Smooth Sailing, Except For Tricky Friday Forecast

***Watch WISN 12 News at 5, 6, & 10pm for the latest weather information!***

Thank you for stopping by the Weather Watch 12 blog!  After last week’s seemingly never ending stretch of cloudy, wet, and cool days, the upcoming sunshine and warm weather will be very welcome.  Along with the good, we may have to deal with a brief dose of clouds and rain for a day.

Let’s start by discussing the good news in the forecast.  Both Wednesday and Thursday will bring sunshine and highs in the 70s to the region.  The warmer of the two days will be on Thursday.  Below is a forecast temperature map from the 12Z NAM.  The map shows temperatures at 1 p.m. Thursday, with 70s across southeast Wisconsin, and the 75 degree line over central and northern Wisconsin.  Just click on the map to enlarge. 

While we enjoy sunshine and 70s on Thursday, parts of the central Plains east to the mid-Mississippi River Valley will see clouds, thunderstorms, and temperatures only in the 50s and low 60s.  The area of unsettled weather is associated with upper level low pressure.

Below is the 500mb(middle of the atmosphere) forecast from the 12Z NAM.  This map is also valid for 1 p.m. Thursday.  The center of the upper low is marked with an ‘L’. 

The upper level low creates divergence.  This means the air is separating at this level.  In turn, air at the surface begins to rise to replace the air at the 500mb level.  Rising motion in the atmosphere can lead to clouds and convection(thunderstorms). 

The upper level low that is over the Plains will move east and begin to impact the weather in southeast Wisconsin on Friday.  Friday has always looked a little iffy due to the low, but the latest data is trending to a cloudier day with an increased rain chance.  At this point, don’t cancel any outdoor plans, but just have an alternate plan ready if it does rain.

The forecast can and will change some between now and Friday, but here is just ONE rainfall forecast from ONE model.  Remember, our latest forecast can be found on WISN 12 News.  In the meantime, we’ve talked about the NAM computer model in our 2 maps above.  Let’s continue to use the NAM and look at a rainfall forecast for Friday.  The map below with the blue shade over Milwaukee represents a rainfall total of 0.50″ to 0.75″.  The lightest shade of green over northern Wisconsin is 0.01″ to 0.10″. 

Along with the clouds and possible rain showers, temperatures will also be cooler on Friday.  Likely in the 60s for highs.  Although we will watch this closely, because if showers would persist on Friday and winds turn off the lake, temps may fall into the 50s for a time. 

Again, the trend could change either way, but we will update you as the latest data arrives in our weather center.  The goods news is any rain would be out of here in time for Saturday, and that means a dry and warm weekend can be expected.  By Sunday and Monday highs should warm into the 80s!

That’s it for now, but you can stay up-to-date by following our forecasts on Facebook at WeatherWatch 12 and Twitter at WISN12News.

Have a great day!

Jeremy Nelson


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