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2022 Mid-Atlantic Severe Wx Thread (General Discussion Etc)


Kmlwx
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  • 2 weeks later...
 ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 090805
   SPC AC 090805

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0305 AM CDT Sun Oct 09 2022

   Valid 121200Z - 171200Z

   ...DISCUSSION...
   ...Wednesday/Day 4 and Thursday/Day 5...
   A cold front is forecast to move quickly eastward across the western
   Great Lakes and mid Mississippi Valley on Wednesday. This will occur
   ahead of a substantial upper-level trough that is forecast to deepen
   during the day. Due to strong forcing associated with the
   upper-level trough and cold front, a line of thunderstorms will
   likely develop Wednesday afternoon. This line of storms should move
   eastward across the southern Great Lakes and Ohio Valley Wednesday
   afternoon. Although a wind-damage threat will be possible along the
   leading edge of this line, limited moisture return and weak
   instability will be problematic for a more widespread threat. An
   isolated wind-damage threat could continue into the evening as the
   cold front and line of storms moves into the central Appalachians.
   The cold front is forecast to move through the Northeast on
   Thursday, and could reintensify by midday from parts of New York and
   Pennsylvania southward into the Mid Atlantic. The wind-damage threat
   could affect areas as far north as New England Thursday afternoon. A
   15 percent contour could be needed in either Day 4 or Day 5, once
   the details become more clear in model runs that come out over the
   next day or two.
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17 minutes ago, Kmlwx said:

As is common in these out-of-season events...the NAM and NAM nest favor south and east of the metros for any enhanced activity. 

meh. 

Very true and unlike coastal snow, severe events, particularly large-scale ones tend to trend south and east.  This looks no different as earlier times are now favored. However, large scale off season high shear low cape events which normally fail to gusty showers end up being our most impressive outbreaks when they do perform.  Probably won't happen this time as the period from early October to early November have never really seen much.

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2 minutes ago, 2010 extreme said:

Very true and unlike coastal snow, severe events, particularly large-scale ones tend to trend south and east.  This looks no different as earlier times are now favored. However, large scale off season high shear low cape events which normally fail to gusty showers end up being our most impressive outbreaks when they do perform.  Probably won't happen this time as the period from early October to early November have never really seen much.

This is true - especially if it's very dynamic at 500mb (negative tilted trough, well timed, and with some overlap in whatever CAPE is available and the shear and forcing). 

November 2006 had a very dynamic event. 

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3 hours ago, Kmlwx said:

As is common in these out-of-season events...the NAM and NAM nest favor south and east of the metros for any enhanced activity. 

meh. 

          Yeah, definitely looks better south and east of here, where the better instability will reside.    A slightly slower system could, however, change things a bit.

          Pros:  good wind fields including some favorable hodographs, good surge of low-level moisture

          Cons:  limited heating leading to crappy lapse rates and very limited CAPE,  no real height falls of note (the trough lifts to the northeast, which also explains why it won't be very cold behind the front)

 

 

 

 

 

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I'm a little more in today and less meh - but still pretty meh. 

The latest (06z) NAM nest looked decent. CIPS had a bit of a signal as well...at least as much as you could expect off-peak season. SREF even paints some sigtor ingredients in our region tomorrow on the 21z frame. 

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4 hours ago, Kmlwx said:

I'm a little more in today and less meh - but still pretty meh. 

The latest (06z) NAM nest looked decent. CIPS had a bit of a signal as well...at least as much as you could expect off-peak season. SREF even paints some sigtor ingredients in our region tomorrow on the 21z frame. 

          Yeah, the timing is better, and instability therefore looks ever-so-slightly better.    There will pretty clearly be a line of strong convection just ahead of the front.    Whether it will contain lightning or be surfaced-based is unclear.    Some of the CAMs even suggest some discrete cells in advance of the line.    The shear is very strong, and some of the models even suggest some healthy low-level shear, so this event certainly warrants some watching.

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4 minutes ago, high risk said:

          Yeah, the timing is better, and instability therefore looks ever-so-slightly better.    There will pretty clearly be a line of strong convection just ahead of the front.    Whether it will contain lightning or be surfaced-based is unclear.    Some of the CAMs even suggest some discrete cells in advance of the line.    The shear is very strong, and some of the models even suggest some healthy low-level shear, so this event certainly warrants some watching.

Seems like the kind of day where a bunch of cells with little or no lightning and tops under 35kft will all seem to take on mini-supercell characteristics and perhaps put down a brief tornado. Chaotic kind of days. 

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LWX afternoon AFD sounds interesting for tomorrow 

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As the main upper level trough of low pressure progresses slowly
to the east across the Midwest and Great Lakes, a strong surface
cold front will push into western Pennsylvania and northwest
West Virginia shortly after daybreak Thursday morning. During
the course of the morning, additional showers are expected to
develop almost anywhere in the CWA with the primary focus in the
Appalachians, Virginia Piedmont, and to the I-81 corridor.
These developing showers will be scattered, but a more develop
line of heavy showers and thunderstorms could develop across
western Maryland and northern West Virginia around Noon or
shortly before Noon just ahead of the strong surface cold front.
This activity could take on such a linear alignment that we may
be noting this as a QLCS. This QLCS like others, take shape
when there is a strong and persistent southerly flow at the
surface and a few thousand feet above ground. Hence, this type
of flow allows for increased moisture and brings a component of
wind shear to the table with developing convection. Such
alignment of showers and thunderstorms brings the main threat
of damaging winds. Also sometimes QLCS can produce embedded
tornadoes. Hail cannot be ruled out either, but doesn`t seem the
higher ranked component as CAPE or instability will be small or
marginal.

Timing of the heavy showers and strong to severe thunderstorms
or QLCS factor seems to be 11am to 1pm in western MD and
northern WV, 2pm to 4pm the I-81 corridor, and 5pm to 8pm the
metropolitan areas and into southern Maryland. As the cold front
clears the respective areas, so does the convection. Once the
front passes, a sharp wind shirt is anticipated from west to
east. Temperatures Thursday will top out middle 60s to lower
70s, then fall rapidly Thursday evening and night into the
upper 30s to lower 40s. As previously mentioned, the airmass
filling in behind the front will be Pacific and not Arctic, so
Thursday night temperatures may not be as uncomfortable as could
be with the airmass discrepancy.
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  • 2 months later...
  • 2 weeks later...
36 minutes ago, yoda said:

SPC mentioned us in their Day 4-8 OTLK and AFD from LWX this afternoon showed intrigue with CAPE discussion and very strong shear

The weather has been so boring lately other than the wind/rain recently. This is not our severe season...so we will probably fail - but I'm intrigued. It's too far out to do a deep dive yet. 

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