Feb 24-25th Severe Weather

[snowlover2]

IND has a nice disco in their newest AFD.

Quote

Area Forecast Discussion
National Weather Service Indianapolis IN
307 PM EST Thu Feb 23 2017


.SHORT TERM /Friday and Friday Night/...
Issued at 307 PM EST Thu Feb 23 2017

The primary focus for the period will be the threat for severe
weather as storms impact the forecast area mainly during the
afternoon and evening ahead of a strong cold front.

Friday morning will start windy and warm as the aforementioned warm
front lifts into northern Indiana. Fair amount of moisture noted in
the lower levels on both model soundings and RH progs and will
likely see stratocu across the region.  With that being said...the
moisture is shallow enough that some sunshine is anticipated into
the early afternoon. Expect gusts to kick up rather fast during the
morning as the initial surge of the low level jet noses into the
area with the surface low tracking from northern Missouri into
northern Illinois.

Focus then shifts to the severe weather threat which will begin to
grown from 19-20Z into the evening. Model consensus has generally
come into line on timing of the greatest threat for severe storms
impacting the forecast area from mid afternoon through mid evening.
Moisture return is a bit problematic and may serve as a mitigating
factor on amount and intensity of storms. With that being said...
overall dynamics associated with the system are strong enough to
overcompensate for the limited moisture fetch.

While the severe weather threat is present over the entire forecast
area...the greatest risk will likely set up over the eastern half of
central Indiana east into western Ohio. Potential exists in this
area for an initial round of potentially discrete convection
developing in the vicinity of the prefrontal trough followed by the
squall line anticipated to organize along the cold front. The low
level jet will transition across the region into the afternoon hours
with the back side of the jet aligned over eastern Indiana and
western Ohio.  Mid and upper level diffluence is pronounced with the
exit regions of both jets over the Ohio Valley.  The upper jet
structure in particular favors a splitting of the northern and
southern jets over the Ohio and Tennessee Valleys...further
accentuating the diffluence aloft. Wind analysis showing best
potential for directional shear through the column will develop from
Indy east around 21Z...maximizing over eastern Indiana and western
Ohio into the early evening. The instability axis will align in this
area too immediately along and ahead of the trough...with MLCAPEs
around 1000 J/KG which is impressive for late February.

Taking all of this into consideration...plausible scenario
developing where local and brief backing of the near surface layer
along and immediately ahead of the prefrontal trough will present a
brief enhanced threat for rotating storms and possibly tornadoes.
Again...this looks to be focused over the eastern half of the
forecast area in the 21Z to 00Z time period. The cold front itself
will arrive during the evening and provide another round of severe
weather in the mode of a thin...low topped and fast moving squall
line with damaging winds as the primary threat. There will exist a
small tornado potential as weak and short lived couplets develop
along the line...a typical occurrence with Ohio Valley QLCSs. The
presence of the stronger dynamics over eastern Indiana may allow for
a strengthening of the convective line as it moves east across the
forecast area.

The cold front and squall line will be east of the forecast area by
03-04Z. Passage of the front will bring an abrupt end to the
unseasonably warm weather enjoyed over the last week or so. Much
colder air will spill into the region immediately behind the front
Friday night with light precipitation redeveloping as wraparound
moisture rotates into the area predawn Saturday. The boundary layer
will become sufficiently cold enough to support rain mixing with or
completely changing over to light snow by Saturday morning.

Temps...generally took a split of the MOS guidance for highs Friday.
Should the sun appear for an extended period of time...could easily
see highs approach MAVMOS levels in the 70-75 degree range. Went
slightly cooler than this in the upper 60s and lower 70s with the
potential for the stratocu. Record high watch once again for Indy as
the high of 71 from 2000 definitely could be threatened.
Temperatures will tumble behind the front Friday night...falling
into the 30s. Continued gusty winds will make it feel even colder.

 

[snowlover2]

ILN AFD

Quote

Area Forecast Discussion
National Weather Service Wilmington OH
422 PM EST Thu Feb 23 2017



.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
the main focus in the short term continues to be the threat for
severe weather late Friday afternoon into Friday night.

