Severe Weather Risk for Wednesday 3/1

[Jim Martin]

Looking like the potential is there for severe weather Wednesday across the region. According to NWS Birmingham, all modes of severe weather look to be possible.

[MattPetrulli]

Widespread 30% risk across much of the viewing region. Probably one of the biggest day 4 outlooks ever spreads from TX to NJ. SPC mentions widespread damaging wind event with MRX saying significant severe weather outbreak. 

[Jim Martin]

Here is the map Matt is referring to.

[MattPetrulli]

20 minutes ago, Jim Martin said:

Here is the map Matt is referring to.

Forgot to post that, thank you.

[Jim Martin]

Not a problem Matt.

[wxrjm]

CIPS Guidance from this morning suggesting a wind threat over a discrete supercell threat (hail/TOR). Looks like a decent setup for a squall line. 

 

[PowellVolz]

Looking like a nice set up for a widespread wind event. Even conservative MRX are saying possible severe outbreak.


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[jaxjagman]

[jaxjagman]

Just got home from my sons gymnastics meet this weekend.Looking at the GFS and Euro both show a shortwave coming from SW TN Tuesday afternoon into the evening.Timing and strength look rather substantial ATM but both show this feature

[jaxjagman]

[jaxjagman]

 

Nice shortwave coming through the Valley on tonight's run,best severe look,looks to be in the Ozarks into the Western Valley Tuesday afternooon.depending on any cloud cover?

[Mrwolf1972]

If we get alot of sun it's gonna be a interesting day.

[jaxjagman]

 Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1257 AM CST Mon Feb 27 2017

   Valid 281200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
   AND NORTHERN ARKANSAS INTO SOUTHEASTERN MISSOURI AND ADJACENT
   PORTIONS OF SOUTHERN ILLINOIS...WESTERN KENTUCKY...AND WESTERN
   TENNESSEE...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE ARKLATEX
   NORTHEASTWARD THROUGH THE LOWER AND MIDDLE MISSISSIPPI VALLEY AND
   INTO THE OHIO VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   Severe thunderstorms will be possible on Tuesday and Tuesday night
   from eastern portions of Oklahoma and Texas northeastward into parts
   of the lower and middle Mississippi Valley and Ohio Valley.

   ...Synopsis...
   Model guidance is in good agreement in showing a larger-scale
   mid-level trough axis moving from the Great Basin/southern CA region
   eastward to the Great Plains late Tuesday night.  A very strong
   500-mb speed max over the Chihuahuan Desert will move downstream
   within a belt of southwesterly flow and be located over the middle
   MS and lower OH Valleys and intensify to 100+ kt by early Wednesday
   morning.  In the low levels, a broad and strengthening southwesterly
   low-level jet will extend from the northwest Gulf Coast
   northeastward into the lower Great Lakes.  The primary surface low
   will develop eastward from NE/IA vicinity eastward to the lower
   Great Lakes during the period.  Concurrently, a warm front will
   advance northward through the OH Valley as a cold front pushes
   southeastward through the lower MO Valley and through eastern OK
   overnight.

   ...ArkLaTex and eastern OK northeastward into the MS Valley and OH
   Valley...
   This remains a complicated forecast and there remains considerable
   uncertainty regarding several factors described below, some of which
   are conditional, that will have large influence on the unconditional
   severe probabilities.

   Low-level moisture will continue to stream poleward within a ribbon
   of strong south-southwesterly flow as a warm front advances
   northward from the lower MO and lower OH Valleys to the southern
   Great Lakes.  Lowest 100-mb mean mixing ratios of 10-13 g/kg will
   translate to 58-62 degrees F dewpoints over the OH Valley and the
   middle 60s reaching as far northeast as the MO Bootheel and
   encompassing areas farther southwest over the ArkLaTex.  A cirrus
   canopy is likely to overspread a large portion of the enlarging
   warm/moist sector and partially modulate heating.  A capping
   inversion located in the 850-700 mb layer will likely delay storm
   development until late in the day across AR and areas downstream
   over the MS/OH River confluence.  By late afternoon/early evening,
   there is uncertainty whether storms will initiate along a
   pre-frontal confluence/850-mb moisture axis bisecting AR from
   southwest to northeast and into southeastern MO.  

