Wyoming, South Dakota and Texas Tornadoes on June 5 1982

                                        Small areas of high end severe weather occurred on June 4-5, 1982. Severe weather on June 4, 1982 was confined
                                        to the Nebraska panhandle and western South Dakota. On June 5, Wyoming, western South Dakota and the Texas
                                        panhandle experienced severe weather. Al Moller decided to storm chase in the Texas panhandle. GOES east satellite
                                        loops for Wyoming and the Texas panhandle as well as the GOES west loop for Wyoming are all very impressive.

                                        The most damaging thunderstorm in the northern high plains appeared to have developed in northeast Carbon county
                                        in Wyoming (elevation 7500ft). This storm produced damaging tornadoes in Converse and Niobrara counties in
                                        Wyoming and Fall River county in South Dakota. A storm that developed around Midwest in Natrona county, WY
                                        resulted in a tremendous hailstorm in Butte county, SD later in the evening.

Meteorological Discussion


                June 4

                                        At 12 UTC, a 500mb trough was located over the western United States. A shortwave trough was moving across
                                       Missouri and Arkansas. The 250mb chart showed a jet from the southern plains into the northeast and another
                                       from central CA into northern Utah. A warm plume over the Rockies separated cold air at 850mb along the west
                                        coast from cool air over the plains. 700mb temperatures were very cold along the west coast.

                                       At 18 UTC on June 4, a cold front was pushing across Wyoming and Utah. A cold front was also pushing through
                                        the southern plains and southeast and extended from Memphis to Monroe, LA to San Antonio. Cool surface high
                                        pressure extended from Kansas into north Texas.

                                        By 21 UTC, the Texas cold front was becoming stationary around San Antonio but was still progressing southeast
                                        through east Texas and Louisiana. The weak northern Rockies cold front was still progressing eastward. By 00 UTC
                                        this front was about to move through Miles City, MT and was through Douglas, WY.

                                        The 00 UTC 500mb chart still showed a deep trough that was centered over northern CA. The shortwave trough
                                        that was centered over Missouri and Arkansas at 12 UTC was progressing off to the east. The 850mb chart showed
                                        rich moisture in central and south Texas. With the 500mb ridge
                                        over the central plains and west-southwest flow from Arizona into west Texas, one would expect lee troughing and
                                        northward moisture transport over west Texas to begin. There was also a 10C dewpoint at North Platte at 00 UTC.
                                        This was not due to the incipient southern high plains moisture surge, but was "residual moisture" from the plain's cool
                                        and rather moist airmass already in place. This moist layer at North Platte was only about 60 mb deep though.
                                        Rich, deep moisture was in place at Del Rio.

                                        Strong 700mb warming has occurred during the day over the southern and central Rockies with 11-13C temperatures.
                                        Of course, part of this warming was diurnal. A warm plume was located over the Rockies. So why did I analyze 850mb
                                        temperatures over the Rockies since 850mb is underground there? Well, I took the temperature at the nose of the low level
                                        inversion on the Rockies' soundings down the dry adiabat to 850mb. This actually gives plain's forecasters an idea of
                                       what 850mb temperatures could be if strong downslope develops.

                                       By 03 UTC the northern Rockies front was now moving across the northern plains and was approaching Glendive,
                                        MT where a thunderstorm was reported. This front was not yet through Laramie.

                                       By 06 UTC (11 pm MST June 4) the front was approaching Williston, ND, where a shower was in progress, and was
                                       approaching Cheyenne. As expected from the 00 UTC UA charts, northward moisture transport was occurring over
                                       west Texas with a 64F dewpoint at Midland and 60F at Lubbock.


                June 5

                                       By 09 UTC June 5, the northern plains front was passing through Brandon, Manitoba and extended to the south-
                                        southwest through Rapid City to near Denver, CO. The surface dewpoint was up to 61F at Clovis and 62F at
                                        Lubbock.