The necessary ingredients for different modes of convection will
come together late Friday afternoon into Friday night as low
pressure tracks northeast toward Lake Huron and its attendant
cold front sweeps east across our region.

First off, unseasonably warm air will be place across the warm
sector for the first part of Friday. It looks like we will see
some sunshine, especially east. On breezy southerly flow, high
temperatures are forecast to in the lower to mid 70s. These will
either threaten or break records. Please see the climate section
below for records at the big three climate sites. Winds will
gust from 25 mph over the southeast to near 35 mph across northwest.

The ingredients are coming together for severe storms across our
area late Friday afternoon into Friday night. As the low tracks
to our northwest and deepens, bulk shear, either 0-3 km or 0-6
km, will be sufficiently strong for organized updrafts/convection.
The key will be how much instability and increasing large scale
ascent will be realized late in the day to break through a weak
capping inversion. CAMs suggest that the first threat for
severe weather will be within a prefrontal trough region where
convergent flow, shear, and MLCAPEs near 1000 J/kg will develop
thunderstorms across the eastern half of Indiana between 4 pm
and 7 pm EST. CAMs also suggest that these storms will likely
contain rotating updrafts and may be supercellular in nature.
Given steep mid level lapse rates between 7.5 C/km and 8.5 C/km,
along with the instability and vertical pressure gradient from
rotation, large hail and damaging winds will be possible from
these storms. Tornado potential will depend on how shallow CIN
remains into the early evening from max heating of the day and
whether parcels remain rooted in the boundary layer. As the
evening wears on, it appears that the convection, either
supercellular or multi cluster/broken lines will try to congeal
more into a QLCS as the cold front/convection along this
boundary tries to catch up to the prefrontal trough convection.
If this occurs, the severe threat will then transition more to
damaging winds for our far eastern zones. However, vigilance
still must be kept on the QLCS for any potential spin up
tornadoes along the shear axis. It appears the convection will
be exiting our eastern zones between 1 am EST and 4 am EST. CAA
and a dry slot will ensue in the wake of the cold front with
lows bottoming out toward sunrise Saturday, which should range
from the mid 30s west to the upper 40s. east.

 

[Stebo]

Detroit really hitting the areas south of 59/69 hard for tomorrow

Retention of cool pre-warm frontal easterly flow to define the early
portion of Friday - particularly with northward extent.  Surface
warm front will then make a more concerted northward penetration
into southern lower Michigan through the afternoon period.
Associated low level destabilization thereafter to leave at least a
weakly unstable profile prior to 00z south of the M-59 or I-69
corridor - differences in northward placement of the boundary still
carries some uncertainty.  Potential for MLCAPE to climb over 1000
J/KG across the warm sector.  However, well defined elevated mixed
layer to accompany this inbound warm sector.  Potential for some
degree of capping to dictate convective prospects will therefore
establish a very conditional risk for convective development through
the early evening hours, contingent on achieving an adequately
buoyant parcel to work through this cap.  This risk does give pause
however, as well established deep layer flow and the likelihood of
localized enhanced vorticity at the warm frontal interface provides
a background environment conducive to discrete rotating updrafts
should the thermodynamics prove adequate to support low topped
development.  Greatest potential for development/expansion early may
focus near the triple point as the low lifts over southern lake
Michigan, where any downstream propagation may anchor on the
slightly elevated warm frontal zone draped across the tri-cities.
Freezing levels remain low enough to present a hail threat for such
activity.

Greatest potential for organized convection still centered within
the 00z-05z window early Friday night, owing to a sizable increase
in mass/frontal convergence into an existing modestly unstable
profile.  Any nocturnal downturn in available instability at the
surface may become essentially negligible, given the high degree of
instability /for late February standards/ that will still exist just
off the surface.  General model signal suggests a lead pre-frontal
trough anchoring weak mid level cold air advection/steeper lapse
rates could become an initial focus, either just upstream or
directly overhead.  Development is expected either on this feature,
the trailing cold front or both.  In any case, magnitude of the wind
field across both the lowest 6 km and 1 km could support a mixed
mode, tending to be discreet/supercellular early before congealing
into linear segments. Greatest risk with southward extent, with
areas south of M-59 appropriately highlighted within an enhanced
risk.

