IEM Daily Bulletin

[Iowa Mesonet]

Iowa Environmental Mesonet Daily Bulletin
Data valid for 18 December 2007

> News
    No news is good news

> Yesterday's Daily Feature

 +----------------------------------------------
http://mesonet.agron.iastate.edu/onsite/features/cat.php?day=2007-12-18
 | Title : Warm above our heads
 | Date  : 18 Dec 07:40 AM
 | Votes : Good: 18   Bad: 3
 +----------------------------------------------

The featured image is a SkewT diagram from the Davenport RAOB site.  This plot shows temperatures (red line), dew points (black line), and winds (barbs) as you go up in the atmosphere.  Temperatures increase to the right in the chart.  You can see that temperatures are the coldest right near the surface with dramatic warming as you go up just a few hundred meters to values above freezing.  This shallow layer of cold air is tough to get rid of as the warmer air from the south will tend to ride overtop of it.  It is kind of like trying to heat your basement in your house, the warm air will struggle to heat up the cold surfaces.  The snow and ice also acts to reflect much of the suns energy away further preventing warming.  What can help us is when winds are stronger, which can help to mix the air up (kind of like running a ceiling fan backwards in the winter). Temperatures are expected to warm a few degrees more today with highs in the mid 30s.

> NWS Watch/Warning Summary
*** Products issued on 18 Dec 2007

             Summary +_________ By WFO ____________+  Watches 
Type         US   IA | ARX   DVN   DMX   OAX   FSD |  US 
Tornado       0    0 |   0     0     0     0     0 |   0
Svr Tstorm    0    0 |   0     0     0     0     0 |   0
Fl Flood      0    0 |   0     0     0     0     0 | N/A

ARX = LaCrosse, WI  DVN = Davenport, IA    DMX = Des Moines, IA 
OAX = Omaha, NE     FSD = Sioux Falls, SD