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


Kmlwx
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29 minutes ago, yoda said:
NOUS46 KOTX 072210
PNSOTX
WAZ036-082215-

Public Information Statement
National Weather Service Spokane WA
310 PM PDT Sat May 7 2022

...Two tornadoes touch down in the Spokane area on May 6th...

A National Weather Storm Survey combined with eyewitness account
and video footage has confirmed two tornadoes on May 6th, 2022
between 700 and 725 PM PDT in the Spokane area. The first tornado
touched down three miles northeast of Airway Heights at
approximately 703 PM PDT leading to tree and powerline damage in
the area. The second tornado touched down in Spokane Valley
between Freya and Dishman Hills Recreational area at approximately
720 PM PDT impacting a mobile home park. Several trees were
uprooted or downed, with a couple trailers overturned.
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8 hours ago, yoda said:

Looks like next chance is Monday

@high risk @Kmlwx  @Eskimo Joe  Besides Monday still being discussed as our next chance for severe in the region... what's ridge runner thunderstorms mean?  I am guessing like MCS complexes?

 

The aforementioned cold front will pass through the area Monday
while while mid-level flow increases significantly in response to an
upper-level low diving through southern Canada. This will increase
the shear profiles, and potentially increase any storm organization
raising the potential for severe thunderstorms Monday afternoon and
evening. The main question will be the timing of the front. If the
front is slower, this will coincide with peak heating and that will
elevate the threat for severe storms. However, if the front is
faster, then drier air may sneak in before peak heating limiting the
severe threat. Will continue to monitor, but confidence remains low
at this time.

High pressure will build overhead for Tuesday into Wednesday,
bringing mainly dry conditions (popup shower cannot be ruled out in
the north and northwest Tuesday, but most places will be dry) along
with lower humidity. The Mid-Atlantic and Ohio Valley region will be
on the edge of a building upper level ridge across the central
portions of the county, with the potential for ridge runner type
thunderstorms somewhere in this area.
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Ummm... :o

 

SEL8

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 208
   NWS Storm Prediction Center Norman OK
   325 PM CDT Thu May 12 2022

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Northwest Iowa
     Southwest Minnesota
     Northeast Nebraska
     Southeast South Dakota

   * Effective this Thursday afternoon and evening from 325 PM until
     1000 PM CDT.

   ...THIS IS A PARTICULARLY DANGEROUS SITUATION...

   * Primary threats include...
     Widespread damaging winds and scattered significant gusts to 105
       mph expected
     Scattered large hail likely with isolated very large hail events
       to 2 inches in diameter possible
     A couple tornadoes possible

   
   ...Guyer
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The PDS Blue Box in the midwest is insane. 2012 Derecho on steroids. For @yoda yea that's the only thing I can think of...storms bubbling up along the edge of a high...IIRC the 2012 Derecho was an impulse riding the edge of a pretty big high pressure system and since it wasn't an airmass change it kept temps from cooling off post event.

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Just a lil gusty storm

BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Twin Cities/Chanhassen MN
616 PM CDT Thu May 12 2022

The National Weather Service in the Twin Cities has issued a

* Severe Thunderstorm Warning for...
  Pope County in west central Minnesota...
  Chippewa County in west central Minnesota...
  Stevens County in west central Minnesota...
  Swift County in west central Minnesota...
  Northwestern Kandiyohi County in central Minnesota...

* Until 700 PM CDT.

* At 615 PM CDT, severe thunderstorms were located along a line
  extending from near Milbank to 6 miles southwest of Appleton to
  near Hanley Falls, moving northeast at 85 mph.

  THESE ARE DESTRUCTIVE STORMS FOR APPLETON AND BENSON.

  HAZARD...100 mph wind gusts.

  SOURCE...Radar indicated. At 608 PM CDT, Madison airport reported
           a gust of 94 mph.

  IMPACT...You are in a life-threatening situation. Flying debris
           may be deadly to those caught without shelter. Mobile
           homes will be destroyed. Expect considerable damage to
           homes and businesses. Expect extensive tree damage and
           power outages.

* Severe thunderstorms will be near...
  Granite Falls and Appleton around 620 PM CDT.
  Maynard and Lake Oliver around 625 PM CDT.
  Clara City around 630 PM CDT.
  Hancock and Raymond around 635 PM CDT.
  Kerkhoven, Chokio and Cyrus around 640 PM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is an EXTREMELY DANGEROUS SITUATION with tornado like wind
speeds expected. Mobile homes and high profile vehicles are
especially susceptible to winds of this magnitude and may be
overturned. For your protection move to an interior room on the
lowest floor of a building. These storms have the potential to cause
serious injury and significant property damage.