                                        The 12 UTC 250mb chart showed the main jst stream of 110 kts over Salt Lake City and Ely, NV. However, part
                                        of this jet branched off into the southern plains and deep south. The 500mb chart showed a weak shortwave trough
                                        moving northeast across the northern Rockies and northern plains. This wave was probably responsible for the weak
                                        cold frontal passage through Cheyenne, Denver and Rapid City. As we suspected, strong moisture advection was
                                        occurring overnight at 850mb. The moisture on the North Platte sounding was not very rich yet, but had deepened
                                        considerably. Much richer moisture was present on the 12 UTC Dodge City sounding. the 850mb dewpoints at
                                        Amarillo and Midland had increased to 16 and 17C respectively. Although this moisture was very rich, it was not all
                                        that deep.

                                       The 12 UTC surface chart showed a 61F dewpoint as far north as Dalhart, TX. The southern surface front was still
                                        stationary near San Antonio. The front that was sagging south into Colorado overnight was difficult to find since
                                       radiational cooling had occurred ahead of the front.

                                       By 15 UTC, the surface moist axis was located from the Texas panhandle into far western Kansas. The cold front
                                       appears to be still pushing south through Colorado but it was not through Pueblo and La Junta yet. The northern
                                        part of the front was still located from west of Bismark to near Rapid City.

                                        By 17 UTC the front that had been moving through Colorado had stalled. the front did not appear to pass through
                                        La Junta and Pueblo despite the east winds at those locations. I analyzed a trough line south of these stations. It is
                                        very common to get east or southeast winds up the Arkansas River valley but that doesn't necessarily mean that
                                        a front has passed. The dewpoint at Douglas jumped from 35 to 47F from 15 to 17 UTC. But was this moisture deep?
                                        60F dewpoints had surged as far north as Goodland, KS and Champion, NE.

                                        By 18 UTC, the front in Colorado had pulled up stationary. This boundary was actually surging north as a warm front
                                        in Wyoming. I still analyzed a trough line south of La Junta and Pueblo. The surface dryline was becoming well defined
                                        south of this trough.

                                        The shallow moisture that appeared at Douglas, WY was already mixing out by 19 UTC. But surface winds in the
                                        Nebraska panhandle were strenghtening from the east-southeast, advecting moisture into far eastern Wyoming.
                                        Locations such as Rawlins, Rock Springs and Craig were already mixed out at local noon and this is typical of
                                        stations above 6000ft. The 1915 UTC visible shot over Wyoming shows some convection developing from west of
                                        Laramie to southwest of Douglas.

                                        By 20 UTC the dewpoints at Rapid City, Chadron and Scottsbluff were up to 56F. But the dewpoint at Douglas, WY
                                        was still 39F. This is surprising given the southeast winds all morning. It is possible that the dewpoint at Douglas is
                                        in error. The 1945 UTC visible shot shows surface based cumulus developing south of Glendo Reservoir and near
                                        Laramie Peak.

                                        The 20 UTC satellite picture over the southern high plains showed a few small cumulus in the clear areas to the
                                        east and south of Dalhart. The 2026 UTC southern plains visible picture indicated 2 areas of cumulus. One was south
                                        of Dalhart and the other to the east. At 2041 UTC, the cumulus to the south of Dalhart in Oldham county seems to be
                                        bigger. The 2050 UTC visible shot shows this area of cumulus still growing. Also, notice how the clouds change
                                        suddenly from cumulifiorm in southwest Oklahoma to stable wave clouds in northwest Oklahoma and southwesrt Kansas.

                                       The 21 UTC surface map shows continued moisture return into eastern Wyoming. The 2045 UTC satellite shot still
                                        indicated cumulus development south of the Glendo Reservoir and near Laramie Peak. Thunderstorms had already
                                        developed over the Bighorn mountains northwest of Casper. Between 2100 and 2130 UTC, a thunderstorm rapidly
                                        developed in the Midwest, Sussex, North Butte area. A thunderstorm was also devleoping over the Black Hills.

                                        Thunderstorms started to initiate in southeast Wyoming around 2145 UTC. The first cells appeared to develop from
                                        south of the Glendo Reservoir and near Laramie Peak.

