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Please just refer to me by my first name, Peter. I'm 22 years old, from West Chester, Ohio. As of Fall 2015, I'm a student at Ohio University studying Meteorology. I'm specifically interested in severe weather and tornadoes.
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ClicheVortex2014
Rank: F5 Superstorm
23 years old
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Athens, Ohio
Born June-30-1993
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ClicheVortex2014

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21 Mar 2017
While we already have a thread open for severe weather in the SE during this time frame, another system will be ejecting out of the Rockies and will create severe weather back in the Southern Plains... again. IMO, this has the potential to be a more significant event than the ones in the previous days. This is because I believe there'll be more moisture available, seeing as a lack of moisture is among one of the inhibiting factors with the previous days' severe weather isn't as potent as it could've been.

All major severe weather events share at least this one thing in common: long-duration moisture return. Sunday will mark the 5th or 6th day of southerly flow from the Tropics to the Gulf, and the 4th or 5th day of southerly flow in the southern US (within 100 miles of the Gulf).

The synoptic setup is enough to make any Great Plains storm chaser drool. As you can see, the cold front from the previous system is weakening and has already begun to turn into a warm front. The fact that it didn't penetrate very far south is key for this event as moisture return is continued south of the front through the entire event, and now will begin another moisture surge with the new system.








In N TX
25 Feb 2017
SPC has back-to-back days outlined for this time period. GFS and NAM have some robust severe potential... especially NAM.



QUOTE
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CST Sat Feb 25 2017

Valid 281200Z - 051200Z

...DISCUSSION...
Severe-thunderstorm potential will focus during the
Tuesday-Wednesday (Days 4-5) period. Medium-range models (GFS,
ECMWF, CMC, UKMET) and ensembles are coming into better agreement
regarding the evolution of a larger-scale mid-level trough moving
from the western states eastward to the MS Valley on Wednesday. The
trough subsequently exits the east coast on Thursday and severe
potential will likely remain low through Saturday (Day 8) as surface
high pressure resides over the central Gulf Coast.

...Arkansas and surrounding states on Tuesday-Tuesday night...
Low-level moisture will contribute to increased buoyancy within a
broad warm-air-advection regime downstream of the mid-level trough.
A cold front is forecast to move into the western part of this area
late Tuesday along with an increasing risk for severe thunderstorms.

...lower MS Valley and TN Valley on Wednesday...
Strong belt of mid-level flow coupled with increasing low-level
moisture will probably support marginal-moderate buoyancy with a
strong shear profile. The timing of a cold front appears to
converge on Wednesday as it sweeps through the area. Scattered to
numerous thunderstorms are forecast, some of which could be severe.
22 Feb 2017
About 4 days after the last severe weather threat, mother nature may have the pattern reloaded and possibly even nastier.

Moisture is very quick to return from the last system. A trough in the SW US will eject a jet streak ahead of it. This jet streak will run over seasonably rich moisture and possibly steep lapse rates. Models are indicating the potential for a double whammy of lee cyclogenesis, as seen below.

00z GFS





Classic EML sounding


12z Euro was really, really impressive with this system. It had 60 dew points up to WI/IL border with a very well-defined dryline crossing through Kansas City.

Here's WPC's thoughts

17 Feb 2017
As the system from the 21st lingers in the Gulf (which ultimately interferes with moisture return for this system), another system comes in and clips through the Great Lakes. Enough moisture is present and lapse rates are steep enough that a broad area of the warm section will have enough instability for thunderstorms. As of right now, I'm thinking the majority of the severe weather will occur in the mid-Mississippi valley.







SPC has already mentioned this time frame for severe weather for the region.
QUOTE
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CST Fri Feb 17 2017

Valid 201200Z - 251200Z

...DISCUSSION...
The potential for severe weather will likely remain low early during
the extended period as a mid-level low meanders eastward over the
Gulf of Mexico and towards the FL Straits. Time-lagged
deterministic and ensemble data indicate a potent mid-level trough
will eject into the Great Plains on Thursday (day 7). In an
otherwise very favorable pattern for severe, return-flow moisture
will likely be limited owing to the aforementioned influence of the
weather system over the Gulf of Mexico and northerly offshore flow
over the northwestern Gulf Coast leading up to Thursday. The
central U.S. disturbance will subsequently move downstream into the
MS Valley and possibly lead to an increased risk for an organized
band or bands of strong to severe thunderstorms on Friday (day 8).
Ensemble model exhibit appreciable variability/spread. Therefore
will refrain from introducing a 15-percent severe highlight for
areas downstream of the central-southern Great Plains (MS-OH-TN
Valleys) and await additional model consistency.
13 Feb 2017
SPC just introduced an enhanced risk for SE TX. They mention any discrete supercells will have the risk of producing strong tornadoes.


QUOTE
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1136 AM CST Mon Feb 13 2017

Valid 141200Z - 151200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
SOUTHEASTERN TX...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN TX
INTO WESTERN LA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR SOUTHEAST
LA ACROSS COASTAL MS/AL AND THE FL PANHANDLE...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL TX
ACROSS THE CNTRL GULF COAST...

...SUMMARY...
Strong to severe thunderstorms are expected to develop from central
into eastern Texas and perhaps western Louisiana throughout the day
on Tuesday, with a few tornadoes and damaging winds expected. A more
conditional threat of isolated severe storms will also exist Tuesday
night into Wednesday morning from the mouth of the Mississippi river
toward the coastal Florida panhandle.

...Synopsis...
A shortwave trough will move eastward across TX and toward the lower
MS valley on Tuesday, losing amplitude overnight and becoming more
zonal. At the surface, low pressure will deepen across east TX ahead
of a cold front, with warm front lifting northward ahead of the low
track. Substantial moisture will be available to support severe
storms as dewpoints rise into the mid to upper 60s beneath cooling
temperatures aloft. Strengthening shear profiles with 60 kt
southwesterly midlevel flow atop a 40-50 kt southerly low level jet
will support the possibility of damaging storms mainly during the
day, including the threat for tornadoes.

...Central and eastern Texas toward the Sabine river...
Substantial low-level moisture is already in place today from the
central TX coast into Deep South Texas, and this air mass will
spread northward on Tuesday ahead of the developing surface low and
cold front. Environmentally, models indicate strong low-level shear
developing with 0-3 km SRH in the 300-400 m2/s2 range, which is very
supportive of supercells given the moist air mass and adequate
instability. Hodographs look most favorable over east central into
southeast Texas between 15Z-21Z, before the low-level jet veers as
the shortwave passes to the north.

As for storm evolution, scattered storms are forecast to be ongoing
along the cold front over central TX at the beginning of the period.
Some of these storms may contain a hail or wind risk, but the threat
should increase further by late morning mainly east of the I-35
corridor. By 15Z-18Z, a marked uptick in storm strength is expected,
with storms both just ahead of and along the cold front. In both
cases, supercells are expected initially, with a threat of
tornadoes. The threat might transition to damaging winds during the
late afternoon and with northward extent, as the cold front and
outflows result in merged storms and instability wanes.

Any discrete supercells will have a threat of tornadoes in this
environment. Mitigating factors to tornado longevity may be some
weakness in wind fields around 700 mb especially in southern areas,
and potential for numerous storm interactions. However, a strong
tornado or two cannot be ruled out.



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