 

[Stebo]

GRR also mentioning isolated tornado potential

Severe weather looks possible for Friday into the evening...mainly
south of a Lansing to Holland line.  The main period looks to be
during the mid afternoon through the evening hours. This is when
the instability will be most favorable. Overall not a lot of
instability is forecasted...but the deep layer shear will be
plenty favorable for organized convection. Forecast soundings do
show some capping for a while for the afternoon. But that
eventually breaks down ahead of the advancing cold front. A narrow
line of convection with possible damaging wind gusts looks likely
with an isolated tornado possible. Strong convective winds gusts
could lead to power outages. Any stronger storm could focus the
damage.  The morning convection could be strong as well with
rather steep mid level lapse rates around.

[Stebo]

IWX also hitting supercell potential

Warm front mixes rapidly north into lower MI late tonight as sfc low
lifts into ern IA. Capping inherent to steep elevated mixed layer
likely to squash any warm sector convective development until mid
aftn at the earliest tied to prospects of arrival of better low
level moisture and upticking sfc based destabilization. Conditional
severe risk based on moisture availability appears greatest along
prefrontal trough feature through ern IN/wrn OH late aftn/early
evening where best overlap of 0-3km shear/MLCAPE ~1200 j/kg exists
suggesting a discrete supercell threat and all modes of severe wx
possible. Secondary concerns would lie along strongly forced cold
frontal zone farther west Fri evening through nrn IN/srn MI as more
unidirectional flow here indicates primarily a wind threat...
sweeping ewd through wrn OH late evening. Otherwise given as yet
still considerable spread present in highres solutions will follow
blended pops Fri aftn/eve.

[Stebo]

Coming in hot:

 

 

Also the HRRR is showing near 60 dewpoints along the warm front as early as noon in Michigan with the moisture pooling along the front. 

[roardog]

2 minutes ago, Stebo said:

Coming in hot:

 

 

Also the HRRR is showing near 60 dewpoints along the warm front as early as noon in Michigan with the moisture pooling along the front. 

You could be in a good area tomorrow evening. I'm sure the warm front will struggle to move north tomorrow but I would think it will at least make it to M59 or so by evening. Meanwhile I'll enjoy my cold rain and northeast wind.

[NTXYankee]

It was nice to get some storms in the Columbus metro this evening, pretty heavy rain and a decent light show.  Of course my drive home got messed up but at least I had something to occupy the time.

[NTXYankee]

15 minutes ago, Stebo said:

Coming in hot:

 

 

Also the HRRR is showing near 60 dewpoints along the warm front as early as noon in Michigan with the moisture pooling along the front. 

That's a change, I looked last night and it really knocked the values down, I think the highest was a small 30 in northern Indiana then dropped off after 0z.

[Anti tornado]

10 minutes ago, NTXYankee said:

It was nice to get some storms in the Columbus metro this evening, pretty heavy rain and a decent light show.  Of course my drive home got messed up but at least I had something to occupy the time.

Chased the cells west north of Dayton. Didn't really get crap. Shear did not materialize...

[janetjanet998]

got a feeling dewpoints won't be quite as high as modeled and/or mix out

 

happens often in the early spring setups until you get vegetation growing

 

that low off FL is preventing 2-4F of higher dews IMO 

[HillsdaleMIWeather]

49 minutes ago, Stebo said:

Coming in hot:

 

 

Also the HRRR is showing near 60 dewpoints along the warm front as early as noon in Michigan with the moisture pooling along the front. 

That's, a little worrying.

[Hoosier]

20 minutes ago, janetjanet998 said:

got a feeling dewpoints won't be quite as high as modeled and/or mix out

 

happens often in the early spring setups until you get vegetation growing

 

that low off FL is preventing 2-4F of higher dews IMO 

We already have dews in the mid/upper 50s near/south of I-70, so if they come in lower, it's gonna have to be because of excessive mixing.  Looking at moisture profiles aloft, the moisture doesn't look extremely shallow/prone to mixing out.  In general I don't think it will be a problem realizing 56-59 type dews in the warm sector tomorrow.

