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Storm Prediction Center



Published: Tue, 22 Aug 2017 18:52:02 +0000

Last Build Date: Tue, 22 Aug 2017 18:52:02 +0000

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SPC Severe Thunderstorm Watch 462

Tue, 22 Aug 2017 18:31:02 +0000

WW 462 SEVERE TSTM IN KY MD OH PA WV 221640Z - 230100Z
(image)

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 462
NWS Storm Prediction Center Norman OK
1240 PM EDT Tue Aug 22 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Far southern Indiana
  Central and northern Kentucky
  Far western Maryland Panhandle
  Southern and eastern Ohio
  Western and central Pennsylvania
  Northern and western West Virginia

* Effective this Tuesday afternoon and evening from 1240 PM until
  900 PM EDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph likely
  A tornado or two possible

SUMMARY...Scattered damaging winds appear likely as numerous
clusters and lines of storms intensify and move east this afternoon.

The severe thunderstorm watch area is approximately along and 105
statute miles east and west of a line from 15 miles northeast of
Dubois PA to 60 miles south southeast of Louisville KY. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU2).

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 461...

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
26025.

...Grams

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SPC Tornado Watch 461

Tue, 22 Aug 2017 18:51:04 +0000

WW 461 TORNADO NY PA VT LE LO 221620Z - 230100Z
(image)

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 461
NWS Storm Prediction Center Norman OK
1220 PM EDT Tue Aug 22 2017

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  New York
  Northern Pennsylvania
  Western Vermont
  Lake Erie
  Lake Ontario

* Effective this Tuesday afternoon and evening from 1220 PM until
  900 PM EDT.

* Primary threats include...
  A couple tornadoes possible
  Widespread damaging wind gusts to 70 mph likely

SUMMARY...Numerous storm clusters and lines are expected to develop
this afternoon and progress east-northeast. Strong gusts producing
damaging winds and a couple tornadoes are anticipated.

The tornado watch area is approximately along and 115 statute miles
east and west of a line from 40 miles north northeast of Saranac
Lake NY to 25 miles southeast of Bradford PA. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU1).

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.

&&

AVIATION...Tornadoes and 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 25030.

...Grams

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SPC Severe Thunderstorm Watch 462 Status Reports

Tue, 22 Aug 2017 18:31:03 +0000

WW 0462 Status Updates
(image)

STATUS REPORT ON WW 462

THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.

..SPC..08/22/17

ATTN...WFO...LMK...ILN...JKL...RLX...PBZ...CTP...


STATUS REPORT FOR WS 462 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

INC019-043-061-123-155-221940-

IN 
.    INDIANA COUNTIES INCLUDED ARE

CLARK                FLOYD               HARRISON            
PERRY                SWITZERLAND         


KYC005-011-015-017-019-021-023-025-027-029-037-041-043-045-049-
063-065-067-069-073-077-079-081-085-087-089-091-093-097-099-103-
109-111-113-115-117-123-127-129-135-137-151-153-155-159-161-163-
165-167-173-175-179-181-185-187-189-191-197-201-203-205-209-211-
215-217-223-229-237-239-221940-

KY 
.    KENTUCKY COUNTIES INCLUDED ARE

ANDERSON             BATH                BOONE               
BOURBON              BOYD                BOYLE               
BRACKEN              BREATHITT           BRECKINRIDGE        
BULLITT              CAMPBELL            CARROLL             
CARTER               CASEY               CLARK               
ELLIOTT              ESTILL              FAYETTE             
FLEMING              FRANKLIN            GALLATIN            
GARRARD              GRANT               GRAYSON             
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SPC Tornado Watch 461 Status Reports

Tue, 22 Aug 2017 18:51:04 +0000

WW 0461 Status Updates
(image)

STATUS REPORT ON WW 461

THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.

FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1549

..ELLIOTT/COHEN..08/22/17

ATTN...WFO...BUF...BGM...BTV...ALY...CTP...CLE...


