Special Weather Statement, NWS Jackson, MS

Area Forecast Discussion
National Weather Service Jackson MS
400 PM CDT Fri Aug 11 2017

.DISCUSSION...
Tonight and Saturday: Some isolated severe convection was seen over
southeast AR this afternoon and still feel confident that the
marginal potential will continue until mid evening primarily over
the ArkLaMiss Delta. Boundary layer theta-e values are around 350K
and CAPEs are still around 3000-4000 J/kg in this area. As the mid
level wave that is driving this convection moves across the forecast
area late tonight into Saturday, the old surface boundary to the
north will move back south and help push the deep moisture southeast
as PWs actually fall below 2 inches for the first time in days. The
best convective coverage and locally heavy rainfall threat will be
over south and eastern sections, while other areas will have chance
to dry out somewhat with lesser coverage./26/

Saturday night through Friday...

The period will start off with broad/flat sub-tropical ridging over
the northern Gulf of Mexico, longwave troughing over the eastern
third of the CONUS, ridging over the Inter-Mountain west and zonal
westerly flow across the central portion of the country. A surface
cold front is also progged to be dropping south over northern
Mississippi. A few areas of mainly diurnally driven convection are
expected to be ongoing across the area at the start of the period
early Saturday evening, especially in the vicinity of the advancing
front, but this activity should dissipate during the the early
evening hours with loss of daytime heating. A shortwave trough over
the Southern Plains will help to initiate an upstream MCS that will
propagate east along the frontal boundary during the overnight hours
into Sunday morning, but should still remain to our west by
daybreak.

Sunday through Tuesday, a wet and active pattern is expected to
continue as the ArkLaMiss remains in westerly flow on the north side
of the sub-tropical ridge with a series of shortwave troughs moving
through the area on top of the aforementioned frontal boundary. Any
remnant outflow boundaries from the upstream MCS could provide an
enhanced focus for convection on Sunday in addition to frontal
boundary itself. The front will drop south towards the I-20 corridor
before retreating back north as a warm front late Tuesday as the sub-
tropical ridging builds back into the ArkLaMiss. Flow oriented
parallel to the frontal boundary will favor training convection in a
moist environment characteristic of 2-2.4 inch PWATs and H850
ThetaE of 342-348K. In addition, the northern portion of the CWA
will be on the nose of 90th percentile integrated water vapor
transport values advecting in from our west. With that being said,
the ongoing limited risk for flash flooding through Tuesday is
warranted but a few tweaks were made on Sunday to focus the main
flooding threat in the west. If the trend for training convection
along the frontal boundary persists an area along and north of I-20
could need to be upgraded to an elevated threat for flash flooding
on Monday and Tuesday with future outlooks. Widespread severe
weather is not expected, but a few stronger and possibly isolated
severe storms cannot be ruled out with gusty winds, especially where
any pockets of enhanced instability materialize and in the vicinity
of outflow boundary interactions and storm mergers, but will not
mention in the HWO given spatial uncertainties. It's also important
to note that some model differences exist in regards to the
evolution of the front with the ECMWF keeping it further north and
slower with the timing, whereas the latest GFS is much quicker and
further south dropping the front south of I-20 by Sunday morning and
shunting the bulk of the precip to the Hwy 84 corridor through
Monday. The GFS appears too aggressive and overdone with the front,
so will put more weight on the ECMWF solution at this point which
keeps storm chances area wide.

Wednesday through Friday, it looks like we'll finally get a "break"
from the wet stretch of weather that has been plaguing the area. Sub-
tropical ridging will build in over the Deep South on Wednesday with
a 594dam high centered in the vicinity of the ArkLaTex through the
rest of the period. The best rain chances look to shift to the
eastern portions of the area away from the center of the ridge,
however given the saturated soils and how wet it has been lately, at
least isolated diurnal showers and storms cannot be ruled out at any
one location. Temps are also expected to return to the 90s, which
combined with 70s dewpoints and still moist ground could lead to the
potential for heat stress concerns primarily in the Delta and north
of I-20, although cloud cover and afternoon convection could help to
hold temps down. /TW/

&&

.AVIATION...
18Z TAF discussion:
MVFR ceilings early in the period will rise to VFR by mid
afternoon with isolated to scattered showers and thunderstorms.
Where storms occur, a brief lowering to IFR/MVFR conditions will
be encountered. The convection will diminish by mid evening with
MVFR conditions developing after midnight and continuing until mid
morning Saturday./26/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       75  90  74  89 /  35  40  14  48
Meridian      74  89  74  90 /  40  54  18  38
Vicksburg     75  90  74  88 /  46  34  13  57
Hattiesburg   75  90  75  90 /  44  67  18  52
Natchez       75  89  74  88 /  41  37  14  56
Greenville    74  89  73  86 /  56  37  17  56
Greenwood     74  89  72  87 /  55  44  17  45

