Heavy rain possible through Tuesday

September 7, 2015: We have had our fair share of heavy rainfall events this summer, with one coming at least once a month dating back to July. September may keep the streak alive with the potential for heavy rain and flash flooding early Tuesday.

Valid Monday evening

Valid Monday evening

So far, the most likely areas for heavy rainfall and flash flooding are in Stephenson County and areas to the west. 2″ or more (some locations could see 3″, to even 4″) for rainfall is possible within the Flash Flood Watch, which lasts through Tuesday evening.  The most likely time for rain will be early Tuesday morning.  Remember, a Flash Flood Watch means there’s potential for flash flooding, but nothing is occurring right now, and it could not pan out as a threat. A Watch means the threat is there, so be prepared.

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Why are we looking at flash flooding as a threat tonight and early Tuesday? A variety of ingredients are lining up to bring the threat to light. First, we need lots of warmth and moisture, to make the air unstable enough to produce thunderstorms, plus high humidity to give the storms extra fuel to create very heavy downpours. We have both with the recent very warm to hot and muggy weather. Secondly, the upper level winds need to be light. These winds are able to push and steer thunderstorms, so if the winds are weak, these thunderstorms aren’t moving too far. Third, we need to have a very slow moving boundary like a front. Since the upper atmosphere winds are weak, and a stationary front is setting up, there’s nothing to move thunderstorms along, allowing the storms to stay in one spot and completely soak only one area.

Watch out for water on the roads and rapidly rising streams tomorrow, especially in the morning. Avoid both, especially flooded roadways. You can easily become stranded on a flooded road if you try to drive through the water, so don’t do it! Turn around, don’t drown!

– Alex

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This post was written by Alex Kirchner on September 7, 2015

Labor Day Weekend Outlook

September 3, 2015: We finally hit 90° in Rockford today, after missing by a degree the last few days. It looks like we may hit 90° at least one more time over the holiday weekend before we are done with the heat for a little while.

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If you are sticking around town, not much changes. Saturday and Sunday will be dry, hot, and muggy, so those values in or near 90° will feel like the middle to upper 90’s, as it has been the last few days. By Monday, cooler weather is starting to work into the region, so we’ll start to see a drop in the heat, plus a chance for scattered thunderstorms as the cold front approaches.

holiday travel

Hitting the road on Friday to get out of town for the extended weekend? There isn’t much that you’ll have to watch out for. There are a few scattered showers possible in the evening along the shoreline of Lake Michigan and into northern Indiana, where a weak cool front has stalled.  Same goes for southern Wisconsin, but after that it should be smooth sailing.

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A lot of the drive will be hot, so make sure your vehicle is prepped with plenty of coolant, and that you and your fellow travelers have plenty of water. Conditions will be a little cooler the farther north you go, especially into Wisconsin with the recent cool front working through. It will remain hot going east, west, or south though.

Wishing you safe travels if you are driving tomorrow (and have a great weekend!), and for those staying home, enjoy the extended weekend and stay cool!

– Alex

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This post was written by Alex Kirchner on September 3, 2015

Humidity and comfort

September 2, 2015: The air has been pretty sticky lately, keeping the “feels like” conditions in the 90’s to near 100 for another afternoon. Hot air is playing a fairly large role, but as you know, you throw a little humidity in, and the weather outside goes from “very warm” to “very uncomfortable”.

Here’s how this works: the higher the humidity, the more moisture is in the air. The more moisture in the air, the less effective your sweat is. Your sweat works on evaporation- the water on your skin evaporates into the air, which cools your skin. If the air has a lot of moisture in it, evaporation doesn’t work that well (your sweat is trying to add more moisture to the air, but the air is already holding plenty in this situation; it’s hard to add more).

Follow me so far? We measure the amount of humidity with the dew point temperature. The higher the dew point, the more moisture in the air. You can see on the chart below (and you can feel it outside), when we get that dew point temperature above 60°, we really start to “feel” the extra moisture in the air:

Dew point temperature and the relation to comfort

Dew point temperature and the relation to comfort

We will be hanging out at around 70° for the dew point- which is right on the border between uncomfortable and oppressive. Make sure you are taking it easy in the heat, take plenty of breaks, and drink lots of water!  Same goes for your children and pets.

threattrack outlookWe’ll see drier and cooler air by early next week. Stay cool!

-Alex

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This post was written by Alex Kirchner on September 2, 2015

August Wrap-up/September Outlook

September 1, 2015: Welcome to September! Today is the first day of Meteorological Fall (with the months of September, October, and November comprising the meteorological definition of the season), which means August wrapped up the summer season.

Taking a look back at August, there were plenty of warm days, but we ended up about a degree below average in all categories, so August 2015 will be considered average to even slightly cool.  There was a slight surplus for precipitation (about 6/10″ above average).

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September starts out plenty warm, but usually cools off quickly, as the amount of sunshine drops. Comparing the start of the month to the end of the month, we lose nearly an hour and a half of daylight as the days grow shorter during the Fall season.

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As a result, the average temperature drops a good 10 degrees between Sep. 1 and Sep. 30, giving us a good taste of “fall weather” by the end of the month (if, of course, the weather pattern follows along, which happens most of the time).

2Obviously, this September will be starting off a little differently, with temperatures 10 degrees above average or beyond for at least the first week. On average, we usually see one day in the 90’s, so this isn’t unheard of.

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Because each day will be shorter than the day before, the decreasing sunshine catches up with us eventually, so don’t look for the hot weather to last too long!

– Alex

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This post was written by Alex Kirchner on September 1, 2015