# MDSS Storm Report: 29 January 2003

## Meteorological Summary

Based on radar and surface observations at the Ames and Des Moines
airports, light snow began falling in the Des Moines area shortly before
0500 CST and in Ames around 0530 CST. Snowfall duration was
approximately 5 hours in the Des Moines/Ames area, but amounts were less
than 1 in. Water content of the snow was likely very low, as air
temperatures ranged from --6 F at the beginning of the event to near 0 F
at the end of the event. The primary forcing for this light band of
snowfall appears to have been a combination of upper-level forcing
(shortwave trough and rear-entrance region of jet stream) and a strong
baroclinic zone oriented from northwest to southeast across Iowa.
Westerly flow aloft may also have undergone some isentropic lift over
the dome of cold area sitting over the Northern Plains. Fig. 1
illustrates the meteorological situation at 0600 CST shortly after
precipitation had begun affecting the area.

![](media/image1.png){width="5.11875in" height="4.769444444444445in"}

Figure 1. Meteorological situation at 0600 CST, 29 Jan 2004. (a) 250mb
(jet-level) winds. (b) 500mb height and vorticity. (c) Mean sea-level
pressure and 1000-500mb thickness. (d) Des Moines NWS radar image at
0555 CST.

Winds during the event were generally NNE from 9-12 mph. In areas where
the pavement remained dry, the light snow was easily blown by the wind
and vehicle traffic. Pavement temperatures ranged from around 0 F at the
beginning of the event to around 20 F near the end of the event in the
late morning hours. However, the pavement temperatures as noted at the
local RWIS sites and from the truck instruments were highly variable
throughout the morning.

## Observer Summary (Brent Shaw)

Although actual snowfall was light, this storm once again had
significant impacts on traffic and DoT operations, particularly in the
Des Moines area. The light nature of the snow and early morning start
caught me somewhat off-guard in terms of the level of activity that
should be expected. I arrived at the Ames garage shortly after 0900 CST,
and operations were already well underway. Dennis Kroeger was already on
a ride-along with Paul Durham. Weather conditions at the Ames garage
consisted of light snow falling, a temperature of --3 F, and a north
wind at 12 mph.

I spoke with Lynn Durham about the ongoing operations. Snow had begun to
stick on I-35 south due to the higher traffic causing the pavement to be
a bit warmer. Thus, they had treated I-35 south with 400 lbs/lane-mile.
Other routes were being selectively treated, mainly on bridges and
entrance ramps. Interestingly, all of the Ames routes had been depicted
as "green" all morning, despite the observed hazardous conditions. At
around 0930, Paul was heard commenting on the radio that highway 210 was
winter normal, and, ironically, at about this same time 210 became the
only "yellow" route in the Ames area.

At around 1000, Dennis returned with Paul. Paul felt that within an hour
or so that the roads would be dry. The purpose in using the salt was to
induce some melting and subsequent evaporation. \\Paul mentioned that
Des Moines was apparently experiencing significant impacts from this
event, and around 1000, Iowa DOT sent out a statement about a closure on
I-80 east of Des Moines due to a multi-vehicle accident. So, Dennis and
I headed south on I-35 to visit the other garages at around 1030.

During our trip down, roads were primarily dry until we started
approaching Des Moines, where we began observing several cars off the
road. A multi-car incident had occurred previously just north of Akeny
(Fig. 2). We arrived at the north Des Moines garage at about 1100 CST.
We discussed their treatment strategy for the morning, which consisted
of treating with a 50/50 salt/sand mixture, followed by pure salt at 300
lbs/lane-mi, followed by brine at approximate 30 gal/lane-mi. The brine
was being used to provide a more quick activation of the salt to speed
melting, with hopes that evaporation would quickly occur. As we were
departing the Des Moines north garage at around 1030, they were
beginning to enter the treatment history into MDSS.

![](media/image2.png){width="4.629166666666666in"
height="3.2465277777777777in"}

We arrived at the west Des Moines garage around 1130. Their treatment
strategy was nearly identical to the north Des Moines garage. Rich
mentioned that he had not had any time to enter treatment histories into
MDSS, particularly because of his responsibility as a supervisor to be
on the road monitoring conditions. Like the other garage supervisors, he
commented that this "minor" storm was causing more problems and work
than some "bigger" storms do. At such cold temperatures, treatment
strategies are difficult. By the time we departed the west garage around
noon, roads were mainly dry.

After lunch in west Des Moines, we headed back north on I-35. During
this portion of our trip, we did encounter another brief round of light
snow, which appeared to be mainly blowing around without sticking to the
road. However, at the Ames garage, Jim Van Sickle was concerned about
the sun coming out and warming the pavement just enough to keep the snow
from blowing off the road.

## Summary

This was another fairly innocuous looking weather event that resulted in
significant workloads at all three garages as well as significant
drive-time impacts to the community. The forecasts from MDSS remained
mainly in the "green" category until well after the event was already
underway. While some of this may have been due to the FSL models not
being available (hardware failure on 28 Jan, awaiting replacement
parts), it would appear that even more research and development could be
put into the MDSS tool for these cold, relatively dry, snow events that,
if occurring near rush hour, can play havoc with operations.
Additionally, it was obvious that in these situations, the garage
supervisor is very busy and that entering data into the MDSS client
falls off the list of priorities. Perhaps we should consider having our
observers assist with this during the demonstration. A future
operational implementation of MDSS would greatly benefit from the use of
automated data collection and transmission directly into the client.