SNOWY START TO THE WEEKEND...
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A LATE SEASON SNOWSTORM?
As always the road has twists and turns but the winter storm that's impacting the region this weekend is finally showing its hand. Snow is or will be falling in all but my far SE counties to start the day Saturday.
If you've been following along two big issues have been challenging regarding the system. One was the difference in track between the GFS and EURO. In the end, it appears to be a draw with the track ending up over NW Indiana. You can see the different solutions below going into Friday. The EURO on the left, the GFS on the right.
The other issue was models cranking out significant precipitation totals in the heart of the deformation zone (the snow band). Those high numbers yield high snow totals. It seems most forecasters were intimidated by the warm surface temperatures, warm ground temperatures and concerns about the timing of the transition from rain to snow. All very valid concerns.
That being the case, the NWS has limited headlines to just winter weather advisories. Those are mainly for my counties NE of the Quad Cities in EC Iowa and NW Illinois. That's where they believe the greatest chances for accumulations of 3-5 inches will be centered. It seems to me amounts will be higher further west into SE and EC Iowa.
As I've said for a couple of days now this is a tough call with track issues and mesoscale features which could kick in such as banding from convection or enhanced forcing and that could create a narrow band where amounts are locally higher. It's difficult and I have agonized hours over how to play it. The last thing I want to do is send out mixed messages with other sources but the last batch of models is doing the talking for me by showing these amounts by the time the snow ends Saturday. Take a look and I'll recap. First the hi-res models.
THE HRRR
The 12k NAM
The 3k NAM
Now the deterministic runs of the EURO and GFS.
The EURO
The GFS
In general, evaporative has snow falling by 2:00am in most areas. After that, periods of heavy snow seems likely through the heart of my area centered in a 150 mile swath that runs northeast from the Quad Cities to Freeport and Janesville. I have seen evidence of banding and even some convective traits so very heavy snowfall rates could occur at times in localized spots.
When you have multiple models solidly showing 4-8" totals (locally higher) I think you have to pull the trigger and I personally feel that the storm ends up producing a band of 5 to perhaps 8+ inches from roughly the Quad Cities northeast. The only thing that could keep amounts lower is if the transition from rain to snow is slower than anticipated, which does not seem to be the case. Amounts will be lower over the far NW and especially as you go further to the SE of the Quad Cities where a dry slot is involved. It's the middle that is under the gun. That area will likely see travel issues early Saturday with low visibilities in heavy snow, gusty winds, and slushy roads.
As I write this rain is or has changed to snow as it spreads NE. It will end in most areas by mid to late Saturday morning. The satellite shows a healthy looking well ventilated storm with a developing deformation band.
I'm out on a limb with my heavier snow forecast on this storm and of course I humbly admit I could be wrong, but at least I'm willing to stick my neck out when the evidence is strong. Time will tell. If nothing else, right or wrong, I've worked my tail off to figure this thing out.
Last thing before I go. There is also the chance of more snow in the area Sunday, especially in the northern third of my area. Some light accumulations have been indicated but we'll get through this system before we travel that road. Roll weather...TS
