Thursday, July 20, 2017

Flash Flood Watches Issued

A Flash Flood Watch has been issued for southern Wisconsin and northern Illinois beginning Friday afternoon and lasting through Saturday morning.  Rainfall amounts from Wednesday evening and Thursday morning ranged anywhere from one to four inches of rain!  Additional rainfall from thunderstorms late Thursday night, and especially Friday night into Saturday could range anywhere from another two, up to four inches!  This would likely cause significant flooding to occur over parts of the Stateline.

Possible Rainfall through Sunday Night
Currently there are Flood Warnings for the Kishwaukee River near Perryville and for the Pecatonica River near Shirland and Freeport, as well as Flood Advisories for the Rock River.   You can monitor local river levels here.

Along with the threat for flooding rain, severe weather is also possible Friday and Saturday.  We are currently under a 'Slight Risk' for strong to severe thunderstorms the next two days.  Biggest threats from storms on Friday would be heavy rain and damaging winds, while on Saturday wind, hail and heavy rain would all be possible.

Please make sure you have a way to receive watches and warnings should those be issued this weekend.  Remain aware of the flooding situation and remember to NEVER drive through a flooded roadway.

Thursday Morning Storms

6:am Update: No severe storm warnings, but strong storms are still making their way through the Stateline. Torrential rainfall and a lot of lightning - right along US-20. Take it slow this morning and watch for ponding on the roads.

 4:30am update: Warning expired over Winnebago county - Warning continues for DeKalb, far southern Boone, and NE Ogle Co. Heavy rain , wind gusts at 60mph, and large hail

 4:20am update: Severe storm warning issued for Ogle, DeKalb, and Boone co. Golf ball sized hail and 60mph winds. Storm has history of producing golf ball sized hail.

 Strom track for severe storm:

Severe thunderstorm warning for Winnebago, Boone, NW DeKalb, & NE Ogle until 4:30am. Moving east @30mph,wind gusts near 60mph, and nickel hail.

Heavy rain, frequent lightning, and wind gusts near 50mph with this strong storm. Heading SE at 45mph - heads up to Rockford, Roscoe, Pecatonica

Wednesday, July 19, 2017

Severe Weather Threat Wednesday Evening

Thunderstorms moving through west-central Wisconsin are currently moving southeast and could reaching southern Wisconsin and northern Illinois around sunrise Thursday.  While the severe weather threat is low - strong winds, hail and heavy rainfall are possible.  Heads up for the morning commute.

A 'wake low' has developed over southern Wisconsin along the back edge of thunderstorms.  This is not severe, however, wind gusts to 50 mph are possible which, with the recent heavy rain, could knock down a few branches or trees.

9:30pm Update: Severe Thunderstorm Watches being cancelled for Jo Daviess, Stephenson, Whiteside.  Severe Thunderstorm Warning being cancelled for McHenry county.  Still some heavy to torrential rainfall in eastern McHenry county.

9:02pm Update: The line of thunderstorms now moving through McHenry and Walworth counties, and exiting DeKalb counties.  Winds still being reported at 70mph, with one report of penny-sized hail in DeKalb.  Heavy rainfall behind the leading edge.

8:20pm Update: Tornado Warning issued for Boone, De Kalb, Ogle, and Winnebago counties until 8:45pm.  Multiple reports of wind damage with trees and power lines downed. Radar indicated 70 mph in this line of storms. 

7:30pm Update: Severe Thunderstorm Warning issued for Winnebago and Ogle counties until 8:15pm.  Damaging winds are expected with this line as 70 mph wind gusts are possible, with reports of 66 mph wind gusts already.  Storms are moving southeast at around 65mph

6:50pm Update: Severe Thunderstorm Warning for Stephenson, Carroll and Jo Daviess counties until 8pm.  Line of thunderstorms moving into northwest Illinois has had a history of producing wind damage.  As storm moves in, remain indoors and away from winds.  Wind gusts to 70 mph are possible.  Storm is currently located over Platteville, Wi and moving southeast at 60 mph.

