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Rainshadow

Monday June 19th Severe Weather/Flash Flood Threat - Enhanced Severe Risk/I95 Flash Flood Watch

48 posts in this topic

12 minutes ago, tombo82685 said:

Gfs did up the llj up a little from meh, to eeeee

We are due for something solid. ¬†ūüĆ©

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SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
A cold front will cross the area Monday afternoon and evening.
Severe thunderstorms will accompany the front with damaging
winds the primary threat and large hail secondary. SPC has
maintained the enhanced risk for SVR for much of our area. In
addition, heavy rains will accompany the activity that could
lead to flash flooding. Scattered showers will occur outside of
the time window of the frontal passage, with activity possible
in the morning prior to the fronts arrival. We have extended the
flash flood watch westward to include Berks county, the Lehigh
Valley and up into Nrn NJ.

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My biggest worry is a fairly nice looking line with severe warnings all over it, but for the most part only heavy rain and thunder with isolated wind reports. Maybe I'll be surprised, but the sort of meh shear along with a lack of dry air aloft makes me leery.

 

High PWATs and a good amount of CAPE should produce a nice amount of lightning at least.

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53 minutes ago, Treckasec said:

My biggest worry is a fairly nice looking line with severe warnings all over it, but for the most part only heavy rain and thunder with isolated wind reports. Maybe I'll be surprised, but the sort of meh shear along with a lack of dry air aloft makes me leery.

Well that's usually how these things play out. Without solid lapse rates (dry air aloft) its harder to bring stronger winds to surface esp with a so so llj. I still think there will be svr stuff tomorrow. We still have modest shear with pretty strong instability and a good trigger running into all that combined with all that tropical air. Something is definitely going to give. It will be interesting to see how things unfold tomorrow. 

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1 hour ago, tombo82685 said:

Well that's usually how these things play out. Without solid lapse rates (dry air aloft) its harder to bring stronger winds to surface esp with a so so llj. I still think there will be svr stuff tomorrow. We still have modest shear with pretty strong instability and a good trigger running into all that combined with all that tropical air. Something is definitely going to give. It will be interesting to see how things unfold tomorrow. 

There's also water loading /downburst potential. Anytime the primary storm mode is QLCS/bowing segments, winds are the primary threat. 

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8 hours ago, irishbri74 said:

There's also water loading /downburst potential. Anytime the primary storm mode is QLCS/bowing segments, winds are the primary threat. 

Yes you can get that too to help bring the winds down in an overly saturated profile. This is exactly what I was talking about yesterday with the gfs. 0z run already had almost .5 of rain at ptw keeping the column saturated, currently clear skies. 

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You can see the 3k NAM with the drier look. Not too dry without an EML present, but that's more typical for us. Anything discrete has a chance to spin something up. But other than that, just watch out for anything bowing out. I'd just like some relief from this tropical Soup and a light show. 

IMG_4328.thumb.PNG.e802f838b78006cc5982cb1c7491993c.PNG

 

 

6z 3k NAM:

 

IMG_4327.GIF.956afcf5be168d8390a10aaf133849ef.GIF

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Good to see lots of clear air between here and the ongoing precip/convection out west.

Best parameters look to be on the NJ side of the border, where CAPE is higher and closer to the axis of the LLJ. The 06Z NAM strangely seems to back off on the CAPE at 21Z but the 09Z HRRR seems to maintain similar CAPE to what the 0Z NAM and GFS progged.

With the HRRR, the core of the LLJ is a little further to the north and east. We are on the fringe of more westerly flow, which could make the already marginal/unidirectional shear into a messier veer/back profile.

09Z HRRR shows some more discrete cells blow up in NJ to the east of the main line/cluster on the PA side.


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Definitely agree the models are convection happy this morning. Mixed cape already near or over 1,000 J/KG, shear should get here with the line it's self. Once the line gets going in a region with more shear it should generate it's own cold pool and become self-sustaining despite weaker shear further east.  

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2 hours ago, tombo82685 said:

Yes you can get that too to help bring the winds down in an overly saturated profile. This is exactly what I was talking about yesterday with the gfs. 0z run already had almost .5 of rain at ptw keeping the column saturated, currently clear skies. 

Good call. 

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2 hours ago, tombo82685 said:

Yes you can get that too to help bring the winds down in an overly saturated profile. This is exactly what I was talking about yesterday with the gfs. 0z run already had almost .5 of rain at ptw keeping the column saturated, currently clear skies. 

0.79" with continuous showers and storms all night long at PHL when the entire night it was clear enough for NASA to launch at anytime they wished.  Even with so many rotten GFS first 12 hr convective forecasts to choose from, this has to rank near the top. 

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OTOH, there really is no cap/CNN so some differential heating / orographic trigger could get cells going before the main line.

Wow I hate autospellcheck,  no CIN, sorry CNN still there.

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34 minutes ago, Rainshadow said:

OTOH, there really is no cap/CNN so some differential heating / orographic trigger could get cells going before the main line.

Wow I hate autospellcheck,  no CIN, sorry CNN still there.

Hopefully we have a lot of FOX... I mean cape!! Haha jk. 

 

Hrrr seems trigger happy with pre-frontal conv. 3k NAM wasn't as enthusiastic. 

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17 minutes ago, irishbri74 said:

Hopefully we have a lot of FOX... I mean cape!! Haha jk. 

 

Hrrr seems trigger happy with pre-frontal conv. 3k NAM wasn't as enthusiastic. 

Gotta watch out with HRRR in regards to temps it can run to hot. That in terms over does convective parameters. 

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Often hard to tell looking at radar, but those storms most certainly look like they are moving a lot faster than forecast.

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Should see a watch go up very soon. Match meeting gasoline 

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9 minutes ago, tombo82685 said:

Should see a watch go up very soon. Match meeting gasoline 

It's up

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HRRR is indeed trigger happy with discrete cells early followed by convective line

hrrr.refcmp.us_ne.2017061914-loop.gif

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Embarrassing performance for the GFS instability, surface CAPE over 3,000 J/KG in NJ. 

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45 minutes ago, Mitchg said:

Embarrassing performance for the GFS instability, surface CAPE over 3,000 J/KG in NJ. 

 

Od7T4lm.png

 

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2 hours ago, Treckasec said:

 

Od7T4lm.png

 

looks like orographic induced pcpn prefrontal which counts us out.

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