   Models show only weak convective inhibition but this area will
   largely be on the eastern edge of 500-mb height falls beginning to
   tease the area.  In other words, only weak forcing for ascent
   primarily in the form of isentropic lift/warm-moist advection, is
   expected with any possible diurnally-driven development. 
   Deterministic models including the ECMWF, UKMET, GFS, and to a
   certain extent the ARWKF, show warm-sector activity developing over
   AR and moving downstream towards the MS/OH River confluence.  The
   NAM and NMMB models are largely void of storm development with this
   scenario and are uncharacteristically "dry".  It appears
   increasingly probable that a cluster of storms develops within this
   corridor.  The supercell-wind profile, moderate buoyancy (1000-1750
   J/kg MLCAPE), and 300-400 m2/s2 effective SRH would favor
   surface-based supercells with all hazards possible, including the
   conditional possibility for a strong tornado(s).

   As stronger DCVA/500-mb height falls overspread the western
   periphery of the warm sector as the cold front begins to accelerate
   southeastward, scattered to numerous storms are forecast to develop
   across the middle MS Valley and farther south over eastern OK and
   northeast TX.  Strong deep-layer shear will aid in storm
   organization and upscale growth into one or more bands of storms
   potentially capable of damaging winds/hail with the stronger storms.
   The strong background low-level shear may support some tornado risk
   into the overnight associated with stronger supercells and/or QLCS
   mesovortices.  The frontal convection will probably reach the MS
   River and lower portion of the OH River by Wednesday morning.

[jaxjagman]

3 hours ago, Mrwolf1972 said:

If we get alot of sun it's gonna be a interesting day.

 Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0228 AM CST Mon Feb 27 2017

   Valid 011200Z - 021200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
   MISSISSIPPI...ALABAMA...AND NORTHWESTERN GEORGIA INTO MIDDLE AND
   EASTERN TENNESSEE AND CENTRAL AND SOUTHEASTERN KENTUCKY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
   MISSISSIPPI VALLEY THROUGH PARTS OF THE SOUTHERN AND CENTRAL
   APPALACHIAN STATES AND INTO THE MID-ATLANTIC STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
   GULF COAST NORTHEASTWARD INTO PORTIONS OF THE NORTHEAST...

   ...SUMMARY...
   Strong to severe thunderstorms will be possible from the lower
   Mississippi Valley northeastward across the Tennessee Valley and
   southern Appalachians, and northward into parts of the Mid-Atlantic
   states and perhaps portions of the Northeast.

   ...Synopsis...
   A mid-level trough will move eastward across the Midwest and into
   the lower Great Lakes during the day-3 period.  The primary
   mid-level vorticity maximum is progged to move from the middle MS
   Valley east-northeastward into the lower Great Lakes by late
   afternoon/early evening.  A surface low will develop northeast from
   Ontario to the St. Lawrence Seaway by late Wednesday night.  A cold
   front, initially near the lower OH Valley and lower MS Valley, will
   sweep eastward across much of the Southeast and the East.

   ...lower MS Valley into the TN Valley and southern Appalachians and
   north into the Mid-Atlantic states...
   An ongoing and likely extensive squall line or broken bands of
   storms are forecast near the MS River and lower OH Valley in
   association with a cold front.  Models vary slightly on the timing
   of the fronts' position during the early part of the day.  However,
   it seems likely substantial low-level moisture (upper 50s-mid 60s
   dewpoints) will extend northeast from the lower MS Valley to the
   WV/KY/OH/VA vicinity.  Despite the prevalence of some mid-high cloud
   cover, very strong low- to mid-tropospheric winds (50-70 kt
   southwesterly flow at 700 mb) should aid in the development of
   squall line with LEWPS/bowing segments capable of wind damage and
   possibly a tornado where greater destabilization occurs.  The
   convective line will likely persist (owing to 60-90m 12 hour 500mb
   height falls) and move across the Appalachian spine and possibly
   yield a continued risk for damaging winds after dark despite the
   loss of daytime heating.  The diminishing of buoyancy with eastward
   extend across the Southeast U.S. will probably lead to a
   corresponding weakening in storm intensity and strong/severe storm
   coverage.

