Special Weather Statement, NWS Jackson, MS

Area Forecast Discussion
National Weather Service Jackson MS
549 AM CST Tue Feb 7 2017

...SEVERE WEATHER EXPECTED TODAY...

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
MVFR ceilings are occurring this morning with a couple of sites still
at VFR. Showers and a few thunderstorms are beginning to develop this
morning across the area. These will only increase in coverage and
intensity through the day. The strongest storms look to occur from
generally I-55 and east, which would impact
KGWO/KGTR/KJAN/KHKS/KMEI/KHBG through about 23z. Some of these storms
will be severe with gusty winds and hail being the main concern. MVFR
ceilings at best will occur during the day. Some VFR ceilings may
return late this afternoon before more low clouds and potential for
fog(including dense fog) occurs late tonight. /28/

&&

.DISCUSSION...
Today and tonight...

Main concern for the short term remains the increasing chance for
severe storms starting this morning and continuing through this
afternoon. As was referenced in an earlier discussion, models are
becoming more robust with the potential for severe weather today
across the ArkLaMiss region. The overall set-up remains the same for
today in that a surface low will deepen as it tracks across the mid-
Mississippi River Valley into Illinois and toward the Great Lakes
region with a shortwave trough on its heels. The ArkLaMiss region,
thanks to the passage of a warm front yesterday morning, remains in
a rather warm and moist airmass. Temperatures this morning are about
5 to 10 degrees warmer than 24 hours ago and dewpoints are 5-10
degrees moister as well. Dewpoints are running in the upper 50s to
lower 60s at most spots across the region. Gusty southerly winds
will help enhance this warm, moist environment through the day. Once
again, temperatures today should reach well into the 70s areawide.

The current thinking for today's storms hasn't changed too much with
this forecast package but only been reinforced with the new model
data and hi-res guidance. Storms already developed overnight across
portions of central Arkansas and northern Mississippi and warm
advection showers are developing across various sections of my CWA.
Storms will affect the western part of the forecast area by
daybreak, and some of these could be strong to severe. Given the
area of development, it is entirely possible that some portions of
the Delta region could miss out on some storms as hi-res guidance
indicates development of main cluster of storms may actually be
across the southwest part of the CWA and track northeast. The
potential for severe storms will ramp up through the morning and
peak during the afternoon as storms will continue to develop across
central portions of the CWA and progress eastward. The atmosphere
should be very conducive for severe weather given MUCAPE around 1800-
2600J/kg, surface temperatures in the 70s and dewpoints into the
lower 60s. Hi-res guidance is in good agreement and confirms that a
mixture of supercells and multi-cell clusters should occur across
central to eastern Mississippi from roughly late morning into mid to
late afternoon.

All types of severe weather will be possible with these storms but
the main concern will be from damaging winds and hail. There is
growing concern that some of this hail could be on the big side as
mid level lapse rates are around 7.5 to near 8 degrees Celsius and
vertical totals are around 30-31C. Will continue to mention golfball
size hail in the HWO and graphics, but it may not be out of the
question for some storms, especially any supercells that develop, to
produce even larger hail than that given such steep lapse rates.
While hail and wind are the primary concern, tornadoes cannot be
ruled out given enough shear and helicities around 200-300 m2/s2.
The 0-3km shear vectors are not overly strong but as storms progress
east, both the speed and orientation gets better for some tornado
potential should any kind of line cluster develop as per the latest
run of the HRRR suggests. It is across the eastern half of the CWA
where the tornado will likely be better as storms evolve and mature
in an unstable environment. There is some growing concern that the
southeast part of the CWA has the best potential for tornadoes as
different guidance suggests a couple of waves of storms, including
some that look supercellular during the afternoon as shear,
instability and updraft helicities peak.

Current timing looks to be generally on track as storms develop in
the west this morning, track across the I-55 corridor by mid/late
morning into early afternoon and then affect eastern portions of the
CWA starting late morning into the afternoon. As alluded to
earlier,portions of the forecast area, in particular the eastern
and/or southeastern part, may actually see a couple of different
waves of storms, hence the reasoning for the larger time window.

