Alert archive / Illinois / Mesoscale Discussions in 2018

Mesoscale Discussion 49

February 5, 201831 counties in Illinois; 6 counties in Indiana; 9 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Feb 5, 2018, 4:57 PM CST for 31 counties in Illinois; 6 counties in Indiana; 9 counties in Iowa. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Feb 5, 2018, 4:57 PM CST (22:57 UTC)
Expired
Feb 5, 2018, 9:00 PM CST
In force
4 hr
Issued by
the Storm Prediction Center
All 46 counties

Cedar County, IA, Clinton County, IA, Des Moines County, IA, Henry County, IA, Lee County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Washington County, IA, Bureau County, IL, DeWitt County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Iroquois County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McLean County, IL, Mercer County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Schuyler County, IL, Stark County, IL, Tazewell County, IL, Warren County, IL, Whiteside County, IL, Will County, IL, Woodford County, IL, Benton County, IN, Carroll County, IN, Jasper County, IN, Newton County, IN, Pulaski County, IN, White County, IN

The radar

The Quad Cities radar (KDVN), 96 km from the middle of the area, began a volume at 22:58 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 11.0 hours before the alert went out and 93 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 2018-02-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 12:00Z on 2018-02-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 60 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1504 m above ground
0-6 km bulk shear
79 kt
0-1 km storm-relative helicity
60 m²/s²
0-3 km storm-relative helicity
227 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

086 
ACUS11 KWNS 052258
SWOMCD
SPC MCD 052257 
INZ000-ILZ000-IAZ000-MOZ000-060300-

Mesoscale Discussion 0049
NWS Storm Prediction Center Norman OK
0457 PM CST Mon Feb 05 2018

Areas affected...Portions of far southeastern Iowa into northern
Indiana

Concerning...Heavy snow 

Valid 052257Z - 060300Z

SUMMARY...Moderate to occasionally heavy snow will continue across
parts of northern Illinois into northern Indiana for a few more
hours. Rates up to one inch per hour will be possible.

DISCUSSION...Regional radar data highlight a progressive, but
organized band of snowfall extending from southeastern Iowa into
northwestern Indiana late this afternoon. Satellite and radar data
suggest that isentropic ascent within the 700-500mb layer is
fostering efficient ice-crystal production aloft, and forecast
soundings indicate that modest aggregation processes may also be
augmenting snowfall rates. These conclusions are consistent with
radar cross-sections showing an increase in reflectivity and
decrease in differential reflectivity in the direction towards
ground (within the heaviest parts of the band). Additionally, while
the dendritic growth layer is not particularly deep (somewhat
limiting rates), adequate ascent above 700mb is favorable for
dendritic/planar crystals, and modest enhancements in KDP are noted
around 12-17K ft. This microphysical profile should continue to
yield snowfall rates up to one inch per hour as the band advances
east. However, rates should gradually diminish later this evening
and with eastward extent, owing to a decrease in ascent within the
-10 to -20 C layer.

..Picca.. 02/05/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...IWX...IND...LOT...ILX...LSX...DVN...

LAT...LON   40439146 41029182 41309184 41669159 41939096 41848935
            41648837 41168669 40948628 40538648 40008916 40149077
            40319145 40439146

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 5, 11:36 AM CSTMesoscale DiscussionSPCHenderson, Mercer, Rock Island, Warren6 hr

Nearby

Mesoscale Discussions in Illinois, 2018Mesoscale Discussions in Iowa, 2018Mesoscale Discussions in Indiana, 2018Every mesoscale discussion in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.