   ...lower Great Lakes and Hudson Valley...
   The northern periphery of appreciable low-level moisture will likely
   move into the area as a warm front advances northward through a
   large part of the Northeast.  A storm cluster or two may be ongoing
   early Wednesday and may delay destabilization.  However, an influx
   of mid-upper 50s dewpoints will likely result in several hundred
   J/kg MUCAPE with a strong wind profile indicative of organized storm
   structures.  One or more bands may develop or move into the area
   during the midday/afternoon as the effective front pushes eastward. 
   Damaging winds will probably be the main severe hazard.  The main
   limiting factor for higher coverage of strong to severe
   thunderstorms will be weak instability.

[jaxjagman]

 ...Ohio and Tennessee Valleys Tuesday morning and afternoon...
   Despite the lack of height falls during the first half of the
   forecast period, forcing for ascent attendant to a weak transient
   midlevel impulse tracking across this region and low-level warm air
   advection suggests an ongoing cluster and/or new thunderstorm
   development will spread from west to east.  The eastern extent of a
   plume of steep midlevel lapse rates spreading east atop low-level
   moistening should prove favorable for mainly elevated storms with
   hail being the primary threat.  However, forecast soundings suggest
   some potential for a few surface-based storms, especially by Tuesday
   afternoon across parts of northern AL through middle TN and eastern
   KY.  Vertically veering winds suggest a tornado and locally strong
   wind gusts cannot be ruled out with these afternoon storms.

 

http://www.spc.noaa.gov/products/outlook/day2otlk.html

[nrgjeff]

Wednesday looks like straight line wind time for our Region. A robust QLCS or two would not surprise me. At least look for some bow echos. Winds aloft are forecast unidirectional but quite strong. Though low press tracks into the Great Lakes, the southern jet stream will be vigorous and zonal.

Outside our sub-forum Tuesday night from Arkansas through southeast MO into southern/central IL could include a few tornadoes. 925 mb is forecast (relatively) somewhat backed, definitely backed compared to levels above. Even though 850 mb is from the southwest, plenty of turning and certainly speed is forecast with height. Hopefully other rain will temper instability since it is overnight. Then I think either way it gets more linear Wednesday for our region.

Thread is going on the main Weather Forecasting forum. This may be my last post depending on if work gets busy day ahead. Either way no chase is planned for the fast moving, sloppy, mainly night time (Midsouth), Dixie Alley mess.

[Mrwolf1972]

DAYS TWO THROUGH SEVEN...Tuesday through Sunday

A significant outbreak of severe weather is possible on Wednesday
as a strong cold front sweeps into the region from the west. In
particular, there will be an enhanced risk for thunderstorms
capable of producing damaging straight-line winds on Wednesday
afternoon and evening, especially along and west of the I-75
corridor. Additionally, these storms would be capable of producing
large hail and potentially a few tornadoes.

Some uncertainty still exists with the specific details of this
system. Exact timing and threat areas will be refined as the event
approaches. Please continue to monitor additional forecasts for
more information. Use this time to make sure you`re prepared and
know what you`ll do if a warning is issued!

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed on Wednesday in support of severe
weather operations.
 3pm up date

314 PM EST Mon Feb 27 2017 /214 PM CST Mon Feb 27 2017/



.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

A significant outbreak of severe weather is possible on Wednesday
as a strong cold front sweeps into the region from the west. In
particular, there is an enhanced risk for thunderstorms capable
of producing damaging straight-line winds on Wednesday afternoon
and evening, especially along and west of the I-75 corridor.
Additionally, these storms will be capable of producing large
hail and potentially a few tornadoes. The main timeframe for
severe weather will occur from roughly noon to 8 pm on Wednesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed on Wednesday afternoon in
support of severe weather operations.

 

[wxrjm]

I was a little surprised to see the wording from MRX too on Sunday, but it's warranted. I bet we see some area of 30% hatched in the enhanced tomorrow if SPC follows their trend. 

 

Just for fun- Time to play find the PDS TOR sounding. Mountain City, TN (1st sounding) from the 0z NAM4. Second sounding is KTRI from SHARpY. 

Most are just TOR soundings. Hodographs and wind profiles have my thinking QLCS with embedded circulations possible. At least the timing is nice for this one. For once a front isn't coming through at 2-5am.. 

