So far this summer June was about 0.5-1 degree below average, July ended 2-3.5 degrees above average for the month as a heat ridge established itself over the Mississippi River Valley in Mid to late June, and proceeded to expand east for July, and so upper 80s to upper 90s and even some 100s with high humidity has been the theme, but im seeing changes in the near future which will make those who want this heat to go away pretty happy
The heat and humidity will continue through Sunday as high pressure has centered itself off the coast and we have a very moist and warm flow out of the Southwest, highs in the upper 80s to low 90s are expected Saturday with high humidity, very similar to Friday and Sunday will be in the mid to upper 80s with VERY high humidity as a strong cold front will be approaching from the west with winds out of the SSW at all levels of the atmosphere. Heat indexes both days will be in the mid 90s to around 100 degrees. There will be a shot at isolated thunderstorms Saturday afternoon with this hot humid air mass in place and some weak disturbances moving through, but the real threat comes Sunday night into Monday
Here is Saturday below and you can see the clear Southwesterly flow , with 500 mb thicknesses exceeding 570 mb and temperatures at 850 mb 15-18 degrees Celsius, along with sunshine will make it a very hot humid day, again in the low 90s for many, you can also see a strong trough and cold front over the Midwest, that’s what I think will begin to erase the brutal heat we have been seeing and start t break down the summer pattern, perhaps a bit earlier than usual but definitely not a unusual time for it to start breaking down
Sunday afternoon we can see the strong cold front marching east, but again on Sunday heights at 500 mb are exceeding 570 mb an 850 mb temps are around 15-18 degrees C , the only thing that will stop 90s will be cloud cover that begins to move in during the afternoon ahead of the system, along with scattered thunderstorms which will be strong to severe, mainly for western sections during the day, highs again in the mid to upper 80s but the humidity will really spike
Sunday night into Monday morning the cold front will come east but at a slow pace thanks to high pressure off the coast, so I expect widespread showers and thunderstorms Sunday afternoon to early Monday morning, some strong to severe Sunday evening , the main threat will be heavy rain and possible flash flooding as these storms will be slow-moving.
By Monday afternoon the front will move off the coast, it will still be warm and humid Monday with highs in the mid 80s but a much drier and comfortable air mass will drop in from the NW Monday night.
This strong cold front along with a negative NAO and a flip to El Nino will force an upper level low to form over the north Pacific, that will for one pump up a ridge in the western US and number 2 force the heat ridge to retrograde and also weaken.
And the end result is this, all the extreme heat shifts west with the ridging, the ridging in the west forces a trough to drop into the eastern US and we become much more comfortable than the recent month of month and a half.
By no means is this a cool and below average pattern as the Polar vortex is still very far north , but this means more in the way of average temperatures maybe slightly below with highs in the lower to mid 80s next week with comfortable levels of humidity Tuesday and beyond
Thursday into Friday another cold front will drop south with yet another round of thunderstorms, a brief rise in humidity ahead of it before another comfortable and modified Canadian air mass drops south. Ridging remains in the west and extends into the Pacific NW where they havent had much of a summer so far.
Looking longer range into next weekend a deeper trough drops south behind the cold front , temps at the 850 mb level are now 10C or below so if this comes to fruition this would mean upper 70s to lower 80s with low humidity. The models always over due troughs and ridges and amp up the pattern to much this far out, and im skeptical that we start seeing troughs this deep develop by next weekend but a slightly weaker trough still means lower to mid 80s for highs with low humidity.
I just want to note that this pattern will bring much-needed relief but is also HORRID if you want an east coast tropical system, like Irene last year
This is what I expect through August, a gradual break down of the summer pattern over the east with occasional troughs and cold fronts, spells of warm and humid conditions ahead of these fronts along with plenty of thunderstorm threats then spells of near normal temperatures to below normal temperatures behind these fronts with low humidity, so in other words , I don’t see August being nearly as brutal as July.