An advancing weather front Wednesday forced the second cancellation of an Air Force explosives test of a newlydesigned munitions storage igloo on the Utah Test and Training Range west of the Great Salt Lake.

The cloud cover and wind direction first forced postponement of the planned 1 p.m. detonation of pounds of composition explosives to 2 p.m. Then the blast was put on hold and eventually cancelled. Air Force officials say the storm front will have to clear out of the area before the blast can be set off, probably Saturday or Sunday.The detonation was first set for Nov. 8 but weather conditions forced its cancellation then, too.

The explosives, the equivalent of a half million pounds of TNT, are being set off in an experimental munitions storage facility designed at Hill Air Force Base called the Hayman Igloo. The building is constructed of prefabricated steel and concrete sections and is cheaper and simpler to put up than the current munitions storage facilities.

Air Force officials say weather conditions, including cloud cover, wind direction, and temperature must be just right before the explosives will be detonated to prevent shock damage such as broken windows to homes along the Wasatch Front.

Using this summer's explosion at a rocket fuel plant outside Henderson, Nev., as an example, Air Force officials estimate that blast, which did millions of dollars of damage to homes and businesses, at the equivalent of 200,000 pounds of TNT. Cloud cover and a temperature inversion created conditions of maximum shock wave and damage, which the Air Force wants to avoid when it sets off the 500,000-pound equivalent blast on the training range.

The test site is just north of the Oasis installation about 26 miles north of I-80 and directly west across the Great Salt Lake from Clearfield, Air Force officials said.