The official first day of summer is Wednesday, June 20th, 2012 and boy will it sure feel like summer outside as a major ridge builds in from the central Plains allowing for a very hot airmass to invade pretty much the entire eastern third of the United States.
While there were stretches of April/May that sure felt like mid-summer the month of June has not been so kind as temperatures are actually running below-average for the month! This, however, will be changing as we move through the work week!
A trough which has been plaguing much of the Northeast will finally be lifting out as ridging which has been in place across much of the Plains and Southern States continues to strengthen and build northward and eastward. As this occurs a warm front is going to be lifting northward and moving through New England during the day on Tuesday and moving well into northern New England by early Wednesday morning. Once that warm front moves through a very hot airmass will have worked into the region.
Several computer forecast models are indicating temperatures at 925mb (~2500ft ASL) will approach +25°C (77°F) along with 850mb temperatures (~5000ft ASL) approaching +21°C (~72°F) to +23°C (74°F). With full sunshine and full mixing this would support temperatures well into the mid 90's across much of the region with the exception of the extreme coast and elevations above 1000'.
Right now it appears that Wednesday and Thursday will be the hottest days as temperatures both days have a very good possibility of reaching the mid to upper 90's across a large chunk of the region and it is even possible that a few locations could flirt with the 100°F mark! This will all depend on exactly how high the 850mb temps are and what the surface wind direction is. If surface winds stay more westerly this will enhance the downsloping component and across a few locations which will increase the likelihood of some locations getting to 100°F.
The next question is do we see an official heat wave out of this? At this point in time I would lean towards this NOT occurring. Remember, to have an official heat wave you must have at least three-consecutive days of 90°F or more. Tuesday looks like we'll only see lower to mid 80's and a cold front will be moving towards the region on Friday. It is the timing of this front which will play a major factor in whether or not we can hit 90°F on Friday. As of now computer guidance is suggesting the cold front will move through the region during the late morning or early afternoon hours. There would also likely be showers/t'storms associated with the front and the increase in cloud cover along with early timing of the front would likely prevent anyone across southern New England from hitting the 90°F mark. However, if the front slows down by several hours than it's very possible some locations can get to the magic number.
Once the cold front passes through on Friday a secondary cold front will work through the region on Saturday bringing in a much more cooler and dry airmass. This front may also be associated with a few showers/t'storms. It also appears that with the passage of this front we will yet again see another pattern change and the final week of June moving forward into July look like it will feature cooler than average temperatures...but we'll save this for another post!
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