Storms look to clear out by late afternoon/early evening as the
upper level trough swings over the region. Clearing skies should
even occur from west to east by late day. There might be some
lingering very light rain in the eastern part of the state into the
early evening but the remainder of tonight should be dry. The actual
cold front won't make it into the region until later in the week,
which means that cooler weather won't move in right away. Overnight
lows tonight will only be in the lower 60s with some mid to upper
50s possible in the Highway 82 corridor. Dewpoints will still remain
in the 50s and 60s so "muggy" conditions will continue, likely
leading to some fog potential for tonight. Dense fog is likely going
to be a concern, especially in locations that saw a good bit of rain
today. /28/

Wednesday through Monday

On Wednesday into Wednesday night there will be low end chances of
rain over the east half for the period. The showers will exit the
region by early Thursday. The cold front will finally move through
the region on late Wednesday night into Thursday. Pwats will be less
than 0.50 inch for any rain to develop ahead of the front for
Thursday. In the wake of the front we will have a brief cool down
before southerly return flow brings the forecast area back into a
warming trend as we move into the weekend. Daily highs will push back
into the mild 70s over the weekend. Upper ridging will build back
over the region over the weekend in response to a closed upper low
over the southwest Conus. This will bring back more chances of rain
for the weekend as pwats to back to around one inch. Rain chances
will continue into Monday as another cold front passes through the
forecast area. Drier conditions will come back for Monday night.

Looking ahead the models and their ensembles show the closed low
over the southwest Conus will phase in with northern stream upper
trough pushing into the Lower Mississippi Valley at the middle of
next week as our next storm system./17/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       77  62  77  47 /  93  11  13  15
Meridian      75  61  75  48 /  97  21  21  20
Vicksburg     78  60  77  47 /  81  11  10   9
Hattiesburg   76  63  77  55 /  97  14  18  18
Natchez       78  62  77  51 /  79  10  10   8
Greenville    75  55  73  41 /  79  11  13   8
Greenwood     75  56  73  41 /  90  13  19  13

&&

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

&&

28

Hazardous Weather Outlook
National Weather Service Jackson MS
613 AM CST Tue Feb 7 2017

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-034-040-041-047-060-
081215-
Ashley-Chicot-Morehouse-West Carroll-East Carroll-Richland-
Madison LA-Franklin LA-Catahoula-Tensas-Concordia-Bolivar-
Washington-Issaquena-Sharkey-Warren-Adams-
613 AM CST Tue Feb 7 2017

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

.DAY ONE...Today and Tonight

TORNADOES
THREAT...Limited
TIMING...Today

SEVERE THUNDERSTORMS
THREAT...Limited
TIMING...Today

Severe thunderstorms will be possible this morning into early
afternoon. Damaging winds up to 60mph and quarter sized hail will be
possible will be the primary concern but a tornado will also be
possible.

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

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

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.

MSZ019-025>033-035>039-042>046-048>059-061>066-072>074-081215-
Sunflower-Leflore-Grenada-Carroll-Montgomery-Webster-Clay-Lowndes-
Choctaw-Oktibbeha-Humphreys-Holmes-Attala-Winston-Noxubee-Yazoo-
Madison MS-Leake-Neshoba-Kemper-Hinds-Rankin-Scott-Newton-
Lauderdale-Claiborne-Copiah-Simpson-Smith-Jasper-Clarke-Jefferson-
Franklin MS-Lincoln-Lawrence-Jefferson Davis-Covington-Jones-
Marion-Lamar-Forrest-
613 AM CST Tue Feb 7 2017

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

.DAY ONE...Today and Tonight

TORNADOES
THREAT...Limited
TIMING...Today

SEVERE THUNDERSTORMS
THREAT...Elevated
TIMING...Today

Severe thunderstorms are expected today, especially this morning and
afternoon. Hail up to golfball size, or potentially larger, along
with damaging winds will be the primary threat. Tornadoes also will
be possible.

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

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

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.

28

&&

...HAZARD LEGEND...

