Severe Thunderstorm Warning 159, NWS Jackson, MS

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1216 PM CDT Sun Apr 19 2020

.UPDATE...
Updated for 18Z aviation discussion

&&

.AVIATION...
18Z TAF discussion: While IFR/MVFR conditions will improve to VFR
at most locations this afternoon, areas between GLH, GWO and GTR
will remain in those conditions through much of the period.
Scattered to numerous showers and thunderstorms will eventually
overspread the area from the west this afternoon with
deteriorating conditions as they do so. IFR/LIFR conditions with
gusty winds can be expected as storms impact each TAF site. The
rain and thunderstorms will move east of the area after midnight
as a cold front moves through, but ceilings will remain IFR
through the remainder of the period./GG/

&&

.DISCUSSION...
Quasi-stationary frontal boundary continues to oscillate
along I20 from northeast LA eastward through central MS. To the
north, elevated parcels with CAPEs around 2000 J/kg continue to be
isentropically lifted resulting in scattered to numerous showers
and thunderstorms. Immediately along the front, light showers and
fog persists. While to the south in the warm sector, widespread
stratus was seen in the satellite imagery, although some breaks
were beginning to occur. RAP data confirming the ascent/theta-e
advection over northeast portions with ongoing convection and over
east TX where new intense convection has developed. While the
latest CAM guidance continues to vary in the scenario this
afternoon, they all do agree that modes will be mixed through the
afternoon and evening as the event plays out. Made some changes to
weather and PoP based on latest trends and thinking. Expect
intense storms in the warm sector this afternoon as the boundary
layer warms with clusters of supercells producing very large hail,
damaging winds and tornadoes, some strong. Also, adjusted temps a
bit, mainly in the north where ongoing precipitation will keep
temperatures cooler./GG/

Prior discussion below:

Today and tonight...
A warm front is slowly lifting through the Gulf States this morning,
providing an increase in rich moisture and warmer temperatures in
the boundary layer, setting up for the severe weather anticipated
today. Overnight and this morning, general ascent across the region
invof and isentropic upglide over the frontal boundary in concert
with steep mid level lapse rates contributed to the development of
some severe elevated convection as well as some more widespread
showers and thunderstorms.  Much of the convection has shifted
north, and though some scattered activity will remain possible
through the morning hours, models are rather consistent with a
broader area of intense convection developing after 18z.

Previous model runs have been a little inconsistent with the
projection of timing, as well as modality for the storm development
this afternoon.  Expecting some version of a wind and hail threat
with some linear segments...but has transitioned into a concern this
afternoon for supercell development as well. An expanding warm
sector will develop as the warm front lifts through the region.
Interaction with the frontal boundary could increase tornadic
potential with early storms, though the main concern initially will
be damaging wind and hail. The situation changes with time however.
Previous model runs have had some issue with whether or not the
morning scattered convection precludes restratifying the column. But
the more recent runs have developed convection just to the west
ahead of a deepening upper trof, moving into far more unstable air
over the region. SBCAPE values in excess of 3000J/kg in the
afternoon ahead of the developing convection in the HRRR 07Z run.
HREF mean sb CAPE is in the same range, more or less, as well as the
RAP, etc. Deep shear of 50-60kts would signal the strong potential
for convection this afternoon to be supercell oriented, and the scp
as well as sig tor parameters all show the same trend. Main threat
will be wind and hail with early scattered convection...but the
afternoon potential for supercells will add in the concern for
tornadoes, potentially strong and long tracked particularly to the
southeast. Given the dynamic set up aloft in concert with 1.5-2" PWs
across the area of most intense convective potential, a flash
flooding concern is added to the mix. Expected rainfall totals range
from 1-4 inches, with a 2.5-4" max axis along and near I-20 across
Mississippi. /HJS/

Monday through Saturday night...
Surface high pressure ridging will build across the area on
Monday. A nice day is on tap with highs mostly in the 70s across
the area. The nice weather will continue on Tuesday as high
pressure ridging continues from a high centered over Missouri. The
surface high will move eastward into the Ohio Valley Tuesday
night into Wednesday, and the surface flow will swing around to
the east then southeast by Wednesday afternoon. A deepening storms
system will approach the region Wednesday, with increasing
chances for storms in the west.

