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  • Tim McGill

A Special Treat Possible In Our Skies This Weekend

October Nights Warming Up

Nothing too scary about Sunday's Halloween forecast. It should be mostly sunny during the day with highs right around average in the middle 50s. Temperatures will be falling into the middle to upper 40s for prime trick or treat time in the evening. A brisk breeze out of the northwest might make it feel a few degrees colder. More detail below.

So typical temperatures for Halloween this time around but October nights have been warming slightly over the past 50 years here. Climate Central did a study of 242 cities to see how temperatures have been trending. Nearly 90% of the cities they looked at have experienced an increase in their average nightly October temperatures. Chicago has seen an uptick in temperatures of 1.4° since 1950.

Some Weather Treats This Halloween Weekend

I think the forecast for Sunday has to be considered more of a treat than a trick. It could be a lot worse. The coldest high for a Halloween was 31° way back in 1873. There has been measurable snow on two Halloweens and at least a trace of snow for five Halloweens.

Another possible treat his weekend is courtesy of a Coronal Mass Ejection or CME that occurred on Thursday. That massive solar flare has sent charged particles out into the solar system and our atmosphere and some of them are hurtling towards earth.

NOAA has labeled this a powerful X1-class solar flare. They have also issued a strong geomagnetic storm watch because of this powerful X1-class solar flare for both Saturday and Sunday. X-class flares are the strongest type of ejection the sun produces.

As a result, a G3 strong geomagnetic storm watch has been issued for both Saturday and Sunday.

The scale for these storms ranges from a G1, or minor storm to a G5, or extreme storm.

The northern lights that could result from this sun storm may be visible as far south as northern Illinois. There is a better chance of us seeing this dazzling display in our night sky on Saturday. Skies should be clearing out Saturday night to allow for a view should this materialize.

There is also a chance of us seeing this phenomena again on Halloween night but the axis of highest probability shifts a bit north. Skies Sunday night should be even more clear than Saturday night.

Cool Weekend Then Colder Next Week

Five of the last eight days have been below average. This relatively cooler pattern continues through the weekend before turning even colder next week. Next week will be the coldest of the season so far and the coldest in nearly seven months.

Some sprinkles and light rain possible early today but mainly south and southeast of the city. Peeks of sunshine will break through low clouds but not enough to warm us above average.

Average highs for today's date are around 56°. The HRRR Model has our highs today near or just below normal in the middle 50s.

Even though there will be more sunshine Sunday it will be countered by a cold front coming through early in the day so temperatures tomorrow will overall be a couple degrees cooler than today. The GFS Model has us our highs in the lower to middle 50s with temperatures even falling into the 40s Sunday afternoon north and northwest of Chicago.

The growing season will come to an end next week with some cold nights coming. Average lows start off Monday near 40° and then fall into the upper 30s. The GFS Model has our lows Wednesday morning dropping into the lower to middle 30s for most of the area with some upper 20s well north and northwest of the city.

It will be dry for trick or treaters Sunday but by the evening hours the combination of cool temperatures and a brisk northwest wind will make it feel like the upper 30s to lower 40s.

Breezy conditions today too with gusts out of the north/northeast over 20 mph at times. The winds shift by tomorrow afternoon to the northwest after a cold front comes through. Expect sunshine at Soldier Field for the Bears' game with temperatures in the lower to middle 50s.

Chilly First Week Of November

The National Blend Of Models has our highs falling into the 40s on Monday and staying there through Friday. We bounce back slightly next weekend with highs in the lower 50s. Lows dip into the lower to middle 30s for next week at O'Hare but that means at least a few mornings north and northwest of there we will see lows in the upper 20s.

The longer range temperature outlooks keep us cooler than average at first and then trend us towards near or just above normal. The 6-10 day outlook has us favored for below average temperatures overall from November 4th through November 8th. The longer range 8-14 day forecast also favors most of us for about average temperatures from November 6th through November 12th with our northern suburbs slightly favored for above average temperatures. Average highs for this period are in the lower to middle 50s.

The even longer term 35 day temperature anomaly forecast has most of us just a bit below average for the period from the end of October to the start of December. The shade of light blue in northern Illinois represents temperatures overall around 1° to 2° below average. There is a portion of the area south of Chicago that is not shaded in light blue. This area is expected to be near normal. This forecast covers the period from October 28th through December 2nd. The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members The model tries to give an idea of the amount of uncertainty in a forecast by running an ensemble of multiple forecasts which are each tweaked a bit with their initial conditions.

Drying Out After Our Wet Week

O'Hare just had its wettest week since the middle of June. 3.58" of rain has fallen since Sunday bringing the total for the month of October to 5.73" which is 2.50" above average. O'Hare has seen 6.96" of rain since the start of fall on September 1st and is now running .54" above average for the period.

The most recent US Drought Monitor analysis was released Thursday. It was the third report in a row to bring good news for Illinois. It did not include our rainfall this past Thursday and Friday. Here is a recap from that report:

The area considered in either a moderate or severe drought diminished at least slightly. Unlike the previous analysis, this most recent one shows even the area considered "abnormally dry" dropped in coverage.

Here is a summary of the impacts the ongoing drought is having on northern Illinois from the National Weather Service:

Volunteer observers across far northern Illinois indicate much lower then typical stream flows on area creeks and rivers, particularly along Beaver Creek and the Kishwaukee River.

Reports also indicate that lawns have gone dormant and there has been some stress to the trees. Few impacts to agriculture have been received recently, though the dry conditions and stressed crops have resulted in an early start to the harvest season across northern Illinois. Data available from the Illinois State Water Survey, USGS, and NCEP indicate that soil moisture, groundwater, and surface water levels remain below normal.

The news for the Midwest region was good almost across the board. The area in either a moderate or severe drought decreased slightly. The 1.20% of the area in an extreme drought did not change from the last report.

Our wet week has helped build up the surplus of rainfall for the month of October. Most of the Chicago area has received between 150% to 300% of average rainfall for October so far with a few spots even seeing up to 300% to 400% of average.

The GFS model's total precipitation forecast through next Sunday squeezes out about a tenth of an inch to a quarter of an inch of rain on the Illinois side and just over a third of an inch in Indiana. Most of this rain will fall early today or has already fallen. After this morning the chances of rain are near zero the rest of the weekend and all of next week.

The GFS model's meteogram for O'Hare shows some light rainfall early today but no rain beyond that. The next nine straight days should be dry.

The precipitation outlook through nearly the middle of November favors us for a dry pattern overall. The latest 6-10 day forecast has the Chicago area favored for below average rainfall from November 4th through November 8th. The longer range 8-14 day forecast has us outlooked for below average precipitation too for the period from November 6th through November 12th.

Here is my 7 day forecast:

Today: Spotty sprinkles/showers early mainly southeast, partly sunny, breezy High: 57

Sunday: Mostly sunny Low: 45 High: 55

Monday: Partly to mostly sunny Low: 35 High: 49

Tuesday: Partly to mostly sunny Low: 32 High: 47

Wednesday: Partly to mostly sunny Low: 31 High: 45

Thursday: Partly to mostly sunny Low: 31 High: 46

Friday: Partly to mostly sunny Low: 31 High: 48


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