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> November 17-18 Midwest/OV/GL Storm, Long-range forecast: 6-10 days
ClicheVortex2014
post Nov 12 2017, 06:15 PM
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A trough is going to swing in toward the end of this week, take a negative tilt and bomb out. GFS is showing pressure as deep as mid-970's in Michigan. The warm sector is narrow but has mid-50 dew points up to northern IN and northern OH. With how strong the wind fields are, there are going to be strong winds and high gusts throughout the day... but I think there'll be especially strong to severe winds with the frontal passage. This setup is pretty typical of HSLC (high shear low CAPE) squalls. Doubt there'll be much thunder, but I think there's just enough moisture and instability that some very strong winds will mix to the surface with the rain.

Bombogenesis: 996mb to 971mb in 24 hours. 500mb winds up to 110 MPH are pushing the system along.







This post has been edited by ClicheVortex2014: Nov 12 2017, 06:21 PM


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

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ClicheVortex2014
post Nov 12 2017, 07:19 PM
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CIPS analog picking up on some severe weather. Two analogs produced some widespread severe weather--one more than the other though. Both are definitely HSLC events.




This post has been edited by ClicheVortex2014: Nov 12 2017, 07:19 PM


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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ValpoSnow
post Nov 12 2017, 07:57 PM
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18z GFS Friday Evening




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ClicheVortex2014
post Nov 13 2017, 12:58 AM
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GFS has a weaker low but still has a HSLC look. Sounding ahead of the cold front in western IN



I'm leaning toward Euro which has a deeper low because of its consistency


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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snowlover2
post Nov 13 2017, 05:05 AM
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Day 5 area now highlighted.
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QUOTE
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CST Mon Nov 13 2017

Valid 161200Z - 211200Z

...DISCUSSION...
Latest runs of the GFS and ECMWF appear very internally consistent,
with respect to runs from 24 hours ago. However, they remain
similarly inconsistent each other with respect to timing as was the
case yesterday. As the developing surface cold front crosses the
central U.S. late Day 4 (Thursday 11-16) and then Day 5 (Friday
11-17), and finally across the eastern U.S. Day 6 (Saturday 11-18),
a 9 to 12 hour timing difference persists between the two models.

With that said, the overall pattern continues to suggest a linear
band of frontal convection, occurring within a pre-frontal
environment featuring modest CAPE but very strong flow from the
lower troposphere to upper levels. As such, damaging winds would be
the main severe potential, with degree of risk at least partially
modulated by the degree of CAPE and associated intensity of the
convection. Given this potential, a 15% risk area is being
introduced at this time, from the Midwest to the Arklatex vicinity.
Partially due to timing differences between the models, a rather
large area is being included in the risk, with fine-tuning of the
lines left for later outlooks as evolution becomes more certain.

At this time, an outlook area will not be included for Day 6 over
the eastern U.S., as the GFS shows the front moving offshore during
the first few hours of the period, while the ECMWF depicts the front
still lying west of the Appalachians through midday. Depending upon
the actual evolution, a risk area may be required in later
forecasts.

..Goss.. 11/13/2017


--------------------
First Flakes: 10/28/17 Watches:

First 1"+ of Snow:

Biggest Snowfall:

# of Winter Storm Watches:

# of Winter Storm Warnings:
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ClicheVortex2014
post Nov 13 2017, 01:40 PM
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Nice quadruple point. Also, insanely quick moving cold front




--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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ClicheVortex2014
post Nov 13 2017, 03:39 PM
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Euro still has the greater severe threat. 200-1000 j/kg of CAPE from MS/OH river confluence to NW OH with 80-90 MPH westerly winds at 500mb. Much like the 11/5 event, the angle between storm motion and the cold front orientation and movement is roughly 45 degrees. Unlike that event, the CAPE/shear balance is going to be way off so I don't think there'll be much of a window, if any at all, for supercells. Damaging winds will absolutely be the primary threat.


