Storm Update: Modest snow totals, but blizzard-like conditions and exceptional cold

The April 8-9 storm system in Colorado will not be remembered for its big snow totals... but will be for its extreme weather conditions, including a remarkable temperature drop, strong winds, tornadoes, and record cold.

Temperatures were very warm across the region yesterday afternoon, with highs reaching 70 for many. The cold front moved through, bringing a dramatic temperature drop, with severe weather occurring in northeast CO ahead of the front.  A dry slot occurred overnight in Denver (the thunderstorms out east "stole" some of our moisture), so the snow really didn't start picking up until this morning.  I forecasted less snow than the NWS... originally called for 4-7" for Denver, then upped it to 5-9".  I think my original forecast is going to end up being correct.  Additionally, as I mentioned yesterday, the mountains west of the Divide (except for the San Juans farther south) are not getting much snow because of an unfavorable wind direction despite what many weather services predicted.  It always surprises me how the major weather service outlets, including the NWS, always predict heavy snow for the ski areas west of the Divide with these types of systems, despite the obvious fact that an unfavorable wind direction associated with an upslope snow event will leave them in a "snow shadow".

Anyways, here are some highlights of weather extremes from the system so far...

• When the cold front first reached Colorado from the north, the temp in Greeley fell from 70F to 49F in about 10 minutes!  Simply incredible.  

Weather graph for Greeley shows an incredible temperature drop at the frontal passage, along with a shift in wind direction from southeast to north

• Between 4 pm yesterday and 6 am this morning, the temp in Denver plummeted from 71F to 15F (56 degree drop!), including a fall from 68F to 50F between 5 and 6 pm, and the first snow flakes started to fall by 9 pm.  See the chart below.  The temperature in Denver is currently 14F, with sustained winds of 25 mph and a wind chill of -5F.  For some perspective, the average high temp in Denver for April 6 is 61F.  Temperatures up on Loveland and Berthoud Passes, both above 11,000 ft., have fallen to 0F.  The cold air has had trouble crossing the Continental Divide to the west, so temperatures in places such as Gunnison, Aspen, and Vail are nearly 20 degrees warmer than in Denver and northeastern CO (see second image below).

Weather data at Denver International Airport, showing a dramatic temperature drop from 71F to 15F in 14 hours

 Surface map showing temperature in red, dewpoint below, and wind speed/direction.  Notice the temperature differences between northeast CO and western CO

• The record low max temp for today is 27F... we're guaranteed to break that, since it was 22F by midnight, and has only fallen since then.  The record low today is 12, so we will probably break that too... tomorrow's record low is 7, which we could also tie or break in the morning.  After tomorrow... April 11, 12, and 18 are the last remaining days in the month with record lows in the single digits, which gives some perspective on how cold this system is for this time of year.

• Last but not least, is the severe weather element that occurred with this system.  Severe thunderstorms fired up across eastern Colorado yesterday afternoon and evening, with four reports of tornadoes touching down.  One tornado occurred near the town of Akron, damaging three buildings and destroying a mobile home.  I don't know if this is confirmed, but amazingly, I heard a report that snow may have occurred with the tornado-producing storm near Akron!  The tornado-producing storms occurred around dusk as the sharp cold front was moving through.

Strong to severe thunderstorms to the northeast of Denver yesterday evening... the red boxes indicate tornado warnings

Tornado-producing storm moving over Akron at about 9:00 pm

Image showing a sharp contrast in temperatures as the front moved toward the southeast at 8:00 pm last night... notice the nearly 30 degree temp difference between Denver and Limon

What to expect in the days following the storm...

Temperatures will remain well below average for the next few days across northeast CO... After near record low temperatures in the single digits to start Wednesday morning, temperatures will warm into the low to mid 30's across the urban region... still nearly 30 degrees below average.

A weak system will move through the mountains behind the main system, bringing a round of snow showers to the northern and central mountains.  A second round of snow should occur on Thursday as well.  Temperatures in Denver on Thursday will warm to around 50 (still chilly for April), but a weather disturbance moving through that evening will bring a chance of rain and snow showers to the city overnight... likely nothing significant, though.  Still some uncertainty regarding the details of weather for the upcoming weekend and early next week, but in general, the weather pattern looks active with good snow chances for the mountains and continued below average temperatures for the Denver region.