You can use the following:
$str = "PALM DESERT SD63376 ";
// note that there are two spaces in the regex pattern
var_dump(preg_split('~ +~', $str, -1, PREG_SPLIT_NO_EMPTY));
Output:
array(2) {
[0] =>
string(11) "PALM DESERT"
[1] =>
string(7) "SD63376"
}