Thunderstorms will spreads east across the area Wednesday evening
through the overnight hours. There are some differences between the
GFS/ECMWF, but they are in fairly good agreement of the timing of
this system across the region. Both of them indicate good
instability and strong shear during the overnight hours, so another
round of severs storms look possible. SPC has not introduced a
severe outlook for this period, but may in future outlooks. Showers
and storms will continue through Thursday morning, but will end from
west to east during the afternoon hours.

High pressure will once again build across the region on Friday, but
this crazy April pattern may rear its ugly head again on Saturday,
as both the GFS/ECMWF move another strong storm system across the
region./15/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       77  58  73  52 /  85  85   0   0
Meridian      77  58  75  52 /  81  90   0   0
Vicksburg     75  58  73  54 /  88  87   0   0
Hattiesburg   83  62  78  54 /  62  71   0   0
Natchez       77  60  73  54 /  67  69   0   0
Greenville    67  55  71  54 / 100  94   0   0
Greenwood     68  55  71  51 / 100  96   0   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Flash Flood Watch through late tonight for MSZ027>033-035>059.

LA...Flash Flood Watch through late tonight for LAZ009-016-025.

AR...None.

&&

Hazardous Weather Outlook
National Weather Service Jackson MS
521 AM CDT Sun Apr 19 2020

ARZ074-075-LAZ007-201030-
Ashley-Chicot-Morehouse-
521 AM CDT Sun Apr 19 2020

This hazardous weather outlook is for portions of southeast
Arkansas, and northeast Louisiana.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Enhanced
TIMING...Today through Tonight

FLOODING
THREAT...Limited
TIMING...Today through Tonight

Today through tonight, severe thunderstorms are likely and
tornadoes are possible. Some thunderstorms may produce damaging
winds up to 70 mph and large hail up to golf ball size.

(https://www.weather.gov/images/jan/graphicast/1.png)

Today through tonight, localized flash flooding is possible,
particularly in low lying and urban areas. Minor river flooding
is also possible.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today
through tonight.

MSZ018-019-025-026-034-201030-
Bolivar-Sunflower-Leflore-Grenada-Washington-
521 AM CDT Sun Apr 19 2020

This hazardous weather outlook is for portions of north central
Mississippi, and northwest Mississippi.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Slight
TIMING...Today through Tonight

FLOODING
THREAT...Limited
TIMING...Today through Tonight

Today through tonight, severe thunderstorms and tornadoes are
possible. Some thunderstorms could produce damaging winds to
60 mph and hail at least to the size of quarters.

(https://www.weather.gov/images/jan/graphicast/1.png)

Today through tonight, localized flash flooding is possible,
particularly in low lying and urban areas. Minor river flooding
is also possible.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today
through tonight.

MSZ027>033-201030-
Carroll-Montgomery-Webster-Clay-Lowndes-Choctaw-Oktibbeha-
521 AM CDT Sun Apr 19 2020

This hazardous weather outlook is for portions of central
Mississippi, north central Mississippi, and northeast
Mississippi.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Slight
TIMING...Today through Tonight

FLOODING
THREAT...Elevated
TIMING...Today through Tonight

Today through tonight, severe thunderstorms and tornadoes are
possible. Some thunderstorms could produce damaging winds to
60 mph and hail at least to the size of quarters.

(https://www.weather.gov/images/jan/graphicast/1.png)

Today through tonight, areas of flash flooding likely and some
roads could be flooded or closed. Some structures may be
potentially threatened by high water. Minor river flooding is
also possible.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today
through tonight.

LAZ009-016-025-MSZ040-042>059-065-066-201030-
East Carroll-Madison LA-Tensas-Issaquena-Yazoo-Madison MS-Leake-
Neshoba-Kemper-Warren-Hinds-Rankin-Scott-Newton-Lauderdale-
Claiborne-Copiah-Simpson-Smith-Jasper-Clarke-Jefferson-Covington-
Jones-
521 AM CDT Sun Apr 19 2020

This hazardous weather outlook is for portions of northeast
Louisiana, and central Mississippi.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Moderate
TIMING...Today through Tonight

FLOODING
THREAT...Elevated
TIMING...Today through Tonight

Today through tonight, significant severe thunderstorms and
tornadoes are likely with strong tornadoes possible. Some
thunderstorms could also produce damaging winds up to 70 mph and
large hail up to tennis ball size.

(https://www.weather.gov/images/jan/graphicast/1.png)

Today through tonight, areas of flash flooding likely and some
roads could be flooded or closed. Some structures may be
potentially threatened by high water. Minor river flooding is
also possible.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today
through tonight.

