Click here for the 2-8-10 update on the 2-9 through 2-10 winter storm and a quick summary of the previous storm.

February 5-6th Snowstorm Details

The period of quiet cold weather for Southeast Ohio is going to come to a quick and snowy end by Friday. Friday evening the first of two major storm systems will begin to bring widespread precipitation to the region. Many things remain uncertain with the Friday-Saturday storm that is making it very difficult to forecast exactly what kind of precipitation the Athens area will receive. First lets see just what will happen with a list of knowns. We know that:

• -There will be large storm system that will affect much of the Eastern US.
• -This system will have access to a large amount of Gulf and Atlantic Ocean moisture.
• -There will be two faces of this storm:
  1. An area of widespread heavy to moderate snow.
  2. A vast large region of heavy rainfall.
• -No strong blocking highs are in place around the system which means there will be no large areas of freezing precipitation.
• -There are also no slow moving or stationary fronts reinforcing the low probability for freezing precipitation.
• -Though no widespread freezing precipitation, there will be a thin narrow transition area that will greatly effect snowfall totals for areas along a west to east axis.

With these knowns, we need to find out where the Athens area will sit in position relative to the storm. This system is originating from the Gulf of Mexico moving north/northeastward along the Appalachian Mountains before pushing out to the Atlantic Ocean off the Maryland/New Jersey coast. This would place Athens just to the north and then the west of the center of the low pressure system. Below is a NAM forecast image for 7pm Friday night representing Ohio University's location relative to the storm and its movement:

This location is very important to the storm. This will be very near the narrow transition point between snow and rain with the storm system. As mentioned earlier, the transition area will be very narrow with very little freezing precipitation (sleet, freezing rain, frizzle, etc). In one way the lack of freezing precipitation simplifies the forecast, but it makes it harder also. Any rain the area recieves will GREATLY reduce any snowfall amounts. Athens' location is at an area of a low pressure system that is characterized by a meteorological phenominon called a "TROWAL," or TROugh of Warm Air ALoft. This region contains a surge of warm moist air that gets lifted and wrapped around a low pressure system into its northwest quadrant. This typically doesn't mean that the surface will be warm and in most cases means the surface is below freezing. Therefore, the precipitation usually associated with a TROWAL is moderate to heavy snowfall that continues for an extended period of time-dependant on the storms movement and length of occulusion. In this situation however, the low pressure will be so close to Southeast Ohio that the warm air will not quite be lifted above a region of cold air at the surface yet on the onset of precipitation. Therefore the precipitation may start out as a very cold rain before transitioning to all snow Friday night.

Already this morning (Thursday) we can see the high clouds in the sky over Athens precursing the storms arrival. Below is a satellite image showing the movement of the cloud cover in advance of the system:

Looking at model trends from the last four runs of the NAM, we can see a trend to perhaps not even any rain falling. Below is the forecast model run for previous 8 runs for the same forecast time, 7pm Friday. Oldest is first with the newest, this mornings run at 7am last.
As you look at the following model runs, notice how the freezing line (purple line) slips further and further south. Also notice how the TROWAL development, along with the actual location of the low pressure system moves further south and east with each new run.


Notice the region circled in red. This map is of the precipitation expected within 6 hours. It will begin to increase with each model run below.


Notice the black circle. The freezing line is much farther south than the rest of the region. This is thanks to cold air damming on the eastern side of the Appalachian mountains that may cause a fairly good amount of ice to accumulate.



What does this movement of the system farther south and east along with its TROWAL mean? As a result the freezing line also moves southward, symbolizing more snowfall than rain on Friday. This will help increase the snowfall amounts greatly although there will still be some time where the freezing line is nearby the Athens region. The valid time for this frame of the model runs is now the furthest north the freezing line gets. Therefore, the window for rain or a mix of precipitation exists from about 4pm to about 11pm. This storm will be slow moving however and the precipitation from the storm will last near 24 hours. That means widespread snowfall the rest of the time.

To show the duration of the event, here are two shots of the storm, the first at 1pm Friday when precipitation is just beginning for the Ohio Valley:

Then, 24 hours later at 1pm Saturday you can see the precipitation, all snow by this point continuing although the system has clearly pulled off the coast already. The area extending westward is the TROWAL, as discussed earlier, in its mature stage that continues to spread snowfall behind the system. 1pm Saturday:

Now onto the estimate of snowfall. With the rain expected to not last as long as originally thought, the snowfall will be pretty high. Below is a graphic from the Hydrological Prediction Center depicting the various probabilities of snowfall amounts:


The top left shows an over 70% chance of 4”+ for the immediate Athens area. The top right shows a 10% chance of 8”+! That is a lot of snow! The bottom left doesn’t have Athens very far out of the 12”+ of snow, but at this point, with rain mixing in on Friday there is a very low chance that the area would see that much. The bottom right show the probablility of freezing rain. None is expected for the Athens region, however, the area where cold air damming will be occuring has over a 70% chance for heavy icing.

Here are a few forecast models with estimated snowfall indexes. NCEP ETA model storm total snowfall: Blue is 8-10” that is just north of Athens and white, which is over Athens represents 6-8”.

Here is the GFS model storm total snowfall for the same time period: This blue is once again 8-10” and it is directly over Athens. The city is just west of 10-12” also!