STATUS REPORT FOR WT 461 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

NYC003-007-009-011-013-015-017-019-023-029-031-033-035-037-041-
043-045-049-051-053-055-057-063-065-067-069-073-075-077-089-097-
099-101-107-109-113-117-121-123-221940-

NY 
.    NEW YORK COUNTIES INCLUDED ARE

ALLEGANY             BROOME              CATTARAUGUS         
CAYUGA               CHAUTAUQUA          CHEMUNG             
CHENANGO             CLINTON             CORTLAND            
ERIE                 ESSEX               FRANKLIN            
FULTON               GENESEE             HAMILTON            
HERKIMER             JEFFERSON           LEWIS               
LIVINGSTON           MADISON             MONROE              
MONTGOMERY           NIAGARA             ONEIDA              
ONONDAGA             ONTARIO             ORLEANS             
OSWEGO               OTSEGO              ST. LAWRENCE        
SCHUYLER             SENECA              STEUBEN             
TIOGA                TOMPKINS            WARREN              
WAYNE                WYOMING             YATES               


PAC015-023-035-047-081-083-105-113-115-117-123-221940-

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SPC MD 1550

Tue, 22 Aug 2017 18:45:03 +0000

MD 1550 CONCERNING SEVERE THUNDERSTORM WATCH 462... FOR MUCH OF THE OHIO VALLEY
(image)

Mesoscale Discussion 1550
NWS Storm Prediction Center Norman OK
0144 PM CDT Tue Aug 22 2017

Areas affected...Much of the Ohio Valley

Concerning...Severe Thunderstorm Watch 462...

Valid 221844Z - 222015Z

The severe weather threat for Severe Thunderstorm Watch 462
continues.

SUMMARY...Scattered bands of strong/severe thunderstorms will
progress across WW462.

DISCUSSION...Multiple bands of strong/severe thunderstorms have
evolved across the OH Valley this afternoon. This activity has
matured within a corridor of stronger boundary-layer heating from
KY, northeast into western PA. Additionally, there appears to be
added ascent ahead of two long-lived remnant MCVs from over night
convection. One MCV is located over north-central OH near MFD and
the other is located over extreme southwest IN north of EVV. Each of
these features may enhance the clustering potential of storms
immediately downstream. Damaging winds appear to be the primary
threat with convection this afternoon.

..Darrow.. 08/22/2017

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

ATTN...WFO...CTP...PBZ...RLX...CLE...JKL...ILN...LMK...PAH...

LAT...LON   37358722 41318070 41317666 37368337 37358722 

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SPC MD 1549

Tue, 22 Aug 2017 18:44:03 +0000

MD 1549 CONCERNING TORNADO WATCH 461... FOR PORTIONS OF NY...PA...VT...NH
(image)

Mesoscale Discussion 1549
NWS Storm Prediction Center Norman OK
0144 PM CDT Tue Aug 22 2017

Areas affected...Portions of NY...PA...VT...NH

Concerning...Tornado Watch 461...

Valid 221844Z - 222045Z

The severe weather threat for Tornado Watch 461 continues.

SUMMARY...The severe-thunderstorm and tornado risk continues across
WW 461, and will spread east to northeast with time. The tornado
risk may be increasing across parts of northern and central NY into
western/northern New England, and areas east of WW 461 are being
monitored for possible WW issuance later today.

DISCUSSION...In association with ongoing cyclogenesis in western
Quebec, observational trends suggest that pressure falls are
increasing in magnitude across the area -- now up to around 3 mb per
2 hours -- focused within a corridor from north-central PA through
central NY and northward into southern Quebec. This aligns with a
strengthening low-level jet within the warm sector of the deepening
cyclone. The mass response to the cyclogenesis process will continue
to focus strengthening low-level shear from south-central NY through
the Adirondacks vicinity and into western/northern parts of New
England amid strengthening deep shear -- i.e. effective shear
increasing upwards of 50 kt. With a sufficiently moist boundary
layer and diurnal heating supporting 1250-1750 J/kg of MLCAPE, these
factors will continue to support organizing convective clusters and
occasional supercells -- a trend that has already been noted from
western NY into northwest PA.

