Thursday, September 29, 2016

We May Hear Some Thunder

It seems like a long time ago that we last saw thunderstorms here in the Stateline. That is because we have been under the influence of fall. That has led to cooler temperatures, low humidity, and a lack of a thunderstorm threat. That trend continues Friday as scattered showers are expected on the back side of an upper-level low that will be situated in Indiana. However, as the low approaches the Illinois border into Saturday, it will bring a slightly more thunderstorm-friendly air mass into the Rockford region. With the center of the low nearby, some minor instability (CAPE) will develop during the day. That is what thunderstorms need to develop and maintain themselves. Think of CAPE (Convective Available Potential Energy) as food for storms.

For the Stateline, there will be minor CAPE in place Saturday. That, in addition to having the upper-level low so close, will support an environment slightly more conducive to thunderstorms than what we have seen lately. It is not a guarantee by any stretch of the imagination that we see thunder and lightning. But the formula for storms will be more complete than it has of late. The good news is that if we do see a thunderstorm or two, it won't be severe.

Wednesday, September 28, 2016

Rare "Black Moon" to Occur Friday

An astronomical event will occur this Friday, the last day of September. The catch? It's essentially invisible. So, what is the point of even mentioning this phenomenon? It is referred to as a "black moon" and has not occurred since March of 2014. It usually happens roughly once every other year. So it's not exactly ultra rare, but it isn't an every year type of happening. The "black moon" title is used whenever a second new moon phase happens in a single calendar month. That will happen for the western hemisphere this Friday.

A new moon is the phase when the illuminated side of the moon faces away from the earth. Therefore, no moon is seen because there's nothing to light the side of the moon that is facing earth up. This phase is normal and occurs in every moon cycle. This particular event is only given a special name because it doesn't happen all the time. The first new moon of the month went completely unmentioned. The one effect this event will have on areas where sky cover is not a limiting factor is it will provide a very dark sky (no moonlight to illuminate the sky). That darkness will supply ideal stargazing conditions. The sad news for the Stateline is extensive cloudiness is anticipated to be in place, as are a few showers. Thus, not only can we not see a "black moon," but we won't be able to see its effects on stargazing.

How Chilly Today?

Today's temperatures ranged from the upper 50's into the lower 60's. Some locations did surpass the pictured range of 58-62°, but that does not change the fact that today featured the coolest high temperatures since May 15th! We can thank the enhanced cloud cover, showers, and north winds for putting a "cap" on our temperatures today. This was one of those days typically thought of as "raw." We are already seeing clearing this evening, but addition rain is likely through midnight with a band of rain moving inland from Lake Michigan. The area of  low pressure responsible for the showers and rain will move far enough east on Thursday to deliver a mainly dry day with warmer temperatures near 70°. However, the same low will meander back west towards Indiana on Friday and Saturday, As a result, we will see a return to "raw" conditions with showers, clouds, winds, and temperatures only in the middle 60's to begin the weekend. Buckle up! Fall is definitely here to stay!

Tuesday, September 27, 2016

Pesky Low Keeps Showers Around

A very pesky "cut-off" low has been swirling in place on the northern shore of Lake Superior for the last 48 hours. It is the same low that swung the cold front through our region late Sunday. The low has kept low clouds, showers, gusty winds, and cool temperatures in place just to our north since Sunday. Although it hasn't moved much at all since Sunday, it will slowly drop south towards the Illinois-Indiana border Tuesday night and Wednesday. That will result in showery, cloudy, and cool weather for the Stateline through Wednesday evening. The low will then slowly move into Ohio, taking the shower activity with it -- only for 24 hours, though.

As the low area of low pressure sits in the Ohio Valley Wednesday night and Thursday, it will be far enough away to allow for a partly cloudy and milder day Thursday. Temperatures should be able to warm into the lower 70's, but the winds will remain breezy. The break in cloudiness doesn't last, however. The low pressure center will meander back westward into Indiana Friday and Saturday. That will bring back the chance of a few showers. The low will edge away from the region late Saturday, which will bring an end to the extensive cloudiness, windiness, and showery weather for Sunday, Monday and Tuesday!

Monday, September 26, 2016

A Look at September Statistics

Despite fall entering with a force today in the form of sunshine, strong winds, and temperatures in the 60's, September has been remarkably warm. In fact, we are currently on track to break the record for the warmest average temperature in the month of September. Of the 26 days that have come and gone, 20 of them were above average. That is good for 77% of September days being above average thus far. Not only that, but our average high temperature for the month is a little higher than 81°. That is a degree warmer than our average high on the first of the month, or the warmest day of the month.
Now let's jump back to the whole, "we could be in for the warmest September ever" statement. If the month ended today, we would break the record for warmest average September temperature by over 1°. To get the average temperature for the month, each day's high temperature and low temperature are taken into consideration. Once all of the data are attained, an average is taken. Of course there are still four more days in the month to get through. Each of those days is expected to feature high temperatures in the 60's and low temperatures near 50°. Thus, we could slip just below that 69.9° threshold by September 30th. It'll be something to watch for the next 96 hours!

Feeling the Difference

Big changes this week! If you've been chomping at the bit to get out and visit one of the many apple orchards or pumpkin patches, this week is a perfect week to do it!

If you spent the day outside yesterday, it had a very summer like feel with highs in the mid and upper 80's (for most) along with fairly muggy conditions. However, a potent cold front that brought scattered storms yesterday afternoon and a few showers overnight is now well to the east of the state.

Now our dew points are falling into the 40's along with plenty of sunshine. It will be a very dry day today, albeit windy and very fall-like. Winds will gust from the west up to 35 mph today as temperatures make it to about 66°. Compared to yesterday, that is a 20° temperature drop in about 24 hours. Not only that, but the week as a whole will be vastly different. The average high temperature last week was in the 80's compared to this week's forecast average  high which is in the 60's. If the forecast pans out, the weekly high will be about 15 degrees cooler.

A deep low pressure system will then sink south over Lake Michigan, dislodging much cooler air with a deep trough over the Midwest and into even the mid-south. Temperatures will only reach near 60° on Wednesday before rebounding back into the low 70's through the weekend.

Heightened Fire Danger for Whiteside County

Very high fire danger today for field fires, for areas along and south of Highway 30. These areas have the best conditions for cropland fires growing rapidly. For the Stateline, this includes Whiteside County, while the rest of the area has more of a limited fire risk.

This happens as the relative humidity drops to about 30-35%, which essentially is a very dry air mass. We combine this with strong westerly winds that will increase and become sustained from 5-15mph to then 15-25 mph, and then gusting to 35 mph. With these combined conditions and now harvested fields it will make for a high fire danger. If an agricultural field were to catch fire, the weather conditions would support it spreading quickly.