Tuesday, February 25, 2014

Early March Storm Potential

If you have spent much time on social media the past few days there is no doubt you have heard the talk about a new winter storm on the horizon for early March.

Undoubtedly some organizations will use this as an opportunity to use scare tactics in order to grow their following. In the StormTrack Weather Center we want to show you the facts of what the outlook is. Without weather models, without the huge snowfall predictions, without the hype. Here is the state of the atmosphere and what we believe is most likely to happen. 

Below is a satellite image of the water vapor in the atmosphere over North America. To many of you it probably looks like a bunch of swirls with a map thrown on it. But to meteorologists THIS is what we look at long before any computer models. It shows the flow of the atmosphere and where large pockets of moisture are present. Think of it as an MRI for meteorologists. 

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For the storm next week we first have to look at the big picture. A strong jet stream and ejecting piece of energy from just north of Hawaii will be the big player here. Right now only satellites are sampling the storm, not actual weather balloons. That means while the data is still being relayed into various computer weather models, it isn't the highest quality like an actual weather balloon could achieve.


Next let's look upstream into where this storm is heading. The large high pressure over the Atlantic Ocean has aided in re-curving many of these storms all winter long into a favorable pattern for eastern US snow storms. The arctic air in place over the northern US will be tough to displace as well. If the storm heads our way, that likely sets the stage for this to be a winter storm vs rain here in northern Ohio. 



The biggest question and one that likely will not be resolved for a few more days yet is exactly how fast this energy 'ejects'. That is to say, does the storm come across the country in one large lump sum or several smaller waves. One big storm would likely increase impacts over a shorter duration but indications right now are indicating a more broken series of lows. This would spread out the effects (although weaker) over several days. 



The bottom line is -- stay tuned. We are watching this storm close but it appears another healthy dose of winter weather is heading our way for late this weekend into early next week but it is FAR too early for snowfall totals with a storm that is 3000+ miles away. 

















Wednesday, February 19, 2014

Flood Threat will be a Marathon

On Wednesday evening we aired our first large news piece regarding the potential for river flooding this year. If you didn't get a chance to watch it we have posted it below. While river flooding is possible as early as this weekend it certainly isn't a one-and-done threat.

             

 We continue to watch the potential for significant river flooding as early as this weekend. Heavy rainfall combined with 1-2" of additional 'rain water' from snow melt will test some local rivers. This is a threat that shouldn't be over looked but this article will focus on the long-term potential for flooding this next few weeks.

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A number of factors point toward the flooding threat not being confined to only around this weekend but the next several weeks.

1) Ice will remain on local rivers and Lake Erie

2) The snow will not completely melt

3) Another cold-snap is likely

Ice on local rivers has been measured at 16" near Grand Rapids on the Maumee and 12" near Findlay on the Blanchard. While the warm-up and rain will thin out the ice to some extent, it will not be enough to completely melt this ice. Combine the river ice with the fact that the western end of Lake Erie is still very much covered in ice and the threat for ice jams will persist, especially on the Maumme. When ice from the Maumee tries to flow downstream it will be slowed by any ice remaining near the mouth to Lake Erie.


You may have noticed it already -- the snow is melting but it's not simply disappearing. It will take time to melt this deep and widespread snow pack. Rainfall on Thursday will certainly help and much of the snow will melt. But again it likely will not be enough to completely remove the snow pack. That means when cold air returns, there will still be some moisture sitting and waiting for the next warm-up. (Although much reduced from where we started this week)

As was hinted at earlier, another cold snap is likely by the middle of next week and into March. That will allow the ground to remain frozen, ice to build back up on rivers and any remaining snow to stick around. While not a foregone conclusion this does prime the potential for more flooding down the road when a more permanent warm-up returns along with the inevitable March rains.


This all means stay tuned if you are commonly affect by river rises. This could be a long flood season.

Monday, February 10, 2014

Deep Snow Pack = Big Flood Concerns

With so much snowfall this season and so much of that snow staying on the ground, the thought may have crossed your mind: "What happens when all this melts"!? That is something that hasn't strayed far from our mind in the Stormtrack weather center this winter. A look at current conditions and a historical context will reveal an uneasy outlook for area rivers the next few weeks.

First what does the current snow pack look like? Right now it is generally over 10" for northern Ohio and Southern Michigan.


And how much water does that snow currently have in it? Satellite analysis and actual samples reveal a widespread 1.5" to nearly 3" base for our entire area. A VERY 'healthy' amount...


So why the concern? This is where we turn to history in our area. At least 70% of the significant floods on our local rivers have come during a winter/spring thaw. On the Maumee river at Waterville that number is actually 100% for the top 10 crests.

It doesn't take much page turning in the history books to find a very recent example of this potential in 2008. That season recorded the 7th most snowfall in a season in Toledo's history. In early February, when there was around 1" of water locked up by snowfall on the ground, a warm-up and heavy rainfall released it quickly into waterways. Temperatures spiked into the 50's and over 2" of rainfall fell. Adding the water already on the ground, frozen ground and ice on the rivers/creeks already made for historic flooding. The Sandusky, Maumee and Blanchard all recorded top 10 crests during that warm-up.




And while the deep snow pack certainly plays a big role in flooding it isn't the entire equation. Thick ice can slow and even block water flow on waterways, a frozen ground that can expedite runoff and additional rainfall are also important factors. Significant ice at the mouth of the Maumee river also could slow any water from running down the waterway into Lake Erie. 



The bottom line is we need a slow, gradual warm-up that would allow this snow to be released gently into area creeks and rivers. Given the very active weather pattern we have been in this winter and look to continue a slow warm-up may be a tall order. Forecast models are already hinting a potential quick hitting warm-up around February 21-25th. We will need to watch this closely. 
















Saturday, February 8, 2014

Big or Small snowflakes?

With all of the snow we have seen this snow, there is no doubt we have already ran the range of snow types. You know what I am talking about: The type that you can sweep away with a broom, the kind of snow that breaks your back because of how heavy it is and everything in between. You may have asked yourself, 'What makes the snow so different'?

The most logical and correct answer is the temperature of course! But it's not a simple as what you might think. It has more to do with the temperature higher in the atmosphere than at the ground where it falls to. A temperature zone in the atmosphere that we follow closely during winter is called the 'Dendritic Growth Zone (DGZ). Snowflakes grow fastest near 15 Celsius. The DGZ encompasses that 15 degree reading at the temperature zone close to it. The longer the snowflakes are expected to remain in this part of the atmosphere the bigger the snowflake is likely to be. The bigger the snowflake, the faster the accumulation.

You can see why this plays such a big role in our forecasts. A system that may not have very much moisture to work with may be very efficient at making snowflakes and can actually produce higher snowfall accumulations than a bigger/wetter system can!

Here is a graphic to show you what we mean. On the left the DGZ is deeper than on the right, where the zone is smaller and so are the snowflakes!