Possible Severe Weather Monday Night

After what has been a very dry summer so far, we could see several rounds of showers and storms this week. Some of those storms could be severe, starting with tonight.

SPC Severe Outlook for Monday Night

The Storm Prediction Center has the entire Stateline under a slight risk for severe weather through Tuesday morning. Storms could be strong wind and hail producers with heavy downpours in spots. Our timeline right now is a chance for storms this afternoon and early evening, with much better storm chances after dark and continuing into Tuesday morning.

Storms are expected to be concentrated along a cold front that will swing south through the area as we go through the night. Since it will be a fairly slow moving front, storms are expected to regenerate over the same areas, which is why we are calling for heavy rainfall in spots. Models are showing an inch or more of rain in some of the hardest hit areas tonight.

Current radar is already showing some activity off to our northwest. Expect this to develop into the Stateline later tonight. Stay with the First Warn Weather Team throughout the day for the latest on any severe weather development.

Livin' on the edge

The lack of rain and the persistent hot weather has almost become the norm across the country with record breaking heat and ongoing drought conditions in the Midwest.  This all looks to be changing as we could be dealing with several rounds of thunderstorms before the weekend gets here.

A little over a month ago the storm track was along the U.S/Canadian border keeping the heavy rain threat closer to Minnesota and Wisconsin.  Now with the position of the jetstream over us this week there will be an increase in the storm threat beginning this evening and lasting through the end of the week.  Weekend Meteorologist Eric Nefstead had discussed in an earlier post a 'Ring of Fire' pattern beginning to set up which usually favors heavy rain and severe storm potential. 

The image on the left is the current water vapor and it really tells a lot this morning.  The darker areas are where sinking air is present and you can easily see where the ridge of high pressure is.  It's located in the center of the country.  Moisture within the atmosphere is flowing up over the ridge from the southwest into the Great Lakes.  This is also where the jetstream is located (blue arrow).  With the placement of the jetstream almost directly overhead any storms that form upstream will hold a greater chance of moving into northern Illinois and southern Wisconsin.  As low pressure moves into eastern Canada a trailing cool front will move south out of Wisconsin later this evening.  A series of upper level disturbances will move from northwest to southeast this week pushing the front south and then lifting it back north by the middle of the week.  A fairly moisture rich environment is in place and with each disturbance that moves across the boundary the threat for rain increases with the first round arriving tonight.  While an isolated thunderstorm may develop this afternoon storm chances increase through the overnight and into Tuesday morning with locally heavy rainfall possible.  Along with an increase in the heavy rain comes the potential for severe weather; the first of which may occur tonight.  While widespread activity isn't anticipated if thunderstorms grow large enough strong winds may become a concern.  Timing out the storm potential continues to remain a challenge, but the way it looks right now the greatest threat appears to be overnight tonight into Tuesday morning, Tuesday night into Wednesday and then again Wednesday night into Thursday.

Some Drought Relief on the Way?

It will be mostly cloudy overnight with a chance of showers and thunderstorms. It will be warm and muggy, too, with a low in the low 70's. On Monday some of the searing heat from the plains will spill across the Stateline with temperatures soaring back into the upper 90s, and afternoon heat indexes will be around 100. Also, there is a  chance of showers and thunderstorms as a cool front across central Wisconsin and southern Minnesota nudges slowly southward. It will be warm and humid with showers and thunderstorms likely on Monday night as the cool front slides across northern Illinois.  The low temperature will be in the low 70's.  The front will continue to inch southward across northern Illinois on Tuesday.  There will be a pretty good chance that parts of the area may see additional showers and thunderstorms.  It will be cooler on Tuesday with a high in the upper 80's.  The front will become stationary across northern Illinois on Wednesday.   The massive high that has caused the severe drought across  the region will be far enough to the west that a ring of fire pattern will develop for most of the week.  Disturbances moving around the periphery of the huge high to our west will cause thunderstorm complexes to develop from time to time.  If two or three of these complexes move across the Stateline, our region could get some significant rainfall before the week is over.  This is not a sure thing for us, but it is worth mentioning.  A cool front will  move though northern Illinois on Friday bringing an end to the showers and thunderstorms as drier air moves in from the northern plains.  Saturday will be sunny and seasonable with a high in the middle 80's.  A warm front will develop off to the southwest of the area on Sunday, and begin to advance toward the Stateline.  There could be some scattered showers and thunderstorms back in the area by Sunday afternoon.  The high will be in the low 80's on Sunday.

