CAUGHT IN THE CROSSFIRE...
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I SAW A SNOWFLAKE...
Tuesday was a huge day for me. Yup, I saw about a dozen snowflakes! So dang exciting. Too much dry air and minimal forcing for snow to get going around here. However, snow did fall in northeast Iowa, southern Minnesota, and a bit of SW Wisconsin. Travel was impacted and some areas around Rochester, Minnesota reported 3-5 inch totals. This image was posted on the NWS site in La Crosse, Wisconsin around 6:30 Tuesday evening. I bet those flakes are Tasty. December snow is a real delicacy.
The clipperesque system that dropped the snow to the north will spread a cold front through the region by early Wednesday refreshing the cold that's been over the region since Sunday night. With weak high pressure in place the day looks mostly sunny but crisp. Highs will range from the upper 20s far north to the mid 30s down south.
IN THE CROSSHAIRS...
That leads us into our next storm which promises to be the first real significant winter event of the year for some. The main event is not slated to arrive until Friday night but strong warm advection will precede it early Thursday. The upglide over the existing cold air will provide the lift for some light precipitation. When it begins, especially to the north of HWY 30, temperatures will be near freezing and that and some initial evaporative cooling may lead to snow or a wintry mix going for a time which could be just enough for some travel issues. However, readings will warm and by noon any freezing precipitation would be over in the far north. After that, little more than drizzle falls. Some guidance is showing highs low 40s north to mid 50s south. However, models tend to overestimate warming with southeast winds in place and I prefer the cooler end of the guidance. That would mean mid 30s north and perhaps 50 in the far south down around HWY 34.
From there on things have turned a tad more interesting with a trend Tuesday of a more southerly track of the primary storm Friday night and Saturday. It will be interesting to see if those trends continue for a couple more runs or if models revert to the original path further north which I anticipate. Whatever happens, if a southern track would somehow verify it could create problems for a small part of my area, especially the NW third where it would lead to a changeover of rain to snow with some slushy accumulations possible.
The 12K NAM is the model suggesting the most ominous solution with the surface low near Bloomington Friday evening. Notice the snow band catching my counties NW of the Quad Cities. I don't see it.
That produces 3-5" of snow NW of a line from Cedar Rapids to Freeport. Very unlikely is all I can say.
The EURO and Canadian GEM are the furthest north with a track that takes the surface low close to the Quad Cities.
That makes a big difference pushing those 3-5" totals NW of a line from Waterloo to Madison.
The GEM has this for total accumulations.
The GFS came in with this. The track was actually a bit further SE than the EURO but its snow swath is the furthest NW as you can see below.
Again, this is all just model guidance and not a forecast. We are 60 hours away from event and to at least some degree things will change. My early read is that the 12K is a major outlier and I suspect too far SE on the track which contaminates its snowfall forecast as well as thermal parameters making it too cold over my area. Another strike against the southern track is that once you are in a spot where its too mild aloft and strong warm air advection is occurring ahead of a deepening storm (which is happening), it's very hard to get that cold air to move back into position to support snow until after the surface low passes and then the worst of the precipitation is over. Also, I personally want it to snow so that's a certain kiss of death for those living near me. I have horrible luck with snow. If the lows passes just SE of the Quad Cities which tonight seems reasonable, I think the far NW fringes of my area could see enough wrap around snow for potentially 1/2 to 1" of accumulation, mainly NW of a line from Cedar Rapids to Dubuque. That's far from certain. Some trace amounts could spin back as far as the Quad Cities....mainly from snow showers on the tail end of the storm.
One thing is certain, this is going to be a significant winter storm for the northern part of the Midwest. Travel is going to be quite difficult Friday night and early Saturday within the heavy snow band. The Weather Prediction Center has minor to moderate impacts indicated in its winter storm severity index for day 3. I'm sure winter storm watches will be out soon only to be followed by warnings.
WPC also shows these odds for an inch or more of snow. These might be too far northwest by a good 50 miles.
It will be interesting to see what sort of precipitation totals we get out of the system. The track right through the heart of my area puts us in the crosshairs and is often a problem with the dry slot creating a split in the coverage. One band goes NW and the other SE. Here's what the latest guidance is showing for total precipitation. All over the board with the GFS looking suspiciously dry.
The 12K NAM
Where it does snow, it won't be around long as phase 6 of the MJO produces 5 day temperature departures like this Monday-Friday of next week (December 12-17th) Yikes, a stinking blow torch. If things come together just right there could be a record or near record high in that hot mess! Seriously, 65-70 for a day is not out of the question.
That's all for now. Enjoy your day and roll weather...TS
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