After a very gorgeous weekend with little to no humidity and cooler temperatures, a warm front will begin to slowly lift through the region during the day on Monday and with the passage of the warm front we will once again see the return of higher dewpoints/humidity along with the threat for showers on Monday. The humidity won't be around for long though as a rather strong cold front is expected to cross the region sometime either late Tuesday or overnight Tuesday into Wednesday. Right now there are differences in some of the computer model data on the exact timing of the cold front.
An amplifying trough moving across the Great Lakes and southeastern Canada will allow for winds aloft to increase over southern New England. Computer model guidance suggests that winds at 700mb will increase on order of 30-40 knots with winds at 500mb increasing to as much as 40-50 knots across the region. While the low-level jet doesn't appear all that great, we still see winds at 850mb increase to 25 to perhaps 30 knots. The region will also be in the right entrance region of a rather potent 100-110 knot upper-level jet streak.
As the trough approaches the region, temperatures in the mid levels of the atmosphere will also begin to cool as 500mb temperatures are modeled to drop as low as -12C to perhaps -13C. With 700mb temperatures around +5C to begin the day (although cooling as the afternoon goes on) this should yield to some much better mid-level lapse rates than we have been dealing with as they should be on order of around 6-6.5 C/KM.
As far as instability goes, that picture is much more unclear right now as we may be dealing with a bit of cloudiness which could hold back temperatures. Given how 925mb temperatures are modeled to be around +20C with 850mb temperatures closer to +14C, that would yield max temps with full mixing well into the mid to upper 80's. However, with clouds expected to be around we probably won't realize this full potential so temperatures should be closer to 80F, although with more sun these temperatures could easily be boosted higher, especially locally where there happened to be more breaks. Dewpoint temperatures are expected to climb into the mid-60s.
The combination of surface temperatures near 80F, dewpoints in the mid-60's, and modest mid-level lapse rates, should yield to surfaced-based Cape values around 1500-2000 J/KG with mixed-layer cape values around 1000-1500 J/KG and surfaced-based lifted index values around -3C to -4C.
When taking into account the combination of strong winds aloft and potential for some modest instability, and a cold front/trough sliding east, we will be looking at the potential for some t'storms during the day on Tuesday.
We will have to watch the exact timing of the front, however, as if the front comes through very late on Tuesday or during the night, then the threat for t'storms will be much more decreased as instability will be minimized. However, some computer model guidance does suggest a pre-frontal trough will setup just east of the Hudson River Valley and that would be a focus for t'storms.
Given the strong shear/cold temperatures aloft, any t'storm would have the potential to produce strong winds and perhaps some hail.
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