NWS estimates (see below) suggest that more than 6 inches may have fallen in some spots, but I'm not sure if any ground-truth measurements came in that high. Here's one list that the NWS provided:
Regardless of the highest amounts, this was a very significant rain event over a large area, including the interior North Slope. Click to enlarge:
The 500mb analysis from Tuesday afternoon (see below) shows the strong Arctic low, and notice the contrast with the extremely strong ridge over southwestern Canada. All-time heat records were shattered in Oregon, Washington, and British Columbia, including an outrageous 121°F in southern BC on Tuesday (by far Canada's highest observed temperature of all time). There was certainly a dynamical connection between the two features - the ridge and the Arctic trough - and the large amplitude of the overall flow anomaly helps explain the extreme rain outcome in northwestern Alaska.