5:45pm Update: New Severe Thunderstorm Watch issued for southern Wisconsin and northern Illinois until Midnight.

A cluster of thunderstorms has maintained its strengthen moving out of the northern Plains and into the Midwest Tuesday afternoon.  Most of the early evening over southern Wisconsin and northern Illinois will remain dry, just very humid.  Thunderstorms are expected to move into southwest Wisconsin and northern Illinois between 8pm and 10pm and then through north-central and northeast Illinois between 9pm and midnight.  Damaging winds will be the biggest threat, followed by heavy rainfall, hail and even a low end tornado risk.

The thunderstorms are following a boundary from the Plains into the western Great Lakes.  South of the boundary and extremely unstable air mass has developed.  North of the boundary there is a little more of a stable air mass.  A second round of thunderstorms is then expected to develop back over the northern Plains late this evening, moving east into central Wisconsin by Thursday morning.  The southern edge of these storms could clip southern Wisconsin and far northern Illinois, posing another wind and heavy rain risk between 5am and 8am.

Remain 'weather aware' this evening, because there will likely be a new weather watch coming out soon for parts of the Stateline.

Tuesday, July 18, 2017

Dangerous Heat Not That Far From the Stateline

You probably noticed a difference in the air Tuesday afternoon.  It felt a little warmer, a little more humid - didn't it?  Heat index values were in the low to mid 90's across northern Illinois and southern Wisconsin Tuesday afternoon.  And the abundance of moisture will help fuel a few thunderstorms later this evening and overnight.  Nothing severe is expected, but heavy rain producing showers will move in between 9pm and 10pm, a little sooner west of Rockford.

As mentioned in an earlier post - Excessive Heat Watches/Warnings and Heat Advisories have been issued for a good portion of the Midwest in anticipation of the high heat expected this week.  Heat index readings to the south and west could very well reach 110 degrees to 115 degrees!

Closer to home the humidity will be on the rise, but it won't get that hot.  The reason - anticipated showers and thunderstorms.  Heavy rain
producing thunderstorms moving over the Plains and Midwest will hold temperatures down a bit, but won't really ease up on the humidity.  Dew point temperatures will climb this week into the low to mid 70's, beginning as early as Wednesday afternoon.  This will push the heat index value into the mid 90's for most.  Thursday has the *potential* to be our hottest day, but thunderstorms moving through during the morning could hold temperatures down, but also bring heavy rainfall to parts of Iowa,
Minnesota, Wisconsin and Illinois.  A similar pattern may unfold Thursday night into Friday afternoon.  Definitely a pattern we want to pay close attention to because areas that receive repeated amounts of rainfall could easily end up with several inches of rain when all said and done.  And if that occurs in locations that are still dealing with flooding from last week, we could have a major disaster unfold later this week. 

Timing the Rain this Week

We've been talking about the 'ring of fire'  pattern that will be setting up over the country this week, where a dome of heat builds across the center of the country, and where more of an active storm track develops on the outer edge of that dome.

The excessive heat expands all the way up into the Quad Cities area, with Excessive Heat Watches and Warnings in place through most of Illinois and into Iowa and Missouri. Since the Stateline is right on the outer edge of the extreme heat, that means we are under the area which favors storm development. Our southwest counties like Carroll, Whiteside, and Lee, have a higher chance though of climbing into the low 90's as the heat expands. As dew points rise we need to watch for increasing heat index values, many of the days will feel like we're in the 90's.

But again we also need to watch for storm development the next several days. With high precipitable water available, heavy rain totals are possible and something that we need to watch out for. We will have multiple storm chances beginning Tuesday evening and lasting through Saturday early afternoon. Timing the energy waves, or vorticities, is always tricky...but right now it looks like the highest chances for storms will be in the evenings.

Storms tonight will be more widely scattered to isolated through Wednesday morning. Most of Wednesday actually ends up fairly dry, with another round of rain Wednesday night into Thursday morning. Storms Wednesday night and Thursday night look to bring the highest potential for heavy rain, but could also pose a threat for a few stronger storms as well. The active pattern continues with storms chances through Friday and into early afternoon on Saturday.