A Tornado Watch remains in effect until midnight CDT for central and
west central Minnesota.

&&

LAT...LON 4575 9625 4576 9514 4533 9512 4489 9525
      4489 9548 4477 9549 4477 9551 4480 9551
      4491 9568 4491 9572 4493 9573 4495 9580
      4516 9604 4518 9610 4541 9612 4542 9625
TIME...MOT...LOC 2315Z 213DEG 74KT 4517 9662 4514 9613 4471 9566

THUNDERSTORM DAMAGE THREAT...DESTRUCTIVE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...100 MPH
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I keep waiting for a "real" severe threat to develop here, and by that I mean something with a legitimate amount of instability, and not those cool season low CAPE - high shear events.    Climo generally says that we have to wait until mid May or so, and right on schedule, it looks like Monday may have some modest potential.

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Sounds like we may finally be getting into some good severe chances next week per afternoon LWX AFD 

LONG TERM /MONDAY THROUGH FRIDAY/...
A strong cold front is forecast to pass through our region Monday
into Tuesday. An accompanying strong upper level trough is forecast
to drop southward toward our region from the upper Great Lakes
region. Ensembles and deterministic models have the trough
going neutral to slightly negatively tilted with the best
forcing mainly focused over PA. Strong warm air advection ahead
of the frontal passage will likely lead to CAPE values rising
above 1000 with decent speed shear of 30 to 40 knots. The
potential for shear above 40 knots and CAPE above 1000 as the
front passes through our region may lead to an increased threat
for severe storms capable of producing damaging winds. Based on
the fact that shear will be unidirectional, the storm mode could
be more QLCS vs cellular. There remains some uncertainty on the
timing of the frontal passage and upper trough axis and whether
it will occur during peak heating.

Behind the frontal passage, high pressure is forecast to build back
over our region through Wednesday leading to moderating temperatures
and mostly dry conditions. A strong shortwave moving through a near
zonal flow may bring another chance for showers and thunderstorms to
the region on Thursday. Warm air advection along with potential for
some directional shear may lead to another threat for strong storms
late Wednesday into Thursday.
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On 5/12/2022 at 6:24 PM, Eskimo Joe said:

The PDS Blue Box in the midwest is insane. 2012 Derecho on steroids. For @yoda yea that's the only thing I can think of...storms bubbling up along the edge of a high...IIRC the 2012 Derecho was an impulse riding the edge of a pretty big high pressure system and since it wasn't an airmass change it kept temps from cooling off post event.

       Sorry, @yoda.    Didn't see your question earlier, but this explanation is correct.      You typically get stronger flow around the edges of a ridge, and there is a typically a "quality" air mass in place beneath.   Add a few disturbances moving through that faster flow, and you're in business.   

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19 minutes ago, Kmlwx said:

Large Day 3 Slight Risk from SPC for our region. Also runs south and way north into the northeast.

... And shear actually looks quite decent (EBWD >= 40kts). Could certainly be some decent storms in spots if we manage > 1000J/kg mlcape to go along with the shear. The later the front moves through the better.

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1 hour ago, George BM said:

... And shear actually looks quite decent (EBWD >= 40kts). Could certainly be some decent storms in spots if we manage > 1000J/kg mlcape to go along with the shear. The later the front moves through the better.

          Agreed.   NAM Nest for Monday afternoon looks impressive, both in terms of forecast soundings and simulated reflectivity.   

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SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A potent upper-level trough will dig from the Ohio Valley into
our area Monday and the cold front associated with this system
will pass through our region during the afternoon into the early
evening. The wind field will increase significantly, causing
moderate to strong shear (deep layer shear most likely around
40-60 knots). The increased shear combined with height falls,
strong forcing along the front, and moderate CAPE enhances the
threat for severe thunderstorms. Convection out ahead of the
front is likely to be moving into the Appalachains Monday
morning, and the strong to severe storms will most likely form
along the differential heating boundary between that convection
and growing instability to the east. This is most likely to
setup near the I-81 corridor before storms intensify as they
move east. Convection will likely develop into line segments
with embedded supercells possible. Therefore, damaging winds and
large hail are a concern. However, the surface flow will be
backed (especially east of Interstate 81), so there is a tornado
threat as well.

