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  • Tim McGill

Graupel & Waterspouts? Why not? It's 2020.

Freaky Fall Weather Checklist

If we've learned anything this year it's that we should be prepared for everything. The next few days could feature frost, graupel and waterspouts. It's rare that all three could happen within a few days but that is where we find this forecast.

Unseasonably cold air aloft combined with converging winds in and near Lake Michigan will create conditions conducive to waterspouts to form mainly over the lake late Thursday into Thursday night. There is even the possibility one could make its way onto land at least briefly.

A National Weather Service expert on waterspouts defines the as "funnel which contains an intense vortex, sometimes destructive, of small horizontal extent and which occurs over a body of water." They come in two types. There are "fair weather" waterspouts and tornadic waterspouts. Tornadic waterspouts originate as tornadoes associated with a strong thunderstorm with rotation over water or move from land to water. "Fair weather" waterspouts form only over open water and are not usually associated with a thunderstorm. The National Weather Service will issue a tornado warning for a waterspout that moves onto land because they can cause damage. A recent waterspout in Myrtle Beach came onshore with winds of 75 mph.

The picture above is of twin waterpouts just offshore from Kenosha about seven years ago.

More recently, 4 years ago about a dozen waterspouts were sighted over the southern end of Lake Michigan from the Illinois and Indiana shores. Both events occurred in fall and in both cases the waterspouts stayed over water and did not cause any damage or injuries.

If skies clear up enough we could see some frost form Friday morning away from the city. There is another chance for some frost Saturday morning too.

Nature's Dippin' Dots

Graupel is the Dippin' Dots of frozen precipitation. Thunderstorms that develop over the south end of Lake Michigan Thursday night could dump some heavy rain in northern Indiana mixed with some "soft hail" or "snow pellets". Those are names also given to graupel. Graupel forms when when supercooled water droplets freeze onto a snow crystal. The supercooled water coats snowflakes and the result is small soft pellets of ice.

Gusty Winds Bring Cool Change

Today will be the third day in a row with below average temperatures. That follows a streak of seven straight days above average. This cool change could stick around through at least Monday. Today's highs will be in the lower to middle 60s. Average highs for this time of the year are around 69°. Gusty northwest winds will deliver this cool air. Watch for gusts to 35 and even 40 mph.

Our highs will fall into the 50s for Thursday and through the weekend. It will be the coolest temperatures we've had in over four months. We will bounce back though by early next week. Highs should climb back above average by Tuesday with some 70s expected.

Warm Up Next Week

Once the warmer air arrives it could stick around through the middle of the month of October at least. The longer range temperature probability forecasts show an expanding area with high probability of above average temperatures widening from the west coast to eventually the east coast by the second week of October. The 6-10 day forecast has us outlooked for near normal temperatures overall from October 5th through the 9th. The 8-14 day forecast has the entire country outlooked for above average temperatures overall from October 7th through the 13th. We saw signs of this growing warm up in yesterday's longer range forecasts.

Looking a little longer range and we find this warm up lasts all the way through the 16th of next month. The multi-model ensemble temperature anomaly forecast continues to keep us outlooked for above average temperatures through the week ending on October 16th.

More Active Rain Pattern For Now

We have several chances for some October rain over the course of the next week. Spotty showers today on our last day of September and again later tomorrow with an isolated thunderstorm possible too. More of a steady rain at times on Sunday and then another round of showers and possible thunderstorms by Tuesday next week.

After this more active pattern we could shift into a more dry pattern for the middle of the month of October. The 6-10 day and 8-14 precipitation probability forecast has us outlooked for below average rainfall overall from October 5th through the 13th.

Here is my 7 day forecast:

Today: Partly to mostly sunny, pm spotty shower or isolated t-storm, windy High: 65

Thursday: Partly sunny, sct. showers & t-storms early & late, breezy Low: 47 High: 58

Friday: Partly to mostly sunny Low: 41 High: 54

Saturday: Partly to mostly cloudy Low: 40 High: 57

Sunday: Mostly cloudy, on & off rain Low: 47 High: 55

Sunday: Partly to mostly sunny Low: 45 High: 62

Tuesday: Mostly cloudy, scattered showers & thunderstorms Low: 48 High: 72



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