Monday, July 17, 2017

Heat and Humidity Bring an Active Storm Pattern

It's been a great start to the work week with clear skies, low humidity, and mild temperatures.  The reason for this is a high pressure system off to the east over Michigan.  This has been keeping the heat and humidity out of our area, and has kept the storms and clouds at bay off to the west.  This high pressure influence will continue through the overnight, where temperatures will cool down to the upper 50°s.

However, the nice weather doesn't last forever as that low pressure system off to the west will begin to influence our area.  Most of tomorrow will be nice, but the high will track southeast during the afternoon and the low will bring in a warm front around 7pm.  This will bring back the heat and humidity, and allow for thunderstorms to develop.  We are under a Marginal Risk for severe weather in Jo Daviess, Stephenson, Green, and Rock counties, with a slight risk in place for northeastern Iowa and southeastern Minnesota.  The storms will track towards our area, but they'll get weaker as they get closer to our area as we'll be farther from that low, so instability will be lower for us.  At the most, we'll see nickel-sized hail with our storms.  Storms are expected to die down around 1am, but rain will linger afterwards.

We have an active storm pattern set up for this week, with a pool of hot and humid air sitting in the plains and a strong upper-level ridging in the jet stream.  These two things combined will allow for strong low pressure systems to develop out in the plains, which will allow for a strong inflow of heat and humidity to move through our area.  Along with that, the strong inflow will be continuous and last for most of the week.  This strong heat and moisture inflow will allow thunderstorms to develop easily, and also increase the chance for strong to severe thunderstorms with that upper level ridge in place.  Stronger thunderstorms are expected after Tuesday evening, but weaker thunderstorms will be expected for the weekend as the jet stream will return to a more zonal flow, pushing the low out of our area.

With this heat inflow, temperatures will get into the upper 80°s to low 90°s, with dew point temperatures looking to be in the mid 70°s.  This will allow for heat index values to be around 100°, so take precaution if you plan on going outside from Wednesday to Saturday.

Temperatures will cool down a little to start next week, with a chance for rain on Monday.

Ring of Fire Pattern Sets up this Week

This week we're talking 'The Ring of Fire'...and no we don't mean the tune by Johnny Cash.
This is a type of upper level pattern that means building heat and stormy weather.

A ridging pattern allows heat to build, sometimes referred to as a 'heat dome' builds across a certain area in the county. For this week it will build through central portions of the Country. On the edge of the high pressure or 'dome of heat' little vorticities or waves of energy ridge along it. That brings scattered storms chances over multiple days along that 'ring' or outer edge heat. This week, that pattern will set up across portions of the Midwest and Great Lakes region.

Because our jet winds will be parallel to a stationary boundary, this will also help to focus potentially the heaviest rain across portions of the Stateline. We really need to keep an eye out for where this front stalls, because it could shift the axis of heaviest rain. If the front stalls to the north, that would shift the heaviest rain north, and same would go if the front shifted to the south.

Right now rain totals between Tuesday night and Sunday have the potential to add up between 1-4" with the higher totals lining up over southern Wisconsin and northeast Iowa. Make sure to check back for updates, as the forecast could change going forward.

Sunday, July 16, 2017

Higher Humidities To Return

This weekend was pretty comfortable by mid-July standards with highs in the low 80's and reasonable humidities - if we don't count the storms! 

We will start off this week with glorious weather on Monday - temperatures in the upper 70's and the very important indicator of humidity - the Dew Point - starting in the upper 50's.   As the Dew Point starts to rise into the mid- and upper-60's, our feeling of comfort starts to degrade.   This week, gulf moisture will start to invade our region again and while we will start out comfortable, it will quickly become uncomfortable.  By Wednesday, the Dew Point will move into the 70's and along with temperatures in the upper 80's to low 90's, it will feel like we are in the Tropics!  Along with higher humidities, our chances for rain and thunderstorms will be on the increase as well.  Care should be taken to avoid over-exertion and potential over-heating in this weather.  The air conditioners will be working overtime!

