Midwest Weekly Highlights - April 10-16, 2004

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Late Season Snow in Ohio Valley

While most of the region remained dry and relatively mild this week, the Ohio Valley region received much need rain and not-so-much needed snow.

After a cold start to the period, the weather warmed as an upper level ridge began building over the Midwest.  Temperatures this period ranged from 5F degrees below normal in southern Kentucky to about 1F degrees above normal in central Minnesota (Figure 1).  For most of the region, it was another very dry week, with the only significant precipitation over Kentucky and southeastern Ohio.  Precipitation there was in excess of 200 percent of normal, while little significant precipitation occurred over the remainder of the region (Figure 2).  The U.S. Drought Monitor this week depicted southern Michigan, northern Indiana, and northwestern Ohio in Abnormally Dry conditions (Figure 3). 

A low pressure system along the Gulf Coast on Sunday began to organize and intensify as a strong upper level low approached from the west (Figure 4). By Monday morning the surface low was located over central Mississippi and was moving to the north northeast.  Precipitation associated with this system was falling from the Texas Gulf coast to the eastern seaboard, with the heaviest precipitation in Tennessee and Kentucky (Figure 5, Unisys). Light precipitation was falling as far north as southern Illinois and Indiana.  Both the upper level low and the surface low continued to intensify, drawing unseasonably cold air into the system’s circulation.  By Tuesday morning the slow moving storm’s center had moved only to the central Kentucky-Tennessee border (Figure 6).  Snow and sleet was falling from far southern Illinois south through western Kentucky and Tennessee.  Most accumulation was on grassy surfaces as temperatures hovered just above freezing. However, there was slushy accumulation on roads in some areas, and poor driving conditions led to a number of accidents.  Four people were killed in Kentucky in two weather-related traffic accidents in Muhlenberg County.

On April 13 snowfall reports from spotters and emergency management officials indicated snowfall amounts up to 6 inches in Breckinridge County northwestern Kentucky, with 1 t o3 inches more common. The snow also extended up into southern Indiana where New Amsterdam in Harrison County reported 3 to 4 inches and New Pekin reported 3 inches. Paducah, KY received a trace of snow, the first time snow has occurred on this date.  Cincinnati-Northern Kentucky Aiport received 1.3 inches of snow. This was not the latest snow for Cincinnati.  That occurred on May 6, 1989 when 0.2 inches were measured.  Snow on the ground was observed in the visible satellite photographs of western Kentucky on the morning of April 14 (Figure 7).

Further east, heavy rain fell in central and eastern Kentucky.  Both London and Jackson KY set new daily rainfall records for April 13.  Jackson received 1.25 inches, breaking the old record of 0.62 inches in 1996.  London’s 0.81 inches broke the old record of 0.62 set in 1980. The slow moving low pressure system produced periods of heavy rain Monday into Wednesday morning.  Thunderstorms, a few severe, occurred in the far eastern counties of Kentucky. Rainfall totals with this storm were generally one to three inches, and produced flash flooding in a number of eastern counties on April 13.  Some of the higher elevations in eastern Kentucky received up to an inch of snow. Further north, some snow occurred in a number of locations in northeastern Ohio with 2 inches reported in Ashtabula County.

Windy conditions occurred through the Midwest on April 12 and 13 as the intensifying low generated strong winds throughout much of the Midwest.  Winds gusted to 40-50 mph in Ohio and Indiana on April 12. Cold air over the region in the wake of the storm on the morning of April 15 prompted frost advisories throughout much of northern Indiana.

By April 15 warmer air was already starting to make is way back into the Midwest.  Southerly winds increased, and that combined with low relative humidity prompted Red Flag warnings for southeast Missouri and southern Illinois.  Red Flag warnings are issued when strong winds with low relative humidity (generally less than 35 percent) produce an increased danger of wildland fires.