Monday, July 24, 2017

River Updates - Rain Totals

The effects of Friday's heavy rain and severe storms are still being felt this morning. There are multiple Flood Warnings in place for both northern Illinois and southern Wisconsin.

Back building storms dumped the most amout of rain over western Stephenson county and Jo Daviess county. In this area, roughly 6-8" of rain fell, while just south of that area 4-6" was recorded. Most of Winnebago and Boone received 2-4" and thankfully McHenry and Walworth counties received the least amount of rain, after the experienced quite a bit of flooding from storms in early July.

Here is a graphic made by the NWS that shows rain totals across northern Illinois over a 72-hour period of time: (you can click on the image to make it bigger).

Heavy rain caused quite a bit of flooding in the Stateline, from Pearl City to Freeport, to portions of Rockford due to swollen rivers. To find out about current river level conditions across the area, click here.
 All you have to do once you are on the page is move your cursor over the river level you want to examine. The different color dots corresponds to the stage of flooding the river is at currently, at the position.

Sunday, July 23, 2017

Brief Break from the Humidity - Returns by the Middle of the Week

Dew point temperatures have been slow to come down Sunday afternoon.  The high moisture and incoming cold front prompted a few thunderstorms, some of which turned severe, to develop Sunday afternoon and early evening.  Most of those storms have now moved out of the immediate area, with skies remaining partly to mostly cloudy through the evening.

Drier air (lower dew points) will follow the front late Sunday night and throughout the day on Monday.  This will help wipe out the high humidity that we've had for the past week.  Unfortunately the break doesn't last too long, because an incoming cold front will shift winds back around to the south late Tuesday night.  This will help draw in quite a bit of moisture into the Midwest during the day on Wednesday and Thursday.

An incoming cold front Wednesday afternoon will likely trigger strong to severe thunderstorms over parts of Minnesota, Wisconsin and northern Iowa.  As the cold front sinks south, the threat for thunderstorms will shift south as well.  The set-up in the atmosphere does not support the repeated rounds of heavy rainfall like we just experienced, however, the high moisture in the atmosphere will support the possibility of thunderstorms to produce quick heavy downpours. 

The good news is the storms will be out by Thursday with drier days leading into the weekend.  The only two days this week with a 'Moderate' Weatherisk are Wednesday and Thursday.  Every other day we've got a 'green' light.

River Levels Crest in Moderate, Close to Major, Flood Stage

Flood Warnings continue for the Rock, Pecatonica and Kishwaukee Rivers with most of the warnings lasting 'Until Further Notice'  There have been a few locations on the Rock and Pecatonica where the river did already crest and will either hold steady at the current level, or begin to gradually come down by the end of the week.  River forecasts suggest that the river levels will remain in flood stage for at least the next 7 days.

It's important to remember to stay away from any area that is experiencing flooding.  Whether that be a river, creek, back yard or stream.  Currents are strong in both rivers and creeks when flooding occurs and this can quickly wash you away if you fall in.  Because of the high river level, debris and fast current the Illinois Department of Natural Resources (IDNR) did close the Rock River 'Until Further Notice' in Winnebago, Ogle, Lee and Whiteside counties.

Below are the current river levels, as of 6pm Sunday evening, and when their expected time is to crest.  Please click here to continue to monitor river levels throughout northern Illinois and southern Wisconsin.

Pecatonica River at Freeport: Did crest just below major flood stage

Pecatonica River at Shirland: Expected to crest at major flood stage early Wednesday

Rock River at Latham Park: Expected to crest at moderate flood stage late Wednesday

Rock River at Rockton: Expected to crest at moderate flood stage late Wednesday

Kishwaukee River at Belvidere: Cresting now in moderate flood stage, expected to go down

Rock River at Byron: Crested Saturday in moderate flood stage

Saturday, July 22, 2017

Cooler and Drier Next Week

We had some light rain linger early this morning, and this didn't help at all with the already flooded areas that we got from the heavy downpours the night before.  Some places had rainfall rates over 1"/hour, which is very high.  Flooding will continue to be a concern going through the weekend and into next week as river levels will begin to crest.  The Pecatonica River in Freeport will crest on Wednesday, and the water levels will be just above major flood stage levels by that time.

Luckily, drier weather is now in place as that low pressure system that brought us the heavy rainfall has begun to move out of our area, causing the cloud cover to decrease.  Clouds will continue to decrease as we head through the overnight, but it'll still be fairly warm and muggy with all the moisture from the rain. 

