be Monday night, but according to the observations the snow continued through Tuesday
morning until 11 UTC. When the NWS updated their forecast at 1 PM CST on 26
January (18 UTC) they added the chance for snow after midnight on Monday night and
extended the winter weather advisory through the night.
.TONIGHT...BLUSTERY...COLDER. AREAS OF BLOWING SNOW. SNOW
THEN SNOW LIKELY AFTER MIDNIGHT. SNOW ACCUMULATION AROUND 2
INCHES. LOW ZERO TO 5 ABOVE. NORTHWEST WIND 15 TO 25 MPH...WITH
GUSTS AROUND 30 MPH.
.TUESDAY...PARTLY SUNNY IN THE MORNING THEN CLEARING.
HIGH NEAR 15. NORTHWEST WIND 10 TO 20 MPH.
So the update did extend the length of snowfall through early morning on Tuesday. The
original forecast from the NWS matched the RWFS precipitation timing before the event
started, but the updated forecast by the NWS indicated a closer end time for the event
than was predicted by the RWFS update.
Another important precipitation variable to look at is the total forecast snow depth, which
has major implications on winter road maintenance decisions. This is a difficult
parameter to forecast because the snow to liquid ratio can be very sensitive to many
atmospheric conditions such as surface temperature, temperature within the cloud where
the precipitation formed, vertical motion within the cloud, available moisture, surface
wind speeds and others.
LEDWI data from the start of this event was missing so actual hourly liquid precipitation
measurements from the tipping bucket gauge, also located at the METAR site, were used
in its place between 03 UTC and 12 UTC, 26 January. For this case the time period
between 12 UTC and 15 UTC, 26 January is used to find the snow to liquid ratio for
reasons stated earlier. During this time period a ratio of 20:1 was found and applied to
the beginning portion of the data. From this estimation, the total snowfall was about 6
inches at the METAR site (Fig. 10.21). Also shown on this graph is the liquid
precipitation, on the right axis. Note how poorly the tipping bucket gauge caught the
snowfall once the winds pick up about half way through the event.
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