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  • Tim McGill

Headed Towards A Hot & Dry Summer?

Models Turn Up The Heat

It's early but summer has gotten off to a warm start. Meteorological summer started on June 1st and our first week has come in more than 7° above average. I looked at three different model's seasonal summer forecasts and they all favor us for above average temperatures overall from June through August.

The Canadian Seasonal to Interannual Prediction System (CANSIPS) and the European Centre for Medium-Range Weather Forecasts (ECMWF) show similar seasonal temperature departures from average for the Chicago area (between 1° to 2°C or about 2° to 4° F above average).

The Climate Forecast System or coupled forecast system (CFS) shows a similarly warm summer forecast for the city and surrounding suburbs. The difference from the other models is that areas well west and southwest of the city are outlooked to be about average.

Most Models Keep Chicago Dry

The CANSIPS and ECMWF models seasonal precipitation forecasts both favor us for below average precipitation overall all from June through August. CANSIPS has northern Illinois' rainfall anomaly about an inch below average for this summer. The ECMWF model has us down about 1.5" to nearly 2" below average.

The CFS offers at least some hope. This outlier has us around 2" or more above average for the season.

Feeling Like Florida

The combination of highs about 5° to 10° above average along with high humidity has made it feel more like the sunshine state than Illinois in early June. We will again top out in the lower to middle 80s.

Dew points will remain in the 60s through Saturday making it feel sticky. A wind off the lake will keep us cooler lakeside but most of us should reach the lower to middle 80s today and tomorrow. Our best chance for some scattered showers and thunderstorms today will be during the afternoon and evening hours. Wednesday's threat of rain isn't as high but there is about a 25% to 30% chance during the afternoon and evening.

The National Blend Of Models keeps the unseasonable warmth coming all the way through a week from Friday. Average highs during this period start off around 78° today and climb to 81° by the middle of the month. Relief from the higher humidity arrives on Sunday after a cold front slides through late Saturday. More comfortable air will settle in for the second half of the weekend and the first part of next week.

High & Low Temperature Forecast For O'Hare (WeatherBell)

Friday should be the warmest day of this week as we enjoy the return of more sunshine. Highs are expected to rise to near 90°.

The temperature anomaly forecast for Friday shows we will warm more above average than most of the rest of the country. Temperatures from the Great Lakes southward into Texas should be about 10° to 15° above average.

More Rain Needed

Some welcome rain fell on Monday but it wasn't the kind of widespread soaking we really need to put a significant dent in the drought. An upper level low pressure system will continue to slowly meander across the Midwest with pinwheeling pockets of energy sparking some scattered showers and thunderstorms through Thursday. There is abundant moisture in the air so some spots could get soaked but overall, the coverage will be about 30% to 50% of the area.

The GFS model suggests the greatest threat of rain will be today into tomorrow. A cold front will cross through the area late Saturday that may spark some scattered showers and thunderstorms late that day into early Sunday morning.

The GFS model total rainfall forecast through this weekend does offer some hope for drought relief. It squeezes out about a half inch to nearly an inch of rain in total. We are now just under 8 inches of rain below average since the start of spring on March 1st. I'll have an update on the drought from the U.S. Drought Monitor on Friday.

A strong signal has developed for next week that is discouraging considering our drought situation. Both long range precipitation probability forecasts not only favor us for a drier than average period but they also have the strongest probabilities centered in and around Chicago. The latest 6-10 day forecast has us outlooked for below average precipitation overall from June 13th through June 17th. The longer range 8-14 day forecast continues to favor us for below average precipitation overall from June 15th through June 21st. This would mean both an expansion and deepening of our drought starting this weekend and continuing into next week.

Trending Towards Average Temps?

The last several long range temperature probability forecasts have consistently shown a strong warm signal but the latest runs now have us trending back to about average overall. The western half of the country, in particular the Rockies, are still the hot spot. The 6-10 day forecast has outlooked us for above average temperatures overall from June 13th through June 17th with probabilities between 40% and 50%. The longer range 8-14 day forecast drops us to about average overall from June 15th through June 21st.

The even longer range Subseasonal Experiment (SubX) temperature anomaly forecast brings back the warmth for the end of June and start of July. The average highs for this period are in the lower 80s. The temperature anomaly forecast for the week ending June 25th has us outlooked for above average temperatures overall but on the lower end of the spectrum. The forecast for the following week ending on July 2nd also has Chicago outlooked for above average temperatures overall with a stronger signal.

Here is my 7 day forecast:

Today: Partly/mostly cloudy, sct. showers & t-storms High: 83 (78 lakeside)

Wednesday: Partly/mostly cloudy, sct. showers & t-storms Low: 68 High: 84 (cooler lakeside)

Thursday: Partly/mostly cloudy, sct. showers & t-storms Low: 67 High: 84 (cooler lakeside)

Friday: Partly to mostly sunny Low: 68 High: 89 (cooler lakeside)

Saturday: Partly/mostly sunny, sct. showers/t-storms late Low: 67 High: 88 (cooler lakeside)

Sunday: Mostly sunny Low: 65 High: 85 (cooler lakeside)

Monday: Mostly sunny Low: 67 High: 86 (cooler lakeside)



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