That low pressure system will linger off to the east tomorrow afternoon, giving us just enough instability to allow for a slight storm chance between 3-4pm.  However, high pressure will begin moving in during the afternoon as well, so more than likely storms won't occur.  Temperatures will manage to hit the upper 80°s with lingering humidity, the reason being that the high won't be close enough to bring in cooler temperatures.

The drier trend for next week will be due to two upper level lows in the Pacific Northwest and the northern Great Lakes.  This will allow for stronger meridional flow in the jet stream to occur over the northern plains, which is where surface lows will form.  This will bring us a storm chance on Wednesday, but that upper low to the northwest will track eastward and push the jet stream further southward.  This will allow for surface lows to stay down in the plains, and the heat and humidity to stay away from us.

Temperatures will cool to the mid to upper 80°s when the high moves in for Monday and Tuesday.  That low, which will develop in the plains due to the upper level ridging, will form on Wednesday and bring us some storms.  The jet will make the southward track on Thursday, and stay that way afterwards through the end of the week.  Temperatures will be in the upper 70°s to end the week.

A Little Cooler Next Week

We've been having thunderstorms move through the Stateline since 4pm Friday, all of which brought heavy rainfall and some strong winds through the Stateline.  There have been multiple reports of trees being down, with radar indicating winds anywhere from 45-60mph.  One storm developed a Bow Echo down in Whiteside county, where radar estimated wind gusts of around 70mph.  This resulted in a barn being blown down, the barn being located 2 miles northeast of Fulton. 

The continuous inflow of heat and humidity is what's fueling these thunderstorms, and it will continue to fuel those storms as we go through the overnight into tomorrow morning.  Luckily, the thunderstorms produced the stronger winds west of the Mississippi River, only producing heavy rain once they crossed over into the Stateline area.  The reason for this was instability and wind shear were much higher out in northeastern Iowa, where our instability and wind shear was much lower, so the storms couldn't stay as strong as they were out in Iowa.

The storms have begun to move more southward since they're trying to feed off the heat and humidity inflow out of the south, so the heavier rainfall will be moving southward and will mostly move through Whiteside county.  Light to moderate rainfall will still be seen across the Stateline going through the overnight into tomorrow morning.  However, any additional rain, whether it's light or heavy rainfall, will still add to the already flooded areas that we've gotten from the heavier, more persistent rainfall.

Flooding will be the main concern going through the overnight and into tomorrow morning.  Tomorrow afternoon will be mostly dry, with a small chance for a thunderstorm late afternoon.  Sunday through Tuesday will be drier with a high pressure influence in place, but it'll still be fairly humid.  Another low moves in mid-week, bringing us showers for Wednesday and Thursday.  We're looking to end the week on a dry note.

Temperatures will stay in the mid 80°s to near 90° for Saturday and Sunday, with dew point temperatures staying around 70°, so we'll keep the heat and humidity for the weekend.  The drier weather on Monday and Tuesday will cool off temperatures, but it'll still be a little humid with dew point temperatures in the mid 60°s.

Friday, July 21, 2017

Severe Weather Friday Evening

(12:35:06 AM) nwsbot: Local Storm Report by NWS DVN: Freeport [Stephenson Co, IL] law enforcement reports FLASH FLOOD at 12:15 AM CDT -- 4 road closures in stephenson county due to flash flooing. highway 20 west closed at dameier road. highway 20 closed at kiever road. highway 20 closed west of galena road to the county line. highway 73 closed at west lousia road

12:15pm Update: Severe Thunderstorm Warning for Jo Daviess, Stephenson and Carroll counties has allowed to expire.  The line of storms have fallen below severe limits, but still could be capable of producing 30 to 50 mph wind gusts.

(12:21:42 AM) nwsbot: Local Storm Report by NWS DVN: Stockton [Jo Daviess Co, IL] co-op observer reports HEAVY RAIN of M5.79 INCH at 12:13 AM CDT -- rainfall since 545 pm...still raining.

Severe Thunderstorm Watch has been extended until 2am for Winnebago, Boone, McHenry, Ogle, Lee and DeKalb counties.

Severe Thunderstorm Watch has been extended until 2am for Stephenson, Jo Daviess, Carroll and Whiteside counties.  Strong winds, hail and extremely heavy rainfall will likely continue into the night. 

Severe Thunderstorm Warning for Jo Daviess, Stephenson and Carroll counties until 12:15am.  60 mph wind gusts and penny sized hail are possible with these storms.  Severe warned storm is currently in northeast Iowa and moving southeast at 40 mph.

