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Saturday, April 1, 2023 Convective Potential


weatherwiz
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Well the official start to severe season is just over a month away, but that doesn't mean we can't get some strong convective threats prior to then. Through the day, an area of surface low pressure moves across southeast Canada with a warm front lifting northward across southern New England and a trailing cold front moving east across New York and Pennsylvania. During the morning, rain and embedded thunderstorms move across the region, then we dry out a bit and become mostly cloudy with temperatures climbing into the 50's and 60's with dewpoints climbing into the 50's. Mid-level lapse rates of 6.5-7.5 C/KM are also expected to overspread the region. The presence of these steep lapse rates will help contribute to several hundred joules of mixed-layer CAPE Saturday afternoon ahead of the front with strong dynamics. While there is an abundance of dry air throughout the column, enough convergence is expected along the front to help aid in the development of a line of rain and thunderstorms. Embedded damaging wind gusts and hail are possible within the strongest cores!!!

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Been watching this one for a few days, the GFS has been relatively consistent with a potential severe event... In fact I almost asked about Saturday in the other thread, but thankfully controlled that impulse. I mean sure the numbers look good, at the moment - or at least they still did last night when I looked at it in detail. But it's Southern New England (sigh), and I've learned the hard way never to get my hopes up. But yeah, by all means lets start a thread and watch what happens. It couldn't hurt... Could it?

 

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Just now, tiger_deF said:

From someone relatively new to tracking severe weather, would an extremely severe event/positive bust in the midwest/TV increase the chances for severe weather here?

No...I don't believe there really is a correlation between what happens there and what happens here. There are many reasons for this, but one striking one is just the atmospheric profile. That region is prone to high-end severe weather events because of the elevated mixed-layer, which tends to weaken with eastward extent. 

Some say there is a connection between what happens in Michigan the day before but I think that is voodoo. That just came about b/c of 1953. I mean I guess you could look at our "bigger" events and then see what happened in Michigan the day before but I think it's a unrelated-correlation. 

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4 minutes ago, Cyclone-68 said:

Looks like parts of that moderate zone are being upgraded to high risk very soon per posts in the Midwest thread 

Scary wording 

MD 390 graphic

 Mesoscale Discussion 0390
   NWS Storm Prediction Center Norman OK
   1037 AM CDT Fri Mar 31 2023

   Areas affected...portions of southeastern Iowa...northwestern
   Illinois...and far northeastern Missouri

   Concerning...Outlook upgrade 

   Valid 311537Z - 311630Z

   SUMMARY...Portions of the Moderate Risk over southeastern IA,
   northwestern IL, and far northeastern MO will be upgraded to a
   categorical High Risk in the 1630 UTC Convective outlook.

   DISCUSSION...An upgrade to a tornado-driven High Risk (30%
   probability) is expected for the 1630 UTC outlook. Environmental
   conditions are quickly becoming favorable to support the potential
   for numerous strong to potentially violent and long-track tornadoes
   across portions of southeastern IA, northwestern IL, and far
   northeastern MO. Please see the forthcoming Day 1 outlook update for
   more information.

   ..Lyons/Smith.. 03/31/2023
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1 minute ago, weatherwiz said:

Scary wording 

MD 390 graphic

 Mesoscale Discussion 0390
   NWS Storm Prediction Center Norman OK
   1037 AM CDT Fri Mar 31 2023

   Areas affected...portions of southeastern Iowa...northwestern
   Illinois...and far northeastern Missouri

   Concerning...Outlook upgrade 

   Valid 311537Z - 311630Z

   SUMMARY...Portions of the Moderate Risk over southeastern IA,
   northwestern IL, and far northeastern MO will be upgraded to a
   categorical High Risk in the 1630 UTC Convective outlook.

