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Thursday, July 13 - Friday, July 14, 2023 Convection


weatherwiz
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As of this writing we have a deepening surface cyclone slowly lifting northeast across southern Quebec province. This is aiding in a northward progression of rich low-level theta-e air with strengthening wind fields in response. There is also a plume of modified elevated mixed-layer air moving across the region. In closer proximity to the surface cold front and surface trough, numerous thunderstorms have developed across upstate New York with mixed modes containing discrete cells and the organization of a squall line. The environment is plenty conducive for numerous strong-to-severe thunderstorms containing damaging winds and/or large hail with the potential for a few tornadoes. In addition, combination of upscale linear growth with slow southeast advancement as the system becomes parallel to the upper-level flow will result in long-duration torrential downpours yielding the risk for flash flooding - perhaps significant in some spots.

As we move deep into the evening, this line should advance across New England, however, as we will lose the diurnal heating this line will be weakening. Enough wind shear and elevated CAPE will keep the low probability for some localized severe weather into the overnight. 

Given the system becoming parallel to the upper-level flow, the progression of the cold front will slow. This is starting to become better identified within forecast model guidance. This will likely allow the development of numerous showers and thunderstorms Friday. While the environment will not be as prime as it is today, the risk for strong-to-severe thunderstorms with al hazards will be in place. Flash flooding will also be possible Friday and some significant flash flooding is possible.

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BTV discussion (will Wiz make his wife read it to him- not for lack of ability to comprehend):

https://forecast.weather.gov/product.php?site=BTV&issuedby=BTV&product=AFD&format=CI&version=1&glossary=1

NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 332 PM EDT Thursday...Active severe weather is ongoing
through this evening as an unseasonably strong low pressure
system drags a cold front eastward through our region tonight.
As expected, ingredients are present for rotating thunderstorms
in this region, near the triple point of a dynamic low pressure
system passing northeastward through the St. Lawrence Valley.
Our thermodynamic environment is impressive with mixed layer
CAPE at 2 PM of 1500-2000 J/kg, steep low level lapse rates and
moderate mid-level lapse rates helping updrafts strengthen.
Southwesterly wind shear is ample to keep storm structures
organized, with effective shear of 30 to 35 knots, and rotation
is substantial with 0-1 km helicity of 100 to 150 m2/s2.
Additionally, strong synoptic southerly winds will gradually
expand eastward, which are being channeled up the Champlain
Valley with wind gusts locally near 35 MPH. An occasional
stronger gust may cause isolated damage outside of the
thunderstorms, especially where we`ve seen very wet conditions.

A mixture of storm modes are present, which include linear
segments and discrete cells, which could include supercells. The
main hazards are damaging winds and flash flooding. Wind damage
has already been reported in the northern New York this
afternoon. Rotating storms have resulted in a reported funnel
cloud, but relatively high cloud bases (3000 feet or higher) may
limit the tornado potential. As thunderstorms expand northward
and eastward off of the Adirondacks, we will be concerned with
rotating storms and enhanced gusts in the Champlain Valley due
to enhanced low level convergence.

As the evening progresses, any discrete storms should tend to
be absorbed into a single fast moving squall line. Brief spinups
are possible along this line, and its fast forward speed will
tend to keep its severity going all the way eastward through
Vermont even as daytime heating. Scattered wind damage is
expected with the squall line. Less wind will be needed to
produce downed trees than typical given saturated soils in most
areas currently in a flood watch. Where a combination of
discrete and linear storms move over the same area, flash
flooding due to multiple rounds of heavy rain remains possible.
A heightened concern for flooding remains in our hard hit areas
of central Vermont, where capacity for additional heavy rain is
low. Improving conditions will arrive overnight with winds
becoming light and drier air settling in behind the cold front.
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Severe Weather Statement
National Weather Service Burlington VT
639 PM EDT Thu Jul 13 2023

NYC031-VTC001-021-132245-
/O.CON.KBTV.TO.W.0001.000000T0000Z-230713T2245Z/
Essex NY-Addison VT-Rutland VT-
639 PM EDT Thu Jul 13 2023

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 645 PM EDT FOR
SOUTHEASTERN ESSEX...SOUTHWESTERN ADDISON AND NORTHWESTERN RUTLAND
COUNTIES...

At 639 PM EDT, a severe thunderstorm capable of producing a tornado
was located over Lake Dunmore, moving northeast at 30 mph.

HAZARD...Tornado and two inch hail.

SOURCE...Radar indicated rotation.

IMPACT...Flying debris will be dangerous to those caught without
         shelter. Mobile homes will be damaged or destroyed. Damage
         to roofs, windows, and vehicles will occur.  Tree damage is
         likely.

This tornadic thunderstorm will remain over mainly rural areas of
southeastern Essex, southwestern Addison and northwestern Rutland
Counties, including the following locations... Benson Bay, Catfish
Bay In Addison County, Huntley Island, Forest Dale, Beadles Cove,
Larrabees Point, Beartrap Island, Kerby Point, Hollands Pasture
Island, and East Shoreham.
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14 minutes ago, CoastalWx said:

Where about is your location? RadarScope it out if you can.

My address is the Stowe dot on this radar.  I labeled it Stowe but that’s my literal address.  Is there a way to get lat/lon off it?

If you are to zoom in, default “Stowe” on RadarScope is like 1 mile ESE on RT 100 (the road shown).  

72C146DB-3078-4C3D-9F90-A579CDAC58DD.jpeg.fdf015873753cd3be90f83d287923a27.jpeg

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2 minutes ago, powderfreak said:

My address is the Stowe dot on this radar.  I labeled it Stowe but that’s my literal address.  Is there a way to get lat/lon off it?

If you are to zoom in, default “Stowe” on RadarScope is like 1 mile ESE on RT 100 (the road shown).  

72C146DB-3078-4C3D-9F90-A579CDAC58DD.jpeg.fdf015873753cd3be90f83d287923a27.jpeg

Oh so you’re basically the default “Stowe” on RadarScope?

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7 minutes ago, CoastalWx said:

Oh so you’re basically the default “Stowe” on RadarScope?

Yeah I’m right there… like a handful of pixels NW.  Right on Mountain Road and the Rec Path.  But if you use default “Stowe” and go a shade NW that’s literally overhead.

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