HEAT AND HUMIDITY FOLLOWED BY SOME HEFTY STORMS

This afternoon's temperature is expected to top ninety degrees making it the 19th time this summer we have seen temperatures at or above 90°. In addition, the humidity will be quite high making it feel like it's close to 100°.

   A disturbance traveling along an approaching cold front will bring us some thunderstorms tonight and there is the possibilty of some localized flooding. The good news is that the weather has been pretty dry the last several weeks with only 1.32" of rain this month which is not even half of what we normally see by this date. The ground should be able to absorb a lot of the rain that falls but with several inches possible flooding is still a possibility.

 Things should settle down by tomorrow afternoon and Sunday looks sensational. After a warm weekend the weather will turn hotter again early next week before we see a nice cooling trend beginning Wednesday.

  Phil

Heat and humidity to return

Skies range from clear to cloudy as of 2pm in Chicagoland. The last vestiges of last night's sprinkle maker have left just enough moisture to produce a patch of cloud cover covering about 1/4 of the area at any given time.  Highs have rebounded back into familiar territory, crossing the 80-degree mark for the 47 time in the past 48 days.  We'll have no problem extending that streak for the next 7 days, as near-90-degree readings return over the next few days. This afternoon, a cold front stretches across the Upper Midwest and will spark strong to severe thunderstorms in Minnesota.  That front is southbound, and its proximity to the Cheddar Curtain may lead to storms late tomorrow in the far northern suburbs.  At this time, I expect the vast majority of the activity to remain in Wisconsin, however.  Friday brings a greater chance of storms, especially at night.  A Pacific cold front will move into the region triggering a few showers and storms.  The air behind that front will not be much cooler, so weekend temperatures will remain well into the 80s.  There are some signs of a brief intrusion of bona fide "cool" air for the end of next week.  Nationally, I'll be showing some amazing dust storm video from Arizona and we'll talk about the deluge that has hit parts of the lower Mississippi Valley due to the remnants of a weak tropical depression.

Mike

Record "hot" streak

Yesterday marked the 46th straight day of 80-degree+ temperatures in Chicago, and as fate would have it, that is the longest we've ever gone.  In fact, the 2nd-longest streak was only 42 days, ending August 7, 1955. I'll have more on the streak beginning on the 4pm show this afternoon.  Today's question is whether the streak ends right here.  An earlier-than-expected cloud deck is putting a lid on the mercury rise this afternoon, and as of 1pm, the high has only been 77.  Rainfall is also a few hours early, falling mainly south and west of the city as of early afternoon.  Light showers will be possible tonight as well.  Amounts should be mostly under .25".  After this disturbance passes by, tomorrow should dry out, then it's back to the heat and humidity for the rest of the work week and possibly into the weekend as well.  What had looked like a weekend cooldown looks anything but now, so check out my forecast this evening for the latest reasoning.

Mike

Say "AHHHHHH."

The day isn't over yet, but there is a slight chance we will not hit 80 degrees today or tomorrow. That would make it the first such thermal occurrence since July 1st!  Whatever the final mercury tally is, there's no mistaking the delightful change in air mass behind this weekend's cold front. Dew points which were pegged in the low 70s for the past week+ have tanked into the upper 40s, giving the air a much more autumnal feel from a moisture standpoint.  Conditions should feel similar tomorrow, although by evening, some clouds may invade the sky, heralding the arrival of a mid-level disturbance which could bring a few showers by Wednesday morning.  Moisture will be on the increase ahead of that feature and as we slip on the west side of the same high pressure system bringing us the relief, temperatures and dew points will be on the rise into the end of the week.  This should be a transient return to the muggy stuff however, as a more progressive pattern should drive another cold front through Chicagoland Saturday morning.  I'll offer some refinement to the timing of possible showers and thunderstorms with both features starting this afternoon at 4.

Mike

Though an excessive heat warning has been issued for Cook County this heat wave will not set any records. Highs will be in the lower 90s with heat indices around 100° While this is certainly hot it's nowhere near the killer heat wave of 1995 when the heat index hit an unbelievable 127°! The problem with this spell of hot weather is its longevity. While the max heat index will barely top 100° the overnight heat index will stay above 75°. The cumulative effect of the heat on the body can sneak up on you so make sure to take it easy especially during the afternoon. Don't forget to check on the elderly espcially those living in a home without air conditioning.
Cooler and drier air will start to return on Sunday so there is some relief on the way.

More heat and Humidity

We have now seen 36 days in a row with temperatures reaching at least 80 degrees. Last summer our longest stretch of consecutive days above 80° was only 12. We have more heat and humidity heading our way for the foreseeable future with the mercury flirting with 90° through Wednesday. A very weak frontal boundary to our north could trigger a few thunderstorms anytime from Monday into Thursday but much of the time will be dry.

 This weak front could slide south of our area on Tuesday allowing for a lake breeze to develop and bringing some temporary relief form the heat. Though temperatures will be above average this week it will remain below the thresholds for a heat watch or warning.

   Phil

Hot weather returns

After a couple of days of relatively mild weather, hot and humid conditions are about to make a comeback.  Fog greeted many of us this morning, especially in the Fox Valley where visibilities were down to virtually nothing.  That fog has since mixed out (fog doesn't "burn" off) affording partly to mostly sunny skies.  There is a fair amount of haze in the air, so it will look somewhat murky as temperatures away from the lake push into the mid 80s.  Tomorrow may begin foggy as well, but as a ridge of high pressure exerts its power, the mercury will climb to 90.  Tuesday should be just as warm, even though a cold front will be pressing in from the west.  That front will spark scattered storms Tuesday-Wednesday, and if it gets hung up a little farther north than expected, might bring additional rains Thursday.  I'll have the latest on the front's impact on temperatures and precipitation this evening at 5 & 10.

Mike

Funnel clouds today... no, seriously!

They're called "cold air funnels" and while they seldom cause any harm, at least one such cloud caused quite the stir in Kankakee County around lunch today.  As the Bears were holding their first practice of the season in Bourbonnais, wind and humidity conditions were just right to create a funnel cloud.  Several photos have appeared in print (I posted one on my Facebook page, btw) taken between 12:10 and 12:30 over Kankakee, Bradley and Bourbonnais.  Cold air funnels are weaker cousins of true tornadic funnel clouds.  They are almost always higher in the sky, are not associated with thunderstorms, and typically don't touch down.  Sometimes, after a cold frontal passage, there's just enough turning of the atmosphere to generate a rotating motion in a cloud.  If there's enough moisture present, that rotation can appear as a condensation funnel, protruding down from the base of the cloud.  Sirens sounded but nothing ever touched ground.

Mike

Watch in effect

The Storm Prediction Center has placed portions of the ABC-7 viewing area under a Severe Thunderstorm Watch until 7pm this evening.  Generally speaking, the watch covers areas south of I-80. Kendall, Will, Grundy, La Salle, Kankakee, Livingston, Lake, Porter, Newton, Jasper & La Porte Counties are included in the watch.  Gusty winds and brief heavy downpours will be possible in he stronger cells.

Mike

4th place

Thanks to the deluge late Friday into Saturday, July 2010 now ranks as the 4th wettest on record.  8.16" is our current rainfall total at O'Hare, ranking just behind 8.33" in 1982, 8.98" in 1957, and 9.56" in 1889.  I think there at least one more chance to add to the total before month's end.  That comes on what will be the hottest day of the week, Wednesday.  A cold front will trigger scattered storms before ushering in a 10-degree temperature drop for Thursday and Friday.  With ample moisture in place by that time, any storm could produce significant rainfall.  I think first place is safe, but 2nd is in jeopardy!

Mike