Damaging wind gusts possible Wednesday evening and overnight

While record warmth will occur Wednesday afternoon, the warm up comes with a lot of wind!  A HIGH WIND WARNING has been issued for Stephenson, Jo Daviess, Carroll and Whiteside counties and a HIGH WIND WATCH for Winnebago, Boone, McHenry, Ogle, Lee and DeKalb counties in northern Illinois, as well as for Green, Rock and Walworth counties in southern Wisconsin.  The watch and warning begins Wednesday late afternoon and will last through 6am Thursday.

A rapidly deepening area of low pressure will quickly move out of the Rockies Wednesday, lifting through Nebraska and into northwest Iowa by Wednesday evening.  The quick intensification of the low Wednesday evening, combined with a very strong jet stream aloft, will cause wind speeds to increase through the evening and early overnight.

Not only are the winds in the jet stream going to be racing in over 100 mph across the Plains, but winds in the lower levels of the atmosphere will also be very strong, especially Wednesday evening and early overnight (through Midnight).

Peak wind gusts of 50-60 mph will be possible through Wednesday night before subsiding some Thursday morning.  Difficult driving conditions, especially for high profile vehicles (in all road directions), sporadic power outages, unsecured outdoor objects flying around, downed tree limbs/branches, as well as possible damage to siding and roof shingles, are all possible Wednesday!

Record high temperatures Wednesday; Possible Thursday

 An unseasonably warm air mass is about to move across much of the middle of the country, bringing temperatures into the 50s once again Tuesday, and then mid and upper 60s Wednesday afternoon and evening.  The official forecast high for Wednesday is 66 degrees, which would break the previous record  high for the 15th of December which is 58 degrees set back in 1971.  While the warmth moves in for Wednesday, it won't be a sun-filled afternoon.  Skies will most likely remain mostly cloudy due to the quick increase in moisture, and periodic rain showers will be likely during the morning and afternoon.

The rise in moisture will also push dew point temperatures into the 50s during the afternoon which may actually make it feel a little muggy during the day.  Thursday's record high is also in jeopardy as temperatures just after Midnight will most likely still sit right around 60 degrees.  Unfortunately the afternoon will feel anything but warm, with temperatures quickly falling into the 40s by sunrise, and remaining in the 40s through the afternoon.

Southwest winds increase Wednesday afternoon gusting 30-35 mph and then increasing to near 50 mph Wednesday night as the low level jet significantly increases ahead of a deepening low pressure system.

A High Wind Watch has been issued for Jo Daviess County beginning Wednesday afternoon, stretching all the way through the Plains.  While nothing has been issued further east, I would not be surprised if at least a Wind Advisory ends up being instead for the rest of northern Illinois and southern Wisconsin.  The strong winds will carry over into early Thursday, but slowly begin to relax by Thursday afternoon.  Colder air will arrive Thursday on the heels of the gusty northwest wind.

Heavy Rain/Isolated T-Storms Possible Friday Evening, Transition to Snow Likely By Saturday Morning

Rainy Afternoon:

As we've been hinting at all week long, this active stretch of weather will conclude with the strongest system of the bunch, bringing the Stateline a mixed bag of everything. A glace at the early morning surface analysis shows this upcoming storm system is still in it's developing stages as it prepares to slide off the Rocky Mountains.

It's expected to move across the Midwest, landing in the western Great Lakes by the later half of our Friday. Ahead of this storm system, the associated warm front will help bring a surge of moisture into the region by this afternoon, resulting in our first rain chances by 2-3PM. With a little instability present in our atmosphere, a few isolated thunderstorms cannot be ruled out. Severe weather is unlikely for us, but a few rumbles of thunder and lightning will be possible.

Snow Showers Saturday:

Guidance shows this potent area of low-pressure sliding into the region overnight. Strong winds on the backside of the cold front will help usher in a much cooler air-mass, cooling temperatures down into the low 30s by Saturday morning. This will help transition our overnight rain chances to wind-driven snow showers by sunrise. 

