First Heat Wave of 2012 Imminent? Threat of storms as well?
By Paul Taschereau JR on June 20, 2012, 12:00am
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The official first day of summer is now less than 24-hours away and it won't take very long at all for the weather to feel like summer as a very hot and humid airmass is currently on it's way to southern New England!
Currently a warm front is located just to the west of southern New England and this warm front will continue working eastward towards the region and eventually clearing the region by late tomorrow morning. Once the warm front passes through a blast of hot and humid air will invade the region lasting through the next few days.
The airmass working into the region is something more commonly seen during those hottest periods of July/August. The degree of the heat that will be seen across the region tomorrow is something that isn't typically seen in these parts this early in the summer.
The combination of strong sunshine, temperatures at 925mb and 850mb (~25000ft ASL and ~5000ft ASL respectively) ranging from around +25C to +28C (~80F) at 925mb to +19C to +21C (~70F) at 850mb, and strong atmospheric mixing will all lead to surface temperatures ranging from about the mid to upper 90's across much of the region...a few locations may even tough 100F! The only areas which will be cooler will be the immediate coastline and elevations above 1000', but even here it will be tough to escape the heat as many of these locations will range from the upper 80's to the lower 90's!
While Wednesday will be incredibly hot with these temperatures it's possible Thursday is even a few degrees higher across some locations. In fact, Thursday maybe the best chance for a few locations to hit 100F. The areas which have the best shot at 100F are Windsor Locks/Hartford, CT, Taunton, MA, Ashford, NH, and Chicopee, MA. The reason being some computer models are hinting at surface winds on Thursday to be mainly from the west to even slightly northwest. A wind direction from here causes down slopping. This is when winds moving down the edges of mountains/very large hills warms the air as it works down the slope of the mountains/very large hills. This down slopping can often tack on as much as 2-3F on surface temperatures.
Besides the high heat over the next few days we will also have to contend with some fairly high humidity levels and high dewpoints. Normally in these cases with extreme heat we don't normally have to contend with high dewpoints throughout the course of the entire day. Normally it is the morning and evening hours which have the higher dewpoints as during the afternoon hours strong mixing brings drier air down form higher up in the atmosphere and this helps to mix out the low level moisture resulting in lower dewpoints. This case will be a little different, however. With the passage of this warm front there is expected to be an abundance of low-level moisture that will work in place. Computer models are showing 925mb dewpoints to be around +20C (~68F) and 850mb dewpoints to be around +15C (59F). With a strong cap in place at 700mb (~10,000ft ASL) it will be very difficult to mix down the much drier air that exists about 10,000ft ASL and higher up. With all this said dewpoints on both says should be into the mid and upper 60's and even a 70F reading or two is possible, especially in the morning hours and then again during the evening hours. Now it's possible dewpoints on Thursday end up being a few ticks lower across the areas affected by down slopping as down slopping will help to dry the air out a little more.