IANAL, YMMV, and other assorted disclaimers.
With that, so long as the gun is INSIDE a fully ziped compartment and is NOT loaded (per Utah code) it is NOT considered "concealed." There is some question about whether putting the "case" inside a glove box or center console would then make it concealed. But certainly in a trunk, or behind the seat is ok. Just be sure the zipper or clasp or tie, or whatever it is that keeps the firearm inside the "case" is fully done up. It need NOT be locked. A holster of any sort is not going to qualify as securing encased. But if you want to put the gun in a holster, and then put the hold thing inside a zippered pouch you should be fine.
You CAN have a fully charged magazine in the firearm so long as there is no live round in the chamber.
From 76-10-501 (note the leading portion of the URL and bookmark it <http://le.utah.gov/~code/TITLE76/htm/76_10_050100.htm>.
(2) (a) "Concealed dangerous weapon" means a dangerous weapon that is covered, hidden, or secreted in a manner that the public would not be aware of its presence and is readily accessible for immediate use.
(b) A dangerous weapon shall not be considered a concealed dangerous weapon if it is a firearm which is unloaded and is securely encased.
(18) "Securely encased" means not readily accessible for immediate use, such as held in a gun rack, or in a closed case or container, whether or not locked, or in a trunk or other storage area of a motor vehicle, not including a glove box or console box.
76-10-502. When weapon deemed loaded.
(1) For the purpose of this chapter, any pistol, revolver, shotgun, rifle, or other weapon described in this part shall be deemed to be loaded when there is an unexpended cartridge, shell, or projectile in the firing position.
(2) Pistols and revolvers shall also be deemed to be loaded when an unexpended cartridge, shell, or projectile is in a position whereby the manual operation of any mechanism once would cause the unexpended cartridge, shell, or projectile to be fired.
(3) A muzzle loading firearm shall be deemed to be loaded when it is capped or primed and has a powder charge and ball or shot in the barrel or cylinders.
So, no round in the chamber, and a full magazine is ok as it takes TWO actions (racking the slide and then pulling the trigger) to fire the gun.
After all this, if at all possible, I highly recommend obtaining a Utah firearms carry permit as soon as possible. It avoids all such questions and allows legal carry in school zones. It also allows legal concealed carry in 30+ other States.