Turning our attention to the winds, the National Weather Service has placed two of our counties, Dekalb and McHenry counties, under a Wind Advisory earlier this morning. This advisory runs from 3AM to 3PM Saturday as winds (especially during the morning hours) could range anywhere from 40-50 mph. As far as snowfall accumulations are concerned, most of what we see will be confined to grassy surfaces and should be quick to melt.

Weekend Outlook:

Once this storm system makes it's way into the Great Lakes, skies will gradually clear during the afternoon with highs only peaking out in the mid to upper 30s. Similar to past cool-downs, this one will be very short-lived as a southwest breeze pushing temperatures into the mid to upper 40s by Sunday afternoon. The warmer times will continue after that as highs will peak in the low 50s both Monday and Tuesday with 60s looking more than likely for Wednesday. The bigger question at hand, will it be record warmth. As of right now, the answer is yes considering that our record high for December 15th is 58° (1971). 

Wind-whipped snow showers likely Saturday

 

Clearing skies will take us into Thursday evening allowing temperatures to fall into the upper 20s early Friday.  As a quick as one system moves out, another one is hot on its tail and expected to move across the Plains, Midwest and Great Lakes during the afternoon and evening Friday.  For us, this will primarily be a rain-maker during the day Friday but as colder air wraps in around the low early Saturday, snow showers are likely through the first half of the day.

Cloud cover returns during the morning Friday as warm air arrives following a warm front Friday afternoon.  The increase in moisture will allow the cloud cover to thicken up during the day, but dry air leading into the start of the evening will keep much of the morning and early afternoon dry.  Rain showers will increase in coverage by the afternoon, most likely after 2pm/3pm, and continue into the evening.

The rain may be heavy at times, especially by the evening, as the low level jet increases through the night.  A rumble of thunder or two is not completely out of the question, especially for locations to the south and southeast.  The risk for severe weather remains well to the south - stretching from near Houston, TX all the way up to northern Indiana.  Parts of east-central Illinois could experience a strong/severe storm or two during the evening.

The track of the low takes it right over (or at least very close to) northern Illinois and southern Wisconsin Friday night.  As the low passes early Saturday a cold front will help to usher in a colder air mass, switching over any rain showers to snow showers.

A significant winter storm is set to take shape from the Rockies all the way through the U.P. of Michigan, where parts of Wisconsin could see up to nearly a foot of snow Friday!

For us, only light snow showers and flurries are expected Saturday with minor accumulations of a dusting possible on grassy surfaces.  Northwest winds will be rather strong

Light Snow/Mix Early Thursday, Rain Chances Return by Friday Afternoon

Morning Wintry Mix:

Although it was a rather chilly day across the region, yesterday's sunshine gave us a much-needed break from this active stretch of weather. Highs under mostly sunny skies reached the low 30s, which lands only a few degrees below average. Now, I wish I could say that Wednesday's beautiful sunshine will be carrying on into our Thursday. 

However, that's far from the truth as our weather pattern shifts to a more active state for the remainder of the work week. Guidance shows the first of two systems is scheduled to arrive today. With today's weak disturbance comes the potential for scattered light snow showers, mainly during the morning hours. Rain may mix in a times, especially once temperatures climb above freezing. Our chances look to come to an end quickly, leaving us with a mostly cloudy sky for the afternoon. 

Friday's Storm System:

Cloud cover will linger into the early stages of our Friday, with temps falling on either side of the 30-degree mark. A trough coming off the Rocky Mountain will bring us the second and stronger system of the two, resulting in rain chances by the early afternoon hours. Tomorrow's activity will be widely scattered and most, if not all of the Stateline will get in on these rain chances. 

Once the cold front slides through, temperatures are expected to dip below the freezing mark by early Saturday morning. This will bring the potential for a mix of light rain and snow before chances come to an end before mid-day. Skies will then slowly clear into the afternoon, with highs topping out in the 30s. The cool-down that follows Friday's storm system will be very short-lived as temperatures will rebound quickly, becoming unseasonably warm by early next week.