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&

TW/26

Hazardous Weather Outlook
National Weather Service Jackson MS
327 PM CDT Fri Aug 11 2017

ARZ074-075-LAZ007>009-015-016-023>025-MSZ018-019-025>030-032>038-
040>045-047>050-053-054-059-122030-
Ashley-Chicot-Morehouse-West Carroll-East Carroll-Richland-
Madison LA-Franklin LA-Catahoula-Tensas-Bolivar-Sunflower-Leflore-
Grenada-Carroll-Montgomery-Webster-Clay-Choctaw-Oktibbeha-
Washington-Humphreys-Holmes-Attala-Winston-Issaquena-Sharkey-
Yazoo-Madison MS-Leake-Neshoba-Warren-Hinds-Rankin-Scott-
Claiborne-Copiah-Jefferson-
327 PM CDT Fri Aug 11 2017

This hazardous weather outlook is for portions of southeast
Arkansas, northeast Louisiana, central Mississippi, north central
Mississippi, and southwest Mississippi.

.DAY ONE...Tonight and Saturday

SEVERE THUNDERSTORMS
THREAT...Marginal
TIMING...Tonight

FLOODING
THREAT...Limited
TIMING...Tonight

Isolated severe thunderstorms will be possible through the
evening. Damaging winds will be the primary threat, however, some
hail up to quarter size will also be possible.

Flash flooding will remain possible, as well, through the
evening hours, as locally heavy downpours pass over ground
saturated by recent above normal amounts of precipitation.

(www.weather.gov/images/jan/graphicast/image1.png)

.DAYS TWO THROUGH SEVEN...Saturday night through Thursday

Additional periods of heavy rainfall are possible across the
region Sunday through Tuesday. Localized one to three inches of
rain may occur in a short period of time. With saturated soils
from recent heavy downpours, any additional heavy rain could
result in flash flooding.

(www.weather.gov/images/jan/graphicast/image3.png)

.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 tonight.

LAZ026-MSZ031-039-051-060>062-122030-
Concordia-Lowndes-Noxubee-Newton-Adams-Franklin MS-Lincoln-
327 PM CDT Fri Aug 11 2017

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

.DAY ONE...Tonight and Saturday

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Saturday night through Thursday

Additional periods of heavy rainfall are possible across the
region Sunday through Tuesday. Localized one to three inches of
rain may occur in a short period of time. With saturated soils
from recent heavy downpours, any additional heavy rain could
result in flash flooding.

(www.weather.gov/images/jan/graphicast/image3.png)

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations is not expected through next Thursday.

MSZ046-052-056>058-063>066-072>074-122030-
Kemper-Lauderdale-Smith-Jasper-Clarke-Lawrence-Jefferson Davis-
Covington-Jones-Marion-Lamar-Forrest-
327 PM CDT Fri Aug 11 2017

This hazardous weather outlook is for portions of central
Mississippi, east central Mississippi, south central Mississippi,
and southeast Mississippi.

.DAY ONE...Tonight and Saturday

FLOODING
THREAT...Limited
TIMING...Saturday

Flash flooding will be possible Saturday as locally heavy
downpours pass over ground saturated by recent above normal
amounts of precipitation.

(www.weather.gov/images/jan/graphicast/image2.png)

.DAYS TWO THROUGH SEVEN...Saturday night through Thursday

Additional periods of heavy rainfall are possible across the
region Sunday through Tuesday. Localized one to three inches of
rain may occur in a short period of time. With saturated soils
from recent heavy downpours, any additional heavy rain could
result in flash flooding.

(www.weather.gov/images/jan/graphicast/image3.png)

.SPOTTER CALL TO ACTION STATEMENT...
The activation of storm spotters, HAM radio operators, and
emergency management personnel in support of severe weather
operations is not expected through next Thursday.

MSZ055-122030-
Simpson-
327 PM CDT Fri Aug 11 2017

This hazardous weather outlook is for portions of central
Mississippi.

.DAY ONE...Tonight and Saturday

FLOODING
THREAT...Limited
TIMING...Tonight through Saturday

SEVERE THUNDERSTORMS
THREAT...Marginal
TIMING...Tonight

Isolated severe thunderstorms will be possible through the
evening. Damaging winds will be the primary threat, however, some
hail up to quarter size will also be possible.