Ring of Fire Pattern Expected to Develop

A weak cool front is stalling out just to the northwest of the Stateline tonight.  It spawned a weak disturbance that generated cloud cover that moved southeast across the area on Saturday evening.  It tried to get some precipitation going, but produced nothing more than a few sprinkles.    Skies will be partly cloudy overnight.  It will be warm and humid with a low around 70 degrees.  On Sunday the front will retreat back towards the north as a warm front.  Temperatures will heat up to around 90 degrees in the afternoon, and there may be enough instability to cause a few showers and thunderstorms to pop up.  Scattered showers and thunderstorms will dot parts of the area on Sunday night.  It will be warm and humid with a low in the 70's with a southerly wind blowing around 10 mph. On Monday heat from the plains will overspread northern Illinois pushing afternoon temperatures up close to 100 degrees.  Expect the heat index to be between 100 and 105.  There will be a slight chance of showers and thunderstorms during the day, but chances of showers and thunderstorms will rise overnight as a cool front pushes southward across the Illinois/Wisconsin border by 6 am.  The front will stall out, and become stationary from Moline to Champaign.  Easterly winds coming off an high pressure area moving across the Great Lakes will drop afternoon highs on Tuesday into the middle to upper 80's.  With the massive high that has been causing days and days of record heat in the plains states retrograding toward the west, a  ring of fire pattern may develop this coming week with disturbances sliding southeastward across the upper mid west generating thunderstorm complexes.  It would be good to see a series of these complexes move across the Stateline next week.  It is by no means guaranteed that this will happen, but at least there appears to be potential for some improvement in our serious drought situation during the next week before the pattern changes again.

Unusually Hot Weather Sticking Around

Despite a couple of days in the 80s to finish the work week (Which are the first back to back 80 degree days we've seen since the last week of June), the heat is expected to be back for the weekend and especially next week.

Temp stats as of July 19th

Normally, Rockford is used to 80 degree weather for the summer months with a handful of 90 degree days, which is nothing like what we've seen so far.

It all started in March when we experienced almost a week's worth of highs in the 80s... typically, we don't see any 80 degree days in March. April was quiet before 90 degree weather took over the end May and a good part of June. The start of July was dominated by100 degree weather.

A look at the forecast shows no big changes. Highs are expected back in the 90s for the weekend, with Monday's highs back in the triple digits. Unfortunately, we'll be flirting with 100 for most of the week.

And it's not just us. Chicago is on pace to break its record set in 1988 of most 90 degree days in a single year. Long term forecasts are showing it's possible, with above average temperatures expected for the next several months.

One can only hope for a pattern change

Maybe the rain the other night was the beginning of a weather pattern change for the Stateline...or maybe not.  But looking ahead into next week there is some hope that with the placement of the jetstream will keep the rain on our radar.

The persistent ridge pattern we've had all summer will hold firm in the Plains this weekend and early next week, but there are some indications this pattern may begin to break down.  As was mentioned in a previous post the position of the jetstream will be key in determining just how hot it gets next week and when/where storms develop.  Right now, it looks like we'll remain right on the southern edge of the stronger winds within the jetstream which would keep any threat for rain just to our north.  There are several weather models we look at when putting together a forecast and the one that has been fairly consistent with the heat and lack of rain has been the European model.  This particular models keeps the heat around through early next week with a gradual break down of the ridge by the end of the week.  The GFS, which is another longer term model, has hinted at the possibility of this jetstream pattern breaking down a little sooner.  It keeps Monday hot but then stalls a weak cool front either over northern Illinois or just a little further south increasing rain chances by the end of the week.  For now, the going forecast keeps the heat for at least the first part of the week with isolated storm chances Tuesday on.

Fire danger

Many people do not realize that there are many factors to determine the severity of a drought.  Placement of the jet stream, heat, and lack of rainfall are just a few of the factors.  There is one factor, called the Keetch-Byram Drought Index (KBDI), which simply measures how severe the fire danger is with droughts.  In this figure, we are in the 401-500 range, which means we are in a "High" fire danger.  What does this mean for you?  Well, it means your town or city has most likely issued a fire ban, which means no burning is allowed at all.  This is because a stray spark in these extremely dry conditions can easily spark a raging fire.

Justin Pletsch
WTVO Weather Intern