Severe Thunderstorms and Excessive Rainfall in the Mid-Atlantic; Heat and Fire Weather Concerns in the West

Scattered strong to severe storms, excessive rainfall, and flooding are expected across parts of the Mid-Atlantic into the Northeast today. Flood Watches are in effect. Heat will continue to impact the West today. Heat advisories are in effect for portions of the Intermountain West; and Extreme Heat Warnings are in effect for portions of Arizona and southeast California. Read More >

Overview

A narrow swath of heavy, very wet snow fell across central Illinois from the late evening of Friday, March 23rd through the evening of Saturday, March 24th.
An extremely sharp snowfall gradient occurred on the northern edge of the snow swath.
A continuous feed of very dry air on gusty easterly winds resulted in significant erosion of the precipitation on the northeastern side. This prevented light snow from falling northeast of the heavier snow bands, further tightening the snowfall gradient.

Total snowfall from the evening of Friday, March 23rd through the evening of Saturday, March 24th.

Illinois Snowfall

Comparison between observations at Pontiac (heavy snow) and Kankakee (no snow) during the late morning and early afternoon of March 24th. The Kankakee observation is ~40mi ENE of Pontiac. The very dry air is evident in the dew point/relative humidity at Kankakee.

Indiana Snowfall
Visible satellite image at 10am CDT March 25th showing the sharp cutoff in snow across central Illinois.

Indiana Snowfall

March 25th early afternoon image from the Space Science and Engineering Center Terra Satellite.

Observed Snowfall

Select Snowfall Amounts
Location (County)            Amount  
Dana (La Salle)              12.0 in
Flanagan (Livingston)        11.0 in
Chatsworth (Livingston)      8.5 in
Loda (Iroquois)              8.0 in
Fairbury (Livingston)        7.8 in
Paxton (Ford)                7.5 in
Streator (La Salle)          6.4 in
Pontiac   (Livingston)       6.0 in
Long Point  (Livingston)     5.6 in
Campus  (Livingston)         4.5 in
Lostant (La Salle)           4.0 in
Dwight  (Livingston)         3.0 in
Harmon (Lee)                 3.0 in
Peru (La Salle)              2.0 in

Regional Snowfall

Forecast Graphics

The following images show the progression of forecast graphics produced in advance of the storm, beginning with the issuance of a Winter Storm Watch on the morning of Thursday, March 22nd.
The progression shows the southwestward shift in higher forecast snowfall amounts as the event neared.
The expected sharp cut-off in snowfall on the northern edge was noted in each graphic, with the forecast totals showing a more distinct cutoff closer to the event.


Thursday morning, March 22nd.	Friday morning, March 23rd.	Friday afternoon, March 23rd.	Saturday morning, March 24th.

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Severe Thunderstorms and Excessive Rainfall in the Mid-Atlantic; Heat and Fire Weather Concerns in the West

March 24, 2018 Heavy Snow