Friday, November 25, 2016

Heavy Rain Event Mon-Tues

Sunday AM Update:

In addition to the information posted Friday night, here is a look at the latest rainfall projections. Some areas may see locally a little more that what the computer model is showing but this gives you an idea of what to expect as rain moves in late tonight and Monday.  Right now there is a threat for storms to become severe to our South but we will be keeping an eye on NW Tennessee and the MO Bootheel to see if any of those storms drift northward amidst the axis of greatest warmth and moisture. I've included the severe storm outlook from the Storm Prediction Center below the rainfall totals. Preparedness reminders are also posted below. 

Friday PM Update:

Moderate drought conditions have plagued the Local 6 area for most of meteorological Fall (Sep-Nov). As we wrap up the month of November we'll also be in the midst of a heavy rain event set to begin late Sunday and Monday and continue through Tuesday. There is also a small chance of rain on Wednesday of next week. While we certainly need rain we don't need it to come in one big dose.
For the first time in many weeks a feed of moisture from the Gulf of Mexico will be readily available for the sub-tropical jet to transport into our region.

Periods of heavy rain are expected to overspread SE Missouri and Southern Illinois as early as Sunday night. This slow moving band of showers and thunderstorms will then push east Monday and early on Tuesday. A secondary push of moisture may bring another quick round of rain on Wednesday. 
This weekend is the time to prepare for rain before it moves in especially if you live near large drainage ditches or low-lying landscape. Recently fallen leaves will likely block proper drainage of heavy rain and cause localized flooding. Clearing drainage areas of these leaves and debris will go a long way to preventing any unnecessary water problems.

Look for updates to the forecast and rainfall projections here throughout the weekend and on Local 6!

Wednesday, October 19, 2016

Winter Outlook for the Mid-South (2016-2017)

By the end of March 2013, we were more than ready to put Winter behind us after bitterly cold temperatures hanging on and periods of snow blanketing the area. We were influenced by a weak La Nina episode and arctic air was readily available to the Eastern United States. Currently the Climate Prediction Center is in "La Nina Watch" mode with a 70% chance of development this Fall and continuing into Winter 2016-2017. A record El Nino episode came to an end early in the Summer and we have been in a neutral period for a couple of months now. Signs of continued cooling in the Pacific waters off the coast of South America points to the likely development of a weak La Nina episode for the cool season.

The reason we look at El Nino and La Nina episodes is because it has a direct impact on the overall weather pattern across North America. It gives us guidance. During La Nina, we tend to see colder winters and a higher likelihood of stormy (wintry) weather. Temperatures during past La Nina winters look like this:
Click to enlarge

La Nina influenced winters have shown in the past:

  • Temperatures: The weakest episodes of La Nina have produced colder temperatures averaged from Dec-Feb. The stronger the episode the less likely it became 
  • Snowfall Totals: During the weaker La Nina episodes during winter months, higher snowfall totals were more common. The stronger the episode, the lower snow totals tended to be as a result. Some of our historically highest snowfall events have occurred during weak La Nina influenced winters. 
  • Precipitation Totals: Total precipitation (rain, sleet, snow, freezing rain) varied quite a bit for each La Nina winter but also trended toward being at or above average. 

Click to enlarge

NOAA will be posting new images on Thursday and I will update them when they are released. Here is what they currently forecast for the Oct-Nov-Dec period which finished up Fall and begins Winter. 
Folklore has been a fun and interesting way to "predict" upcoming winter seasons. In the Mid-South, many of us are familiar with two popular indicators, the persimmon seed and the woolly bear. I was driving through the campus of WKCTC last month and collected a few persimmon fruits to cut open a couple seeds. The result of the seeds opening are shown below. As for the woolly bear caterpillar, I "analyzed" one that a viewer sent me a picture of from South Fulton, TN. The segments/colors are also explained below.

One thing that can have a very large impact on the winter weather pattern is where the actual jet stream will set up for most of the season. It can make a big difference between cool & mild, snowy/icy/rainy across the Local 6 area alone. We've seen it time and time again. 

Here are some key points from the guidance that we've looked at and what folklore supports/suggests:

  • TEMPERATURE: Average or below average temperatures are most likely. A few warming periods are almost always expected during any winter in the Local 6 area.
  • PRECIPITATION: Average precipitation of including all forms is most likely. With average or below temperatures expected, a trend towards snow/sleet/freezing rain may be likely.
  • SNOWFALL: Average or above average snowfall is likely. Normal snowfall for the winter season is 8".