[jaxjagman]

Updrafts being shown into the Mo and Ohio Valley makes ours look petty on the 3K NAM and ours are nothing to sneeze at

 

 

[Runman292]

Here's the latest discussion from MRX:

.LONG TERM /Wednesday through Monday/...
Biggest weather event of concern will be the chance for severe
weather as a trough moves across the northern plains and a surface
low moves through the Great Lakes Region with it, and this system
drags a cold front through our area on Wednesday. We could have some
ongoing convection Tuesday night into Wednesday morning which could
help stabilize the atmosphere and alter the chances for severe
weather. Soundings suggest that any ongoing convection would be
pretty weak and could wain in the overnight hours as dry air in the
mid levels hinders convection, and we could get some cloud clearing
during the day. If this hindrance does occur then the atmosphere
should be primed for much stronger storms as we roll into Wednesday
and the front moves closer to our area. Best timing for the
strongest storms still seems to be the afternoon hours till a bit
after sunset. During this time mid level jet will put us in the
favored region for some upper level support and the low level jet
will be cranking from early in the morning until the front moves
through. Low level jet speeds of 50-60+ knots will help create
strong shear as well as strong pre-frontal winds on Wednesday.
Forecast models indicate the possibility of 500-1500 J/kg of CAPE
depending on the model and location in our forecast area. This
combined with strong 0-1km and 0-6km shear will lead to a good
possibility to see damaging winds from a line of severe
thunderstorms. In addition with this set up we could also see large
hail and a few tornadoes as well.

[jaxjagman]

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CST Tue Feb 28 2017

   Valid 011200Z - 021200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   MISSISSIPPI AND NORTHERN ALABAMA ACROSS PARTS OF
   TENNESSEE...KENTUCKY...SOUTHERN OHIO AND WEST VIRGINA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK FROM THE SOUTHEAST STATES INTO THE MID-ATLANTIC REGION
   AND SOUTHERN NEW ENGLAND...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK....

   ...SUMMARY...
   Strong to severe thunderstorms will be possible from the lower
   Mississippi Valley northeastward across the Tennessee Valley and
   Appalachians, and northward into parts of the Mid-Atlantic states
   into southern New England.  Damaging winds are forecast to be the
   predominant severe hazard.  However, a few tornadoes will be
   possible, especially during the day, from the Tennessee Valley into
   the middle and upper Ohio Valley.

   ...Synopsis...
   An energetic progressive flow pattern is forecast to persist through
   Wednesday as the current full-latitude western US upper trough moves
   eastward into the Plains tonight and then lifts east-northeastward
   across the northeast states through Wednesday night.  Very strong
   winds aloft accompany this system with 100+ kt maxima at 500 mb and
   60-65 kt at 850 mb which will provide intense low-level and
   deep-layer vertical shear supportive of severe storms.

   At the surface, a low over southeast lower Michigan at the start of
   the period is expected to deepen as it moves across the lower Great
   Lakes during the day, reaching northern Maine by the end of the
   period.  A trailing cold front initially extending southwest from
   the low across the middle Mississippi Valley to the upper Texas
   coast will progress eastward and southeastward during the period,
   crossing the Appalachians by 00Z and moving offshore into the
   Atlantic between 06-09Z and extending across northern Florida into
   the eastern Gulf of Mexico by the end of the period.

   ...Tennessee Valley into the middle/upper Ohio Valley...
   Strong to severe storms are likely to be ongoing early in the period
   in association with several pre-frontal convective systems from
   parts of Ohio southwestward into parts of the mid-South region.  The
   mesoscale/near-storm environment west of the Appalachians is
   expected to be characterized by 60-65F surface dew points, MUCAPE
   ranging from 750 J/kg in Ohio to 1200 J/kg in the mid-South, and an
   expansive region of very strong vertical shear of 50-70 kt in the
   lowest 6 km AGL will support some rotating updrafts, especially if
   more discrete cells can be maintained.  Nevertheless, strongest
   storms will have potential to produce all severe hazards including a
   few tornadoes, especially during the daytime hours, as cells move
   rapidly eastward/northeastward along and ahead of the advancing cold
   front.