   DISCUSSION...An upgrade to a tornado-driven High Risk (30%
   probability) is expected for the 1630 UTC outlook. Environmental
   conditions are quickly becoming favorable to support the potential
   for numerous strong to potentially violent and long-track tornadoes
   across portions of southeastern IA, northwestern IL, and far
   northeastern MO. Please see the forthcoming Day 1 outlook update for
   more information.

   ..Lyons/Smith.. 03/31/2023

It just doesn’t get any scarier than that 

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HOLY CRAP TWO AREAS

MD 392 graphic

 Mesoscale Discussion 0391
   NWS Storm Prediction Center Norman OK
   1044 AM CDT Fri Mar 31 2023

   Areas affected...ArkLaTex into parts of the Mid South

   Concerning...Severe potential...Tornado Watch likely 

   Valid 311544Z - 311745Z

   Probability of Watch Issuance...95 percent

   SUMMARY...The threat for tornadic supercells will increase this
   afternoon. PDS Tornado Watch issuance is eventually expected for
   parts of the region.

   DISCUSSION...Weak elevated convection has been ongoing across parts
   of AR this morning, within a plume of rich low-level moisture and
   along the periphery of a lead shortwave moving across eastern
   portions of the central Plains. Additional convective development
   has been noted recently into southeast OK and northeast TX.
   Widespread cloudiness will tend to limit diurnal heating to some
   extent, but gradual warming amid increasingly rich low-level
   moisture will support MLCAPE increasing into the 1000-2000 J/kg
   range and weakening MLCINH with time. 

   Area VWPs already depict very favorable wind profiles, with strong
   low-level (0-1 km SRH of 200-400 m2/s2) and deep-layer shear
   (effective shear of 60+ kt) expected to persist through the day.
   Tornadic supercells are expected to eventually evolve across the
   region this afternoon, with a few longer-lived supercells capable of
   producing strong/intense tornadoes possible, especially across AR
   toward the MS Valley. Onset timing of the greater threat remains
   somewhat uncertain, but one or more Tornado Watches will be required
   by early afternoon, with PDS Tornado Watch issuance expected across
   parts of AR toward the MS Valley.

   ..Dean/Hart.. 03/31/2023
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1 hour ago, weatherwiz said:

No...I don't believe there really is a correlation between what happens there and what happens here. There are many reasons for this, but one striking one is just the atmospheric profile. That region is prone to high-end severe weather events because of the elevated mixed-layer, which tends to weaken with eastward extent. 

Some say there is a connection between what happens in Michigan the day before but I think that is voodoo. That just came about b/c of 1953. I mean I guess you could look at our "bigger" events and then see what happened in Michigan the day before but I think it's a unrelated-correlation. 

But still got to wonder if there's not a "spillover" effect where extreme and repeating patterns of tornado outbreaks in the Midwest and South such as seem to be setting up this year might increase the chances for anomalous severe weather outbreaks in our region when conditions become climatologically favorable (late spring). 1995 (Great Barrington) was nationally, a very active year. 1973 (West Stockbridge) was according to Wikipedia, the most active tornadic year across the Midwest and South to that time. Of course much fresher in memory is 2011 and the extreme outbreaks across the South and Midwest that preceded June 1 here in Western Massachusetts.

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Just now, Hailstoned said:

But still got to wonder if there's not a "spillover" effect where extreme and repeating patterns of tornado outbreaks in the Midwest and South such as seem to be setting up this year might increase the chances for anomalous severe weather outbreaks in our region when conditions become climatologically favorable (late spring). 1995 (Great Barrington) was nationally, a very active year. 1973 (West Stockbridge) was according to Wikipedia, the most active tornadic year across the Midwest and South to that time. Of course much fresher in memory is 2011 and the extreme outbreaks across the South and Midwest that preceded June 1 here in Western Massachusetts.

It is certainly possible. If the upper air pattern favors the advection of elevated mixed-layers (and for them to maintain their integrity) into our region then we'll certainly see our higher end severe events. This was the case in 1995 (as you said) as well as 1998. 2011 was also like this to an extent. 

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