Tuesday, September 19, 2017

Strong Thunderstorms Over the Northern Plains

The light rain we had over northern Illinois and southern Wisconsin late Monday night and early Tuesday wasn't much, but at this point we'll take whatever we can get.  The skies Tuesday will remain dry in the Stateline, but strong thunderstorms are currently moving through the northern Plains.  A Tornado Watch has been issued for parts of North Dakota, South Dakota and western Minnesota, while several Severe Thunderstorm Warnings and even Tornado Warnings have been issued.

Active weather Tuesday night will remain well northwest of the Stateline.  As the cold front moves east and southeast Wednesday morning, there could be a few weakening showers/storms approaching the Stateline, but I don't think those will have too much of an impact on the area.

The cold front will move towards Wisconsin and Iowa late Wednesday, and eventually into northwest Illinois early Thursday.  Thunderstorms are possible for the Stateline Wednesday evening and overnight.  The overall severe threat is low, but a line of thunderstorms forming along and ahead of the cold front could be capable of producing gust winds.  The front will be pulled back north as a warm front Thursday keeping our skies dry through the weekend.

Summer is Back

We've been talking about a changing pattern recently that will bring summer-like temperatures across the Stateline. An amplified ridge will build across the Midwest as an upper level trough digs across the west. This will put Iowa, Illinois, and Wisconsin under southwest flow aloft. This essentially transports a warm and moist air mass across the Midwest as temperatures build underneath the ridge.

Temperatures by Wednesday will climb into the upper 80's and will stay there through the weekend with this amplified ridge overhead. Friday even has a shot at 90° with a little more sunshine in the forecast that day. But not only hot, it will be humid too as dew point numbers climb into the 60's and even skirting near 70°.

While it will be anywhere from 10-15° above average, it doesn't look like we will break any records. Friday will be the closest to the record of 93° which was set in 1937. The records for Thursday, Friday, and Saturday were all set in the 1920's and 1930's.

The ridge is forecast to start breaking down next week, which will usher in a cooler air mass.

Monday, September 18, 2017

Monday Evening Weather Update

Light rain showers are trying to move into northern Illinois from the southwest, but are encountering a little more dry air.  While a few light rain showers are possible later tonight, likely closer to Midnight, more of the steady rain will occur over central Illinois.

Clouds are beginning to thin out back west over Iowa and this is where fog has quickly developed.  It's possible that as the rain shifts east early Tuesday morning, fog may settle in around sunrise.  The fog and low clouds could limit temperatures, in some spots, from warming back near 80 degrees Tuesday.

Hurricane Maria Could Be More Devestating than Hurricane Irma

9:00pm Update: Hurricane Maria is now a Category 5 hurricane with maximum sustained winds of 160 mph.

Hurricane Maria quickly strengthened from a Category 1 hurricane late Sunday evening, to a Category 4 hurricane Monday evening.  Maximum sustained winds have been measured at 130 mph as the storm moves west/northwest at 9 mph.  As the storm moves into a favorable environment for continued development, Maria could reach Category 5 status within the next 24 to 36 hours.

In the direct path of Maria are some of the Caribbean Islands that were devastated by Hurricane Irma just less than two weeks ago.  As many residents on the islands evacuated to Puerto Rico following Irma, those people may now be bracing for a direct impact as Hurricane Maria is forecast to move over Puerto Rico early Wednesday morning.

Hurricane Irma moved a little north of the Puerto Rico, but still producing a significant amount of wind damage causing thousands to lose power.  Hurricane Maria will track a little south of Irma's track, bringing the strongest winds of the hurricane through the U.S. Virgin Islands and the northern coast of Puerto Rico.

Hurricane Maria will maintain its strength as steers towards Turks and Caicos and southern Bahamas by the weekend.

Sunday, September 17, 2017

Mid Summer Heat at the End of September

The official start of Fall may begin later this week, but temperatures are expected to feel anything but fall-like.

Highs Sunday were a little more seasonable following the passage of a cold front.  Temperatures Monday will remain in the mid to upper 70's ahead of a warm front that is expected to bring quite a bit of warmth back into the Midwest.

The jet stream pattern this week will be 'stuck' in a blocking pattern with high pressure centered over the Great Lakes and East, and low pressure over the West.  Hurricane Jose is moving up the East Coast, and while not a direct impact on land, is still affecting the weather pattern over the lower 48.  A strong ridge of high pressure won't move much to the east due to Hurricane Jose and this will continue to push temperatures well above average over much of the Midwest, Great Lakes and Southeast.  Meanwhile, cooler than normal conditions are expected over the west with rain and snow.

