ANOTHER STORM BITES THE DUST...
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ANOTHER WINTER STORM BITES THE DUST...
Another winter storm has come and gone with a wide varitety of impacts. As is usually the case, the complex nature of these systems make it difficult to see small features that can make big differences. In this case, the heavy snow fell where it was anticipated in a northeast oriented swath about 70 miles wide northwest of a line that cut through the Quad Cities.
Southeast of that, a warm tongue of air aloft caused snow to mix with sleet and freezing rain lowering the accumulations. This was very close to where the 850 low tracked, about 50 miles further north than most models indicated yesterday. Intricate details like that are very important but tricky to pinpoint with all the latent heat released by the energy. NW of the 850 circulation you get the heavy snows. southeast you get a mix or plain old rain. Even further southeast is the dry slot which keeps precipitation light and liquid (that played heavily in the southeast third of my area.
Getting to the tale of the tape. Here are some totals from the Iowa Mesonet. They are incomplete, meaning more will be added or that others were posted before additional snow was accounted for. That southeasterly shift I anticipated on the heavy snow band Wednesday certainly verified. So too did the localized banding of high end amounts where forcing was maximized...again something that's very hard to pinpoint until it shows up on radar. In my area, it's readily apparent banding too place from near Iowa City (Johnson County) to Lowden in Cedar County where 9 -11.5 inches of snow was reported. SC Iowa also shows a similar banding effect with 9-10 inch totals.
On the radar, here's what banding looks like. This was at 4:45 Thursday afternoon when a swath of intense snow relatively narrow in width was advance across the Mississippi. Where you see the yellows it's coming down fast and furious, at least an inch per hour.
Jenny Hollis Miller of my hometown of Coralville, Iowa (next to Iowa City) sent me this picture of snow on her deck. Just short of 11 inches! Nice going Jenny.
Here's some of the individual plots in the Iowa City/ Cedar Rapids region.
Far southeast Iowa and WC Illinois escaped the worst of the storm but overall, that was anticipated. Even so, the cut-off was very distinct. That little shift north in the 850 circulation kept amounts lower in the SE tip of Iowa than I had expected.
Now that the snow has departed a much colder air mass has invaded the region. As a result, temperatures Friday will struggle to get much above 20 where the deeper snowcover exists. Upper 20s are possible where there is little to no snow in the far southeast. Wind chills will be a factor as well running below zero Friday morning over the NW half of my region, some as cold as 15 below.
Warmer air does make a run at the area over the weekend. Highs will be back in the mid 30s over the snowfields but areas near and south of HWY 34 should hit the low 40s Saturday and 45-50 is possible Sunday. That snowcover is a temperature killer to be sure.
The weather remains quiet Monday as a weak clipper passes to the north ensuring another mild day with 30s north to 40s south. The clippers cold front passes Monday night laying down the groundwork for another active period of weather next week.
The next impulse to enter the picture could bring some light snow or freezing rain to the north next Tuesday night. The EURO is the most aggressive with the threat and even it keeps most of any snow accumulation near or north of HWY 20. The GFS keeps it all further north than that and is a nothing burger.
Things get very complex next week as a massive trough gets carved out over the western third of the nation. Without a doubt that is going to be trouble for the upper Midwest where cold air will be firmly entrenched to produce a prolonged period of wind driven snow.
For my area, the general idea is that the pattern draws enough warm air aloft for most of our precipitation to be rain. However, it's uncertain how the energy will eject so things are not fully set in stone. If it comes out in peices there may be an opportunity at some point for the boundary to oscillate enough to bring colder air a little further south. However, if all the energy gets bundled into one major storm, the odds are strong it will tug some very mild air into the region with the storm tracking northeast through Iowa.
One thing seems certain, a trough of that calibur is going to bring aboundant moisture northward. That is already reflected in water vapor with PWAT's Wednesday of 1.00 to 1.38 inches across my area.
Those values are 3 to 4 times higher than typical mid February values.
What is concerning to me at this time is the EURO solution. It keeps east to southeasterly winds over my northern counties, north of the baroclinic boundary that remains anchored over southern Iowa. That sets the north up for a potential freezing rain scenario with cold air at the surface being overrun by warm air aloft. The EURO indicates a significant band of ice across the norther tier of my area, mainly north of HWY 30.
The GFS is further north and lighter on accumulations and eliminates the problem altogether. I may be wrong but I suspect the GFS is too far north and may come south in future runs, the question is how far south?
Really there is so much uncertainty in the outcome right now it's not worth speculating further on the issue any more than I already have. Suffice it to say, another potent storm set-up is brewing for next week that needs to be watched. Be it rain, freezing rain, sleet, or snow, it's coming and it's coming with wind. Stay tuned and roll weather...TS