Chameleon High

No...it is not a result of some new fancy drug that is taking America by storm.  It is a large sprawling Canadian source region high pressure system that will deliver cooler and drier air for Thursday and Friday (actually will feel it this afternoon), but then once it passes to our east and south, the return flow will result in typical heat and humidity as the clockwise circulation advects air from our SW.  The visible satellite pic below clearly shows the leading edge of this dry cool air creating an area of showers and some embedded t-storms within the frontal boundary.

 When we widen out our view, you can clearly see this large high pressure system (1025 mb) that is centered northwest of Lake Gitche Gumee.

Here is the current synoptic map for Wednesday morning.

So once this area of showers and storms passes south of PA during our midday time period Wednesday, we are looking at a nice stretch of weather for the next several days with low humidity and near normal temps to slightly below normal.  But by this weekend, the chameleon high will begin to rear its ugly side and pump heat and humidity northeastward towards PA.  The maps below show the positioning of the surface high pressure Thursday and then again on Sunday.
First Thursday's surface prog:

Here is Sunday morning's surface map.  Couple that same high pressure (clockwise circulation) and that weak low off the Carolina coast (counterclockwise circulation) and we in PA will have a rather persistent easterly flow that will make things "murky" here with clouds, moderate humidity, and somewhat dreary conditions for the middle of July.  What the map below doesn't really show is that some impressive heat will again be re-loading over the southern plains and the desert SW US.  Note the high over the 4 corners where clear skies and dry air will allow that part of the US to bake!

So, a chameleon high will give us nice weather followed by a return to heat and humidity, although the heat will be tempered at first due to the on-shore flow off the Atlantic thanks to the  karma chameleon high and the Carolina low.  So I leave y'all with this....if you need a flashback to the 1980s and George Alan O'Dowd's hit that still to this day gets plenty of air time!

Have a nice Wednesday!

Smitty

AA:  Brief showers and maybe a storm bring in nice weather for the next 2 days.  Then, on-shore flow will make things a bit murky for the weekend.....somewhat anyhow.....enjoy the 80s flashback!