The tornado risk will likely increase as this activity spreads
eastward to northeastward amid the strengthening low-level and deep
shear. Despite low-level shear vectors being oriented somewhat
parallel-oblique to evolving convective lines, low-level SRH is
strengthening and line-orthogonal deep shear is enhanced. Also, of
particular note, the isallobaric response to the deepening surface
cyclone is resulting in locally backed winds from northern NY into
adjacent New England -- enhanced locally by terrain-induced flow
channeling -- resulting in appreciable low-level hodograph curvature
supporting around 300 m2/s2 of effective SRH. The ample streamwise
vorticity within the convective inflow should boost the tornado
risk. Increasing cellular development has been noted around the
Adirondacks in response to warm advection and weak capping, and
supercell structures with tornado potential could develop from this
regime and spread into New England. It is possible that this
activity could warrant new WW issuance later today.

Otherwise, swaths of damaging wind gusts will likely accompany
evolving, more quasi-linearly oriented activity as it matures
through and beyond peak heating. More-than-adequate low-level shear
will support small-scale rear-inflow-jet surges attendant to
line-embedded meso-vortices enhancing the severe-wind risk across
the Watch area.

..Cohen.. 08/22/2017

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

ATTN...WFO...GYX...BTV...ALY...BGM...BUF...CTP...

LAT...LON   41917848 42647772 44487505 44867381 44997216 44847147
            43857128 43527223 43177380 41887594 41487672 41367799
            41577853 41917848 

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SPC Aug 22, 2017 1630 UTC Day 1 Convective Outlook

Tue, 22 Aug 2017 16:01:09 +0000

SPC 1630Z Day 1 Outlook
(image)
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1057 AM CDT Tue Aug 22 2017

Valid 221630Z - 231200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NY/PA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OH VALLEY TO
WESTERN NEW ENGLAND...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHERN HIGH
PLAINS TO NEW ENGLAND...

...SUMMARY...
Scattered to numerous swaths of damaging winds are expected from the
Ohio Valley to western New England through this evening. A couple
tornadic storms are possible, mainly over parts of New York into
Pennsylvania.

...OH Valley to western New England...
Minimal change necessary this outlook with numerous storms expected
to develop in the next few hours. A pronounced shortwave trough over
the Upper Great Lakes will continue to amplify while approaching
Quebec tonight. Associated surface cyclogenesis will drive a cold
front southeast across the Lower Great Lakes and OH Valley. Primary
focus for storm development will be along the remnant
outflow/differential heating zone ahead of the front. Strong
tropospheric winds will support effective shear of 30-40 kt
southwest to 40-50 kt northeast. In spite of poor mid-level lapse
rates, robust diabatic heating will contribute to MLCAPE of
1500-2500 J/kg southwest to 1000-2000 J/kg northeast. An initially
mixed mode should transition to line segments with swaths of
damaging winds expected, especially with bowing segments. Stronger
low-level shear and enlarged hodographs are expected across parts of
NY into northern PA. Although storm mode may limit the sustenance of
rotating updrafts, embedded QLCS mesovortices should support a
threat for a couple tornadoes. 

For additional short-term discussion, please see MCDs 1547 and 1548.

...Southern High Plains to Mid-South...
Deep-layer flow and shear will be substantially weaker along a
southward-sagging cold front and pre-frontal outflow near the I-40
corridor. Loosely organized multicell clusters are expected
mid-afternoon to mid-evening with isolated downbursts and marginally
severe hail possible.

..Grams/Cohen.. 08/22/2017

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SPC Aug 22, 2017 1730 UTC Day 2 Convective Outlook

Tue, 22 Aug 2017 17:01:00 +0000

SPC 1730Z Day 2 Outlook
(image)
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1159 AM CDT Tue Aug 22 2017

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN MID-ATLANTIC AND EASTERN CAROLINAS...