The middle of the country will remain the 'active zone' with low pressure systems developing over the southern Plains and lifting into the Upper Midwest.  We will see a few showers and thunderstorms this week in northern Illinois and southern Wisconsin, but the chance for those remain isolated and low.

To better understand why exactly our weather pattern has taken such a drastic change from where we started out the month, we have to look roughly 18,000 feet above our heads.

The upper level pattern in the atmosphere resembles the negative phase of the Pacific North American teleconnection, or PNA.  According to the Climate Prediction Center, the PNA is 'one of the most prominent modes of low-frequency variability in the Northern Hemisphere extratopics'.  Basically, it has an impact on the weather that occurs over the United States and identifies where height anomalies occur in the atmosphere.

Think of the atmosphere like an apartment building.  Just like an apartment building has different floors, the atmosphere consists of different height levels.  When the air mass over a certain region warms, that air mass expands causing the height levels over that area to rise.  The opposite happens when the air mass cools.  These above average and below average anomalies correlate well with what's occurring over the United States, and could explain why our temperatures are warming like they are.  Heights levels the Midwest and Great Lakes have been rising above average, while falling below average out west.  While the high heat might not last, the above average warmth (remember our average high by the end of the month is the low 70's) could last through the end of September.


Saturday, September 16, 2017

Upcoming Rain Chances with Summer-Like Temperatures

It was another gorgeous, summer-like day in the Stateline hitting the mid to upper 80's again.  However, we now have some rain moving in from the west, which is why we're seeing some clouds build up on our MercyHealth Skycam out in Freeport.  The rain is developing ahead of a cold front, and is moving through some of our western counties.  The front will slowly make its way towards the Stateline as we go through the night, so we'll keep rain chances in play this evening out west as a few more showers could develop ahead of the front.  Everywhere else will see mostly clear skies this evening with temperatures in the upper 70s to low 80s.

The front will move in around 4am, by which the better rain chances out west will come into play.  The front will then move further into the Stateline around 7am, giving rain chances to everyone else.  By around 1pm, the front will move out and we'll have a gorgeous end to the weekend with sunshine and more mild temperatures in the upper 70's. 

Lots of warm air and moisture will be moving into our area as we go through the work week, which will warm our temperatures while also increasing our rain chances.  Our first round of rain will come up on Monday, with thunderstorms looking to move in on Wednesday.  Slight chances for a couple isolated storms Thursday and Friday, but the best rain/storm chances will be Monday and Wednesday.  Tuesday we'll see drier conditions with sunshine and temperatures in the mid 80's.

It's a good thing we've got a more active weather pattern coming up because we desperately need the rain.  The U.S. Drought Monitor has classified northern Illinois as Abnormally Dry, which is on the lower end of the drought scale.  We're building on a fairly large deficit from August and are already in a big deficit for this month, but at least these rain chance coming up will point us in the right direction.

Friday, September 15, 2017

Summer-Like Weather with Rain on The Way

We had another gorgeous day across the Stateline, but you may have noticed something a little unusual....it was really warm! Temperatures hit the upper 80's this afternoon, 10° above our average for this time of year.  Luckily, for those of you who are sick of the heat, the skies will stay clear this evening, which means our temperatures will cool off pretty quickly.  We'll drop back into the upper 70's around 9pm, before cooling to the mid 60's overnight.  There is some moisture flowing into our area out of the south, so we may see some light fog early tomorrow morning.

We'll go into the weekend with the same weather we had today, sunshine and temperatures in the upper 80's.  However, it will be fairly muggy as dew point temperatures will be in the low 60's, and a few places could see heat index values around 90°, so keep that in mind if you plan on going outside during tomorrow afternoon. 

Even though the weather's been gorgeous this week, it has come with a bit of a consequence....no rain!  We haven't seen significant rain since August 28th, where we saw a little over 2 inches.  Since then, we've been dry, and we're building on that 1.57 inch deficit from the entire month of August from the lack of rain we've seen this month.  We're supposed to already have seen around 1.5 inches of rain this month, and so far we've seen under one-tenth of an inch, so we got a ways to go.

Luckily, we do have a cold front on the way, and that'll be settling into our area early Sunday morning.  It'll bring a few showers and a couple thunderstorms across the Stateline, but only for the morning.  We stay dry during the afternoon with highs in the low 80's and mostly cloudy skies.

However, once we get into next week we'll have more warm air and moisture move into our area, and this will give us a few rain chances going through the work week.  We'll have rain chances on Monday and Thursday, with only slight chances on Wednesday and Friday.  It doesn't seem like a lot, but at least it'll be a step in the right direction.  Along with those rain chances, temperatures will be in the low 80's on Monday followed by the mid 80's for the rest of the week, before slightly cooling to the low 80's by the end of the week.