HAILSTORMS AND HAILSTONES^SCHAEFER 



343 



azimuth of 250°. The radar photos and their geographic relationship 

 to the hail damage zone is shown in plate 3, figure 1. 



1. ORIGIN AND FEATURES OF THE STORM 



During the latter part of June, the area east of the front range of 

 the liockies experienced a series of severe hailstonns. On June 26, 

 the leading edge of a cP air mass moved out of Wyoming with the 

 center of the low over the Wyoming plains near Rawlins early that 

 morning. This low moved northeastward during the next 18 hours 

 with hail and thunderstorms drifting slowly eastward as shown in 

 plate 3, figure 2. Although a temperature difference of 5° to 10° 

 Fahrenlieit marked the division between cP and mT air, the major 

 difference in surface flow during the daylight hours of the 27th was 

 a wind shift from south to north following the squall-line passage. 

 Toward evening an intense zone of surface convergence was centered 

 in the vicinity of Plall County and presumably intensified the two 

 large cells which produced the hail damage. The situation at the 

 surface at 2200 is shown in plate 4, figure 1. 



During the late afternoon and early part of the evening until 2000, 

 large CB and towering cumulus were noted by Weather Bureau ob- 

 servers at Grand Island in the area from the northeast to the south 

 of that station. 





0400 ObOO 0300 IDOO 1200 |400 IfaOO f^SJ^ / 2000 UDO e<iOO 



- C. 5.T. 



Figure 1. — Pressure, temperature, dewpoint, and precipitation at Grand Island, Nebr., 



June 27, 1959. 

 579421—61 27 



