RSS Mesoscale Discussions from Storm Prediction Center
WW 6 TORNADO AL TN 232100Z - 240400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 6
NWS Storm Prediction Center Norman OK
300 PM CST Sat Feb 23 2019
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Northern and central Alabama
Middle Tennessee
* Effective this Saturday afternoon and evening from 300 PM until
1000 PM CST.
* Primary threats include...
A few tornadoes likely with a couple intense tornadoes possible
Scattered damaging wind gusts to 70 mph possible
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...Multiple areas of potential severe storms should affect
parts of Alabama and Tennessee through this evening. The greatest
threat for tornadoes should exist across the western portion of the
watch area.
The tornado watch area is approximately along and 55 statute miles
either side of a line from 10 miles northwest of Nashville TN to 45
miles south of Tuscaloosa AL. For a complete depiction of the watch
see the associated watch outline update (WOUS64 KWNS WOU6).
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 5...
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 450. Mean
storm motion vector 23040.
...Grams
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WW 5 TORNADO AR LA MS TN 231825Z - 240200Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 5
NWS Storm Prediction Center Norman OK
1225 PM CST Sat Feb 23 2019
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Eastern Arkansas
Northern Louisiana
Mississippi
Western Tennessee
* Effective this Saturday afternoon and evening from 1225 PM
until 800 PM CST.
* Primary threats include...
Several tornadoes and a couple intense tornadoes likely
Scattered damaging winds likely with isolated significant gusts
to 75 mph possible
Scattered large hail events to 1.5 inches in diameter possible
SUMMARY...Scattered severe storms are expected to develop mainly
during the mid to late afternoon and early evening across parts of
the Lower Mississippi Valley and Mid-South. The greatest tornado
risk should exist across northern and central Mississippi into far
southwest Tennessee between about 3 to 7 PM.
The tornado watch area is approximately along and 85 statute miles
east and west of a line from 35 miles southwest of Natchez MS to 15
miles northwest of Jackson TN. For a complete depiction of the watch
see the associated watch outline update (WOUS64 KWNS WOU5).
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 65 knots. A few cumulonimbi with maximum tops to 450. Mean
storm motion vector 21045.
...Grams
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WW 0006 Status Updates
STATUS REPORT ON WW 6
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..LEITMAN..02/24/19
ATTN...WFO...BMX...HUN...OHX...
STATUS REPORT FOR WT 6
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ALC007-009-021-033-043-055-057-059-063-065-073-075-077-079-083-
089-093-095-103-105-107-115-117-119-125-127-133-240140-
AL
. ALABAMA COUNTIES INCLUDED ARE
BIBB BLOUNT CHILTON
COLBERT CULLMAN ETOWAH
FAYETTE FRANKLIN GREENE
HALE JEFFERSON LAMAR
LAUDERDALE LAWRENCE LIMESTONE
MADISON MARION MARSHALL
MORGAN PERRY PICKENS
ST. CLAIR SHELBY SUMTER
TUSCALOOSA WALKER WINSTON
TNC003-021-037-043-055-081-083-085-099-101-103-117-119-125-127-
135-149-161-181-187-240140-
TN
. TENNESSEE COUNTIES INCLUDED ARE
BEDFORD CHEATHAM DAVIDSON
DICKSON GILES HICKMAN
HOUSTON HUMPHREYS LAWRENCE
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WW 0005 Status Updates
STATUS REPORT ON WW 6
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..LEITMAN..02/24/19
ATTN...WFO...BMX...HUN...OHX...
STATUS REPORT FOR WT 6
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ALC007-009-021-033-043-055-057-059-063-065-073-075-077-079-083-
089-093-095-103-105-107-115-117-119-125-127-133-240140-
AL
. ALABAMA COUNTIES INCLUDED ARE
BIBB BLOUNT CHILTON
COLBERT CULLMAN ETOWAH
FAYETTE FRANKLIN GREENE
HALE JEFFERSON LAMAR
LAUDERDALE LAWRENCE LIMESTONE
MADISON MARION MARSHALL
MORGAN PERRY PICKENS
ST. CLAIR SHELBY SUMTER
TUSCALOOSA WALKER WINSTON
TNC003-021-037-043-055-081-083-085-099-101-103-117-119-125-127-
135-149-161-181-187-240140-
TN
. TENNESSEE COUNTIES INCLUDED ARE
BEDFORD CHEATHAM DAVIDSON
DICKSON GILES HICKMAN
HOUSTON HUMPHREYS LAWRENCE
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MD 0129 CONCERNING HEAVY SNOW FOR FAR EASTERN NE...WESTERN/CENTRAL IA...SOUTHERN MN
Mesoscale Discussion 0129
NWS Storm Prediction Center Norman OK
0526 PM CST Sat Feb 23 2019
Areas affected...Far eastern NE...western/central IA...southern MN
Concerning...Heavy snow
Valid 232326Z - 240430Z
SUMMARY...Heavy snow rates of 1-2"/hour (locally greater) are
expected into this evening, with localized blizzard conditions
possible later this evening as winds increase from west to east.
