If you are getting the gardening fever, temper it a little bit on the warm-loving plants. Here’s a look at what we have coming over the next few weeks and if it could lead to frost.
Here’s the simple answer to the question of whether we are done with frost. No. A chilly spell will move in next weekend and could easily bring our early morning temperatures down to at least 35 degrees. A temperature of 35 degrees is the number typically used for the prediction of frost. An official thermometer is six feet off the ground. If a thermometer reads 35 degrees at six feet, the ground temperature could be 32 degrees or any spots lower than the thermometer could easily drop to 32 degrees. Remember that for the future when you are watching for frost. The magical number is 35 degrees.
This week has a very springy storm heading into the Great Lakes region Wednesday. Unlike last week we should be on the warm side of this storm initially. This could lead to a round of robust thunderstorms. After the storm passes the cooler air moves in for Saturday, Sunday and Monday. Afternoon temperatures will only warm to the 40s and low-50s Saturday and Sunday. Another key temperature number for assessing your chance of a frost the next morning is 55 degrees. If you only reach 55 degrees in the late afternoon and have a clear, calm night coming, the temperature can drop 20 degrees overnight. Do the simple math of an afternoon high at 55 degrees minus a 20 degree temperature drop and we get 35 degrees the next morning.
Here are the low temperature forecasts for Saturday, Sunday and Monday.
The weather pattern says any of us in Lower Michigan could have a frost Saturday, Sunday and/or Monday. Frost always depends on the clouds and wind at the time, so we will have to wait until Thursday to get a more exact feel how low the temperatures will drop.
What about after this weekend? Are we done with frost then? For that discussion we should look at historical normals- what has happened in the past. We should also look at the general extended model forecasts.
Going by historical normals and taking Grand Rapids as an example, the AVERAGE date of the last 35 degree temperature is May 11. This means that half of the years still have a 35 degree reading after May 11. Ann Arbor has an average last 35 degree reading on May 10. In other words we still have to strongly expect frosts into early May in southern Michigan. If the upper-air pattern takes on a very warm look about May 1 we can probably think about being free of frost.
Right now the surface temperature anomalies forecasted out into the end of April lean toward slightly warmer than normal. This would lean toward frost being over toward the end of April.
For now, frost is coming next weekend or early the following week. We will have to wait until then to take a look at the 10 day forecast for an all-clear on frost in early May in southern Michigan.
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