                                        In the southern plains the surface winds have backed at Elkhart where the dewpoint jumped from 57 to 64F in 1 hour.
                                        Also the winds were veered at Dalhart and backed at Amarillo. So the dryline seems to have sharpened in the far
                                        western Texas panhandle. The 2053 UTC satellite shot shows an even larger cumulus south of Dalhart in Oldham
                                        county. There was explosive convective development between 2100 and 2130 UTC to the east or southeast of
                                        Dalhart. Other convective clouds were rapidly developing between Amarillo and Clovis. At 2144 UTC, a towering
                                        cumulus can be seen west or southwest of Amarillo ahead of the surface dryline, or about half way between Amarillo
                                        and Tucumcari.

                                        The 22 UTC surface chart still showed backed winds from the south-southeast at Amarillo with the surface dryline
                                        in the same location. The convective cloud west of Amarillo was still developing rapidly. The initial thunderstorm that
                                        developed raced off to the northeast.

                                        The dewpoint at Laramie jumped from 39F at 21 UTC to 44F at 22 UTC. The surface dewpoint at Gillette is likely
                                        much too low. Also, it is very uncommon for the dewpoint at Cheyenne and Laramie to exceed the dewpoint at
                                        Douglas in strong upslope flow cases. At 22 UTC, several storms were in progress across Johnson, Campbell,
                                        Big Horn and Washakie counties. By 2215 UTC, thunderstorms had developed southwest and west of the Glendo
                                        Reservoir and in northern Albany county to the southwest of Laramie Peak. By 2245 UTC, as the initial cells were
                                        moving off to the northeast and about to weaken, more storms were developing further west due to advection of
                                        higher dewpoints onto the high terrain. One cell in particular was rapidly developing in far northeast Carbon county.

                                        The following table shows the important contribution of elevated heating to equivalent potential temperature over the
                                        high terrain. The temperature/dewpoint at Laramie were only 61F/44F compared to 73F/63F at Emporia, KS. Even
                                        though the T/TD were 12F/19F higher respectively at Emporia, the theta-e was about the same at the 2 locations. The
                                        44F dewpoint at Laramie has about the same amount of moisture as a 51F dewpoint at Emporia. So on a "level playing
                                        field", the dewpoint was about 12F higher at Emporia. The potential temperature at Laramie was 101.5F, compared
                                        to 77.8F at Emporia. So despite the mixing ratio being 61% higher at Emporia, the theta-e was about the same at
                                       the 2 stations since Laramie was potentially so much warmer.


22 UTC	Elev(ft)	Pres.(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)
Laramie	7270	769.3	61	44	8.0	101.5	336.8
Douglas	4900	839.0	69	43	7.1	96.2	330.8
Emporia	1208	969.1	73	63	12.9	77.8	336.3

                                        Surface based, deep convection was imminent to the north-northwest of Laramie a 22 UTC. To get an idea of how
                                        much instability was present in this area, I will use a method of computing liftex that to my knowledge that has only
                                        been used by myself. Let's take the surface temperature at several stations in the dry air across southern Wyoming
                                        and western Colorado from 18 to 20 UTC (after mixout) up the dry adiabat to 700mb and then 500mb and document
                                        the temperature at those levels. This will give us an idea of the low to mid level thermal profile in the dry air. With
                                        moderate 500mb flow from the southwest, we can assume that stations to the northeast of these will experience similar
                                        500mb temperatures. Then we will take the surface temperature and dewpoint at stations in the moist air up to the
                                        lifted condensation level and then up the moist adiabat to 500mb. Subtracting this temperature from the former
                                        temperature (environmental temperature) will give us the lifted index in the moist air. Using the above information,
                                        along with the T/Td at Laramie at 22-23 UTC, yields a surface based lifted index of -7.


20 UTC	Elev(ft)	Alt	Pres.(mb)	SLP(mb)	T(F)	Pot. T (F)	700mb T	500mb T
Rawlins	6813	23.15	783.9	1000	68	106	10.6	-15.3
Rock Springs	6760	23.14	783.5		66.5	104.4	9.8	-16.2
Craig	6193		800	998.0	71	105.9	10.6	-15.3
Eagle	6540	23.38	791.6	998.0	75	110.3	13	-12.9
Grand Junction	4858	24.83	840.7	998.5	80	107.4	11.3	-14.0
Alamosa	7539	22.66	767.3		70-73	113.1	13.6	-12.3
Aspen	7820		760		70	112.0	14	-12.0