Active Weather Pattern Returns…Rain, Freezing Rain & Snow Possible
by Cody Matz
December 11, 2011 7:14 PM
It looks like our dry streak over the past several weeks is about to come to an end as a more active weather pattern will set up over the Midwest through Midweek. This is both good and bad news of course because we really need the moisture, however travel will likely become more difficult through the end of this week. Another cut off low is dropping into the Desert Southwest and over the course of the next couple of days, pieces of energy from that low will rocket through the Midwest bringing with it the possibility of some significant precipitation. But at the moment, it doesn’t look like it’s going to be all snow. In fact, there is enough warm air and moisture out ahead of these disturbances that precipitation may fall as mainly rain and freezing rain which does not spell good things when its December.
This “heat” and moisture I’m talking about is already streaming into our area. Check out the surface observation map for the Midwest from Sunday afternoon. Notice all of the areas I have circled.
This can be a little confusing to read, but notice all of this filled in colored dots, those indicate low cloud cover. Also look at the lines streaming out of those colored dots called wind barbs; they show the direction and speed of the wind. Notice that they are all facing a southerly direction. This means southerly flow has taken hold, and lots of moisture is transporting into the area. Now, we obviously need moisture for snow as much as we do for rain, however, it’s the lack of cold air through the entire column of the atmosphere that will likely prevent many areas from getting snow this week.
Check out the latest precipitation maps from a couple different models for Tuesday night. Notice there is still a pretty big discrepancy on where the precipitation will fall.
The first model is much further north with the precipitation then the second model. So it does look like the southeast will get some moisture soon, but the north and west may not.
Now, because these maps only show liquid equivalent precipitation (they don’t delineate between snow and rain) then we have to look elsewhere to determine what type of precipitation is going to fall. The picture below is one such map we can look at. This shows what this particular forecasting model thinks will happen with the precipitation type across the country. The upper left is areas that will receive rain, the upper right is snow, the lower left is sleet, and the lower right is freezing rain.
Notice that the southeast has a pretty good chance at some freezing rain, with the north coming in with mostly snow. This can be further analyzed by checking out the Hydrological Prediction Center (HPC). They produce a forecast that shows the probability of receiving different amounts of freezing rain. Below is the probability of collecting at least a tenth of an inch of freezing rain over a 24-hour period starting Tuesday evening.
Good chances for accumulating freezing rain in the southeast Tuesday night with probabilities over 50 percent to get at least a tenth of an inch of icing. This will obvisouly make travel treacherous but the magic number seems to be about a quarter inch when it comes to freezing rain. Once you receive a quarter inch, that’s when trees and power lines begin to snap and power outages become an issue. For the moment, it looks like we wont have to deal with quite that much, but this scenario is far from certain and will have to continue to watch to see what happens.
As for total amount of precipitation, the HPC shows that the heaviest of the precipitation will fall in the southeast with up to a half-inch of liquid possible, check it out in the image below.
Stay tuned to KDLT and KDLT.com for the very latest on this upcoming winter storm.