Weekend Wows and 1 Worry

A refreshing change of air masses is underway as drier air spills in from the north.  A cold front which sparked a few isolated but drenching thunderstorms yesterday has swept away the tropical humidity levels of the past few days, and the last vestiges of cloud cover behind the system are moving south of the city this afternoon.  That sets the table for a delightful buffet of sunshine and seasonably warm days for the next few days.  However, the extended holiday weekend may not be completely dry.  A new cold front will be moving through the Midwest late Sunday and Monday and is likely to spark a few thundershowers here.  A few days ago, it appeared as though the rain would hold off until late Monday night.  Now I like a faster solution which presents an interesting possibility.  Our in-house MicroCast computer model brings the front through around daybreak Monday.  That would have the following consequences: 1) T'showers would be coming in at a time of day when they would be in a weakening state  2) Any showers that DO occur would likely be in and out of here before picnics, parades, and parties.  3) Monday's temperatures will be cooler than Saturday and Sunday, but still very pleasant.  We are still about 85-90 hours away from all of this and timing can certainly change.  But at worst, we're looking at an hour or two of rainfall in an otherwise spectacular extended weekend.

Mike

To storm, or not to storm

That is the question for today anyway.  The strength of this week's mini heatwave is beyond its peak as a weak cold front slips into Chicagoland.  Highs away from the lake will reach into the 80s again today, but the near-90-degree readings are over.  With the approach of the front, there should be some enough lift to create a few thunderstorms this afternoon.  The westward lake breeze front might aid in what's called surface convergence to enhance the storm potential.  Think of convergence as two streams of air blowing into each other on the ground.  Since the air can't go down, it's forced up.  Upward motion in the presence of ample moisture is one of the keys to shower and thunderstorm development.  So I'll be watching the radar for signs of rapid storm development this afternoon.  As for the upcoming holiday weekend, it looks almost perfect.  Today at 4, I'll expand on the "almost" part of that forecast!

Mike

An early 90 coming?

Am I the only one who finds it odd that here we are in the middle of a July-like heatwave, and our team is still playing ice hockey!  Yesterday as the mighty Blackhawks were sweeping up the suddenly hapless Sharks, the mercury soared to 89... our hottest blast since last August.  Today should be even hotter, especially away from the lakefront.  A strong ridge of high pressure is sitting over the area and has allowed temperatures to climb.  In fact, this morning's low for the day, 70, will break the record high minimu for the day assuming we don't fall below 70 before midnight. With all of this heat and the high dew points in place, the atmosphere has plenty of CAPE... which stands for Convective Available Potential Energy.  In a high CAPE environment, storms are often possible.  But there are negating factors in place as well. One is a pronounced cap... or wayer of warm air aloft which inhibits air from rising into thunderstorms.  That cap could be broken if we had a lifting mechanism such as a front to force the air past the cap and into a colder environment.  While a pop-up storm will be possible today and tomorrow, I think most areas will remain rain-free for most if not all of the week ahead.

Mike

Showers today, summer heat coming

Last night and this morning, a general 1/3rd of an inch of rain fell over most of Chicagoland.  In its wake, a murky, humid airmass is in place with areas of fog.  There will be holes in that pall of grey, allowing the sun to break through.  At the same time, a few thunderstorms may pop up due to the surface heating.  The most numerous t'showers as of this writing (11am) are in NW Indiana.  Drenching rainfall, frequent lightning and perhaps gusty winds will be possible in some of the stronger cells this afternoon.

Starting tomorrow, all signs point to the major warmup which has been long advertised here on ABC-7. Highs tomorrow will be close to 80, but on Sunday and Monday they will be closer to 90!  Enjoy the early taste of summer!

Mike

Welcome changes

The sun is out, and the mercury is climbing!  After the recent string of mainly cloudy and cool days here, it's nice to have some warmth in the forecast.  Temperatures are firmly in the 70s today and should be in that ballpark tomorrow. A storm system is targeting Chicagoland for showers and some thunder tomorrow night into Friday, but beyond that, the warmest weather since August 16th is on the way.  Mid 80s will be likely on Sunday.  I've been forecasting 85 all week, but computer guidance hints at 88.  The past two weekends have been cold to only cool.  This weekend will be a vast thermal uptick...welcome to most Summer-hungry Chicagoans.

