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SPC Severe Thunderstorm Watch 458

WW 458 SEVERE TSTM KS NE 192245Z - 200600Z
      
WW 0458 Image

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 458
NWS Storm Prediction Center Norman OK
545 PM CDT Sat Aug 19 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northwestern and north central Kansas
  The central third of Nebraska

* Effective this Saturday afternoon and Sunday morning from 545
  PM until 100 AM CDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible
  Isolated very large hail events to 2.5 inches in diameter
    possible

SUMMARY...Thunderstorms are forecast to increase in coverage and
intensify over the next couple of hours, with risk for large hail
and damaging winds likewise increasing in and near the watch area. 
Severe risk will continue for several hours, before diminishing in
the late evening hours.

The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 30 miles northwest of
Oneill NE to 30 miles west southwest of Hill City KS. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU8).

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 457...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
28030.

...Goss

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SPC Severe Thunderstorm Watch 457

WW 457 SEVERE TSTM OH PA WV 191845Z - 200100Z
      
WW 0457 Image

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 457
NWS Storm Prediction Center Norman OK
245 PM EDT Sat Aug 19 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  East Central Ohio
  Western and Central Pennsylvania
  Northern West Virginia Panhandle

* Effective this Saturday afternoon and evening from 245 PM until
  900 PM EDT.

* Primary threats include...
  Scattered damaging wind gusts to 65 mph possible
  Scattered large hail events to 1.5 inches in diameter possible

SUMMARY...Storms developing over eastern Ohio into northwest
Pennsylvania are expected to move eastward with potential to produce
damaging wind gusts and occasional large hail.  The activity will
continue into parts of central Pennsylvania into the early evening
hours before weakening after sunset.

The severe thunderstorm watch area is approximately along and 50
statute miles north and south of a line from 20 miles west northwest
of Zanesville OH to 45 miles east of State College PA. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU7).

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.

&&

AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 55 knots. A
few cumulonimbi with maximum tops to 450. Mean storm motion vector
27030.

...Weiss

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SPC Severe Thunderstorm Watch 458 Status Reports

WW 0458 Status Updates
      
WW 0458 Status Image

STATUS REPORT ON WW 458

THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.

..GLEASON..08/19/17

ATTN...WFO...GLD...DDC...GID...OAX...LBF...


STATUS REPORT FOR WS 458 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

KSC023-039-051-063-065-071-089-109-123-137-141-147-153-163-179-
181-183-193-195-199-203-200040-

KS 
.    KANSAS COUNTIES INCLUDED ARE

CHEYENNE             DECATUR             ELLIS               
GOVE                 GRAHAM              GREELEY             
JEWELL               LOGAN               MITCHELL            
NORTON               OSBORNE             PHILLIPS            
RAWLINS              ROOKS               SHERIDAN            
SHERMAN              SMITH               THOMAS              
TREGO                WALLACE             WICHITA             


NEC001-003-009-011-017-019-029-035-041-047-057-059-061-063-065-
071-073-077-079-081-083-085-087-089-093-099-101-107-111-113-115-
117-121-125-129-135-137-141-143-145-149-163-169-171-175-181-183-
185-200040-

NE 
.    NEBRASKA COUNTIES INCLUDED ARE

ADAMS                ANTELOPE            BLAINE              
BOONE                BROWN               BUFFALO             
CHASE                CLAY                CUSTER              
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SPC Severe Thunderstorm Watch 457 Status Reports

WW 0457 Status Updates
      
WW 0457 Status Image

STATUS REPORT ON WW 457

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 S AOO TO
30 ESE UNV TO 10 N IPT.

..MOSIER..08/19/17

ATTN...WFO...PBZ...CTP...