Flash flooding will remain possible, as well, through the
evening hours and again Saturday afternoon, as locally heavy
downpours pass over ground saturated by recent above normal
amounts of precipitation.

(www.weather.gov/images/jan/graphicast/image1.png)
(www.weather.gov/images/jan/graphicast/image2.png)

.DAYS TWO THROUGH SEVEN...Saturday night through Thursday

Additional periods of heavy rainfall are possible across the
region Sunday through Tuesday. Localized one to three inches of
rain may occur in a short period of time. With saturated soils
from recent heavy downpours, any additional heavy rain could
result in flash flooding.

(www.weather.gov/images/jan/graphicast/image3.png)

.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 tonight.

26

&&

...HAZARD LEGEND...

*SEVERE THUNDERSTORMS*
High...Significant severe thunderstorms are expected.
Moderate...Severe storms expected with significant
 severe weather possible.
Enhanced...Severe storms expected.
Slight...Severe storms possible.
Marginal...Isolated severe storms possible.

*FLOODING*
Extreme...Confident in significant flooding.
Significant...Significant flooding possible.
Elevated...Confident in flooding.
Limited...Flooding possible.

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

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

Tropical page...
   www.weather.gov/jan/tropical
National Hurricane Center Home Page...
   www.nhc.noaa.gov/
Find NWS JAN on Facebook...
   www.facebook.com/NWSJacksonMS
Follow NWS JAN on Twitter...
   @NWSJacksonMS
Follow NWS JAN on Youtube...
   www.youtube.com/user/NWSJacksonMiss

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

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

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

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

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

Special Weather Statement
National Weather Service Jackson MS
238 PM CDT FRI AUG 11 2017

MSZ062-063-112015-
Lawrence MS-Lincoln MS-
238 PM CDT FRI AUG 11 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHERN LINCOLN AND
SOUTHWESTERN LAWRENCE COUNTIES UNTIL 315 PM CDT...

At 238 PM CDT, Meteorologists were tracking a strong thunderstorm
over Bogue Chitto, or 9 miles south of Brookhaven, moving southeast
at 20 mph.

Dime size hail and winds in excess of 40 mph will be possible with
this storm.

This strong thunderstorm will be near...
  Bogue Chitto around 245 PM CDT.
  Enterprise around 250 PM CDT.
  Ruth around 310 PM CDT.
  Jayess around 315 PM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

High winds can bring down trees and large limbs resulting in serious
injury or property damage. Exercise extreme caution when outdoors
during such strong winds...and be especially aware of older trees.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3146 9063 3154 9042 3135 9012 3135 9063
TIME...MOT...LOC 1938Z 302DEG 18KT 3145 9050

NF

Special Weather Statement
National Weather Service Jackson MS
245 PM CDT FRI AUG 11 2017

LAZ026-MSZ060-112015-
Concordia LA-Adams MS-
245 PM CDT FRI AUG 11 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN CONCORDIA PARISH IN
NORTHEASTERN LOUISIANA AND NORTHEASTERN ADAMS COUNTIES UNTIL 315 PM
CDT...

At 245 PM CDT, Meteorologists were tracking a strong thunderstorm
over Spokane, or near Ferriday, moving southeast at 20 mph.

Winds in excess of 40 mph will be possible with this storm.

This strong thunderstorm will be near...
  Vidalia around 305 PM CDT.
  Natchez around 310 PM CDT.
  Stanton around 315 PM CDT.

Other locations impacted by this storm include Ridgecrest.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

High winds can bring down trees and large limbs resulting in serious
injury or property damage. Exercise extreme caution when outdoors
during such strong winds...and be especially aware of older trees.

&&

LAT...LON 3173 9154 3176 9142 3175 9138 3173 9138
      3175 9136 3173 9131 3169 9129 3167 9130
      3166 9127 3165 9127 3163 9123 3163 9117
      3138 9147 3164 9166
TIME...MOT...LOC 1945Z 305DEG 19KT 3168 9149

NF

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Special Weather Statement
National Weather Service Jackson MS
403 PM CDT FRI AUG 11 2017

MSZ073-074-112130-
Lamar-Forrest-
403 PM CDT FRI AUG 11 2017

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL FORREST AND EAST CENTRAL
LAMAR COUNTIES...

At 403 PM CDT, a strong thunderstorm was located over Hattiesburg,
moving southeast at 15 mph.

Winds in excess of 30 mph are possible with this storm.

Locations impacted include...
Hattiesburg, Petal, Mclaurin, Sunrise and Rock Hill.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 3127 8945 3138 8926 3129 8914 3119 8914
      3107 8930
TIME...MOT...LOC 2103Z 310DEG 12KT 3128 8931

NF