A Cold and Snowy Start to February

After a warmer than average January, which included a few days with temperatures rising into the upper 50s to lower 60s, February has began much colder and snowier.

Above is a map of snowfall across the area for the past 6 days ending around 9 AM Tuesday, February 5th. These observations were collected from official NWS climate sites, cooperative observers, and CoCoRaHS observers that reported snowfall each of these 6 days. Daily snowfall maps can be found on our website here.  The table below shows selected locations and the 6 day snowfall total.

Much of this snowfall was a result of a pattern change beginning Wednesday January 30th. Large scale upper level troughing and resulting northwest flow across the Great Lakes region helped bring a cold surge of air into the region, after temperatures were well above normal on the 29th and 30th. This helped bring lake effect snow to mainly northwest portions of the area. Northwest flow persisted through the 4th of February, with a series of upper level disturbances bringing more widespread snow to the area, and persistent lake effect snow in the wake of each system.

500mb Analysis-12Z Jan 30 thru 12Z Feb 4	850mb Analysis-12Z Jan 30 thru 12Z Feb 4

Above are upper/lower level charts every 12 hours (12Z/00Z) beginning 12Z Jan 30 and ending 12Z Feb 4. The 500 mb analysis on the left shows a deep trough moving northeast through the Great Lakes and Ohio valley regions on Jan 30. Then a series of upper level disturbances track east/southeast through the Great Lakes region, as northwest flow persists over the next few days. The axes of the disturbances are marked with a solid red line. The 850 mb analysis on the right shows southwest flow intitally on Jan 30, which resulted in temperatures well above normal that day. As the aforementioned deep 500 mb trough tracks through the Great Lakes, 850 mb temperatures, indicated by the dashed lines, drop considerably across the region. This, along with west/northwest 850 mb, helped active lake effect snow showers downstream of Lake Michigan, affecting lower Michigan and northern Indiana. The effect snow continued and intesified behind each upper level disturbance.

Snowfall over the past 6 days has helped add to seasonal snowfall totals which were running well below normal by the end of January. The graphic below shows season-to-date snowfall totals (December 1, 2012 - February 4, 2013) for select cities across the region.

Updated 3 pm 2/5/2013

NG/CEO