Your Hometown Weather: September 8. 2010: A difficult forecast

September 8, 2010

Chances for rain will increase over the next 24 hours - a cold front will move through the region on Saturday with additional showers and storms...

There will be a sharp cutoff between heavy rain and light rain - 50-75 miles could mean the difference between 1/2" of rain and 2-3" of rain...

We have a difficult forecast over the coming days. The main concern is the track and movement of tropical depression Hermine. As you know from reading some of my information over the last month - it is my belief that the best shot at ending this drought would be for a tropical system to push through our region. We now have a tropical system on the map and it is going to move across portions of Oklahoma, Kansas, Arkansas, Missouri, and Illinois.

The only question left is how much rain will we receive. There are some differences in forecasts from local meteorologists and the federal agencies. The problem is that the exact track of Hermine is a bit uncertain. It is important to get the track right in order to get the rainfall totals correct. Tough forecast. But, I will give it my best shot. If Hermine moves further south than expected then we will have to increase our rainfall totals.

Here is a view of the remnants (click for extra large view) of Hermine - impressive swirl in Oklahoma and Texas. Lot of moisture being pulled northward with the system.

My forecast thoughts are that the heaviest rains will fall across portions of Oklahoma, southeast and eastern Kansas, western Missouri into southern and central Missouri then into east central Missouri and then into the southern part of central Illinois and the northern part of southern Illinois (including Belleville over to Mt Vernon).

Areas south of there - including southeast Missouri, the rest of southern Illinois, southwest Indiana, and western Kentucky will receive rain, as well. But, I don't believe as much as areas just west and north of our immediate local counties. Right now it appears that most of our area (including Cape Girardeau, Marion, Carbondale, Metropolis, Paducah, Golconda, Mayfield, Murray) should receive 1/2-1" of rain from Hermine - locally heavier rain especially as you move further north in that outlined area. Areas in the heaviest band (the ones mentioned earlier in this post - outside of our area) could receive anywhere from 3-4" of rain with local amounts exceeding 5". Impressive totals if they verify.

Basically the further south you go into the area the less rain you will receive. The heaviest totals will be north towards St Louis and the lesser totals will be near the KY/Tn border. Assuming the track is correct. Again, if the track is further south then I will need to update the forecast.

Areas included in the heavier rain bands would include - Springfield - Jefferson City - St Louis - Columbia - Farmington, Missouri and Belleville - Salem - Fairfield, Mt Vernon, Illinois. Rough outline. Assuming Hermine tracks as expected. You can view the current flash flood watch outlines by clicking here.

Again, there are disagreements on this forecast. The HPC (in charge of forecasting heavy rainfall amounts) has placed most of our local area in the 2-4" range. Although they did back down some from previous forecasts. If the track of Hermine is further south and east then our local counties will receive more rainfall than I am forecasting. If this appears to be the case then I will update accordingly. :) I don't think many of us would be upset if I was wrong on the rainfall totals. We need rain - desperately.

When will the rain chances increase?

The chance for rain will begin late tonight and continue into Friday evening. There are already some showers occurring over northern Arkansas. The main brunt of the system is still back in Oklahoma and Texas (see regional radars below).

In addition to Hermine, a cold front will approach our region on Saturday and push through the region on Saturday afternoon. This will give us another chance for showers and locally heavy thunderstorms. So, we at least have a few more chances of rain in the coming days. I know many of us missed out on yesterdays rainfall. I did not receive a single drop here at the Weather Observatory in central Massac County. Much of the area continues to experience drought conditions.

Don't forget there are burn bans in effect for many of our counties.

Your seven day forecast from the National Weather Service can be viewed here
Local and regional radar (watch Hermine moving in) can be viewed here and a large radar image can be viewed here.

Overall the forecast is for normal to above normal temperatures over the next 6-10 day period. A few days (after frontal passage) will likely be a bit below normal in the temperature department.

Here are some of the different rainfall forecasts from the National Weather Service and computer models - as you can see there are different opinions on how this all unfolds -Click image for larger view: