First Frost, Upcoming Rain, First Snowflakes?

Many of us woke up to frost out on the car windshield this morning or on the ground.  Gardens may have been nipped by the coolest air of the short fall season so far.  Temperatures starting things this morning were in the lower to middle 30s.  Typically temperatures below 37° will produce frost on the ground.

It may seem abrupt but the first instance of frost on October 13th is actually a bit late in the season, by about 1 to 2 weeks depending on location.

We'll get a short reprieve from those marks for the next couple of days but replacing the frost is rain.  Due to enter the picture late Monday, after sunset, and into Tuesday as a strong storm system enters the upper midwest.  The heart of the storm will pass almost directly overhead early Tuesday morning...

...leaving the highest amounts of rainfall shifted to our northwest.  Rain will be heavy at times, and most of it will fall Monday night.  However, we'll try to wrap up some drier air on the back side of this system Tuesday, which will keep activity light and sporadic.  Some sunshine peaking through will even be possible.  Rainfall amounts locally will be around a half inch to three quarters of an inch.

Colder air returns into the end of the week.  A spoke of energy will descend from the north out of Canada as the jet stream digs into the upper midwest.  This will open the gates for colder air.

Some light precipitation will be possible on Friday.  The question is, how cool can temperatures get.  One model has been rather consistent at hinting at our first few snowflakes of the year.  This image shows how cool the atmosphere will be between certain altitudes.  Generally speaking, north of all these different colored lines will mean the atmosphere will be supportive of snow; south, rain.  As you can see here by Friday evening, all but one of these lines will be to our south.

October snow isn't a rarity.  It's the time of year where we start to see our first flakes.  SE Minnesota averages just shy of an inch in the month of October.  In fact, four of the last five years have had snow recorded in October. (None in 2011) 

This scenario is still five days out.  For now, we've left the forecast on the warmer side of the scenario but it bears watching closely.  Friday could just bring our first snowflakes of the season.  Although, even if we do see them, it won't be a lot.

Storm Tracker 6 Chief Meteorologist
Chris Kuball