DISCUSSION...Latest surface analysis depicts a deepening cyclone
centered near Kansas City at 23Z. WV imagery shows a well-developed
dry slot moving into southern IA, with thunderstorms noted on its
leading edge. Very strong deep-layer ascent to the northwest of the
low track is resulting in heavy snowfall rates in excess of 1"/hour
across eastern NE, with occasional blizzard conditions. The
rain/snow line has advanced through the Omaha area within the last
1-2 hours, with portions of northwest IA beginning to transition to
snow.
As the cyclone moves northeastward this evening and thermal profiles
cool due to strong ascent and increasing cold advection, heavy snow
will spread into a larger portion of central/northern IA and
southern MN. Snowfall rates of 1-2"/hour (locally higher) will
continue through the evening, with some thundersnow possible as
convective elements that develop on the apex of the dry slot feed
into the primary snow band.
Blizzard conditions may also develop from west to east across this
region later this evening as low-level northwesterly flow increases
in response to the deepening surface low. While the increase in
winds may tend to coincide with decreasing snowfall rates on the
backside of the precipitation shield, increasing cold advection will
result in less water content with the remaining snowfall, resulting
in a greater tendency for reduced visibility due to blowing snow.
..Dean.. 02/23/2019
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...DMX...FSD...OAX...
LAT...LON 41669637 43019591 43879552 44499424 44619302 44329224
43819214 43319242 42629283 41949356 41489425 41259476
41169521 41089563 41169618 41669637
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MD 0128 CONCERNING TORNADO WATCH 5...6... FOR FAR EASTERN MS INTO WEST-CENTRAL AND NORTHWEST AL AND SOUTH-CENTRAL TN
Mesoscale Discussion 0128
NWS Storm Prediction Center Norman OK
0501 PM CST Sat Feb 23 2019
Areas affected...far eastern MS into west-central and northwest AL
and south-central TN
Concerning...Tornado Watch 5...6...
Valid 232301Z - 240100Z
The severe weather threat for Tornado Watch 5, 6 continues.
SUMMARY...Corridor of greatest tornado potential the next few hours
will extend from far east-central MS into northwest/west-central AL
and far south-central TN.
DISCUSSION...Radar trends over the last 30 minutes or so have
indicated some strengthening in mid and low level storm rotation
both in semi-discrete convection to the northwest of Meridian MS and
further north associated with bowing line segment in Monroe County
MS. Additional semi-discrete storms moving into far south-central TN
also continue to show signs of rotation. Overall, storms appear to
be struggling due to a weakness in storm relative flow in the low to
mid levels. Additionally, stronger forcing for ascent remains well
west/northwest of the region and height falls have generally been
rather weak. All of these factors have impacted organization and
longevity of intense convection.
Convection currently moving out of eastern MS into western AL and
south-central TN will encounter the best environment of the day,
with regional VWP data indicating increased flow through the lowest
3km over over the last 30-60 min. Weak backed low level flow has
also been noted in this narrow corridor as well. This should help to
maximize low level shear in axis of greatest heating and
instability. As such, the greatest severe threat, and tornado
potential, will exit the next few hours, mainly across west-central
into northwest AL and adjacent south-central TN. In fact, recent
LSR from MEM confirmed a tornado had been sighted in Alcorn County.
..Leitman.. 02/23/2019
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OHX...BMX...HUN...MEG...JAN...
LAT...LON 33198866 34158835 35378802 35618778 35668748 35578708
35358686 34768679 33238704 32818728 32618765 32558832
32668864 32808881 33198866
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MD 0125 CONCERNING HEAVY SNOW FOR SOUTHEASTERN NEBRASKA
Mesoscale Discussion 0125
NWS Storm Prediction Center Norman OK
0152 PM CST Sat Feb 23 2019
Areas affected...Southeastern Nebraska
Concerning...Heavy snow
Valid 231952Z - 240045Z
SUMMARY...Heavy snow rates of 1-2 inches/hour are possible in
portions of southeastern Nebraska this afternoon/early evening. Snow
rates should generally taper off by 6-7 pm CST. An intensifying
surface pressure gradient is also expected and may yield blizzard
conditions in some areas later tonight.