Conditions will improve this weekend with lower Dew Points and moderate temperatures as high pressure approaches from Canada.  Have a great start to your week! 

Saturday, July 15, 2017

Storm Threat Tonight with Tropical Weather Returning Next Week

We've had a nice start to the weekend with sunny skies and temperatures hitting the low 80°s.  However, you'll want to enjoy the nice weather while you can because we are under a Slight risk for severe weather tonight.  Clouds will start to build up around 7pm, but thunderstorms won't start until between 9-10pm when a cold front will move in.

The main threats will be hail and winds, but those threats vary depending on where you are in the Stateline.  The larger-sized hail will stay up in central Wisconsin, but quarter-sized hail, and possibly a little bit larger, is expected in Green, Rock, and Walworth counties where instability will he higher for when the front moves in.  Jo Daviess, Stephenson, Winnebago, Boone, and McHenry counties are only expected to see pea to dime-sized hail.  Counties south of that have a low hail chance.

Strong, straight-line winds are expected mainly for counties along the Stateline. The front will be tracking to the south, but most of these storms will be tracking southeastward, which is why Whiteside, Lee, and the southern portion of Dekalb county have a low wind threat.  However, parts of Carroll and Ogle counties have a chance for seeing some of the strong winds.

The cold front will move into our northern counties between 9-10pm, our central counties around 1am, and our southern counties around 4am.  However, these storms will be weakening as they move through our area as instability will be lower down to the south.  By the time the front reaches our southern counties, the storm chance will be low, but isolated showers are still possible.  The front will move out around 7am, but around that time fog will be possible due to the lingering moisture we'll have on Sunday.

Scattered cloud cover on Sunday, but more sunshine will be seen on Monday before the heat and humidity moves back in on Tuesday.  It'll stay with us for the rest of the week afterwards, and because of that we'll also have a chance for isolated thunderstorms during the week.  However, we'll get a break from the storms on Friday before they return on Saturday.

Temperatures will be in the upper 80°s to low 90°s next week, with dew point temperatures expected to be in the mid 70°s.

Friday, July 14, 2017

Storm Threat Tomorrow with Heat and Humidity Next Week

It's been a cloudy and cooler day as temperatures only hitting the upper 60°s, with only a couple locations hitting the low 70°s.  The reason for the cooler temperatures is a high pressure system to our west, and a low pressure system to our east.  This is creating a channel of cooler air out of the north, but it's also lowering our humidity values.  As this high pressure system moves closer to our area clouds will start to break down, leaving us with partly cloudy skies by around 8pm.  The skies will completely clear during the overnight when the high pressure system reaches our area and because of that, temperatures will be cooler in the upper 50°s.

That high pressure influence stays with us through most of tomorrow, but will begin to track southeast during the afternoon.  This will allow for warm and humid air to flow into our area from the south.  Along with that, that lingering low pressure system to the northeast will bring a cold front through our area during the evening.  The front and the inflow of warm and humid air will allow for thunderstorms to develop, with stronger thunderstorms expected in central Wisconsin where there's a slight risk for severe weather in place.  The front will drift southward during the late-night hours, bringing those thunderstorms to our area, which is why we're under a marginal risk.  However, by the time those storms reach us they will be weaker as our instability won't be as high as it will be in central Wisconsin.  This will only give us the chance for seeing smaller-sized hail with our thunderstorms.

The storms will stick to our counties that are on the Stateline, with only rain expected for our southern counties as temperatures will be cooler by the time the front reaches them, allowing for much lower instability.  The storms and showers are expected to clear up a little after 1am.

We'll end the weekend will cloudy skies as that low pressure influence lingers, but temperatures will still stay fairly cool with winds moving in from the north.  Sunshine expected on Monday when another high pressure system moves in, but another low pressure system moves in on Tuesday, bringing back the heat and humidity, along with thunderstorms for the rest of the week.  Temperatures expected to climb to the upper 80°s to low 90°s.

