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After a nice quiet day day of weather Wednesday, the pattern quickly turns active the next 72 hours as the first significant winter storm of the season takes aim on the upper Midwest. While the center of the storm does not reach us until Friday evening, the first impacts arrive as early as Thursday morning as warm advection attempts to fuel saturation and kick up some light precipitation. Due to dry air amounts will be small and the central and south may end up with just trace amounts and nothing more than drizzle. Locations north of HWY 30 in EC Iowa and NW Illinois stand the best chance of seeing any measurable amounts which would still be no more than a few hundredths of an inch . In those areas with temperatures near freezing and some evaporative cooling to work on a quick burst of snow or mixed precipitation is possible mainly before noon. There could be a few spots near and north of HWY 20 where some very minor snow accumulations occur. Temperatures will eventually climb above freezing in all areas with the greatest warming in the far south where highs in the upper 40s to near 50 are possible. Elsewhere in the north and central, highs will range from the upper 30s to mid 40s closer to I-80.

Thursday night and most of Friday appear uneventful as the primary storm comes together in southwest Kansas. Clouds will be plentiful and showers will eventually develop later in the day Friday. These will become more numerous Friday night as the surface low tracks northeast very close to the Quad Cities. Models have been pretty consistent showing a split in the precipitation band as the dry slot follows the low into my area. For that reason rain totals should generally be light 1/4 inch or so. Where a little banding takes place here and there some spots might scare up 1/2 inch amounts but those should be few and far between. Here's what models are suggesting.




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Snow will be a major player in the cold sector of the storm. It still looks like the most significant amounts will remain to the northwest of my area. However, there may be a period at the tail end of the storm where rain briefly changes to snow before ending late Friday night. Some spots NW of a line from Cedar Rapids to Dubuque could see up to an inch. The 1-3" line is currently shown near and north of a Waterloo to Madison line. Totals really go up after that as you go north. Here are the latest snowfall outlooks, just model guidance not hard forecasts. We'll be more certain on those tomorrow but no doubt winter storm warnings and advisories will be issued off to the northwest.




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Here's the winter severity index from WPC and you can see moderate impacts are expected for a large swath of southern Minnesota and central Wisconsin. Good sledding up that way.

The snows will be melting fast after Sunday as a massive ridge aloft builds into the central Unites States. The core of the warmth is aimed right at the central Midwest and models are going wild with what could very well be record warmth, certainly near records.

Over the 5 day period Monday-Friday highs are running about 25 degrees above normal per day.

That is really exceptional! Thursday morning the GFS has temperatures running 40-45 degrees above normal. That's about as extreme as you are going to see around these parts.

So, how long does all this last? Well, its my belief that the MJO is going into phase 7 and eventually 8 around December 22nd. Assuming that takes place, it should open the door to colder air the last 8 days of December. You can see the temperature analogs for phases 7 and 8 in December are cold. You can also see what 6 brings and that's exactly what's in the table next week and slightly beyond.

Below you can see the bias corrected MJO forecast for both the EURO and GFS indicating the move from phase 6 into 7 and eventually 8. We shall see what modeling does in response to such a phase change in coming days.

That's all for now. Enjoy your day and roll weather...TS


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