As I mentioned before, with the rain on Friday evening, it will be very hard to get over 8” of snow from this system. From looking at the above models and looking at a few other things, 6” most likely will not be a problem for Athens and surrounding regions. The farther east you go the higher the snow totals will be. The farther south and west you go the lower the snow totals will be. Either way, this will be a major storm for the region. Please make plans accordingly and prepare for the worst. Travel isn’t advised from Friday evening into Saturday evening if it can be avoided. Please be safe and prepared, but most of all, enjoy the snow!

Come Sunday, I will update this write-up to include the second system that will move through Tuesday through Wednesday. As of right now it seems like a much faster moving storm system that will be an all snow event. It will not have much access to rich, deep Gulf moisture like the past storm did, so amounts aren’t expected to be as high. It remain something to watch however.

The February 9-10th winter storm and quick summary of the 5-6th storm.

5-6th Storm Summary

While the the predictions were for widespread 6+ inches of snow, that never happened for the immediate Athens area. Why was this? The answer can be quickly summarized into one thing: rain. The steady rain that occured throughout the day Friday greatly reduced the snowfall totals for much of the Southeast Ohio area than what was predicted. Athens recorded over 0.6 inches of rain in less than 12 hours! This heavy rain was thanks to the warm air aloft becoming more entrenched over the region than was previously expected. This proves that many a-time the models can be wrong, even if they were trending colder with time. When you are looking at such fine detail, to such a high resolution also, the global models can be often misleading and inaccurate on the meso/microscale level.

Another interesting factor that may have led to the lack of snowfall and wintery precipitation was the lack of snow early in the event. The rain began in the early morning with no precursing winter precipitation. If snow or sleet would have fallen before the rain began and accumulated, there would've been a layer of cold air at the surface from this frozen precipitation. This could've allowed for more snowfall and freezing rain to occur throughout the day.

On a final note, though Athens was lucky and received less snow than predicted, many areas accumulated much more snowfall than had been previously been forecasted. Much of the northern tier of the system received greater snowfall totals because the system drifted slightly, around 25/50 miles northward than had been expected. This allowed Columbus, Akron, Youngstown, Pittsburgh, etc to recieve nearly a foot plus of snow. The winning region of the Eastern US that received the most snow was the Mid-Atlantic area, around Washington D.C.. Many locations received over two feet to even three feet of snow!

Upcoming 9-10th second winter storm.

As if one storm wasn't enough, a second comes bearing right on its heels! This system, unlike the last, is slightly more complex in overall development-although will have nearly the same characteristics of the previous one for this region. Winter Storm Warnings are posted for the entire region once again stating that an additional 5-8 inches of snow are possible over the coming 36 hour period beginning around 7am Tuesday for the Athens area. Once again, things are "supposed" to start out as snowfall in the early morning on Tuesday and continue through the day before switching to a wintery mix later in the evening. This mix will then switch back over to all snow and continue into Wednesday.

As a forecaster, I would have to agree with the thinking of the timing of the event. However, unlike the previous storm, snowfall will occur before the rain with snow already on the ground and such cold air in place already. With this entrenched cold air, the warm air will have a slightly harder time intruding. Models are agreeing however with putting a warm air surge northward over the region in the afternoon. This air looks like it will stop its northward movement nearly excatly at the same place as it did on Friday. This will mean that the mix and snow will give way to all rain again for much of the day Tuesday. This will cut the total snowfall from the storm in half. Snow should kick back in by the late evening and then gradually taper off for several hours overnight Tuesday/Wednesday morning as a dry slot works its way around the low pressure system. With this advancement northward of the dry slot, the heaviest snow should occur just beforehand, probably around midnight Tuesday/Wednesday. The snow will once again redevelop in the late morning Wednesday but remain very light and showery with no major accumulations but a inch or so expected.

As I mentioned, this system(s) is much different than the previous. Here was the track the low took on Friday through Saturday:
And, here is the current satelitte on February 8th:
Notice several things. The overall magnitude of the storm is much smaller than that of last weekends. Also, there are two low pressure systems embedded into the storm-a southern tracking one that will go up the coast and one that will track along the southern Great Lakes. This combination of systems are moving more rapidly than the previous storm. This will not allow the systems to access Gulf moisture for as long as Fridays system. This speedy movement will also prevent it from overspreading heavy precipitation for long durations in the same area. Hence, why this storm will affect a much broader swath of land than the previous one but snow totals will be much less in many places (except near the Great Lakes where lake enhanced will allow for a easy foot or more).

Now, you could ask-though the systems are moving faster than the last, how is it going to spread precipitation over the Athens region for a longer duration of time than that of last weekend? This is going to occur because of the phasing (interactions) between the two different centers of low pressure. With the southern storm rushing eastward more rapidly, the Great Lakes one will spread precipitation after the southenmost system has already moved out. This will drag out the precipitation for a longer time.

So, once again. Snow to start out Tuesday-an inch or two. Rain most of the afternoon Tuesday and into the evening. Change back to snow for several hours late Tuesday evening, heavy at times-additional two inches. Dry slot ending precipitation after midnight. On and off snow showers and strong, gusty winds with areas of blowing snow Wednesday-another inch possible. That would bring a storm total to 5 inches at the maximum. It should be standard drill by now-please be prepared for slippery roads, have an emergency kit ready, and be safe! Don't forget to take that moment and enjoy it, winter only comes one time a year!


Christopher Redmond cr898005@ohio.edu