Yesterday turned out to be a great fall day, just a touch on the warm side but still not bad. Today we’ll feel the drier air moving in as the first cold front of the week pushes through the area. The morning map (300 mb isobars/dewpoints) shows the dividing line between dewpoints in the 60’s and dewpoints in the 40’s. Temperatures won’t change too much with this first frontal passage, but it will feel more like fall with the drier air. Notice how the isobars are pretty much left to right… that’s a zonal flow and it’s not much help in getting colder air this far south.
But the colder air is making its way south as I type.
Still on track to see large lobe of the Arctic tropopause swing towards the eastern US over the weekend in response to strong cold air advection behind surface low forecast to move through the Great Lakes region. Guidance is consistent with moving cold front into the CWA late Thursday night into early Friday morning and bringing it across the region during the day on Friday. Front will have a little moisture to work with so could squeeze a light shower or two out on Thursday to Friday, though guidance isn’t particularly aggressive with it. GFS and GEFS show a little accumulation, but not enough to introduce PoP’s beyond a small chance in far central GA on Thursday and far NE mountains Thursday night. Bigger story will be the
temperature swing with fall airmass moving in Friday into Saturday. Forecast temperatures across the CWA are 5-10 degrees below normal on Saturday with highs in the 60’s and low 70’s. Temperatures return back to normal ahead of the next system on Tuesday to Wednesday of next week.
Again, you don’t hear them talk much about the tropopause. The tropopause is the boundary layer between the troposphere (where all the weather occurs) and the stratosphere, and it ranges from 11 miles high near the equator to about 5.5 miles high at the poles. It is also the point in the atmosphere where temperatures cease cooling with height and start to warm. Regardless… it’s cold up there. Temps at that level right now are around -60F. This is exactly what we want to see in the winter. I am assuming you want snow and cold, right? 🙂
When the tropopause gets close, so does the cold air. This will only be a glancing blow this time, but our temperatures will fall well below normal for a day or two. This image shows the temperature anomalies for Saturday morning at 8 AM.
And those anomalies correspond to these temperatures. I think the heat island effect for Atlanta is overdone here.
Looking at what is normally the coolest reporting location in the state, this is what the GFS sees for highs and lows. You can see that another cold front will be making an appearance next week, dropping the temperatures even further. Still stepping down. 🙂
Here’s a broad view of the upcoming temperature anomalies.
This will be some “real” fall weather and just in time for more college football! 🙂
I hope you can get out today and enjoy this great weather! It should be really nice all week long with almost zero chance for rain.
Have a great Tuesday!