SPC Severe Thunderstorm Watch 166

WW 166 SEVERE TSTM AR MO MS TN 262155Z - 270400Z
      
WW 0166 Image

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 166
NWS Storm Prediction Center Norman OK
455 PM CDT Wed Apr 26 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  East central and northeast Arkansas
  The Missouri Bootheel
  Northern Mississippi
  Western Tennessee

* Effective this Wednesday afternoon and evening from 455 PM
  until 1100 PM CDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible
  Isolated large hail events to 1.5 inches in diameter possible

SUMMARY...Squall line in Arkansas will likely persist through the
evening hours while moving eastward into western Tennessee and
Mississippi.  Damaging winds with embedded bowing segments will be
the main severe threat.

The severe thunderstorm watch area is approximately along and 60
statute miles east and west of a line from 35 miles north northeast
of Dyersburg TN to 55 miles west southwest of Oxford MS. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU6).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 162...WW 163...WW 164...

AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
26040.

...Thompson

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SPC Severe Thunderstorm Watch 165

WW 165 SEVERE TSTM IN OH 262155Z - 270400Z
      
WW 0165 Image

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 165
NWS Storm Prediction Center Norman OK
555 PM EDT Wed Apr 26 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  central and northeastern Indiana
  northwestern Ohio

* Effective this Wednesday afternoon from 555 PM until Midnight
  EDT.

* Primary threats include...
  Isolated very large hail events to 2 inches in diameter possible
  Isolated damaging wind gusts to 70 mph possible

SUMMARY...An area of strong to severe thunderstorm activity is
expected to rapidly develop northeastward across the region through
mid to late evening.  This likely will include much of the
Indianapolis metropolitan area by 8 pm EDT, with strongest storms
capable of producing severe hail and potentially damaging wind
gusts.

The severe thunderstorm watch area is approximately along and 50
statute miles east and west of a line from 55 miles north northeast
of Fort Wayne IN to 35 miles west southwest of Indianapolis IN. For
a complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU5).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 162...WW 163...WW 164...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 400. Mean storm motion vector
24045.

...Kerr

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SPC Tornado Watch 164

WW 164 TORNADO AR LA MS TX 262145Z - 270400Z
      
WW 0164 Image

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 164
NWS Storm Prediction Center Norman OK
445 PM CDT Wed Apr 26 2017

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Southeast Arkansas
  Central and northern Louisiana
  West central Mississippi
  Southeast Texas

* Effective this Wednesday afternoon and evening from 445 PM
  until 1100 PM CDT.

* Primary threats include...
  A couple tornadoes possible
  Scattered damaging wind gusts to 70 mph likely
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible

SUMMARY...Squall line will begin to accelerate eastward through the
evening hours, with some increase in the damaging wind risk
expected.  A couple of tornadoes and large hail will still be
possible, especially with embedded circulations and any
sustained/discrete storms ahead of the line.

The tornado watch area is approximately along and 80 statute miles
east and west of a line from 40 miles north of Greenville MS to 55
miles southwest of Fort Polk LA. For a complete depiction of the
watch see the associated watch outline update (WOUS64 KWNS WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 162...WW 163...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean
storm motion vector 25035.

...Thompson

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SPC Severe Thunderstorm Watch 166 Status Reports

WW 0166 Status Updates
      
WW 0166 Status Image

STATUS REPORT ON WW 166

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 40 N GLH TO
35 WSW MEM TO 30 NNW DYR.

..KERR..04/27/17

ATTN...WFO...MEG...


STATUS REPORT FOR WS 166 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

MSC009-013-027-033-071-093-107-115-119-135-137-139-143-145-161-
270140-

MS 
.    MISSISSIPPI COUNTIES INCLUDED ARE

BENTON               CALHOUN             COAHOMA             
DESOTO               LAFAYETTE           MARSHALL            
PANOLA               PONTOTOC            QUITMAN             
TALLAHATCHIE         TATE                TIPPAH              
TUNICA               UNION               YALOBUSHA           


TNC017-023-033-045-047-053-069-075-077-079-095-097-109-113-131-
157-167-183-270140-

TN 
.    TENNESSEE COUNTIES INCLUDED ARE

CARROLL              CHESTER             CROCKETT            
DYER                 FAYETTE             GIBSON              
HARDEMAN             HAYWOOD             HENDERSON           
HENRY                LAKE                LAUDERDALE          
MCNAIRY              MADISON             OBION               
SHELBY               TIPTON              WEAKLEY             
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SPC Severe Thunderstorm Watch 165 Status Reports

WW 0165 Status Updates
      
WW 0165 Status Image

STATUS REPORT ON WW 165

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 10 S MIE TO
40 WNW MIE TO 40 SE AZO.

FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 0567.

..LEITMAN..04/27/17

ATTN...WFO...IWX...IND...


STATUS REPORT FOR WS 165 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

INC001-003-009-033-035-053-069-075-135-151-169-179-183-270140-

IN 
.    INDIANA COUNTIES INCLUDED ARE

ADAMS                ALLEN               BLACKFORD           
DE KALB              DELAWARE            GRANT               
HUNTINGTON           JAY                 RANDOLPH            
STEUBEN              WABASH              WELLS               
WHITLEY              


OHC039-051-069-125-137-161-171-270140-

OH 
.    OHIO COUNTIES INCLUDED ARE

DEFIANCE             FULTON              HENRY               
PAULDING             PUTNAM              VAN WERT            
WILLIAMS             


THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY.  PLEASE
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SPC Tornado Watch 164 Status Reports

WW 0164 Status Updates
      
WW 0164 Status Image

STATUS REPORT ON WW 164

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 40 NNE BPT
TO 40 N GLH.

..KERR..04/27/17

ATTN...WFO...LZK...JAN...SHV...LCH...HGX...


STATUS REPORT FOR WT 164 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

ARC003-017-270140-

AR 
.    ARKANSAS COUNTIES INCLUDED ARE

ASHLEY               CHICOT              


LAC003-009-011-013-021-025-029-035-039-041-043-049-059-061-065-
067-069-073-079-083-085-107-111-115-123-127-270140-

LA 
.    LOUISIANA PARISHES INCLUDED ARE

ALLEN                AVOYELLES           BEAUREGARD          
BIENVILLE            CALDWELL            CATAHOULA           
CONCORDIA            EAST CARROLL        EVANGELINE          
FRANKLIN             GRANT               JACKSON             
LA SALLE             LINCOLN             MADISON             
MOREHOUSE            NATCHITOCHES        OUACHITA            
RAPIDES              RICHLAND            SABINE              
TENSAS               UNION               VERNON              
WEST CARROLL         WINN                


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SPC Severe Thunderstorm Watch 163 Status Reports

WW 0163 Status Updates
      
WW 0163 Status Image

STATUS REPORT ON WW 163

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 NE ARG TO
25 SE MDH.

WW 163 WILL BE ALLOWED TO EXPIRE AT 270000Z.

..LEITMAN..04/26/17

ATTN...WFO...PAH...LSX...ILX...


STATUS REPORT FOR WS 163 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

ILC003-153-181-270000-

IL 
.    ILLINOIS COUNTIES INCLUDED ARE

ALEXANDER            PULASKI             UNION               


MOC201-270000-

MO 
.    MISSOURI COUNTIES INCLUDED ARE

SCOTT                


THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY.  PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.

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SPC MD 568

MD 0568 CONCERNING SEVERE THUNDERSTORM WATCH 166... FOR WESTERN TENNESSEE...NORTHERN MISSISSIPPI
MD 0568 Image


Mesoscale Discussion 0568
NWS Storm Prediction Center Norman OK
0736 PM CDT Wed Apr 26 2017

Areas affected...western Tennessee...northern Mississippi

Concerning...Severe Thunderstorm Watch 166...

Valid 270036Z - 270200Z

The severe weather threat for Severe Thunderstorm Watch 166
continues.

SUMMARY...A risk for primarily potentially damaging wind gusts
continues at least another couple of hours with the squall line
advancing across northern Mississippi and portions of western
Tennessee.  This may include areas in close proximity to, but east
of watch 166, before activity weakens, but it is not yet certain
that a new watch will be needed.