[PowellVolz]

SPC has upgraded the severe weather risk northwest of here. Tempted to chase, but may hold off since it will be dark. Part of me is curious if something similar could happen in middle Tennessee tomorrow, but I doubt it as I default to the sum of nocturnal systems + cap-inducing ingredients/cloud cover = weak middle Tennessee threats. Interestingly, it doesn't look like we have a nocturnal event on our hands, but all this cloud cover today has to limit instability, right? Modest lift can still generate, granted, but it seems all the ingredients rarely come together here (at least this decade).

With a cap in place tomorrow I doubt we'll see much in the way of clouds. Especially in E Tennessee.


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[nrgjeff]

Cap in early spring can actually trap low clouds, keeping it overcast through morning. Also I have questions about instability based on overturning the last two days. However that intense LLJ may recharge everything overnight, even in those no sunshine hours. This afternoon the theta-e advection in the Mississippi Valley is impressive. Will it translate to the Tennessee Valley tomorrow?

It kind of feels like a Valley crap out Wednesday after tonight (Mid-South action), but I could be biased by current drizzle in CHA. One cannot discount the low CAPE high shear examples of the past. We will not have that kind of turning with height; however we will have remarkably strong mid-level winds and even stronger upper level winds. Probably a lot of straight line wind is the best forecast, with isolated spin-ups. If for some reason low level winds back more than forecast, esp if up to about 925 mb, one would have to watch for a broken line. Could be anywhere from a few tornadoes (unlikely) to a weakening line (almost as unlikely). Most likely Wednesday will feature a good line of storms, perhaps a LEWP or two if it really gets going.

[Mrwolf1972]

3pm update

[Matthew70]

2 hours ago, nrgjeff said:

Cap in early spring can actually trap low clouds, keeping it overcast through morning. Also I have questions about instability based on overturning the last two days. However that intense LLJ may recharge everything overnight, even in those no sunshine hours. This afternoon the theta-e advection in the Mississippi Valley is impressive. Will it translate to the Tennessee Valley tomorrow?

It kind of feels like a Valley crap out Wednesday after tonight (Mid-South action), but I could be biased by current drizzle in CHA. One cannot discount the low CAPE high shear examples of the past. We will not have that kind of turning with height; however we will have remarkably strong mid-level winds and even stronger upper level winds. Probably a lot of straight line wind is the best forecast, with isolated spin-ups. If for some reason low level winds back more than forecast, esp if up to about 925 mb, one would have to watch for a broken line. Could be anywhere from a few tornadoes (unlikely) to a weakening line (almost as unlikely). Most likely Wednesday will feature a good line of storms, perhaps a LEWP or two if it really gets going.

I remember the Murfreesboro tornado because I was in it.  It was cloudy & cool with rain showers. I remember saying to cloudy & cool for severe wx.  I was so wrong.   Then a couple hours later an EF4 came thru.  

[PowellVolz]

Cap in early spring can actually trap low clouds, keeping it overcast through morning. Also I have questions about instability based on overturning the last two days. However that intense LLJ may recharge everything overnight, even in those no sunshine hours. This afternoon the theta-e advection in the Mississippi Valley is impressive. Will it translate to the Tennessee Valley tomorrow?

It kind of feels like a Valley crap out Wednesday after tonight (Mid-South action), but I could be biased by current drizzle in CHA. One cannot discount the low CAPE high shear examples of the past. We will not have that kind of turning with height; however we will have remarkably strong mid-level winds and even stronger upper level winds. Probably a lot of straight line wind is the best forecast, with isolated spin-ups. If for some reason low level winds back more than forecast, esp if up to about 925 mb, one would have to watch for a broken line. Could be anywhere from a few tornadoes (unlikely) to a weakening line (almost as unlikely). Most likely Wednesday will feature a good line of storms, perhaps a LEWP or two if it really gets going.

Strong 850mb winds should help with low clouds.


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[dwagner88]

Essentially every local school system is closed tomorrow. Even UTC. I'm very surprised. 

[rbowman]

I hear some of the east Tennessee schools are closing for tomorrow. Probably a smart move to play it safe. Metro Nashville has not closed, but should. They really got themselves into a mess during that small snow in January with several busses getting stuck. They need a met on staff, or at least someone smart enough to look at a forecast and radar to help make the decision to go or not.

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[jaxjagman]

Updrafts on the latest HRRR

 

[Runman292]

MRX just posted the following graphic. The 4th bullet point is an eyebrow raiser.