Narrative:

Departed msp for dlh forecast for dlh marginally required alternate. We planned for hib. WX at dlh when we departed the gate was 100 overcast 15 mi visibility and light snow showers. The forecast at dlh was for no lower than a 2000' overcast and 3 mi and light snow. As we approached dlh the ATIS gave a visibility of 7 mi. When we contacted approach they stopped using the ATIS because visibility was dropping so fast they couldn't keep up. We asked the controller for WX at our alternate. Hib reported 1/4 mi visibility and heavy snow. All other airports within a safe range of dlh were below landing minimums. With fuel low we told the controllers we would have to attempt landing at dlh. During this event we realized that a major winterstorm had developed our forecast had just been issued an hour prior to departure. It was obvious that this storm had made extensive nward progress and was no longer within forecast parameters. It also became apparent this situation was getting critical and emergency action was necessary. We elected to begin executing approachs with the remaining fuel. The idea was to land if we broke out and were able to make a safe landing before fuel forced us into an unsafe situation. The first approach went perfectly, the tower reported 1/2 mi and heavy snow. However, RVR was indicating a range of 1200 to 2400 RVR. At 200' above the middle marker we had ground contact. At 100' above the marker the lead in lights were clearly visible. At the marker the runway was in sight and clearly a safe landing could be made despite a highly erratic RVR. The controllers seem to understand the situation and performed their duties perfectly. The landing was made safely with no other complications. I did notice a large amount of snow on the ground. One explanation for the erratic RVR could be ground snow being picked up by the wind in close proximity to the RVR components. Clearly the visibility was 1/2 mi or better.

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Original NASA ASRS Text

Title: FLT CREW OF COMMUTER STARTED APCH WITH RVR REPORTED BELOW MINIMUMS, LANDED WHEN ARPT CAME IN SIGHT WITH APPROPRIATE MINIMUMS.

Narrative: DEPARTED MSP FOR DLH FORECAST FOR DLH MARGINALLY REQUIRED ALTERNATE. WE PLANNED FOR HIB. WX AT DLH WHEN WE DEPARTED THE GATE WAS 100 OVCST 15 MI VISIBILITY AND LIGHT SNOW SHOWERS. THE FORECAST AT DLH WAS FOR NO LOWER THAN A 2000' OVCST AND 3 MI AND LIGHT SNOW. AS WE APCHED DLH THE ATIS GAVE A VISIBILITY OF 7 MI. WHEN WE CONTACTED APCH THEY STOPPED USING THE ATIS BECAUSE VISIBILITY WAS DROPPING SO FAST THEY COULDN'T KEEP UP. WE ASKED THE CTLR FOR WX AT OUR ALTERNATE. HIB RPTED 1/4 MI VISIBILITY AND HVY SNOW. ALL OTHER ARPTS WITHIN A SAFE RANGE OF DLH WERE BELOW LNDG MINIMUMS. WITH FUEL LOW WE TOLD THE CTLRS WE WOULD HAVE TO ATTEMPT LNDG AT DLH. DURING THIS EVENT WE REALIZED THAT A MAJOR WINTERSTORM HAD DEVELOPED OUR FORECAST HAD JUST BEEN ISSUED AN HR PRIOR TO DEP. IT WAS OBVIOUS THAT THIS STORM HAD MADE EXTENSIVE NWARD PROGRESS AND WAS NO LONGER WITHIN FORECAST PARAMETERS. IT ALSO BECAME APPARENT THIS SITUATION WAS GETTING CRITICAL AND EMER ACTION WAS NECESSARY. WE ELECTED TO BEGIN EXECUTING APCHS WITH THE REMAINING FUEL. THE IDEA WAS TO LAND IF WE BROKE OUT AND WERE ABLE TO MAKE A SAFE LNDG BEFORE FUEL FORCED US INTO AN UNSAFE SITUATION. THE FIRST APCH WENT PERFECTLY, THE TWR RPTED 1/2 MI AND HVY SNOW. HOWEVER, RVR WAS INDICATING A RANGE OF 1200 TO 2400 RVR. AT 200' ABOVE THE MIDDLE MARKER WE HAD GND CONTACT. AT 100' ABOVE THE MARKER THE LEAD IN LIGHTS WERE CLRLY VISIBLE. AT THE MARKER THE RWY WAS IN SIGHT AND CLRLY A SAFE LNDG COULD BE MADE DESPITE A HIGHLY ERRATIC RVR. THE CTLRS SEEM TO UNDERSTAND THE SITUATION AND PERFORMED THEIR DUTIES PERFECTLY. THE LNDG WAS MADE SAFELY WITH NO OTHER COMPLICATIONS. I DID NOTICE A LARGE AMOUNT OF SNOW ON THE GND. ONE EXPLANATION FOR THE ERRATIC RVR COULD BE GND SNOW BEING PICKED UP BY THE WIND IN CLOSE PROX TO THE RVR COMPONENTS. CLRLY THE VISIBILITY WAS 1/2 MI OR BETTER.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.