A warm front is expected to lift through southern New England Friday morning which may produce a few showers or a rumble of thunder. As the warm front lifts into central New England dew points south of the front will climb through the 50's and into the lower 60's. As clouds begin to break, strong May sunshine should help boost temperatures through the 70's during the afternoon. The combination of temperatures in the 70's and dew points into the 60's will result in a modestly unstable air mass.
A cold front begins to approach southern New England by early evening. The combination of a modestly unstable air mass, strong wind shear aloft, and forcing from the approaching cold front and shortwave energy yielding strong height falls, will result in the development of rain and thunderstorms in the form of a squall line. This squall line will move southeast through the region during the evening hours and will be capable of producing damaging wind gusts.
Assessing severe weather potential:
The potential is there for a more significant severe weather event (despite the presence of steeper mid-level lapse rates), however, not all the ingredients will align to make this happen. Forecast models stall the warm front across central New England. Just south of the warm front the air mass will be unstable thanks to warm temperatures and humidity along with rather strong wind shear; including the presence of directional wind shear (winds changing direction as you ascend from the surface through the lower atmosphere). In this scenario, the potential would be there for supercell thunderstorms capable of producing tornadoes, however, this potential will be mitigated by the lack of a trigger and rising heights through the afternoon.
As the cold front approaches during the evening and the associated line of rain and thunderstorms, instability will begin to weaken due to the loss of daytime heating, however, strong wind shear aloft and just enough instability will keep the potential for scattered pockets of damaging winds and hail possible as the line of thunderstorms progresses southeast through southern New England. Expecting the line to begin moving through between 7:00 PM EDT and midnight EDT. Greatest risk for any damaging winds north and west of the I-84 corridor. There is the low probability for a tornado across southern VT/northwestern MA in the vicinity of the warm front as there will be enough wind shear to yield the potential for an embedded supercell within the line.
Thursday, May 14, 2020
Wednesday, May 6, 2020
Historic May Snowstorm on the Way (Friday, May 8, 2020 - Saturday, May 9, 2020)
For the most part, my blog posts focus on Connecticut, however, due to the historic nature of what is about to unfold as we move into Mother's Day Weekend I am expanding the focus to cover all of New England. (However, my snow map will focus on Connecticut due to time constraints).
An unprecedented air mass (for the month of May) is set to enter New England Friday into Saturday. A piece of the polar vortex is expected to break off from the main vortex and swing through southeastern Canada and move through New England. This will be associated with 500mb heights as low as 516-518 meters. On average, the 500mb level is about 18,000 feet above the ground (and typically a bit higher as we move closer to the summer solstice), however, the 500mb level will be as low as 16,000 - 17,000 feet above the ground! This will also be associated with temperatures at this level as low as -35C to -40C...these heights and temperatures would be record breaking and perhaps record shattering.
At the surface, a cold front will be moving through the region. As the polar vortex dives in an associated shortwave trough will amplify (strengthen) as it digs through New England. This will promote strengthening jet stream dynamics aloft which will be favorable and conducive for cyclogenesis (strengthening) of a low pressure system along the cold front.
As the low pressure strengthens and with the passage of the cold front, we will see anomalous cold across southeast Canada will advect into New England. This cold will set the stage for what looks to be a historic winter storm for interior New England, however, as far south as Connecticut is not out of the woods. The biggest key will be track of the low pressure. Should this track a bit farther southeast than what forecast models indicate, heavy snow would be likely across much of Connecticut away from the shoreline.
While surface temperatures may remain as high as 33-35F, temperatures just a few thousand feet above the ground will be extremely cold which will yield precipitation to remain as all snow...the only problem is it will be very wet and heavy. For any areas which see more than 3-4'' of snow, concern will be high for widespread power outages (which could last for several days in some places) and tree damage. As of now, the greatest potential for this to happen would be; Northwest Hills of Connecticut, western Massachusetts, a large part of Vermont, New Hampshire, and Maine away from the coast.
This is an extremely complex situation due to the unprecedented and historic nature of this air mass and subsequent storm. Significant changes to this forecast are possible as the details become clearer. Right now, the greatest concern for power outages and tree damage in Connecticut is confined to the Northwest Hills.
Timeline for Connecticut:
An unprecedented air mass (for the month of May) is set to enter New England Friday into Saturday. A piece of the polar vortex is expected to break off from the main vortex and swing through southeastern Canada and move through New England. This will be associated with 500mb heights as low as 516-518 meters. On average, the 500mb level is about 18,000 feet above the ground (and typically a bit higher as we move closer to the summer solstice), however, the 500mb level will be as low as 16,000 - 17,000 feet above the ground! This will also be associated with temperatures at this level as low as -35C to -40C...these heights and temperatures would be record breaking and perhaps record shattering.
At the surface, a cold front will be moving through the region. As the polar vortex dives in an associated shortwave trough will amplify (strengthen) as it digs through New England. This will promote strengthening jet stream dynamics aloft which will be favorable and conducive for cyclogenesis (strengthening) of a low pressure system along the cold front.
As the low pressure strengthens and with the passage of the cold front, we will see anomalous cold across southeast Canada will advect into New England. This cold will set the stage for what looks to be a historic winter storm for interior New England, however, as far south as Connecticut is not out of the woods. The biggest key will be track of the low pressure. Should this track a bit farther southeast than what forecast models indicate, heavy snow would be likely across much of Connecticut away from the shoreline.
While surface temperatures may remain as high as 33-35F, temperatures just a few thousand feet above the ground will be extremely cold which will yield precipitation to remain as all snow...the only problem is it will be very wet and heavy. For any areas which see more than 3-4'' of snow, concern will be high for widespread power outages (which could last for several days in some places) and tree damage. As of now, the greatest potential for this to happen would be; Northwest Hills of Connecticut, western Massachusetts, a large part of Vermont, New Hampshire, and Maine away from the coast.
This is an extremely complex situation due to the unprecedented and historic nature of this air mass and subsequent storm. Significant changes to this forecast are possible as the details become clearer. Right now, the greatest concern for power outages and tree damage in Connecticut is confined to the Northwest Hills.
Timeline for Connecticut:
- Showers arrive into the state by Friday afternoon with some heavier rain by the evening.
- During the evening temperatures quickly crash, allowing for rain to transition over to heavy, wet snow in the Northwest Hills with rain changing to snow by late evening and early overnight across much of the state away from the immediate shoreline.
- Greatest accumulations across the Northwest Hills (4-6'' possible) with highest likelihood for widespread power outages and tree damage.
- Thundersnow is possible
- Saturday features near record-cold with scattered snow showers, snow squalls, and the potential for thunder/lightning along with grauple and small hail.
- Below is my current thinking for Connectuct:
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