outlook is for portions of north central Illinois...northwest Illinois...west central Illinois...east central Iowa...northeast Iowa...southeast Iowa and northeast Missouri. .DAY ONE...TONIGHT Light snow is possible tonight across much of the outlook area with snow accumulations of less than a half an inch expected. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY A band of snow is expected to develop and spread across parts of eastern Iowa, and northwest Illinois Thursday afternoon and continuing overnight. Periods of snow are possible through the day on Friday. Confidence on the exact amounts of snow is low. A Winter Storm Watch has been issued along and north of Interstate 80 for Thursday afternoon through Friday afternoon. Please see the watch for more detailed information and continue to monitor the forecast for possible replacement with either a Winter Weather Advisory or a Winter Storm Warning. Another round of accumulating snow is likely on Saturday and Saturday night as a mid level disturbance moves across the region. Several inches of snow is possible and winter weather headlines are possible. At the moment, the favored area for accumulating snow is south of Interstate 80. .SPOTTER INFORMATION STATEMENT... DC/ZU/08
The national radar mosaic for the moment the first event began.
3 heavy snow. Local standard time, as filed.
Trained spotters reported heavy snow across Carroll County, with 2 miles west southwest of Chadwick reporting 7.0 inches of snow, and 6.0 inches of snow in Lanark, Illinois.
Trained spotters reported heavy snow in northeastern Jo Daviess County with 6.3 inches of snow 1 mile east northeast of Nora.
Trained spotters reported heavy snow across much of northern Stephenson county, with 8 inches reported 1 mile east of Freeport, and 6.5 inches reported in the city of Freeport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2018Every state in 2018This day in weather historyWarnings in Illinois, February 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 739053, 739054, 739055.