DISCUSSION...As the significant short wave trough approaching the
lower Mississippi Valley takes on an increasing negative tilt,
stronger low-level convergence and mid-level forcing for ascent
likely will become focused across northern Mississippi northward
into the lower Ohio Valley during the next few hours.  This is
forecast to coincide with further strengthening of southerly 850 mb
flow to 50+ kt ahead of the ongoing pre-frontal squall line which is
now advancing east of the Mississippi River.  However, the northward
return of richer boundary layer moisture is becoming increasingly
cut-off from this region, and the maintenance of vigorous boundary
based storm development beyond the next couple of hours is
increasingly unclear.  The segment of the squall line north of
Greenville MS into the vicinity of the MISSISSIPPI/Tennessee state
border seems to provide the greatest risk for potentially damaging
wind gusts through the 01-03z time frame, with at least some
northeastward acceleration possible.

..Kerr.. 04/27/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OHX...BMX...HUN...MEG...JAN...

LAT...LON   36158881 36488844 36418745 34788792 33908807 33508891
            33628998 34278996 34808962 36158881 

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SPC MD 566

MD 0566 CONCERNING TORNADO WATCH 164... FOR PARTS OF CENTRAL/NORTHEASTERN LOUISIANA...WESTERN/CENTRAL MISSISSIPPI
MD 0566 Image


Mesoscale Discussion 0566
NWS Storm Prediction Center Norman OK
0702 PM CDT Wed Apr 26 2017

Areas affected...Parts of central/northeastern
Louisiana...western/central Mississippi

Concerning...Tornado Watch 164...

Valid 270002Z - 270130Z

The severe weather threat for Tornado Watch 164 continues.

SUMMARY...The risk for a couple of tornadoes and potentially
damaging wind gusts with storms overspreading the region will
continue at least into the 9-10 pm CDT time frame.  It is not
certain that an additional watch will be needed to the east of watch
164, but trends will continue to be monitored for this possibility.

DISCUSSION...Sustained vigorous thunderstorms within a pre-frontal
squall line continue to advance eastward into/through the lower
Mississippi Valley, as a supporting short wave trough pivots into an
increasing negative tilt orientation as it approaches the region. 
New convective development is ongoing ahead of the line, but is
generally confined to a narrow corridor ahead of it, before merging
into or being overtaken by the line, as the leading edge of
mid-level cooling contributes to a gradual west to east erosion of
the plume of capping elevated mixed layer air.  

The leading edge of  an inland returning plume of seasonably moist
boundary layer air (characterized by surface dew points in the upper
60s/lower 70s) remains stalled over southern/eastern Louisiana and
southwestern Mississippi, and the squall line appears likely to
increasingly cut-off inland return of higher boundary layer moisture
from the Gulf of Mexico.  As it does, easterly inflow of less
unstable air into the storms may tend to contribute to weakening of
updrafts as early as 02-03Z, although it is possible that this may
be counter balanced somewhat by at least some strengthening of
southerly 850 mb flow (and low-level shear).  Until convection
begins to wane, a period of increasing risk for strong surface gusts
remains possible into early evening, along with continued potential
for a couple of tornadoes.

..Kerr.. 04/27/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MEG...JAN...LIX...LCH...SHV...

LAT...LON   33469078 33969011 33888938 32978950 31949013 30499167
            30179265 30449347 32549152 33469078 

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SPC Apr 27, 2017 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0759 PM CDT Wed Apr 26 2017

Valid 270100Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE LOWER MS VALLEY AND VICINITY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHERN IN AND NORTHWEST OH...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
THE SOUTHERN GREAT LAKES REGION TO THE NORTH-CENTRAL GULF COAST...

...SUMMARY...
Severe thunderstorms will remain possible from portions of the
north-central Gulf Coast region northward to the southern Great
Lakes region into tonight. Widely scattered damaging wind gusts and
perhaps a couple of tornadoes may accompany storms moving across
parts of the lower Mississippi Valley and vicinity into the
overnight hours, while a cluster of storms moving across portions of
northern Indiana and northwest Ohio may produce widely scattered
damaging winds into the evening hours.