STATUS REPORT FOR WS 457 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

PAC001-037-041-043-055-057-067-075-081-093-097-099-109-113-119-
133-200040-

PA 
.    PENNSYLVANIA COUNTIES INCLUDED ARE

ADAMS                COLUMBIA            CUMBERLAND          
DAUPHIN              FRANKLIN            FULTON              
JUNIATA              LEBANON             LYCOMING            
MONTOUR              NORTHUMBERLAND      PERRY               
SNYDER               SULLIVAN            UNION               
YORK                 


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 - No MDs are in effect as of Sun Aug 20 00:00:25 UTC 2017

No Mesoscale Discussions are in effect as of Sun Aug 20 00:00:25 UTC 2017.


SPC Aug 19, 2017 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0234 PM CDT Sat Aug 19 2017

Valid 192000Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OHIO
INTO PENNSYLVANIA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWEST
KANSAS INTO CENTRAL NEBRASKA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL PLAINS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OHIO INTO
SOUTHWEST NEW YORK...

...SUMMARY...
Scattered severe thunderstorms are possible across parts of Nebraska
and Kansas late this afternoon and through the evening.  Other
storms will persist from central Ohio into central Pennsylvania
during the afternoon and ending by the early evening.

...Plains area...
Have expanded low wind and hail probabilities into southeast KS,
northeast OK and southwest MO based on current development and
possible isolated activity through evening. Strong instability
exists in this zone, and despite lack of large-scale lift, subtle
convergence may yield additional activity.

For more information see mesoscale discussion 1530.

...OH into PA area...
An east-west oriented zone of storms with complex storm modes
continues to evolve over eastern OH and western PA. Mean westerly
flow aloft should continue to steer storms across the Slight Risk
area, with low-end severe wind or hail.

For more information see mesoscale discussion 1529.

..Jewell.. 08/19/2017

.PREV DISCUSSION... /ISSUED 1123 AM CDT Sat Aug 19 2017/

...Central Ohio into Central Pennsylvania...
Water vapor imagery and 12Z regional upper air data indicate a
strong upper trough is progressing eastward across the middle and
upper Ohio Valley toward the northeastern states.  This feature is
associated with cool mid-level temperatures near -12C at 500 mb, and
12Z observed soundings exhibited steep low-mid level lapse rates
within a non-saturated layer below 500 mb.

Visible satellite imagery suggests ample diabatic heating will
spread from Ohio into Pennsylvania as a weak convective cluster
north of Pittsburgh shifts eastward and clouds diminish from the
west.  Although low-level moisture has decreased in the wake of a
downstream front along the Atlantic seaboard, surface dew point
values in the mid-upper 60s will contribute to MLCAPE of 1000-1500
J/kg across the area.  Large-scale NWP and CAM model guidance
exhibit considerable agreement indicating storms will develop over
eastern Ohio during the early afternoon and spread into Pennsylvania
during the mid-late afternoon.  Steep lapse rates will promote
development of hail with stronger cells, while 30-40 kt flow in the
700-500 mb layer coupled with drier air above the PBL will support
potential for damaging gusts as mid-level westerly momentum is
transferred downward to the surface.  The severe threat should
diminish by early evening.

...Central Plains...
Low-level moisture is returning northward over the central High
Plains where surface dew points are now in the low-mid 60s.  12Z
soundings at DNR, LBF and DDC showed steep tropospheric lapse rates
in place, and with strong diabatic heating expected this afternoon,
the environment will become quite unstable with MLCAPE reaching
2000-2500 J/kg.  Dynamic forcing for large-scale ascent will be
generally modest at best, however, water vapor imagery does show a
weak perturbation moving slowly eastward across southeast Wyoming
and extreme northern Colorado that may enhance convective
development late this afternoon and evening.  A few storms are
expected to develop from far northeast Colorado into adjacent parts
of Nebraska and northwest Kansas with activity spreading eastward
this evening as a moderate low-level jet develops over the central
Plains. 

Despite modest westerly mid-upper level winds, veering profiles with
height will provide sufficient effective shear for organized severe
storms to develop including isolated supercells.  Large hail and
damaging wind gusts will be possible through the evening hours with
activity slowly weakening after 03-06Z.

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