...SUMMARY...
A few strong/marginally severe storms may impact parts of the
southern Mid-Atlantic and eastern Carolinas Wednesday. Gusty,
damaging winds will be the main threat.

...Synopsis...
Broad cyclonic flow will envelop much of the eastern US on
Wednesday, with a corridor of 40-60 kt mid-level flow from the
Dakotas to the Canadian Maritimes. At the center of this regime, a
closed low will gradually lift northeast across northern Quebec.
Meanwhile, a compact shortwave trough will advance southeast from
the Canadian Prairies towards the northern Plains. The surface
pattern will feature expansive high pressure building southeastward
across much of the Mississippi and Ohio Valleys. Along the leading
edge of this building surface ridge, a cold front will push towards
the Southeast US and Gulf Coasts, while having cleared much of New
England early in the day.

...Southern Mid-Atlantic and Eastern Carolinas...
Along the southern fringe of the synoptic trough, a weak/sheared
impulse, likely in association with the surface front, will approach
the region during the mid-day/afternoon hours. Higher terrain, the
front, and a pre-frontal trough may all serve to focus initiation
through the day. Plentiful boundary-layer moisture and some diurnal
heating will overcome meager mid-level lapse rates for the
generation of moderate mixed-layer buoyancy by afternoon.
Low/mid-level flow appears quite modest, with west/southwesterly
winds around 25 kt or less through 500 mb. Therefore, convection
will likely organize into multicell clusters initially, perhaps
followed by small corridors of upscale growth, as cells propagate
into greater moisture towards the coast. The warm/moist environment
and expected mode evolution suggest isolated pockets of damaging
gusts will be the primary threat with this activity during the
afternoon and evening hours, before convection weakens with a loss
of heating.

..Picca.. 08/22/2017

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SPC Day 1 Fire Weather Outlook

Tue, 22 Aug 2017 16:52:32 +0000

SPC Day 1 Fire Weather Outlook
(image)
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1150 AM CDT Tue Aug 22 2017

Valid 221700Z - 231200Z

...Portions of Northern CA into Southern/Central OR and Far
Northwestern NV...
Some minor adjustments have been made to the ongoing isolated
dry-thunderstorm area based on short-term guidance, but the overall
forecast rationale remains unchanged. While some rainfall will be
possible near the strongest cores, widespread wetting rains are not
expected and thunderstorm activity will pose a threat of ignitions
given the dry fuels in place. See the previous discussion below for
more details.

..Dean.. 08/22/2017

.PREV DISCUSSION... /ISSUED 0145 AM CDT Tue Aug 22 2017/

...Synopsis...
Upper ridging will remain prominent over much of the western CONUS
today, while an upper low located off the coast of southern/central
CA moves little. Mid-level monsoonal-related moisture will advance
northward along the Sierras into the southern Cascades and vicinity
along the northern periphery of the upper low this afternoon.

...Portions of Northern CA into Southern/Central OR and Far
Northwestern NV...
Isolated to scattered thunderstorms will develop by this afternoon
and continue through the evening hours across portions of northern
CA into southern/central OR. Terrain-driven circulations will likely
be the primary impetus for convective initiation. Precipitable water
values around 0.7 to 1.0 inch and modest (~15-20 kt) mid-level
southwesterly flow along the Sierra/Cascade crest will likely allow
for a mix of wet/dry thunderstorms. A dry antecedent low-level
airmass coupled with diurnal heating will act to lower RH values
across this region, which should limit the potential for wetting
rainfall outside of the heaviest thunderstorm cores. Strong and
erratic outflow winds will be possible with any thunderstorm in this
environment. Fuels also remain generally dry to very dry and
receptive to large fire starts. Therefore, an isolated dry
thunderstorm area continues with no changes across northern CA into
southern/central OR and far northwestern NV.

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

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