*TORNADOES*
Extreme...Confident in strong tornadoes with ratings EF2 or
 greater.
Significant...Strong tornadoes possible with ratings EF2 or
 greater.
Elevated...Confident in tornadoes.
Limited...Tornadoes possible.

*SEVERE THUNDERSTORMS*
Extreme...Confident in severe thunderstorms with wind gusts of
 75 mph or greater and/or 2 inch diameter or larger hail.
Significant...Severe thunderstorms possible with wind gusts of
 75 mph or greater and/or 2 inch diameter or larger hail.
Elevated...Confident in severe thunderstorms with winds gusts of
 60 mph or greater and/or 1 inch diameter or larger hail.
Limited...Severe thunderstorms possible with wind gusts of 60
 mph or greater and/or 1 inch diameter or larger hail.

...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

Find NWS JAN on Facebook...
   www.facebook.com/NWSJacksonMS
Follow NWS JAN on Twitter...
   @NWSJacksonMS

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

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

Latest Weather Briefing...
   www.weather.gov/jan/weather_briefing

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/

Special Weather Statement
National Weather Service Jackson MS
552 AM CST TUE FEB 7 2017

MSZ054-071215-
Copiah MS-
552 AM CST TUE FEB 7 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN COPIAH COUNTY UNTIL
615 AM CST...

At 551 AM CST, Meteorologists were tracking a strong thunderstorm
near Barlow, or 15 miles west of Hazlehurst, moving northeast at 40
mph.

Nickel size hail will be possible with this storm.

This strong thunderstorm will be near...
  Dentville around 600 AM CST.
  Crystal Springs and Gallman around 615 AM CST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3187 9070 3185 9071 3185 9072 3196 9071
      3205 9053 3205 9032 3195 9026 3177 9068
TIME...MOT...LOC 1151Z 235DEG 34KT 3190 9064

17

Special Weather Statement
National Weather Service Jackson MS
652 AM CST TUE FEB 7 2017

MSZ055-063-064-071330-
Simpson MS-Lawrence MS-Jefferson Davis MS-
652 AM CST TUE FEB 7 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN LAWRENCE...EASTERN
SIMPSON AND NORTHWESTERN JEFFERSON DAVIS COUNTIES UNTIL 730 AM CST...

At 652 AM CST, Meteorologists were tracking a strong thunderstorm
over Shivers, or 8 miles south of Pinola, moving northeast at 45 mph.

Nickel size hail will be possible with this storm.

This strong thunderstorm will be near...
  Magee and Sanatorium around 715 AM CST.
  Martinville around 720 AM CST.

Other locations impacted by this storm include New Hebron.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3177 9007 3181 9006 3204 8975 3189 8968
      3180 8966 3178 8969 3177 8975 3175 8976
      3167 9002
TIME...MOT...LOC 1252Z 235DEG 41KT 3176 8999

17

Special Weather Statement
National Weather Service Jackson MS
721 AM CST TUE FEB 7 2017

MSZ044-045-050-051-071345-
Leake MS-Newton MS-Neshoba MS-Scott MS-
721 AM CST TUE FEB 7 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN NESHOBA...
NORTHWESTERN NEWTON...SOUTHEASTERN LEAKE AND NORTHEASTERN SCOTT
COUNTIES UNTIL 745 AM CST...

At 720 AM CST, Meteorologists were tracking a strong thunderstorm
near Tuscola, or 7 miles northeast of Harperville, moving northeast
at 55 mph.

Dime size hail and wind gusts up to 50 mph will be possible with this
storm.

This strong thunderstorm will be near...
  Prospect around 725 AM CST.
  Dowdville and Madden around 730 AM CST.
  Neshoba and Dixon around 735 AM CST.
  Philadelphia and Pearl River around 740 AM CST.
  Bethsaida around 745 AM CST.

Other locations impacted by this storm include Standing Pine, Tucker,
Walnut Grove and Sebastopol.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3254 8925 3252 8932 3246 8946 3261 8957
      3292 8920 3267 8897
TIME...MOT...LOC 1320Z 237DEG 48KT 3259 8942

DC