Eastern Wyoming Tornado
Nebraska Hailstorm
 April 12 1967

Jonathan D. Finch

Boulder Area Tornadoes Webpage

Cheyenne Area Tornadoes Webpage

US tornado cases webpage

May 7-8  1965 Front Range Tornado

June 14-17  1965 Front Range Superstorm

April 23 1960 Cheyenne Ridge Tornado

The July 16  1979 Cheyenne Tornado

High plains and front range topo maps



Overview


                                        On April 12, 1967 , a thunderstorm developed west of Cheyenne, WY and moved NE over over open mostly
                                        wide open country. The first tornado was seen 4 miles south west of Veteran, WY. This tornado moved NE and then
                                        north, passing 4 miles west of Torrngton. No large hail was reported. Its is possible that the core of this storm on
                                        the northern and northwest side of the storm hit no populated areas. Also, phone calls were not made to collect
                                        hail reports in the 1960s. Hail was only documented if someone actually called the report in to the office. Hail as
                                        large as golfballs did occur in the Nebraska panhandle near Chadron.
                          
                           

Meteorological Discussion


                                               
                                        At 12 UTC April 12  1967, a very deep 500mb upper trough was located over southern California.  A 700mb
                                        warm plume covered the plains with 700mb temps up to 7C.  A high level speed max was located over the
                                        northern plains but another jet streak was entering southeast Arizona.  500mb temps were fairly cold (17-19C)
                                        from ABQ to DEN to RAP.  Even though the 700mb temperature was cooler at Albuquerque at 12 UTC (-1C) the
                                        700mb cold front had not passed yet. It is just that elevated heating and rapid transport downstream was leading to
                                       warmer 700mb temperatures to the east of Albuquerque(ABQ).

                                        By 18 UTC, a warm front stretched from central Colorado into northern Kansas and Missouri. Low level upslope
                                        flow was apparent across northeast Colorado, western Nebraska and southeast Wyoming. This in conjunction with
                                        elevated heating was leading to rapid destabilization across the central high plains and front range. A surface cold
                                        front stretched from western CO to near ABQ. The cold front passed ABQ shortly after 18 UTC as shown by the
                                        surface observation sheet. Another cold front stretched from North Dakota into eastern Wyoming. A well defined
                                        outflow boundary existed across the southern plains. A surface dryline was located from west Texas to just east of
                                        Goodland. I was able to pinpoint the location of the dryline by using the surface observation sheets from Goodland
                                        and Garden City. I pinpointed the warm front using surface observations from various sites including Akron, Denver
                                        and Goodland. The warm front was a little harder to find across western Kansas.

                                        By 20 UTC, the warm front stretched from just south of Denver to just south of Akron to near North Platte. The
                                        pacific cold front was about to pass Las Vegas, NM. The dryline had pushed east of Garden City. The dryline
                                        was well east of Goodland, KS but had not yet passed east of Imperial, NE. The T/TD at Cheyenne were up to 
                                        59F/39F with upslope winds.

                                        A thunderstorm developed west of Cheyenne around 3 pm and moved generally northeast. At 5 pm this storm produced
                                        a tornado southwest of Veteran, WY. This tornado moved northeast then north destroying 10 buildings. Severe weather
                                        probably occurred between Cheyenne and Veteran but this is a sparsely populated area.
                                       
     
                                        The surface T/Td at Cheyenne and Fort Collins at 18 UTC were 53F/39F and 61F/41F respectively. The surface
                                        dewpoint at Muskogee was 62F/60F. However, the theta-e was actually higher at Fort Collins and about the same at
                                        Cheyenne. This is despite the dewpoint being much lower on the front range. But why? The key is that elevated heating
                                        compensates for the lack of moisture on the front range. In this case, the potential temperature was 32F higher in
                                        Cheyenne than Muskogee even though it was 9F cooler in Cheyenne. Since the 500mb temperature was much cooler
                                        at Cheyenne and Fort Collins, the lifted index was much lower there.


18 UTC Elev(ft) Pres.(mb) SLP(mb) T(F) Td(F) MR(g/kg) theta(F) theta-e(K) H5 T LI
Cheyenne 6140 795.4 991.0 53 39 6.4 87.6 323.5 -18 -3.5
Fort Collins 5000 828 990.6 61 41 6.6 89.8 325.6 -18 -4
Muskogee 607 980.2 1005
 62 60 11.4 65 323.9 -11 +3


                                        The surface T/Td at Cheyenne at 20 UTC was 59F/39F. The surface T/Td at Topeka and Emporia were 67F/60F 
                                        and 70F/57F respectively. However, the theta-e was actually about the same at all 3 locations. Again, the key is 
                                        elevated heating. Since the 500mb temperature was much cooler at Cheyenne, the lifted index was much lower
                                        at Cheyenne.


20 UTC Elev(ft) Pres.(mb) SLP(mb) T(F) Td(F) MR(g/kg) theta(F) theta-e(K) H5 T LI
Cheyenne 6140 793 990.6 59 39 6.4 94.5 327.7 -19 -6
Topeka 881 971 1003.6 67 60 11.5 71.3 328.2 -11 +2
Emporia 1207 960.6 1003.3
 70 57 10 69.5 328.2 -11 +2




                                        An approximate sounding for Cheyenne at 20 UTC shows about 1800 j/kg surface based CAPE. I used the 00
                                        UTC Rapid City wind profile at and above 500mb. The winds veer between the surface and 500mb, but the
                                        speeds and directions in this layer are not known. The 700mb wind field on the high plains, front range and
                                        intermountain west can be very difficult to resolve since 700mb is on the boundary layer. Sometimes 700mb is in
                                        the moist layer and sometimes not. The only way to know the low level wind profile on the front range is to have a
                                        dense sounding or profiler network. However, there is greater than 50kts of shear between the surface and 400mb
                                        or in the lowest 6 km. This is very respectable.

                                        I also created an approximate sounding for Scottsbluff, NE which is east of where the tornado occured. The surface
                                        based CAPE is about 1300 j/kg.