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April 26th Slight Risk Observations


Bananashadow
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Later today, storms along the cold front will increase in intensity
   as it encounters the heating air mass. A line of storms will result,
   possibly a broken line of cells or QLCS, with damaging winds likely.
   The strongest low-level shear will remain near the warm front, which
   will lift northward into PA and NJ. Here, forecast soundings show
   larger looping hodographs which may favor tornadoes, either with
   supercells just ahead of or embedded within the line. In addition,
   the relatively cool temperatures aloft near 700 mb will maximize
   low-level instability which will also aid rotation in storms.

mcd0451.gif

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NJ_swody1.png.86a37ac954a4dbbe24dbb821c2122006.png

Tor: 5%

Wind: 30%

Hail: 5%

Congrats Phili

 

Quote

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
   OF SOUTHEAST PENNSYLVANIA...SOUTHWEST NEW
   JERSEY...DELAWARE...EASTERN MARYLAND...AND EASTERN VIRGINIA....

   ...SUMMARY...
   The main threat for severe storms today will be from eastern North
   Carolina to southeastern Pennsylvania and southern New Jersey,
   including the DC, Tidewater and Delmarva regions.  Damaging wind
   should be the most common event, though a few tornadoes also are
   possible.

   ...Mid Atlantic Region...
   Water vapor imagery shows a strong upper trough approaching the Mid
   Atlantic region, with large midlevel height falls forecast across
   the region this afternoon.  Visible imagery shows broken cloud cover
   throughout the area, allowing daytime heating and destabilization to
   occur.  This should result in widespread thunderstorm activity later
   today, with the potential for damaging winds and a few tornadoes.

   The primary severe threat appears to be associated with a line of
   convection currently over eastern WV and western PA.  This activity
   will intensify by mid-afternoon as it tracks into the warmer and
   more unstable air across central VA/PA.  Strong westerly flow aloft
   and considerable low-level shear will promote bowing segments in the
   line capable of damaging wind gusts.  A few tornadoes are also
   possible along the line.  Other storms are expected to form ahead of
   the line in a weakly capped environment, also posing a risk of
   damaging winds and perhaps tornadoes.  Have upgraded to ENH risk to
   cover this region for this afternoon.

 

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Quote

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 105
   NWS Storm Prediction Center Norman OK
   135 PM EDT Fri Apr 26 2019

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     District Of Columbia
     Delaware
     Central and Eastern Maryland
     Southern New Jersey
     Central and Southeast Pennsylvania
     Northeast Virginia
     Coastal Waters

   * Effective this Friday afternoon and evening from 135 PM until
     900 PM EDT.

   * Primary threats include...
     A couple tornadoes possible
     Widespread damaging wind gusts to 70 mph likely
     Isolated large hail events to 1 inch in diameter possible

   SUMMARY...Thunderstorms will intensify along a cold front this
   afternoon and spread across the watch area, posing a risk of
   damaging wind gusts and a few tornadoes.

   The tornado watch area is approximately along and 75 statute miles
   east and west of a line from 20 miles east northeast of Williamsport
   PA to 15 miles west southwest of Patuxent River MD. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU5).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and severe thunderstorms in and close to the watch
   area. Persons in these areas should be on the lookout for
   threatening weather conditions and listen for later statements
   and possible warnings.

 

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Are we really getting the warming for that level of storms? Maybe still to be expected? Tons of shear for sure, but PHL is right on the 1000 J/kg line as far as surface CAPE goes at the moment. For that level of intensity I would expect we would need more energy -- SPC day 1 outlook mentions broken cloudcover ahead of the line...It's thinning a BIT, but I would think more is needed.

1kmv.gif

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9 minutes ago, Rockchops said:

Are we really getting the warming for that level of storms? Maybe still to be expected? Tons of shear for sure, but PHL is right on the 1000 J/kg line as far as surface CAPE goes at the moment. For that level of intensity I would expect we would need more energy -- SPC day 1 outlook mentions broken cloudcover ahead of the line...It's thinning a BIT, but I would think more is needed.

We'll likely be able to gauge the potential for severe weather as we watch the line organizing to our west ... At this moment, it's likely too early to tell, though I feel that the line isn't as organized at the moment as it could be. Out here in the coastal plain, will have to see how the environment recovers from the storms that've been passing through. It seems like the threat may not be so great once the line gets to my area due to marine shank + some loss of daytime heating.

 

I agree with you that, so far, things aren't looking spectacularly, but the conditional threat is still there. In a few hours, we should be able to re-evaluate, though a mess of storms has been progged for today, and it is a limiting factor for any severe weather.

 

Oh! And I thought that I should say ... 1,000 J/kg CAPE can be enough in setups like these! More important than raw CAPE values in severe weather setups is whether or not the CAPE is "skinny" or "fat" ... In places like Florida, you can often get 3,000+ J/kg of CAPE, but because it's so long and skinny, updraft accelerations are not as strong... But tall, skinny CAPE is pretty good for getting heavy rain, especially in saturated environments! 

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Areas affected...southeastern Pennsylvania...northern Maryland and
   Delaware...southwest New Jersey

   Concerning...Tornado Watch 105...

   Valid 261809Z - 262015Z

   The severe weather threat for Tornado Watch 105 continues.

   SUMMARY...Storms will rapidly develop and evolve over the next
   several hours, with damaging winds and a tornado or two possible.
   The greatest tornado threat area appears to be from northern
   Maryland into southeast Pennsylvania between 18-22Z.

   DISCUSSION...Storms are increasing in coverage along the cold front
   from central PA into central VA, and just to the east near the warm
   front. These storms will continue to evolve as they proceed east
   into an unstable and warming air mass, with increasing large-scale
   lift aiding organization as well. Given the motion of the front, the
   entire event may clear the coast by 00Z.

   The 16Z IAD sounding shows 0-2 km mean winds in excess of 40 kt,
   along with effective SRH over 200 m2/s2. This is favorable for
   damaging winds, as well as occasional rotation in storms. Shear
   profiles are stronger farther north into PA, where effective SRH is
   in excess of 300 m2/s2 just on the cool side of the warm front.
   Meanwhile, an axis of warmer air continues to mix northward into
   southeast PA. This appears to be the most favorable area for a
   tornado, either with any leading cells that develop and/or with cold
   front/QLCS activity. Wind damage is possible with any storm.

   ..Jewell.. 04/26/2019

mcd0452.gif

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31 minutes ago, Rockchops said:

Are we really getting the warming for that level of storms? Maybe still to be expected? Tons of shear for sure, but PHL is right on the 1000 J/kg line as far as surface CAPE goes at the moment. For that level of intensity I would expect we would need more energy -- SPC day 1 outlook mentions broken cloudcover ahead of the line...It's thinning a BIT, but I would think more is needed.

Cleared out nicely in the past half hour.

COD-GOES-East-local-Virginia.02.20190426.182120-over=map-bars=.jpg

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Heavy rain, breezy, a few rumbles in NW Chesco.   .75" for the day so far.   Every time the ground gets close to being tillable, we get another deluge.   Different year, same crap.

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