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  • Tim McGill

Summer Surging Back Soon

Heat & Humidity On The Rise

8 of the first 12 days of July have been below average. The month is now running just under 3° below average. It has been nearly a week since we hit 80° or more. After feeling like fall summer is set to return soon as heat and humidity build back into the Chicago area.

The HRRR model has our highs today near 80° today. This would be warmer than what we have seen lately but still 5° below average.

As the heat rises the next couple of days so will the humidity. Dew points will climb to near 70° Thursday. Dew points are the preferred measurement of moisture for meteorologists. Dew points will drop again for this upcoming weekend to more comfortable levels. They will settle into the lower 60s by late Friday night and stay there through early next week.

Highs tomorrow should be nearly 10° warmer as we top out near 90°. Dew points stay moderately high through Wednesday and begin to climb Wednesday night into Thursday.

A scattered shower or thunderstorm possible today and then a mainly dry Wednesday is expected with very low chances of rain. More sunshine tomorrow with a stronger breeze shifting to the southwest to help pump up the heat and humidity.

The National Blend Of Models has highs climbing to near 90° Wednesday and then sliding back into the upper 70s Friday. Aside from Friday, the rest of the next 11 days will see highs mostly in the lower to middle 80s.

The longer range temperature probability forecasts keep us favored for an above average period towards the end of the month. The 6-10 day forecast has outlooked us for above average temperatures overall from July 18th through July 22nd. The longer range 8-14 day forecast also favors us for above average temperatures overall from July 20th through July 26th. We are on the lower end of the probabilities favoring this warm pattern with a much stronger signal over the northern plains and out west. Average highs are in the middle 80s for the middle of July.

The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts keeps us sandwiched between an expected warmer than average plains and western half of the country and a cooler middle and eastern part of the US. A close examination of these forecasts shows we are expected to be right around average overall for the end of July as start to August. The temperature anomaly forecast for the week ending July 30th has us outlooked for temperatures near normal. The forecast for the following week ending on August 6th also has Chicago outlooked for about average temperatures too.

Feast Or Famine Rain

Lasalle and Grundy county feasted on rain yesterday while the most parched portions of our area stayed mainly dry. Nearly a half a foot of rain fell well south of the city causing flash flooding last night. Here is a summary of the flooding from the National Weather Service:

O'Hare officially picked up just .04" of rain. July is now down 1.12" of rain below average. Even taking into consideration our wet June, O'Hare is around five and a half inches of rain below average since the start of meteorological spring on March 1st.

Here is a recap on the latest US Drought Monitor analysis that I posted on Friday (it does not include any of our weekend rainfall or rain this week so far):

Comparing this week's analysis to last week's shows only the slightest improvement. The portions of Illinois in a moderate drought (level 1 of 4) dropped from 7.55% to 7.40%. The severe drought area (level 2 of 4) remains unchanged at 2.22%. The extreme drought area (level 3 of 4) is unchanged at .96%.

Much of our already parched portions of northern Illinois saw between 0% to 5% of average rainfall for the first week of July.

The latest GFS model run has our best chances for rain over the next 10 days coming either today or Thursday into early Friday. The model dries us out for the weekend all the way through next Thursday.

Some of Thursday's storms may be strong. The Storm Prediction Center has placed us in a marginal risk area for severe weather. The greatest threat would be damaging winds with heavy downpours.

A marginal risk is level 1 out of 5 possible risk levels. It is the low end of the risk categories but means "an area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity".

The GFS model total rainfall forecast through tonight shows around a few tenths of an inch to a third of an inch of rain possible. Most of this would fall during the day.

Running the model out to Friday morning to include Thursday's rain is a bit more promising. It shows some hope for our worst drought stricken areas to the north of the city. The model suggests over an inch of rain is possible there.

The longer range precipitation probability forecasts continue to discourage. We continue to be favored for a drier than average pattern for the end of July. The latest 6-10 day forecast has the Chicago area favored for below average precipitation overall from July 18th through July 22nd with the highest probabilities over our area. The longer range 8-14 day forecast keeps us favored for below average precipitation overall from July 20th through July 26th.

Here is my 7 day forecast:

Today: Peeks of sun, scattered showers (isolated t-storms possible) High: 80

Wednesday: Partly to mostly sunny, breezy, warmer & more humid Low: 69 High: 88

Thursday: Mostly cloudy, showers & thunderstorms likely Low: 70 High: 85

Friday: Partly to mostly cloudy, sct. showers & t-storms Low: 71 High: 79 (cooler lakeside)

Saturday: Mostly sunny Low: 65 High: 83 (cooler lakeside)

Sunday: Mostly sunny Low: 67 High: 85 (cooler lakeside)

Monday: Partly to mostly sunny Low: 68 High: 86 (cooler lakeside)


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