Mike

Murky Monday

Clouds dominate the sky this Monday but warmer and sunnier days lie ahead!  We are on the northern fringe of an area of rain passing to our south.  The bulk of any measurable rainfall will be found south of Chicago today, but sprinkles could fall anywhere.  Wrap around precipitation from the departing low will back into Chicagoland tomorrow morning, then the rain and clouds will move away.  The normal high this time of year is 70.  We will be well below that today and tomorrow, but from Wednesday on, the mercury will be rising. 80s are very likely this weekend, and it appears as though a solid week at least of above-normal warmth is on the way.

Mike

Flooding to Severe Storms?

Many streets, yards and basements are under water early this afternoon.  Overnight rainfall was hefty, especially in the northern burbs where 3" totals were not uncommon. Farther south, the rainfall has been significantly less, generally around 1/2" south of I-80. But we're not done with the storms.  A warm front which was parked in Central Illinois early this morning is surging northward, and will soon place us in the warm sector of a powerful storm system.  Dew points will be climbing well into the 60s as the mercury soars into the 70s.  That combination coupled with the lift provided by the frontal system will trigger new storm development.  The Storm Prediction Center has placed most of the Chicago area under the slight risk for severe weather this afternoon, and I would not be surprised if a Severe Thunderstorm Watch were issued later today. 

Mike

Rains outbound... next system inbound.

A solid soaking for Chicagoland with many areas picking up an inch of rain is ending as of the noon hour.  A few spotty sprinkles might fall from a mostly overcast sky this afternoon, but nothing of consequence.  That will set the stage for about 30 hours of dry weather before the next system spawns showers and thunderstorms here starting tomorrow night.  Temperatures today and tomorrow will be well below seasonal normals, topping out in the 50s in most areas.  My colleague Phil Schwarz is putting together a recap of yesterday's devastating tornado outbreak in Oklahoma which left at least 5 people dead.  There was some terrific video taken of those twisters including a spectacular multiple-vortex tornado which is the best example of its kind I've ever seen.  That story will lead our 4pm newscast so be sure to catch his summary and that awesome video.

Mike

Different Week... Same Story

This is supposed to be another wet week here in Chicago.  Two storm systems are targeting the area with potentially heavy rainfall.  The first arrives late tonight and tomorrow morning.  Computer projections range from 2/3" to 1.5" of rainfall with this initial round of precipitation.  I do wonder whether those amounts are once again overdone, as they have been all Spring.  A major severe weather outbreak will be ongoing tonight in the Southern Plains.  It's not unreasonable to envision those 10-mile-high storms serving as a blockade to gulf moisture which might otherwise feed the showers and storms here.  The next storm arrives Wednesday into Thursday.  It too is progged to be a bountiful rain producer.  In fact, the National Weather Service is justly alerting all of us to the possibility of 2.5" to 3.5" of rainfall before Friday.  Do I believe we will actually get that much rainfall?  No.  But I do admit it's all there on the computer models once again, and there's no question that it WILL indeed rain several times this week.

Mike

Less than touted

As I opined here yesterday (and really almost all spring) another mega-blockbuster rain event was supposed to inundate Chicagoland... and it didn't. Now don't get me wrong.  It rained. It thundered. It even hailed in Will and Kankakee Counties.  Few would question that it was a wet morning... just as expected.  But consider what was being heralded by the point-and-click forecasts, including our own in house MicroCast model.  The computer projections were cranking out 1" to 2.5" rainfall amounts for the entire area just yesterday.  Well, that didn't happen. What we did get is a solid .5 to .8" rainfall, with a few spots maxing out at just more than 1".  So let's say we got HALF of what was touted.  For the balance of the day, a few more showers may develop, especially in Indiana where stronger storm are even possible.  I think the severe weather threat is much higher east of say Michigan City and Rensselaer.  As for the weekend, tomorrow will be flat-out cold for this time of year.  A few instability showers may pepper the area as well. Then the stage is set for frost tomorrow night into Mother's day morning.  I'll take a stab at the lows on the 4pm show.

Mike