Champlain Valley Weather Discussion:
Today is looking like an active day for portions of New England, and New York. An approaching front from the west, and a very moist atmosphere, along with a low pressure system riding up along the front, may prove to be a problem across the region today and tonight.
Currently across our region temperatures are in the mid to upper 70's already. Infact overnight lows, especially across the Champlain Valley, were very warm. Overnight lows generally ranged from 65-70F. With a few warmer spots out there such as Burlington, Highgate, and Swanton Village where the overnight low was 72F degrees. Current dewpoints are in the mid to upper 60's. This is resulting in already humid conditions across the area this morning. Things will only get worse as high temps will range from 82-87F, and dewpoints will climb to near 70F. Today will be a warm, and humid day.
Since we have been talking about temperatures lets talk quickly about the potential for severe weather today. As stated temps are already in the mid to upper 70's with nearly full sunshine across the area. This with high dewpoints have resulted in Convective Available Potential Energy (CAPE) values already in the 400-800 j/kg across the region, with the highest values across the Champlain Valley, and St. Lawrence Valley, and Lifted index's are already in the 0 to -2 range. Skies are expected to remain sunny for at least a couple more hours across much of the region, before high clouds build in, and thicken. CAPE values should max out in the 1200 to 1600 j/kg range, and lifted index's should range from -3 to -6. With such good destabilization it wont take much for any storms that develop to become strong to occasionally severe. With this all in mind I have issued a Severe Thunderstorm Watch already this morning. I am confident that at least a few severe thunderstorms will form this afternoon. The primary severe threat will be strong to damaging winds, and isolated large hail. Across extreme southern Vermont, an isolated tornado or two is possible. With all storms this afternoon, and evening very heavy rainfall is possible. Discussion on heavy rainfall potential is next.
With warm temperatures, and significant destabilization for the potential of severe storms, the most significant threat today and tonight will be the potential for heavy rain, with training/ back building thunderstorms. An approaching front, from the west is allowing a strong southerly flow to develop across the Eastern United States. This is helping transport warm sub-tropical moisture into our region. As stated above dewpoints are in the mid-upper 60's and will likely peak out to around 70 this afternoon. Precipitable Water (PWAT) Values are currently about 1.4 inches across the entire area. PWAT values are expected to rise into the 1.6 - 2.0 range later this afternoon. This is very moist, and any storms that develop in this atmosphere will have torrential downpours, and with the slow moving front and weak storm speeds, training/ back building of storms wont take much to occur, and with slow moving/ training/ back building storms, it wont take much to drop a couple inches within one hour. With that in mind, I have also issued a Flash Flood Watch for portions of the area. At this point it appears the heaviest rain will fall across Central, Eastern, and especially Southern Vermont. The GFS and ECMWF models are in nearly perfect agreement on this situation. One model is throwing a fly in the ointment, and that's the NAM model, although currently an outlier, it has proven before in these heavy rain situations that it can be right, even when its being an "outlier". The NAM is indicating the heavy rain axis will be across Eastern New York, and Western Vermont, while all other models are indicating the heaviest rain across Eastern, Central, and Southern Vermont. Only time will tell, either way stay tuned for further updates on this developing situation.
There are no official alerts from the National Weather Service for our area at this time, but there has been some talk of possibly issuing a Flash Flood Watch later this morning or early this afternoon. Stay tuned!
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