Rockford's Record Heat

It's been a fairly warm summer so far, we've had eight of our average fifteen 90° days. June was on average 1.7° warmer than it's average, and so far this July is .7° warmer than the monthly average. No 90's in the forecast this weekend, the Stateline is in store for a few very nice days, but there's something for everyone I like to say. Highs this Friday will climb into the mid and upper 70's, mid 80's on Saturday, and low 80's on Sunday.

It will be perfect weather for the many activities and events going on this weekend. But on this day 81 years ago, Rockford recorded its record hottest day. Temperatures on July 14th, 1936 climbed to 112°! Holy smokes that's hot! That is 27° warmer than our average of 85°. That's a big difference from where Stateline temperatures will be today, our highs in the mid and upper 70's are about 5-10° below average.

Not a fan of the 'cooler' temperatures and want more heat? Don't worry we've got a few days at 90° next week! 

Thursday, July 13, 2017

Heat and Humidity Possibly Returning Next Week

The jet stream pattern is changing once again next week with another ridge of high pressure developing over the center of the country.  This would place the strongest winds within the jet stream very close to the Stateline beginning next Tuesday.

Low pressure will develop over the central Plains early next week.  This will allow a warm front to develop and lift closer to the Stateline beginning Monday night.  Following the front will be a very hot and humid air mass.  If the front stalls near northern Illinois and southern Wisconsin, showers and thunderstorms will be likely holding temperatures down Wednesday and Thursday.  The threat for heavy rainfall would also be high due to the amount of increasing moisture in the atmosphere.  If, however, the front slips further north highs will easily warm into the low 90's beginning Wednesday.  It doesn't look like the heat would last as a little cool down arrives late in the week and for next weekend.

Weekend Weather Looks Decent for Any Outdoor Activities

There are many activities taking place this weekend in the Stateline, with ByronFest being one of them.  No matter what your plans are for the weekend, the weather looks like it should cooperate.  The only day where a shower/storm may pop up would be Sunday, and that chance looks to be a little further south in the afternoon and evening.

So, get out and enjoy because it looks like the heat may possibly be returning by the end of next week.

Still A Little Muggy Thursday, but Comfortable Friday

Despite a cold front passing through southern Wisconsin and northern Illinois Thursday morning, the afternoon still felt a little muggy.  That's because the dry air is lagging behind the cold front.  Dew point temperatures this morning were near 70 degrees!  They've come down a little and are currently in the mid 60's.  By tonight dew point temperatures will have fallen into the low 60's, and then into the upper 50's by Friday morning.

Dew point temperature is a direct measurement of how much moisture is in the atmosphere.  The higher the dew point temperature is above 65 degrees, the more humid it feels.  Friday afternoon should feel a lot more comfortable with temperatures expected to sit right around 80 degrees.  Saturday will start to feel a little warmer just because moisture will be pulled in from the west ahead of a cold front.

Weekend Outlook

Its been a very active week to say the least with multiple rounds of heavy rain and storms battering northern Illinois and southern Wisconsin. Thursday turns the page into a  bit more of a quiet pattern, though there is a small chance for a passing afternoon shower. Still expect Thursday to be a bit muggy feeling, but it will feel better through the weekend. A cold front passing south this morning will help to filter in cooler and drier air. A few clouds will be sticking around through Friday, high pressure arrives and we will get a little sunshine into Saturday.

Low pressure will develop near the Rockies and will move east, it's cold front will allow for storms to develop in Wisconsin Saturday afternoon. These could be on the strong to severe side with a slight risk for severe storms in Wisconsin. A low end Marginal risk will be in place for the Stateline Saturday evening as those storms sink south. A few of those storms will linger into Sunday morning but will be out of here quickly. Temperatures fall into the low 80's behind that front on Sunday. Overall the storm threat shouldn't impact any plans through the weekend with temperatures hoovering near average.

