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Hoosier

Spring 2019 Discussion

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Might be a decent shot at severe weather in the subforum on Thursday looking at recent guidance as very strong wind fields (broad 55-65+ kt LLJ) and cold air aloft overspread mid-upper 50s dewpoints (perhaps low 60s further south towards the OV). Could be one of those events where you have a large amount of instability concentrated in the low levels.

These types of events tend to do some dirty work in this region.

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16 minutes ago, Moosey2323 said:

I'm interested to see what the Day 3 Convective Outlook looks like.

It will be a marginal at best on Day 3, they will wait as long as possible to go higher, I am sure of that.

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1 hour ago, andyhb said:

Might be a decent shot at severe weather in the subforum on Thursday looking at recent guidance as very strong wind fields (broad 55-65+ kt LLJ) and cold air aloft overspread mid-upper 50s dewpoints (perhaps low 60s further south towards the OV). Could be one of those events where you have a large amount of instability concentrated in the low levels.

These types of events tend to do some dirty work in this region.

What are your thoughts on the substantial weakening of the surface low on approach?  I am thinking it may not hurt because it could result in somewhat less forcing.  

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Usual caveats of instability concerns applies this far north this early in season.  I;m waiting for warmer temps and richer dew points.  But ya never know.  Your point on forcing is well taken. o6z NAM 3k says that Thursday afternoon and evening could be rather volatile around parts of central IL and IN.

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12 hours ago, Hoosier said:

What are your thoughts on the substantial weakening of the surface low on approach?  I am thinking it may not hurt because it could result in somewhat less forcing.  

Yeah I’m thinking the same thing, plus it’s the position that I’m paying attention to mainly since it is still a pretty strong surface low despite being filling.

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On ‎2‎/‎26‎/‎2019 at 2:26 PM, bowtie` said:

Had a small V of sandhill cranes honking the way back north today. A sure sign that Spring is soon on the way.

If that was the advance guard two weeks ago, today was the whole fam damily. Multiple upon multiple V's of sandhill cranes all circling wagons north. Book it.

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GRR AFD

Quote
With the assumption that we mix out into the warm sector on
Thursday, another low-level jet impulse ahead of the cold front may
be well timed with afternoon peak heating. Surface-based
thunderstorms may develop. MLCAPE around 500 J/kg, 0-1 km shear of
30 kt, and 0-3 km shear of 50 kt is possible, so any relatively
robust updrafts could achieve some organization. Cells that do
develop would race quickly to the northeast, and given the strong
low-level wind fields in place, even weak downdrafts could result in
gusts around 60 mph. The nested 3 km NAM has shown more backing of
surface winds than other models, and if that verifies, it suggests
some isolated tornado potential in southern Michigan with STP values
climbing to around 1 or 2. Tornado or not, the greater potential
will be from straight-line winds, possibly strong enough to cause
power outages from falling tree limbs. SPC has placed areas south of
I-96 in a marginal risk for severe winds Thursday afternoon.

 

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DTX

Could see a lull for a few hours in the wake of the morning activity
as the low level warm sector slides through SE MI. With strong low
level jet in place (50 knots down to around 4kft possibly) and warm
mixed layer lifting through the area, could see some strong
southwesterly winds in the afternoon Thursday. Though models have
been supporting higher gusts Thursday it should be noted that local
probability graphics show a decreasing trend in likelihood of seeing
wind gusts in excess of 40 mph. A several hour period with gusts of
30-40 mph seems reasonable at this point. Caveat to that will be if
any showers can persist or afternoon redevelopment of showers mixes
down the stronger winds. Strong southwesterly warm air advection will
help temperatures climb into the 60s for most locations Thursday
steepening low level lapse rates. CAPE values of a few hundred j/kg
may aide in the development a broken line of storms moving across
lower MI. Strong winds will be the primary threat with any storms or
stronger showers as the low level jet will still be strong. Dry slot
surging into the area overnight will help shut off the showers for
most of the area overnight.

 

IWX

Focus then shifts to convective potential in warm sector Thurs
afternoon as well as gusty winds outside any convection. For the
gradient winds, trends continue to point towards a period of near
advisory criteria as low level flow in excess of 60 knots resides
not far off the surface. To complicate things, this same wind
field could be tapped by low topped convection that may form
during the afternoon hours with plenty of bulk shear (50 kts to as
high as over 80s depending on model of choice). Keys to severe
potential will be if breaks in clouds can occur and if we advect
in low to maybe mid 50 dewpoints which will translate to around
500 J/KG of MUCAPE. SPC has marginal risk across the area with
damaging winds the main threat. However, given the strong wind
fields and shear/helicity values a non-zero threat for qlcs
tornadoes exists. A lot has to come together for this and always a
tough one in March, but still needs to be watched. Have kept highs
upper 60s to near 70, but if breaks can occur, than MAV guidance
in the mid 70s could be realized (and cause a greater severe
threat).

 

 

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To further the notion, yeah those are multiple fast moving supercells there, it's not picking up on a squall line.

I tend to put a lot of weight in the 500 mb setup assuming thermos are adequate in these kinds of cases. This 500 mb setup with a powerful vort lifting ENE out of a mean positive tilt long wave trough, with an elongated west-southwesterly upper level jet and the surface low position, is notorious in the Great Lakes for significant severe weather events.

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Yes, I think the April 11, 1965 Palm Sunday tornadoes in IN had a positive tilt trough.  Supposed to get  near 70 here in IN this Thursday. Current CAMS are concerning.

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7 hours ago, Indystorm said:

Yes, I think the April 11, 1965 Palm Sunday tornadoes in IN had a positive tilt trough.  Supposed to get  near 70 here in IN this Thursday. Current CAMS are concerning.

Add the 06Z HRRR to the chorus. Has a couple strong supercells going over IN as early as 17Z tomorrow. It oversold 2/23 and last Saturday a bit (did pretty well with 3/3). I haven't really paid much attention to the HRWs before, but I might have to start.

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New seasonal forecast for AMJ from ECMWF looks active in terms of -PNA/pattern favouring cutters and severe wx.

 

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Well, if we get that trough in the west established there will certainly be enough moisture in the plains/midwest with current flooding situation to guarantee adequate moisture.  So I don't think we have to worry too much about that variable in the coming months.  And I always look forward to your scientific insights and discussions on svr wx, Andrew.  Way to go!

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3 hours ago, Indystorm said:

Wow does April 3 look potent for northern IL and IN on the 18z GFS.  Too bad it's 384 hours.

Maybe the first time I've replied to you with this:  :weenie:    lol

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4 minutes ago, Hoosier said:

Maybe the first time I've replied to you with this:  :weenie:    lol

Just getting the itch for svr wx season.  That EF-0 near Lowell did surprise me, though.

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Long range GFS looks absolutely miserable for pretty much everyone. That Alaskan ridge might be a permanent feature thanks to melting sea ice and warming Pacific waters.

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13 minutes ago, NegativeEPO said:

Long range GFS looks absolutely miserable for pretty much everyone. That Alaskan ridge might be a permanent feature thanks to melting sea ice and warming Pacific waters.

... as long as I'm not trying to drive in a kitchen sink of winter precip on April 14 like last year...

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