TAKING A CHILL PILL...
This was one of those weeks when the weather just went downhill on a daily basis. They were at their worst Friday afternoon when temperatures fell from highs of 45-50 into the upper 30s as rain and snow showers swept across much of the area. On top of that, winds of 50 mph joined the fray. You can see the hit and miss showers on the Doppler towards evening.
What I found fascinating is that temperatures were in the 40s when snow was falling at my place around 3:00 Friday afternoon. What that indicates is that the surface warmth was very shallow and the freezing level was only a couple thousand feet above the ground. That allowed the larger snowflakes and some graupel to reach the ground before it could melt. It goes to show it doesn't have to be 32 at the surface to snow if its very cold aloft!
These showers were cellular in nature meaning they grew vertically due to high instability from the cold air aloft. The same process drives thunderstorms and indeed there were a few of those scattered in. On the satellite below you can see the cellular structure of the showers generated by a strong upper level disturbance over Wisconsin. The powerful winds and cold air advection were allowing the cells to move at speeds up to 50. The showers weren't in one spot for long keeping precipitation amounts light.
As I mentioned the instability was so great that the Storm Prediction Center even put out a mesoscale discussion for potentially damaging winds from some of the stronger thunderstorms in northern Illinois. Again, this just caps a week of wild weather that's seen about everything. March madness.
The strongest winds have passed the region Saturday morning but we will remain blustery and raw. The day starts with temperatures in the 20s. The 3k NAM indicates this.
Far worse will be the wind chills which will range from the single digits north to the low to mid teens elsewhere.
Highs over the weekend will be way below normal in the 35 to 40 range from north to south. What happened to spring?
A WINTRY LOOK TO THE PATTERN AFTER MIDWEEK...
Looking forward into next week and beyond, the overall pattern is not conducive for much in the way of warmth. Temperatures are expected to average below normal for most of the next 2 weeks. Fortunately, we are not in January as this type of set-up would deliver air masses capable of sub-zero temperatures, especially at night. The longer days and strength of the April sunshine wont allow that to happen but we could see a lot of days in the 30s and 40s along with sub freezing lows. The EURO meteogram tells the story out 10 days. That's ugly.
The GFS shows average 10 day temperature departures that look like this March 31-April 10th. Fresh to say the least.
And while there is low confidence in amounts and placement, both the GFS and EURO are showing an unusual amount of snow well into the central United States for early April. It's a bullish trend that needs to be watched as the cold air is in place for those in the path of any storm that takes the right track. The GFS ensembles show this for snow over the next 16 days ending April 10th.
This is the 500mb jet stream flow March 31st and boy is that a wintery look. Very interesting and no doubt active.
THE NEXT STORM
Our best chance for a brief warm day comes Wednesday of the coming week. All the major models are indicating another significant storm in the Tuesday-Thursday period. The animation shows the formation of the surface low and the precipitation features during the period Tuesday morning to Friday morning. Another well developed storm with plenty of dynamics and moisture. Even a few thunderstorms are possible.
Here's the warmth I mentioned for Wednesday.
As for rain, models are again pointing at the potential of another inch of precipitation. It looks banded as well due to convection and that could mean some localized 2 inch totals but its far too early to focus on precisely where. The EURO indicates this for precipitation.
The GFS below has a scaled back but similar idea.
Both the EURO and GFS indicate a big dump of cold air behind the system with snow showers possible Thursday. The EURO even shows some minor accumulations. That's far from certain and we'll worry about that when the time comes. However, places just to our NW could do some serious shoveling.
Well, that's the long and short of it for now. It certainly looks like an active period of weather is in the works for next week. It will be interesting to see if it can top what we just experienced this past week. Have an excellent weekend and as always, roll weather....TS