DRG ARRIVAL AT 2125 EST, SIMMONS AIRLINE FLT 1746 WAS ADZD BY WURTSMITH AFB APCH CTL THAT THE 2052 EST WX AT PHELPS COLLINS ARPT WAS: SKY PARTIALLY OBSCD, CEILING 100' OVERCAST, VIS 1/2 MI WITH LGT DRIZZLE & FOG, & TO EXPECT AN ILS APCH. HOWEVER, AT 2119, A SPL WX OBS WAS TAKEN WHICH SHOWED THE VIS HAD DECREASED TO 3/8 MI, WHICH WAS BLO MINS. THIS INFO HAD NOT REACH WURTSMITH UNTIL SOMETIME LATER SINCE THE SYS FOR SENDING WX FROM PELLSTON FSS TO WURTSMITH WAS NOT AUTOMATED & WAS SLOW. FLT 1746 CONTD THE APCH, BUT THE PLTS DID NOT CLRLY SEE THE RWY LGTS, SO THEY MADE A MISSED APCH &ELECTED TO MAKE A 2ND ILS APCH. AT 2146, ANOTHER SPL WX OBS WAS TAKEN WHICH SHOWED THE VIS HAD DECREASED FURTHER TO 1/4 MI. THIS INFO WAS PROVIDED TO THE SIMMONS STATION MGR AT ALPENA, WHO TRIED TO CONTACT FLT 1746, BUT WAS UNABLE. AT APRX 2200 EST, THE ACFT HIT TREES & CRASHED ABOUT 1-1/2 MI SHORT OF RWY 1. THERE WAS EVIDENCE THAT FLT 1746 HAD CONTD BLO THEILS GLIDE SLOPE & DECISION HEIGHT (DH) WITHOUT OBTAINING VISUAL REFERENCE OF THE RWY.