JUST A BIT FLAKY...
Rain and wind pounded the Midwest Monday as an initial wave of energy carved a path across Iowa and NW Minnesota. Rain, while widespread, was generally confined to the light to moderate category. The intense low pressure of 29.03" near Sioux City ramped up the winds, with many spots seeing gusts of 45-50 mph. Peak gusts of 53 mph were measured around midnight Monday in both Cedar Rapids and Dubuque, at a time when temperatures were in the low 60s. Adding additional interest to the night were scattered thunderstorms.
In Dubuque, another healthy rain fell Monday that brought the 21-day total to 6.80 inches. (Prior to that, only 1/4 inch (.25 inches) fell the previous 60 days). Measurable rain has occurred 13 of the past 21 days in Dubuque, with more on the way today, only this time what falls is mainly as snow.
The initial wave of energy Monday was just phase 1, with phase 2 arriving Wednesday afternoon. It's tied to the transfer of vorticity to a secondary storm that wraps up in eastern Michigan. That and a cold pocket of air aloft will generate the lift and instability to drive snow showers Wednesday afternoon and night. A few more could linger on Thursday, especially east of the river. Further east, in Wisconsin and eastern Illinois, several inches of wet snow are expected closer to the center of the intense upper air storm forming in Michigan.
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Temperatures Wednesday will be in the mid 30s north to low 40s south before precipitation blossoms in the afternoon, rain or a rain/snow mix is initially possible. However, with temperatures at 850 -8 to -10 C., dynamic cooling will quickly cool the column, allowing snowflakes to reach ground level. That also enhances evaporative cooling, which allows a rapid drop in temperatures that will have readings in the low to mid 30s come Wednesday evening. Wind chills could reach the low to mid 20s by midnight.
The best snow chances are going to be across the N/NE but with very warm ground conditions and only minimal amounts of snow anticipated, not much more than a dusting is expected, mainly on grassy and elevated surfaces. A wild card in this scenario are parameters that point to the possibility of scattered snow squalls. Brief but intense bursts of snow combined with wind gusts of 35-40 mph, which could dramatically reduce visibilities for short periods of time. It's possible that a few squalls could develop that bring 1/2 to an inch of snow in isolated spots. Late afternoon or early evening would be the most likely time for the stronger snow showers or squalls, especially north of I-80. Here's what models are suggesting for snow accumulations, mainly late Wednesday and Wednesday night. I'll start with the hi-res CAMS.
The HRRR
The 3k NAM
The hi-res Canadian GEM
The EURO
The GFS
Aside from the snow showers, wind and cold are going to be serious players for the first time this fall according to the pressure gradient that sets up late Wednesday night. Tightly packed isobars such as this ensure a whipping NW wind.
The HRR indicates peak gusts between Wednesday night and Thursday of 45-50 mph.
Temperatures late Wednesday night and early Thursday are at (or several degrees below) freezing.
Toss that powerful wind into the mix, and wind chills are expected to reach the mid to upper teens.
With the big storm shifting east, dry weather returns for Friday and continues through the upcoming weekend. Winds will ease some Friday but should remain quite brisk at 15-30 out of the northwest with highs in the 40s.
Saturday and Sunday look better, with lighter winds and seasonal highs in the mid to upper 40s. Cool, calmer, and collected.
By the way, with some snowflakes on the way, here's some perspective. Typically, we see our first measurable snow around November 15-20th in my area. As always, that's arbitrary, as averages are comprised of extremes. I've seen it be a month earlier as well as a month later. Here you can see the typical November snowfall around the Midwest, which isn't all that impressive.
Across Iowa, typical November snow amounts range from an inch southeast to 5 inches northwest.
Here's what's fallen so far this winter across the nation. Not very good for snowfall east of the Rockies!
While amounts won't be impressive, it does appear that at least parts of my area will get in the game with their first measurable snow. Like it or not, it was bound to happen and this is pretty close to being on time. Roll weather...TS