Feeling More Like October:

Guidance shows the jet stream taking a trip to our north, allowing a much warmer air-mass to filter into the Midwest and the Great Lakes. Instead of feeling like mid-December, we'll feel more like mid-October as highs jump into the 50s both Monday and Tuesday, with the potential for 60-degree weather come Wednesday. 

In case you were wondering, Rockford on average sees three days with highs of 60 degrees or higher during the month of December. It'll be important to monitor how models trend with temperatures over the next few days as the warmth may continue into the second half of next week.

Sunshine Returns Today, Pattern Turns More Active for Thursday and Friday

It's Been Awhile:

Winter was in full force on Tuesday. With a low of 9-degrees and a high of just 24-degrees, Tuesday not became the coldest day of the season thus far, and the coldest day in nearly 10 months. Similar to the many cold snaps we've experienced during the fall season, this one will also be short-lived. 

Wednesday begins on a cloudy note, with sunshine quickly returning by the mid-day hours. Highs will jump from the low 20s Tuesday to the low 30s, which is still considered seasonably chilly for the December 8th time-frame. Tonight begins with a few passing clouds, with clouds and our surface winds increasing into the early stages of Thursday. This is all in response to our next weak disturbance that will bring a brief round of precipitation to the area. 

Active Pattern Returns:

Guidance shows a scattered mix of light rain and snow sliding in shortly before sunrise. Chances then look to continue into the mid to late morning hours, with mostly cloudy skies being left behind for the afternoon hours. Despite the cloud cover, a decent southerly breeze will allow highs to surge even further. By Thursday afternoon, temperatures will top out in the low to mid 40s.

Friday's System:

A second and stronger storm system will quickly develop behind Thursday's weak disturbance, taking aim at the region for the late-day hours on Friday. Forecast models continue to show this low sweeping across the central plains, sliding south of the Stateline Friday night into Saturday. What starts off as a light mix of rain and snow will quickly transition to rain by Friday afternoon.

Winds will remain out of the south, which will allow temperatures to jump into the mid to possibly upper 40s. Early Saturday morning, a cold front is expected to pass on through, bringing a quick round of cold air from the northwest. 

This will allow for a quick transition to light snow before chances come to an end by mid-late morning. Highs will fall a couple of degrees with most landing in the mid to upper 30s. Ridging aloft is expected to slide in behind Friday's strong system, allowing an upward trend in our temperatures into next week. Sunday and Monday will feature highs in the mid to upper 50s, with 50s in the works for next Tuesday. In other words, the ups and downs continue as we enter the third week of December.

Frigidly Cold Tuesday, Slight Improvements in the Temperature Department on the Way

Coldest Day of the Season:

Northern Illinois and Southern Wisconsin spent a majority of  the morning hours on Monday under a Wind Advisory And for good reason as most of our regional airports registered a peak wind gust between 40 to 50 mph. With that being said, Monday's blustery conditions allowed the COLDEST air of the season thus far to usher in from the north. 

Temperatures early Tuesday morning are sitting in the single-digits, with wind chills registering on either side of the 0-degree mark. This frigidly cold morning is a sign for things to come as highs this afternoon will struggle to climb out of the twenties.

Clouds thicken up early in response to our next system that glides in from the west. This system was poised at one point to bring the Stateline it's first  accumulating snowfall of the season. However, with models trending downward in the storm system's intensity, that's not the case anymore. With that being said, a few flurries and snow showers will be possible into the evening hours. Highs for most look to top out in the low to mid 20s, a mere 10°-20° degrees cooler than where we typically are at this point in December.

Midweek Outlook:

Cloud cover is expected to stick around overnight, resulting in a very slow temperature drop into Wednesday morning. The day starts off in the low 20s, with highs climbing back into the mid 30s by the afternoon. This is all thanks to a little mixed sunshine and a warmer wind out of the west and southwest. Much more significant warming follows as the week draws to a close. Temperatures head back well into the 40s Thursday, despite there being a chance for a light rain or snow shower.