Current Alert Details:
The National Weather Service in Burlington, VT continues a Flood Watch for much of Vermont, and portions of Northern New York for the potential of flooding from heavy rains, and the potential for ice jam flooding due to expected rapid rises on area waterways. They also have issued A Wind Advisory, which is in effect for the Western slopes of the Green mountains for Southeast winds of 25-35MPH with gusts up to 50MPH possible after midnight tonight.
The National Weather Service in Albany, NY continues a Flash Flood Watch for extreme Southern Vermont for the potential of flash flooding due to heavy rains, and possible ice jam flooding due to significant rises on area waterways.
Champlain Valley Weather continues a Flood Watch for much of Vermont, and portions of Northern New York for the potential of a widespread 1-2 inches of rain, with locally higher amounts, which will lead to potential flooding, and significant rises on area waterways, which will also produce great risk of ice jam flooding. A High Wind Warning now replaces the previous High Wind Watch, for the Western slopes of the Green mountains for the potential of strong southeast winds of 25-40MPH with gusts up to 60MPH, with isolated higher gusts in most favored mountain gap locations.
Champlain Valley Weather Discussion:
A significant storm system, will begin to impact the region later this evening, with strong to potentially damaging winds, moderate to heavy rain, and potential flooding on Monday.
Currently, a 984mb low pressure system over Northeastern Wisconsin, will continue to move North-Northeast today, and this evening. Out ahead of this system a strong, and moist southerly flow upon a tightening pressure gradient will continue to result in temperatures rising, moisture pushing into our area, and winds to increase.
Heavy rain and the flood potential is the primary concern with this system. Rain will develop later this evening, and become heavy at times after midnight. Rain will continue heavy at times through Monday morning, and begin to diminish in intensity Monday afternoon. Rainfall totals are depicted on the map at the top of this post, so please make sure to check that out. The heaviest rain still appears to be across Central, and Southern Vermont. Its not out of the question for isolated amounts in excess of 3-4 inches to occur, especially across the Southeast upslope areas of the Central, and Southern Green mountains. This amount of rain combined with snowmelt, from temperatures being in the 40's to near 50 Monday, will result in rapid rises on area waterways.
With the ground being frozen the rainfall, and snow melt will flow directly into area waterways, and not be absorbed by the ground at all, which is very significant. I was thinking about following the National Weather Service in Albany, NY and issue a Flash Flood Watch for everyone, but a large question remains as to how much the current snowpack will be able to absorb and hold the rain. In the Champlain, and St. Lawrence Valley's there is around 4-9 inches of snow. The snowpack across these places wont be able to absorb the rain as the snowpack is not that great. Across the higher terrain though especially about 1000 feet, snowpack of 12+ inches remains. These areas will be able to hold the rain better, but with warmer temperatures the past week or so, with slight melting everyday, and the expected warmer temperatures today, and Monday the snowpack may be ripe, and if it is, then rapid snowmelt will occur as well in the higher elevations. But its not knowing, which is holding me off from a Flash Flood Watch.
Eitherway, rapid rises on area waterways will occur, and with the rivers rising, and a solid sheet of ice across them, this ice will become unstable and begin to break. This will result in a significant ice jam threat, and their associated flooding risks. So overall I feel a flood watch is the safe bet, and we will remain with that.
Right now the pressure gradient is tight, but no where as tight as what it will be later tonight or tomorrow morning. Already we are seeing a primarily southerly wind, which is being enhanced in the Champlain Valley resulting in sustained winds in the 10-20MPH range, with gusts in the 25-35MPH range. Earlier a wind gust of 41MPH was recorded at the National Weather Service office in Burlington, Vermont. The 41MPH wind gust appears to be a more localized stronger gust, and remains shy of the 46MPH gust criteria for a Wind Advisory. These winds will continue to be monitored, but at this point I am not going to issue a Wind Advisory, and you will likely not see one issued for the National Weather Service for the Champlain Valley either.
As the winds slowly shift to a more southeasterly direction things will become more interesting overnight, especially along the western slopes of the Green mountains, where the National Weather Service has issued a Wind Advisory. I feel winds are going to be stronger then anticipated and I have issued a High Wind Warning. I feel there will be a time period long enough for High Wind Warning type winds to occur before the heaviest rain moves in to stabilize the lower layer of the atmosphere. Even then I feel damaging wind gusts will be able to mix down and funnel through the favorable mountain gaps, and passes of the Western slopes of the Green mountains. Therefor in areas such as Richford, Bakersfield, Cambridge, Jericho, Huntington, Appalachian Gap, Rutland, and Bennington, winds will increase into the 25-40MPH range by late tonight, with gusts in the 60MPH range. Some of these gusts will be able to accelerate better through some of the mountain gaps, and isolated wind gusts to 70MPH are possible in the most favorable gap locations. The strongest winds should occur prior to the heaviest rainfall, but even after the heaviest rain moves in, isolated damaging wind gusts will likely continue, but be less often, and likely be well under 70MPH. The strong to damaging winds should start to diminish later Monday afternoon.
The last concern is the potential for some light icing at the onset of precipitation tonight, especially across the sheltered valley's of eastern Vermont, and the extreme Northern St. Lawrence Valley of New York. The National Weather Service in Burlington has issued a Freezing Rain Advisory for the Northeast Kingdom and Eastern Vermont for the potential of up to a tenth inch of ice accumulation. I am holding off on issuing a Freezing rain advisory, while I feel the areas that receive ice accumulation in eastern Vermont will be very isolated. Also I feel if any area has a greater threat of seeing icing, it would be the extreme Northern St. Lawrence Valley, where winds remain out of the northeast, and the temperatures are still below freezing. The atmosphere is also very dry, and as the precipitation tries to fall through the atmosphere it will result in evaporative cooling, which will help lower temperatures a couple degrees area wide. So places currently hovering around freezing will likely fall below freezing, resulting in some sleet/ freezing rain. I will continue to monitor this potential, for the possibility of issuing a Freezing Rain Advisory for the Northern St. Lawrence Valley, and perhaps portions of eastern Vermont. Stay tuned to Champlain Valley Weather, and your locally weather and media outlets for further information on this upcoming storm system. I will try to have another update later this evening.
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