Wednesday, July 12, 2017

Storm Threat Wednesday Evening

11:50pm Update: Showers continue over northern Illinois with a band of more moderate rainfall occurring just south of the immediate area.  This is where the heavy rain threat is currently focused.  The cold front is moving through Wisconsin now, but has had very little activity fire up along the front.  Scattered showers and thunderstorms may still continue as the front comes through, but the severe threat is very low.  Still some heavier downpours with the stronger storms, but overall a much more quiet night than Tuesday night.

Thunderstorms over northern Illinois are currently below severe limits, but are producing moderate to heavy rainfall.  Stronger thunderstorms are lining up just south of the immediate viewing area, however storms are slowly beginning to build back west over Stephenson County and if this trend continues into the night, flooding would become a concern.

A Flash Flood Watch remains in effect for Winnebago, Boone, McHenry, Ogle, Lee, DeKalb and Whiteside counties through Thursday.

Atmospheric Pattern Continues to Favor Heavy Rainfall

As mentioned earlier, a Flash Flood Watch will go into effect at 9pm for Winnebago, Boone, McHenry, Ogle, Lee, DeKalb and Whiteside counties.  It's appears as if the flooding potential may be a bit further south than where it was located late Tuesday night.  Which will be good news for those who are suffering from the significant flooding.

Thunderstorms are beginning to develop over Wisconsin and central/eastern Iowa this evening.  A few thunderstorms have reached severe limits, with a couple reports of very heavy rain near Cedar Rapids, IA.  These storms will continue to move east, but will then shift southeast as a cold front moves through Wisconsin.

As the front begins to shift south it will turn more parallel with the winds that are moving above in the atmosphere.  This type of set up is ideal for 'training' thunderstorms and typically is the cause of heavy rain events.  Like Tuesday night, it won't be a widespread event but for locations that do receive thunderstorms, rainfall rates of nearly one inch per hour are possible.  Right now, that highest risk looks to be over west-central Illinois and for some of our southern counties - Whiteside, Lee, Ogle and DeKalb.

The amount of moisture that is present in the atmosphere is significant this evening.  The image on the left is a current analysis of our precipitable water - or how much moisture the atmosphere is currently capable of holding.  Precipitable water values near two inches are found over west-central and central Illinois.  This is an extremely high amount of moisture and means that any thunderstorms that move through that area will be very efficient at producing heavy, possibly significant, rainfall. 

Thunderstorm coverage should begin to increase towards 9pm/10pm over western/northwestern Illinois.  It's important to remember that not everyone will experience heavy rain producing thunderstorms.  But those that do could see high rainfall rates.  So be prepared.

Flash Flood Watch Issued for Northern Illinois

A Flash Flood Watch has been issued for Winnebago, Boone, McHenry, Ogle, Lee, DeKalb and Whiteside counties this evening.  Storms that developed late Tuesday night and early Wednesday morning produced quite a bit of rainfall.  Highest rain amounts were seen over northeast Illinois, southeast Wisconsin and far northeast Iowa.

An incoming cold front has caused thunderstorms to develop from Wisconsin, back down through central Iowa.  These storms are moving east and will eventually turn southeast towards southern Wisconsin by sunset.  Rainfall rates in some of the stronger thunderstorms could be near one inch per hour.

More on the heavy rain threat coming in a later post.

Wednesday Morning Storms

Strong storms over NE Carroll Co moving east at 30 mph. Watch for half dollar sized hail and wind gusts near 40mph.

Flash Flood Warnings continue for McHenry county through 2:00pm and 2:45pm. Heavy rain/strong storms possible later today

10:45am update:

Heavy rain and lightning now moving into Freeport, Pearl City, Stockton, and Lanark

7:15am Update

Cloud tops in Severe Warned storm over McHenry co has cloud tops at 50,000ft! Half dollar sized hail and wind gusts near 60mph. 

Severe storm is moving east at 30 mph and the severe thunderstorm warning goes until 8:15am.

6:30am update
Strong storms have been marching east - bringing torrential rain, small hail and even wind gusts near 40mph this morning. This is over areas where there have been already very heavy rain from storms late last night. The Flash Flood Warning continues for McHenry County through the morning.

A strong storm is currently over Janesville this morning with wind gusts near 40mph possible and even large hail.