Another Weekend Storm Ahead
by Cody Matz
December 12, 2012 8:40 PM
After months of warm and dry weather, the pattern may finally be shifting. With another below average month of precipitation in November, some drastic steps are needed for Mother Nature to produce some significant rain or snow. Well some of us finally received what we were looking for this past weekend with widespread amounts of 3-10 inches of snow… and over a foot in a few locations. However, from what we can tell, it doesn’t look like the overall weather pattern has shifted to a wetter one…. But there is reason for hope with another storm on the way. What many of you may not know is that weather patterns can really start to snowball (no pun intended). Once your area starts a certain pattern, like the warm and dry one we have experienced since May, it can be very difficult for the earth to change. It’s a lot like what we saw back in 2009 and 2010; record rain in the summer and record snow in the winter. We got stuck in a very wet pattern. Well, now it’s the opposite, but our luck might be changing. Another storm is headed our way less than a week after our last one. There are still a lot of uncertainties regarding the details of this next system, but it does look like we could get more precipitation with some having the potential of receiving a bunch… at least by December standards.
At this point we have more questions than answers, but what we do know is that this storm will be ejecting out of the desert southwest and forming in the western plains sometime on Friday. It will then move northeastward through our area Friday night and Saturday. The big difference between this storm and the last one is the amount of cold air encompassed in it, or in this case, the lack thereof.
As this storm progresses northward, it will bring plenty of warm air and moisture along with it. This will allow temperatures to rise Friday night and early Saturday before slightly colder air sneeks in behind this storm as it travels northeast of our area. This brings to question what TYPE of precipitation will we see? Right now it looks like rain and/or freezing rain will kick the storm off in many locations, but by early Saturday morning, cooler air will get funneled into the back side of the storm which should allow precipitation to slowly switch over to snow from west to east.
Well lets analyze that. Of course, all of the computer forecasting models are showing a different track and intensity. But the key difference, is over the last 24 hours, they have all shifted it further north with many now including much of our south and east into the precipitation sectors. Notice the amounts of precipitation in the 2 different forecasting models below.
The first one shows a pretty significant storm with plenty of precipitation in the southeast. The second image shows the storm a little further south (mainly south of our area) and precipitation bottle up in more of a line, than a circle. But just how much moisture would accompany this storm?
The Hydrometeorological Prediction Center creates a forecast showing the probability of an area receiving at least a quarter inch of liquid precipitation over a 24-hour period. This map is valid from 6pm Friday to 6pm Saturday.
Notice that the chances are over 90 percent in parts of the southeast with next to no shot at moisture in our northwest. The next image shows the probability of receiving at least a half-inch of liquid precipitation over a 24-hour period from Friday at 6pm to Saturday at 6pm.
The probability is still quite high in northwest Iowa at over 50 percent. For the month of December this is a pretty good storm. Now, we are also talking about the potential for some freezing rain. For those that don’t remember, freezing rain is rain that is falling while temperatures are below freezing. When this happens, the water freezes to anything it lands on; trees, cars, rooftops, traffic lights, roadways… the list goes on. This creates extremely hazardous travel with small amounts, and can be damaging to property at a quarter inch of accumulation. For example, if all of our upcoming precipitation fell as freezing rain, then widespread road closures, power outages, and tree damage would be expected. Now, we are not expected a significant icing event, however some light icing looks pretty likely. The image below shows the probability of receiving at least .01” of freezing rain over a 48 hour period from 7am Thursday to 7am Saturday.
This shows that much of our area could see some light icing. Now, this may not sound like much, but this is all it takes for roads to become extremely slick.
The National Weather Service issued the graphic below in anticipation of the storm to alert everyone of the precipitation type. It matches up with ours quite well.