LAZ008-015-023-024-026-MSZ060>064-072>074-201030-
West Carroll-Richland-Franklin LA-Catahoula-Concordia-Adams-
Franklin MS-Lincoln-Lawrence-Jefferson Davis-Marion-Lamar-Forrest-
521 AM CDT Sun Apr 19 2020

This hazardous weather outlook is for portions of northeast
Louisiana, and south central Mississippi.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Moderate
TIMING...Today through Tonight

FLOODING
THREAT...Limited
TIMING...Today through Tonight

Today through tonight, significant severe thunderstorms and
tornadoes are likely with strong tornadoes possible. Some
thunderstorms could also produce damaging winds up to 70 mph and
large hail up to tennis ball size.

(https://www.weather.gov/images/jan/graphicast/1.png)

Today through tonight, localized flash flooding is possible,
particularly in low lying and urban areas. Minor river flooding
is also possible.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today
through tonight.

MSZ035>039-041-201030-
Humphreys-Holmes-Attala-Winston-Noxubee-Sharkey-
521 AM CDT Sun Apr 19 2020

This hazardous weather outlook is for portions of and central
Mississippi.

.DAY ONE...Today and Tonight

SEVERE THUNDERSTORMS
THREAT...Enhanced
TIMING...Today through Tonight

FLOODING
THREAT...Elevated
TIMING...Today through Tonight

Today through tonight, severe thunderstorms are likely and
tornadoes are possible. Some thunderstorms may produce damaging
winds up to 70 mph and large hail up to golf ball size.

(https://www.weather.gov/images/jan/graphicast/1.png)

Today through tonight, areas of flash flooding likely and some
roads could be flooded or closed. Some structures may be
potentially threatened by high water. Minor river flooding is
also possible.

(https://www.weather.gov/images/jan/graphicast/2.png)

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations may be needed for portions of the region today
through tonight.

21

&&

...HAZARD LEGEND...

*SEVERE THUNDERSTORMS*
High...Significant severe thunderstorms and tornadoes are
 likely with strong or violent tornadoes possible.
Moderate...Significant severe thunderstorms and tornadoes are
 likely with strong tornadoes possible.
Enhanced...Severe thunderstorms are likely and tornadoes are
 possible.
Slight...Severe thunderstorms and tornadoes are possible.
Marginal...Isolated severe thunderstorms are possible.

*FLOODING*
Extreme...Widespread and significant flooding is likely.
Significant...Widespread flash flooding is likely
 and significant flooding is possible.
Elevated...Areas of flash flooding likely.
Limited...Localized flash flooding is possible.

...USEFUL WEATHER WEB PAGES (URLS)...

NWS JAN Home page...
   https://www.weather.gov/jan
Stay Aware, Stay Safe NWS JAN Briefing Page...
   https://www.weather.gov/jan/safe
Latest Weather Briefing...
   https://www.weather.gov/jan/weather_briefing

Find NWS JAN on Facebook...
   https://www.facebook.com/NWSJacksonMS
Follow NWS JAN on Twitter...
   @NWSJacksonMS
Follow NWS JAN on Youtube...
   https://www.youtube.com/user/NWSJacksonMiss

...ADDITIONAL URLS FOR SEVERE WEATHER ISSUES...

Storm Prediction Center (SPC)...
   https://www.spc.noaa.gov/
Meso Analysis...
   https://www.spc.noaa.gov/exper/mesoanalysis/
Day 1 through 3 Outlooks...
   https://www.spc.noaa.gov/products/outlook/
Storm Reports...
   https://www.spc.noaa.gov/climo/online/
...ADDITIONAL URLS FOR FLOODING ISSUES...

Current Watches and Warnings...
   https://www.weather.gov/jan/safe_HeavyRain

Observed Precipitation Images...
   https://www.weather.gov/jan/precipmaps

River Forecast Center...
   https://www.weather.gov/lmrfc/
Significant River Flood Outlook...
   https://www.wpc.ncep.noaa.gov/nationalfloodoutlook/index.html
Day 1 through 3 Excessive Rainfall...
   https://www.wpc.ncep.noaa.gov/qpf/excess_rain.shtml
Excessive Rainfall Discussion...
   https://www.wpc.ncep.noaa.gov/discussions/qpferd.html
Day 1 through 7 QPF...
   https://www.wpc.ncep.noaa.gov/qpf/qpf2.shtml
QPF Discussion...
   https://www.wpc.ncep.noaa.gov/discussions/qpfpfd.html

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