GOOD RIDDANCE MARCH...
Scattered showers and thunderstorm have been roaming the area since Tuesday night. Due to the complex interaction of forcing and phasing, precipitation has been on again, off again as the storm slowly gains maturity. Rain expanded in coverage Wednesday evening and now is in the process of mixing with or changing to snow as colder air is drawn into the intensifying storm. Doppler estimates of precipitation totals look like this through early Wednesday evening. Thursday morning these will be higher as the final wave of energy delivers another round of rain and snow.
Additional precipitation should end up in the 1/4 to 1/2 inch range by the time it ends Thursday afternoon. Models are indicating this for this final wave of rain and snow which includes what fell Wednesday night.
The 12k NAM
The 3k NAM
Now we get to the thousand dollar question, how much of this precipitation falls in the form of snow. For the last 48 hours models have been consistently showing strong cold air advection behind what is projected to be a 977mb low. The intense dynamics will allow the column to steadily cool from top to bottom, leading to parameters cold enough for snow to develop in much of my are late Wednesday night into Thursday morning. The primary trowel, where the heaviest snows are expected should set up through SE and EC Iowa and NW Illinois, (basically near and northwest of the Quad Cities. In this area, an inch or two of wet snow is possible, mainly on grassy and elevated surfaces. Some models show local spots with up to 3-4 inches. This is a very tough call to make based on marginal temperatures and the uncertainty of how soon critical thickness evolve enough to allow snow to reach the ground. I do think the NW 1/3 to 1/2 of my area sees at least some accumulating snow on the order of 1 to perhaps 2 inches. If we get into banding, which is on the table, there may be some higher amounts in a narrow corridor. I'm using a broad brush approach as this is one of those situations where nowcasting (watching evolving trends and radar) will be the only way to keep up on this complex transition. With that, here's what models are indicating for snow. My assumptions above are based on an average of these solutions which are not official forecasts.
The 12K NAM
The 3K NAM
With clouds, periods of snow, and brisk NW winds Thursday will pretty much suck eggs. Highs will not get out of the mid 30s in most areas and wind chills in the mid 20s will prevail through the day. Good riddance March!
Friday look for substantial improvement as the April sunshine does its thing and warms readings into the range of 45 to 50. Still well below normal but far more tolerable.
Just when things are looking up, the next system enters the picture Saturday. Rain, snow or a mix is possible. The GFS indicates a broad area of low pressure tracking south of my area Saturday morning. This is not a powerful storm but it does have enough dynamics, moisture, and cold air to work with to potentially produce a band of snow mainly near and north of I-80. South of there it looks like rain or perhaps a mix of rain and snow. This is the GFS interpretation of the surface and precipitation fields Saturday morning.
It's still a bit early and changes in track or intensity are a real possibility. We'll need another day or two to pin down the essentials. Stay tuned.
Overall this cool active pattern is likely to continue through the first week of April. However, I am seeing positive signs around April 10th of a pattern change that should make all of you warm weather fans feel much better by mid April. Fingers crossed. Below you can see the 5 day temperature departures for the period April 9th to the 14th.
Alright then, here's to the last day of winter and to what hopefully is the last time we see snow for many months. I have my doubts but it's worth a wish. Roll weather everybody...TS