Thunderstorms have developed over northeast Iowa and northwest Illinois as the low level jet has started to develop out to the west.   This has caused a line of thunderstorms to develop and remain fairly stationary over Iowa and Illinois.  Ongoing flooding over northwest Illinois will only worsen with the incoming rain.   We've received reports of roads closed in Lena due to flooding as well as in Cedarville due to standing water on several county roads.

(10:15:42 PM) nwsbot: Local Storm Report by NWS DVN: Cedarville [Stephenson Co, IL] law enforcement reports FLASH FLOOD at 09:00 PM CDT -- portions of several county roads barricaded due to high water. time estimated by radar.

(10:28:36 PM) nwsbot: Local Storm Report by NWS DVN: 1 N Lena [Stephenson Co, IL] emergency mngr reports FLASH FLOOD at 09:00 PM CDT -- highway 73 at louisa road closed due to flooding. time estimated by radar.

Heavy rain coming down over northern and southern DeKalb County.  Please remember to NEVER drive through a flooded roadway, especially at night.

Extremely heavy rain coming down from Winnebago, southwest into Carroll County.  Rainfall rates close to an inch and a half per hour are likely.

(8:48:36 PM) nwsbot: Local Storm Report by NWS DVN: SW Stockton [Jo Daviess Co, IL] trained spotter reports HEAVY RAIN of M1.66 INCH at 08:46 PM CDT --

(8:56:23 PM) nwsbot: Local Storm Report by NWS LOT: SSW Ashton [Lee Co, IL] cocorahs reports HEAVY RAIN of M0.67 INCH at 08:28 PM CDT -- 0.67 inches of rain fell in 12 minutes.

Flash Flood Warnings have been issued for Jo Daviess, Stephenson, Winnebago, Boone, McHenry, Ogle, Carroll and Whiteside counties through early Saturday morning.  Significant rainfall has been falling throughout the Stateline with radar estimated totals over two inches. 

Severe Thunderstorm Warning for DeKalb County until 9pm. 

Severe Thunderstorm Warning for Ogle County has been cancelled.  Storm is still capable of producing strong wind gusts

6:30pm Update: Severe Thunderstorm Warning for Ogle County has been issued until 7:15pm.  Storm is located near Ridott and moving southeast at 35 mph.  Wind gusts to 70 mph and quarter sized hail possible.

Flash Flood Warnings have been issued for Ogle, Stephenson and Jo Daviess counties until 1:45am.  Radar estimated rainfall totals of two inches have bee recorded, with additional 1" to 2", possibly 3" per hour. 

A Severe Thunderstorm Warning has been issued for Stephenson County until 7pm.  Storm was located just west of Freeport and moving southeast at 30 mph.  Quarter sized hail will be the biggest threat for storms, but also watching the potential for strong winds just southwest of Freeport.  Remain indoors and away from windows until the storm passes.

A Severe Thunderstorm Watch has been issued for all of northern Illinois and southern Wisconsin until Midnight.  One round of thunderstorms moved through earlier Friday afternoon, with additional thunderstorms expected to move in from the west.  Damaging winds, hail and very heavy rainfall will all be possible.

Friday Night Storm Potential

It's been a hot, humid, and active week....and unfortunately the forecast for Friday will be more of the same.

A few isolated to widely scattered storms will be possible later Friday afternoon, as a stationary boundary lifts through northern Illinois as a warm front. The warm front lifting into southern Wisconsin is in response to a low pressure system strengthening in the Plains. Any storm that develops this afternoon will still have periods of heavy rain that will be possible because of the very muggy air mass. It's a very tropical airmass with dew points that will be climbing into the mid and upper 70's.

The time period we really want to pay attention to is this evening, especially after midnight. Storms late today will develop west in Minnesota and will head southeast this evening. Storms will form into an MCS type system which is essentially a cluster of storms which can produce heavy rain and strong straight line winds.

One forecast update from Thursday, is that the axis of heaviest rain has been shifted slightly north. This is good news for the Stateline, which has already been hit with an abundance of heavy rain. The Stateline area isn't out of the woods though just yet, 1-2" of rain is still possible across far northern Illinois, and 2-4" is more likely through southern Wisconsin.

This could pose big problems for those planning to head out to Country Thunder in Twin Lakes Wisconsin. If you are camping overnight Friday, make sure to have multiple ways to receive any watches and warnings should we have them.

There is still an enhanced risk for strong to severe storms across far northwest Illinois and southwest Wisconsin, while the rest of the area will be under a slight risk.

The biggest threats will be strong winds and very heavy rain with the possibility of flash flooding.

Make sure to check back for more forecast updates through the day and into the weekend.