Winter storm system

Ice storm NOT expected for most of Metro area

No major changes yet from my last couple blogs. A lot of cold rain, then a transition to a wintry mix. The ice storm looks to be in South Carolina/NC and adjacent areas.

Many models overnight trended a bit farther North with the track of the surface low. Ideal track for a widespread nice Atlanta snow is along or South of the Gulf Coast, but that is still not expected.

CANADIAN RGEM 3PM SUNDAY:

AMERICAN HRRR MODEL 3PM SUNDAY:

Ice accumulation for most of Metro Atlanta is expected to range from only a tenth to a quarter of an inch or less.

A reminder that computer models show what falls from the clouds, they can not and do not show how much on your deck or driveway or on the highway at mile marker X.

Many models lump snow, sleet and freezing rain together in those maps people look at and share (people don’t know what they’re looking at because they understandably don’t have the training to know what’s under the hood).

Please read previous blog posts for better understanding if you didn’t already read them


Keep in mind, that with the rain and soggy soils the strong gusty winds forecast can cause POWER OUTAGES in some spots even without ice on trees or power lines. Ice is expected to be minimal in most of West Georgia, NW Georgia and most South suburbs. The areas in the CORE of the CAD/WEDGE (East and NE suburbs into South Carolina) have the greatest risk of significant ice accumulation. Heavy snow North of the icy area, especially the Northeast Georgia mountains for heaviest.

As always the devil is in the details and new data and new models coming in today and tonight can and will adjust the forecast that is out now.

Part of this system is a closed upper “bowling ball” low. Long-time followers/blog readers know I’ve said before “upper level lows, weatherman’s woes” due to their erratic and abnormal weather effects, they often bring unforecast surprises. The upper low is expected to move over AL to Atlanta then on NE.

MODEL PROJECTED TEMP 7AM SUNDAY:

2PM SUNDAY TEMP:

7pm SUNDAY TEMPS ECMWF MODEL:

3PM SUNDAY:

MULTI-MODEL ENSEMBLE MEAN:

ECMWF MODEL SNOW TOTAL ENDING LATE SUNDAY NIGHT:

MULTI-MODEL BLEND AVERAGE SNOW ACCUMULATION:

Here is what the National Weather Service is forecasting:

The forecast “bust” potential (estimated) i.e. the range of outcomes from this system according to models mean:

This map that I put out yesterday (above) still looks ballpark. Remember what I said in the Tweet about the lines. Rain first for all, then a transition. Because this is such a complex, disjointed, sloppy system the range for most of us in Metro Atlanta really is from just a dusting to 3″ for the lucky (depending on if you want it or not of course). As shown in the January 1996 example where close to zero happens and where a coating or more happens can and probably will be random and mixed even with nearby or adjacent areas. Remember, I don’t specifically forecast for the mountains or for Rome or Athens areas.

METRO ATLANTA MAP:

The only thing I can think of that would make snow or ice accumulation worse and more widespread is if either (A) models are way off on the low-level thermal profile way too warm OR (B) the dynamics of the upper-level low lifting produce heavy snow/sleet rates unexpectedly that provide more accumulation farther South than currently modeled.

CAN WE USE WEATHER HISTORY AS A GUIDE?

Below is the result of a computer trying to match this system to past similar systems and showing the top ten best matches (analogs). Notice the big range, including plenty that show a lot of nothing in terms of ice or snow:

As I mentioned in an earlier blog, more cold air to come later this month and the pattern remains favorable to at least keep the window of opportunity open for a couple more systems this month into early February. The next “signal” is next weekend. You miss a Tweet or a blog you miss a lot.

This will probably be my last blog on the system as I am after all retired and going to watch football the rest of the weekend next to a nice fire in the fireplace.

Follow me on Twitter @MellishMeterWSB.


Kirk Mellish

Kirk Mellish

Meteorologist

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