Denver and Thornton wrapped on the first month of 2008 dry.  Official measurements at Stapleton and at ThorntonWeather.com recorded only 0.08 inch of precipitation making it the 7th driest January since recordkeeping began in 1872.  This was 0.43 inch below the 0.51 normal, so a pretty big drop.  Only two days had measurable precipitation in the form of snow at Stapleton while in Thornton we recorded four. 

Officially only 3.1 inches of snowfall was recorded near the former Stapleton International Airport and in Thornton we recorded a bit less at 2.8 inches.  This was 4.6 inches below normal for Denver.  Thornton’s seasonal snowfall stood at 26.4 inches at the end of the month (the official Denver measurement was 29.5 inches) which is below the official normal of 33.3 inches for this period. There were no precipitation records set or tied during the month.

In regards to temperature, the normal average for the month is 29.2 degrees which we finished slightly below at 27.9 (28.2 in Thornton).  Illustrating the wide range of temperatures we experience in Colorado, we had a high temperature of 66 degrees on the 27th and a low of -1.7 on the 22nd (Denver recorded 63 and -3 on those days).  All but one day of the month, the 4th, recorded low temperatures below freezing and five days had high temperatures that never got above freezing.  While the month was below normal, it was still warmer than what it was just one year ago in 2007 when the average was 22.8 degrees! 

Some other interesting statistics…  We did have sunshine 79% of the possible time so it was pretty sunny at least.  Wind is of course a fact of life on the plains and we did have 12 days with wind gusts registering over 25mph.  On the 25th of the month we registered the highest gust of the month at 38mph. 

For a day by day log, click here to view our climate log for January 2008.

Much to everyone’s surprise, what was forecast to be not much more than a dusting of snow turned into quite a bit more.  In Thornton from about 6:00pm to 7:00pm we saw 1.5″ fall very quickly with near blizzard conditions for that brief period.  Much of the Denver metro area saw more snow than that, primarily west of I-25 and south of I-70.  Not far from us Broomfield reported 3.4″ and Federal Heights 3″.

Why did this storm offer more than predicted?  Here is what 7News’ meterologists offer:

Computer models had shown little if any snow across Denver.  However, instability in the atmosphere provided enough juice for a convective-type snowfall.  Reports of thundersnow came from southwest Denver near Chatfield State Park as a result of the instability early Wednesday afternoon.

This type of snow is called CSI, Conditional Symmetric Instability. It is generated when enough instability exists in the atmosphere to give snow showers a thunderstorm-type development.  With help from upslope flow, these snow events can dump a lot of snow in a short period of time.  While these events don’t last more than a few hours in most cases, snowfall rates as high as 2 to 3 inches can amount to excessive accumulation.

For the foreseeable future we expect to stay pretty dry.  Our next chance for snow comes Monday and into Tuesday.  No predictions yet on amounts of snow as it is too far out and the models aren’t consistent yet.  Until then, temperatures should be pretty seasonable.

February comes and serves as a bit of a month of transition between winter and spring. Average temperatures start to climb and things are generally pretty quiet.  However the month can have its extremes as well.  Click here to read our February 2008 climatological preview.