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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ClicheVortex2014
post Nov 13 2017, 03:43 PM
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ILN wrote a book

QUOTE
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Surface high pressure will be east of the Ohio Valley on Wednesday
morning, as heights fall in advance of a mid-level wave moving into
the Great Lakes. An area of surface low pressure will moving
near/north of Lake Superior on an eastward track, with the mid-level
trough strengthening as it moves across the Great Lakes. A SW-to-NE
cold front attached to the surface low is expected to pass through
the ILN CWA between 15Z-00Z, and while this front may be at its
strongest early in the day on Wednesday, there remains high
confidence (and good model agreement) regarding the timing and
placement of a band of rain moving through the area. PoPs have been
refined and increased to 90 percent with this system, though the
overall arrangement is essentially unchanged from the previous
forecast. Ahead of the front, temperatures should be slightly warmer
than on Tuesday -- with highs in the lower to middle 50s. For the
northern and northwestern CWA, where rain and clouds should be an
impact for most of the day, highs will be a little cooler (upper
40s).

There will be a transition through high pressure on Thursday /
Thursday night, leading into the return to southerly flow on Friday.
The next system, moving in for the Friday-to-Saturday time frame,
remains complicated from a forecast stand point. Thus, it is not a
surprise that model solutions are still not particularly consistent
in its depiction. One piece of information that seems in agreement
among all 12Z runs (GFS/ECMWF/CMC) today is an overall slower
progression of this system. This means that the warm front will not
get into the area until Friday, which removes the formerly-likely
scenario of non-diurnal temperatures leading into Friday morning. It
also delays the start of precipitation until late Friday morning /
Friday afternoon.

To describe the scenario -- there will initially be a surface low
and mid-level trough moving across the plains provinces of Canada,
but a secondary trough is expected to develop ahead of a jet streak
coming across the central plains. This will allow for another
surface low to develop in the middle Mississippi Valley. This low
will move NE into the lower peninsula of Michigan, and the system
will be relatively compact with regards to its frontal structure.
Models remain in decent agreement with regards to the track of this
system, but timing differences remain problematic. However, the
biggest issue is that there are now considerable differences in the
forecast intensity of the surface low -- with both the ECMWF/GFS
coming in with weaker solutions. This has notable implications with
regards to the wind forecast. There also remains uncertainty with
when the cold front actually comes through the region, bringing what
will end up being the best solid chance for precipitation.

As model differences continuing to evolve for an event still on Day
5 / Day 6 in the forecast cycle, this forecast event is an
emblematic example of two principles. For one, keeping PoPs on the
lower side while timing differences are refined remains a good
decision. With slightly better agreement in timing today, PoPs were
increased to likely (60%) for a period on Friday night, but the
variability in model runs suggests a higher probability forecast
remains unrealistic. For two, making specific predictions for wind
intensity and potential hazards is problematic at this distance in
the forecast. While there still remains a signal for the potential
for strong winds -- both with the frontal passage and in the ambient
flow on Saturday afternoon -- the distance out in time and
uncertainty regarding the strength of the surface low do not warrant
inclusion in any public products (HWO etc) as of yet. It should also
be noted that models suggest only extremely small amounts of shallow
instability just ahead of the front, so from a convective
forecasting standpoint, the potential for traditional severe weather
appears quite low. Nonetheless, the concern will still be mentioned
here in the discussion. With a SSW low-level jet of 50-60 knots, and
an intense jet streak at the base of the upper trough, it could
still be a wind headline scenario to some degree.

After the front passes through, the position of the upper trough
could lend itself to some light precipitation continuing over the
northeast sections of the CWA headed later Saturday or maybe into
Sunday -- and depending on temperatures, some snow could mix in.
Otherwise, the rest of the extended period looks fairly uniform --
moderate to strong cold advection under deep-layer northwesterly
flow.


IND

QUOTE
.LONG TERM /Thursday Night Through Monday/...

Issued at 224 PM EST Mon Nov 13 2017

ECMWF suggests a strong strong system moving through the Ohio
valley and Great lakes on Thursday night through Saturday morning.

A strong warm front will arrive ahead of a strong low pressure
pressure system. This will result in rain chances arriving late on
thursday night into Friday. Much of Friday will be spent within
the warm sector and the ECMWF and GFS suggest favorable
shear...but little in the way of instability and upper support.
However models do suggest ample moisture in the area. Thus we will
continue to go with a wet Friday...and watch for the potential for
severe weather also.