Another round of convection is possible along the front, and
given the shear profiles with falling heights some of that can
be severe as well. However, confidence is much lower for this
since the atmosphere may be worked over by widespread convection
associated with the first round.

There is also an isolated flood/flash flood threat with the
convection as well. Faster storm motion suggests that threat
will be limited, but FFG is low due to recent rainfall. Also,
if bowing segments develop, the southern portion of the bowing
segment could be parallel to the cloud layer wind for a period.
If this does occur, that could enhance the flood/flash flood
threat.
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Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1218 PM CDT Sun May 15 2022

   Valid 161200Z - 171200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
   VIRGINIA INTO NEW YORK...

   ...SUMMARY...
   Scattered severe storms are expected Monday from central New
   York/western New England southward into the Carolinas. Damaging
   winds, hail, and few tornadoes will be possible through about 00Z.

   ...Synopsis...
   A shortwave trough will move quickly from the OH Valley toward the
   Mid Atlantic during the day, taking on a negative tilt across New
   England after 00Z. Deep-layer wind fields will strengthen with this
   trough, with substantial large-scale ascent from VA into NY.

   A surface trough will deepen as it moves into eastern NY and PA,
   with dewpoints holding near 60 F within the zone of convergence.
   Farther south, the main cold front push will occur from MD into VA,
   coincident with a midlevel dry slot. Here, dewpoints around 65 F
   will be more common, with a plume of steep low-level lapse rates
   emanating out of the southwest.

   ...Northeast and Mid Atlantic into the Carolinas...
   Thunderstorms will likely be ongoing Monday morning from western PA
   into WV along the developing cold front, and SBCIN will likely be
   removed by 15Z due to cool 700 mb temperatures. Storms are expected
   to become severe between 15-18Z as they develop into south-central
   NY, central PA, and toward far northern VA. MLCAPE is expected to
   average 1000-1500 J/kg, with effective deep-layer shear of 40-50 kt.
   Mixed storm modes may occur, including supercells and QLCS. Damaging
   wind gusts will be most likely. The tornado threat is expected to
   increase during the late afternoon as the surface low/trough
   deepens, low-level lapse rates are maximized, and effective SRH
   increases to around 200 m2/s2. Cool temperatures aloft and elongated
   hodographs will also favor sporadic hail in the stronger cells.

   Although shear will be weaker farther south into the Carolinas,
   strong heating and plentiful moisture will result in 2000 J/kg
   MUCAPE with sufficient westerly shear to support multicells with
   wind and hail threat. A few cells may linger toward 00-02Z.
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Not that it means a ton 24 hours out, but some of the Sim reflectivity has left a little to be desired. Definitely a solid setup though. I'm a little concerned the best activity goes N of our area. @mappyville looks solid 

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So, if the 12z NAM 3km is correct about the DC/Baltimore/Fredericksburg area having 1800 to 2500 MLCAPE this region will have some instances of significant severe weather tomorrow. The 300 to 700mb flow is focused towards our area during mid to late afternoon tomorrow.

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effective thunderstorm moving through here.  this really is one of, if not my favorite, kinds of weather days.  great for outdoor hoops and then topped off with a thunderstorm.  trails will inevitable be a mess tomorrow, though.  only downside.

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Latest take on potential for tomorrow from Mount Holly-

Monday continues to appear quite interesting. The mid level short wave trough that was producing thunderstorms in the middle Mississippi River Valley this afternoon will head our way. It should move up the Ohio River Valley overnight and on Monday morning. The trough is expected to begin taking on a negative tilt on Monday and its axis is anticipated to pass over our region early on Monday night. Conditions are forecast to become favorable for severe weather in our region in advance of the approaching short wave and its associated cold front from Monday afternoon into Monday evening. Mixed layer CAPE values are expected to rise into the 1000 to 1500 J/kg range as surface temperatures rise mostly into the upper 70s and lower 80s with dew point readings well into the 60s. The expected wind profiles suggest deep layer shear in excess of 40 knots with storm relative helicity rising near 200 m2/s2. Not only are damaging winds and hail forecast but we will need to watch for brief spin-ups in our area. The storms are expected to be progressive. However, with precipitable water values in the neighborhood of 1.5 inches, locally heavy and flooding is areas of poor drainage are additional concerns.

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