MORE SNOW, WINTER STORM #2

terryswails1
1 minute ago
4 min read

A WINTER WEATHER ADVISORY IS IN EFFECT FOR MUCH OF THE AREA

The second winter storm in a week is destined to produce several more inches of snow Saturday night. The clipper that generates the snow tracks from Nebraska into NE Missouri laying down a swath of snow that covers the majority of my area asid from the far south.

The event does not begin until Saturday evening and due to the quick movement of the clipper, most of the accumulations occur in a relatively short 6-8 hour period. In other words, the snow is winding down and exiting from west to east come daybreak Sunday. By then the damage is done with much of my region near and north of I-80 picking up 2-6 inch accumulations, perhaps as much as 7 in a few spots near HWY 20. South of HWY 34 amounts taper off rapidly to an inch or less.

A winter storm warning is out for much of NC central Iowa extending as far east as Waterloo and Marshalltown. Further east, from the Quad Cities north and west a winter weather advisory is in effect from 6:00pm to 6:00am Saturday night. Based on the data I have seen the advisories will likely be extended further east beyond the Mississippi to include much of my counties near and north of I-80. With hi-resolution CAMS showing higher totals of 6 or more inches north of HWY 30, it's possible a a winter storm warning could even be issued for my northern tier of counties. It's marginal but not out of the question if recent trends hold.

The greatest impacts from the storm are expected to occur in NC Iowa where up to 8 inches of powder is possible but as I mentioned a wing of heavier snow is now indicated for the northern third of my area.

The official NWS snow forecast looks like this with slightly heavier amounts northwest of the Quad Cities.

Here's what the latest model guidance is suggesting for snow totals Saturday night. These are not forecasts, just raw model output that forecast are derived from. Numbers are up from Friday afternoon across the northern half of my area.

The EURO

The GFS, an outlier with most other solutions about 50 miles north with the max snow band

THE HRRR, easily the most aggressive with higher snow totals.

The 3K NAM

The Canadian 10 K RDPS

The NBMv5 A blend of 30 models and ensembles

The NBM 2.5 a blend of models

Some minor alterations in track are still possible but for the most part confidence is high the majority of my area from about I-80 north will see 2-6 inch totals along with hazardous travel conditions later Saturday night and early Sunday. It is possible a few 7 inch reports could pop up in a narrow axis along HWY 20 in my northern counties.

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UP, DOWN, AND ALL AROUND...

Behind the clipper, strong NW winds will kick up for a time reaching 25 to 30 mph Sunday morning before diminishing later in the day. This will produce areas of blowing and drifting snow, mainly in the open country. The gusty winds will also deliver strong cold air advection and temperatures Sunday should hold steady or even fall in the south after reaching highs in the morning of 18 north to 32 south.

Sunday night with fair skies, diminishing winds, and fresh snow, temperatures are likely to tank with lows of 0 to minus 6. Some of the cold air drainage locations (which are typically colder in situations like this) may reach 10 below.

Next week NW flow is dominate which will continue to deliver regular clippers. However, with the flow less amplified the trend is for them to pass north of my local area into Minnesota and Wisconsin early in the week. The most vigorous of the clippers tracks near Minneapolis Tuesday night and should bring a brief period of light rain or snow to the north Tuesday evening. More important, the track allows a brief surge of mild air that should get temperatures above freezing, perhaps as warm as the low 40s south with mid 30s reaching my northern counties. The surge is short as a cold front hits Wednesday morning bringing strong winds and falling temperatures into the 20s.

That amplifies the NW flow once again and keeps temperatures well below normal the remainder of the week and into the weekend. Highs during this period will steadily decline, reaching there coldest levels Friday or Saturday of next week. After that there is much uncertainty as the GFS keeps temperatues well below normal through December 21st. Here's its 2 week meteogram.

The GFS shows a similar trend through next weekend before resorting to a much warmer solution December 15th through the 20th.

Looking at the radical temperature departures in the week 2 period it's obvious models are having issues resolving energy and thermal parameters after December 14th. It's nearly impossible to say how it will play out as this distance. Having said that, the MJO being in a cold phase with plenty of snow cover producing negative feedback, I'm inclined to lean a bit toward a more scaled back "moderate" version of the GFS. That's nothing more than an educated hunch. Confidence after December 14th is low to say the least with respect to temperature trends. I'm sure you are going to hear a lot more about this battle for thermal supremacy in coming days.

That's it for now. I'll get some new snowfall output to you around midday Saturday when the morning models have cleared. Until then, roll weather...TS.