DISCUSSION...A band of heavy snow has developed along a line from
Hastings to York in response to strong mid- and upper-level ascent
from a vigorous shortwave trough now over western Kansas. This
ascent should continue to progress to the northeast through the rest
of the afternoon, coincident with saturated DGZs in RAP forecast
soundings. Heavy snow rates of 1 inch/hour, with some areas locally
higher, will be possible through about 6-7 pm CST. A deepening
surface cyclone now in south-central Kansas will also move off to
the northeast this evening. As this occurs, a strengthening surface
pressure gradient may yield blizzard conditions even as heavier snow
rates wane.
..Wendt.. 02/23/2019
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OAX...GID...
LAT...LON 40729883 41219832 41589747 41849687 41909639 41779621
41069628 40519686 40189712 40059775 40089830 40179865
40419889 40729883
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SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0150 PM CST Sat Feb 23 2019
Valid 232000Z - 241200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
THROUGH NORTHERN MISSISSIPPI INTO SOUTHWEST AND SOUTH CENTRAL
TENNESSEE AND NORTHWEST ALABAMA...
...SUMMARY...
Threat for a few strong tornadoes, scattered damaging winds, and
isolated large hail should persist through this evening across the
Lower Mississippi Valley into the Tennessee Valley. The most likely
period for strong tornadoes is expected through 8 PM CST across
northern Mississippi, southwest and far southern Middle Tennessee,
and northwest Alabama.
...Lower Mississippi through Tennessee Valley region...
Primary change to previous outlook has been to trim from the west
behind broken line of storms. The warm sector continues to
destabilize from northeast LA and especially central through
northern MS where pockets of diabatic warming have boosted
temperatures into the mid-upper 70s. The special 18Z RAOB data from
Jackson MS sampled the warm sector and indicated around 1000 J/kg
MLCAPE. Scattered pre-frontal showers and thunderstorms have been
slow to intensify due to an inversion present around 700mb. However,
as the primary zone of forcing along the warm conveyor belt shifts
eastward and interacts with the destabilizing boundary layer, some
storms should evolve into supercells given favorable wind profiles
with 60+ kt effective bulk shear and 200-400 m2/s2 0-1 km storm
relative helicity along the strengthening low-level jet.
..Dial.. 02/23/2019
.PREV DISCUSSION... /ISSUED 1018 AM CST Sat Feb 23 2019/
...Lower MS and TN Valleys...
No change made to previous outlook except behind ongoing convection
in the Ark-La-Tex. Overall forecast scenario is anticipated to
unfold from midday through tonight.
A surface cyclone over far northwest OK will translate quickly
northeastward, reaching southern WI around midnight. The cyclone
will deepen rapidly in conjunction with an ejecting midlevel
shortwave trough and the left-exit region of a strengthening (100+
kt) mid-upper jet streak. The deepening cyclone will draw the moist
warm sector northward from the central Gulf Coast States into parts
of the Mid-South to perhaps as far north as the Lower OH Valley
later this afternoon/evening to the east of a cold front, as a 50-60
kt low-level jet shifts across the northern part of the warm sector.
Marginally severe hail could occur with the stronger elevated storms
across the mid MS Valley, but the primary severe threat is expected
farther to the south in the warm moist sector.
Ongoing convection across the Sabine Valley into southern AR will
increase in coverage/intensity as large-scale ascent overspreads the
northwest portion of the rich moist sector characterized by upper
60s to lower 70s boundary-layer dew points. The most robust
insolation appears to be underway downstream of this activity across
northern LA into central/northern MS where surface temperatures
should warm into the upper 70s. This will support afternoon MLCAPE
of 1000-2000 J/kg, with only weak convective inhibition.
Semi-discrete storms are expected within the lingering band of
ongoing convection, and in the open warm sector, given strong
deep-layer shear and substantial cross-boundary shear vectors. The
tornado threat will be greatest from about 20-02Z across
central/northern MS into northwest AL and southwest TN. A few strong
tornadoes appear probable given 0-1 km/effective SRH of 300-500
m2/s2 and effective bulk shear near 60 kt in the rich moist
environment. Thereafter, storms should weaken by 03-06Z, though
isolated tornado/damaging wind potential could persist into the
early morning across northeast AL/northwest GA where storms will
encounter a remnant wedge front.
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