[Stebo]

12 minutes ago, Hoosier said:

We already have dews in the mid/upper 50s near/south of I-70, so if they come in lower, it's gonna have to be because of excessive mixing.  Looking at moisture profiles aloft, the moisture doesn't look extremely shallow/prone to mixing out.  In general I don't think it will be a problem realizing 56-59 type dews in the warm sector tomorrow.

Yeah good dews at 850mb, this isn't a shallow moisture regime, I would really be surprised if it mixed out any to be honest.

[Jim Martin]

I could easily see some locations tomorrow ending up with a headache from large to very large hail.

[Stebo]

4 minutes ago, Jim Martin said:

I could easily see some locations tomorrow ending up with a headache from large to very large hail.

If the HRRR is right and we are talking widespread 1000 to 1500 J/kg over southern MI, that would be enough CAPE for good updrafts and good hail production.

 

[Hoosier]

18 minutes ago, Stebo said:

Yeah good dews at 850mb, this isn't a shallow moisture regime, I would really be surprised if it mixed out any to be honest.

The one concern I'd have as far as moisture mixing out some would be if anybody gets prolonged full sun.  Looks like there will be enough clouds around though.

[Stebo]

Just now, Hoosier said:

The one concern I'd have as far as moisture mixing out some would be if anybody gets prolonged full sun.  Looks like there will be enough clouds around though.

Maybe Indiana, but on the flip side down there, that could enhance the wind potential later in the day with an inverted-V sounding.

[Jrad08]

9 minutes ago, Stebo said:

Maybe Indiana, but on the flip side down there, that could enhance the wind potential later in the day with an inverted-V sounding.

I think the Indiana Ohio border indeed sees quite a bit of sun, adding to the instability. Maybe some discrete rotators around there.

[Anti tornado]

Not impressed by tomorrow at all. 

[nwohweather]

If the HRRR is right and we are talking widespread 1000 to 1500 J/kg over southern MI, that would be enough CAPE for good updrafts and good hail production.

 

You going to chase tomorrow? I'm thinking about heading to around Defiance to wait and see what happens

[NTXYankee]

1 hour ago, Hoosier said:

We already have dews in the mid/upper 50s near/south of I-70, so if they come in lower, it's gonna have to be because of excessive mixing.  Looking at moisture profiles aloft, the moisture doesn't look extremely shallow/prone to mixing out.  In general I don't think it will be a problem realizing 56-59 type dews in the warm sector tomorrow.

Yeah the dew point in Columbus was around 56-57 today and some decent lift as we had some storms with nice cloud structure, similar to late spring.  Lack of vegetation does pose a little problem but we haven't had a dry winter so I really don't think upper 50's maybe some localized 60 readings aren't completely out of the question.

[Hoosier]

8 minutes ago, Anti tornado said:

Not impressed by tomorrow at all. 

Seems like it's going to come down to what happens with the prefrontal trough.  If that sort of busts, then this probably ends up being largely forgettable.

[Hoosier]

This lapse rate/EML plume overspreading the warm sector tomorrow is nuts for February.  700-500 mb lapse rates around 9C in some areas.  That would be great in spring/summer.

[Hoosier]

[HillsdaleMIWeather]

02Z HRRR gets almost 2000 j/kg CAPE in spots, and good clearing for a while.

[Stebo]

50 minutes ago, nwohweather said:

 

You going to chase tomorrow? I'm thinking about heading to around Defiance to wait and see what happens

No I work tomorrow, if I were to be chasing I would go near Angola Indiana or Coldwater Michigan and wait there and see what happens.

[Stebo]

41 minutes ago, Hoosier said:

This lapse rate/EML plume overspreading the warm sector tomorrow is nuts for February.  700-500 mb lapse rates around 9C in some areas.  That would be great in spring/summer.

If it were April/May with this setup, we'd be talking wedges tomorrow and massive hail.

[andyhb]

1 hour ago, Anti tornado said:

Not impressed by tomorrow at all. 

Thanks for the input.

[cyclone77]

Just had a nice little 3 minute hailstorm with peas.  Enough to whiten up the ground quite nicely.  First time I've seen hail here at the house in a few years.