...Portions of the north-central Gulf Coast region northward to the
southern Great Lakes region...
A corridor of convective bands extends from the lower OH Valley to
the north-central Gulf Coast vicinity. The northern portion of this
activity is pinching off the northernmost extent of more appreciable
moisture return, which 00Z observed soundings suggest resides closer
to the coast. While poleward return of more substantially modified
maritime air will occur ahead of the convection, the richer moisture
and related substantive buoyancy (MLCAPE around 500-1500 J/kg)
should remain generally near and south of western/middle TN. This is
where sufficient deep shear (45-65 kt of effective bulk shear) will
also exist in favor of continued quasi-linear convective modes
capable of widely scattered damaging winds. This activity will
spread into western AL through the overnight hours, and sufficient
low-level shear may exist for occasional line-embedded and
line-preceding supercell structures to support a couple of
tornadoes. Some isolated severe risk could extend even farther east
later in the night.

Farther north, a sustained cluster of storms continues advancing
northeastward across northern IN, and may eventually affect parts of
northwest OH before weakening in southern Lower MI this evening.
Moderately steep midlevel lapse rates around 7.3 C/km, based on the
Detroit 00Z sounding, will support sufficient buoyancy amid modest
moisture return for some severe risk persisting in the short-term.

Relatively weaker low-level lapse rates and limited moisture return
between the Slight Risk areas suggest that the severe risk should
remain more isolated across parts of the lower/middle Ohio Valley
region and vicinity. However, locally damaging wind gusts may
accompany the most pronounced bowing convective line segments.

..Cohen.. 04/27/2017

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SPC Apr 26, 2017 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook AMEND 1
NWS Storm Prediction Center Norman OK
0518 PM CDT Wed Apr 26 2017

Valid 262210Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE LOWER MS VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER MS
VALLEY INTO INDIANA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
THE MID AND LOWER MS VALLEY INTO THE SOUTHERN GREAT LAKES REGION...

AMENDED FOR NORTHWARD ADJUSTMENT OF MARGINAL/SLIGHT AREAS IN THE
SOUTHERN GREAT LAKES REGION

...SUMMARY...
Severe thunderstorms will continue across the Lower Mississippi
Valley.  Tornadoes, large hail, and damaging winds are most probable
from northeast Texas across parts of Arkansas and northern Louisiana
this afternoon and evening. Isolated severe thunderstorms may extend
as far north as Illinois/Indiana this afternoon and evening, and
into the central Gulf States during the overnight hours.

...2210Z Outlook Amendment...

The Slight/Marginal areas have been extended northward across
portions of the southern Great Lakes region.  Please reference
Severe Thunderstorm Watch 165 for additional details.

...20Z Update...

...Lower MS Valley...
Outflow boundary continues to surge eastward across northern and
central AR ahead of the approaching cold front. Anafrontal character
to the ongoing convection is expected to continue with the cold
front eventually catching up to the outflow later this
afternoon/evening. Farther south, a more composite outflow/cold
front already exists with some severe storms currently ongoing.

Linear nature of this convection is expected to persist throughout
the evening with little indication in either recent observations
(i.e. backed mid-level flow on the 18Z SHV sounding) or recent
guidance that robust discrete development will occur.  As a result,
reduced the tornado probabilities across the area to 10%. Given the
strength of the shear, some QLCS tornadoes are still possible.

Strongest storms are expected to remain along the southern end of
the line where the best low-level moisture exists and the mean flow
is more orthogonal to the advancing cold front. 

...OH Valley...
Based on current convective trends, expanded the Slight a bit more
northeastward into more east-central IL and southwest IN.

..Cohen.. 04/26/2017

.PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Apr 26 2017/

...Lower MS Valley...
Few changes have been made to the ongoing forecast.  A squall line
currently extends from south-central MO into northeast TX.  Several
bowing structures along this line will pose a risk of damaging winds
gusts, large hail, and perhaps a QLCS tornado or two this afternoon.
The activity will likely spread into southeast MO and western KY/TN
by early evening, with a continued severe threat.

Farther south, most model solutions suggest that the capping
inversion will slowly weaken this afternoon.  This should help to
allow a few discrete storms to form in the warm sector ahead of the
more organized convective line.  Local VAD and forecast hodographs
in this region continue to support a risk of supercells capable of
tornadoes (some strong) if discrete initiation materializes. 
Therefore will maintain the MDT risk and 15% tornado forecast. 
These storms are expected to track northeastward through the evening
into western/central MS where damaging winds and isolated tornadoes
will remain possible.

Overnight, it is uncertain how far east the organized severe threat
will persist.  Nevertheless, will make no changes to the eastern
extent of the SLGT risk at this time.

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