--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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ClicheVortex2014
post Nov 13 2017, 10:57 PM
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WPC slowed the front down a lot in their latest forecast. GFS is caving to Euro... go figure laugh.gif

QUOTE(ClicheVortex2014 @ Nov 13 2017, 01:40 PM) *
Nice quadruple point. Also, insanely quick moving cold front





This post has been edited by ClicheVortex2014: Nov 13 2017, 11:03 PM


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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MichelleOH
post Nov 14 2017, 11:11 AM
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SPC removed the threat from Fri/Sat until they reevaluate tomorrow.
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ClicheVortex2014
post Nov 14 2017, 02:34 PM
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I anticipate a slight risk being re-added for the lower OV/mid-Mississippi valley. Euro still has <600 CAPE in the lower OV with very strong speed shear. This moves eastward but weakens, down to <200 CAPE at 00z for east Ohio.

Severe threat not looking as 'good', but a strong low that's deepening should still make for something to talk about I guess.


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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StormChaser4Life
post Nov 14 2017, 03:50 PM
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QUOTE(ClicheVortex2014 @ Nov 14 2017, 01:34 PM) *
I anticipate a slight risk being re-added for the lower OV/mid-Mississippi valley. Euro still has <600 CAPE in the lower OV with very strong speed shear. This moves eastward but weakens, down to <200 CAPE at 00z for east Ohio.

Severe threat not looking as 'good', but a strong low that's deepening should still make for something to talk about I guess.

Only caveat is that if this trough gets more positive tilt you may see a majority of the forcing behind the cf aka anafront. That wouldn't be conducive for severe. But this remains to be seen
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nkovatch85
post Nov 14 2017, 05:42 PM
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At this point I'm more excited about tomorrow morning's convection than Friday's. laugh.gif


--------------------
I wish every day was either a PDS Tornado Watch or a Blizzard Warning...or both.
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ClicheVortex2014
post Nov 15 2017, 09:51 AM
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SPC says a marginal or slight risk might be added for Saturday but from the sound of it, it won't be that large.

Oh well, interesting system to track.


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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ValpoSnow
post Nov 16 2017, 07:50 PM
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Surprised no one cares about this.....
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snowlover2
post Nov 16 2017, 09:36 PM
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0z NAM a little more south with secondary low and possible snowfall.
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--------------------
First Flakes: 10/28/17 Watches:

First 1"+ of Snow:

Biggest Snowfall:

# of Winter Storm Watches:

# of Winter Storm Warnings:
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snowlover2
post Nov 16 2017, 09:47 PM
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0z 3K NAM
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--------------------
First Flakes: 10/28/17 Watches:

First 1"+ of Snow:

Biggest Snowfall:

# of Winter Storm Watches:

# of Winter Storm Warnings:
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StL weatherjunki...
post Nov 16 2017, 10:08 PM
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QUOTE(ValpoSnow @ Nov 16 2017, 08:50 PM) *
Surprised no one cares about this.....

I think most are just unaware of the potential. Surface temperatures will also be marginal (just look at the chunk of no snow south of Lake Michigan), but could be an inch or three of slushy accumulations under the heaviest banding.

This post has been edited by StL weatherjunkie: Nov 16 2017, 10:11 PM


--------------------
All model guidance is just that, guidance. It is the responsibility of the forecaster to take that information, make it better, and to appropriately communicate the forecast to the users.

Fervent supporter of the idea to make GFS output beyond hour 168 proprietary! Anyone wanting to post/share/tweet/etc GFS output beyond day 7 should have 1) a limited set of graphics available with the option to 2) contribute a nominal fee to get a full suite of products while improving future GFS output. #EURObusinessfor-the-win
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ValpoSnow
post Nov 16 2017, 11:13 PM
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QUOTE(StL weatherjunkie @ Nov 16 2017, 09:08 PM) *
I think most are just unaware of the potential. Surface temperatures will also be marginal (just look at the chunk of no snow south of Lake Michigan), but could be an inch or three of slushy accumulations under the heaviest banding.


Yeah, certainly nothing to get crazy about, but possibly the first accumulating snow for some. Thought more would care since severe weather certainly isn't happening.

I like the 0z 3K NAM, btw. 4" just to my south with that heavy band pointed in my general direction. I live 3 miles east of the lake which isn't far enough, probably, but we'll see.....
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Juniorrr
post Nov 17 2017, 01:15 AM
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Interesting NAM runs. We'll see, GFS and CMC say no and not sure about the Euro.
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