Severe Thunderstorm Warning 209, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
941 PM CST Sat Dec 17 2016

.UPDATE...

Updated for ongoing severe...wind...and winter weather hazards.

&&

.DISCUSSION...

Complex weather situation ongoing across the Mid South tonight as
an upper trough and associated arctic cold front advances
southeastward.

First and primary threat at hand is the ongoing severe
thunderstorms. This severe threat continues along and ahead of the
arctic frontal boundary. The worst of the weather will be along
the front where the potential for damaging winds and isolated
tornadoes will continue well into the predawn hours of Sunday
morning. A tornado watch has been issued for these locations until
3 am cst and several warnings are being issued at discussion time.

The second threat remains very strong wind gusts immediately
behind the front for up to an hour. These powerful non
thunderstorm wind gusts will reach between 50 and 60 mph from the
northwest. Issued a Special Weather Statement to highlight this
threat. This should continue through the night as the front
progresses southeastward.

The final hazard to address will be winter weather which is now
occurring across northern tiers of the forecast area. As much
colder air rushes southward...with up to 40 degree temperature
drops in two hours behind the front...light rain will transition
to light freezing rain and sleet as temperatures drop below
freezing. A winter weather advisory is now in effect for the
northern half of the region with the potential for up to one tenth
of an inch of ice as well as minor sleet accumulations. This will
result in icing of elevated surfaces such as bridges and
overpasses...especially after midnight across the winter weather
advisory area. Low temperatures will drop well into the 20s prior
to sunrise with icy spots possible on all road surfaces into
sunrise Sunday even after precipitation ends.

All in all a very active evening weatherwise across the forecast
area. Please stay tuned to later updates as we progress through
the late evening and overnight hours. Stay alert to any severe
weather warnings and be ready to act to protect yourself if a
warning is issued for your location.

Updated products have been sent.

JLH

&&

.PREV DISCUSSION... /issued 251 PM CST Sat Dec 17 2016/

Active weather over the 18 hours across the Midsouth, with severe
storms this afternoon and evening followed by possible light
freezing precipitation late tonight.

Midafternoon temperatures were running around 25 degrees above
normal as a tropical maritime airmass prevailed over the Midsouth.
100mb mixed-layer CAPE was nearing 1500 J/KG. This instability
should be increasingly tapped by storms as the elevated mixed
layer erodes with midlevel height falls through early evening.
Assuming storms become rooted in the near boundary layer, sufficient
vertical shear will exist to support rotating updrafts and a
tornado threat into middle evening. Severe weather threat will
fall to zero behind the Arctic front as is slowly drops to near
the I-40 corridor by 9 PM CST. This will be the strongest Arctic
cold frontal passage of the season thus far.

Regarding overnight winter weather potential, little has changed
from earlier forecast. 12Z NAM/GFS and later HRRR/RUC models show
rainfall ending around the time surface temps fall below freezing.
A Winter Weather Advisory was issued earlier for locations where
there is most likely to be subfreezing temps overlapping with
light rain. Precip should exit areas east of the Natchez Trace
Parkway near or shortly after sunrise Sunday.

The center of the 1041mb Arctic surface pressure ridge will lift
from the Kansas City area midafternoon Sunday, eastward along the
I-70 corridor. Sufficient low level pressure gradient will remain
across the Midsouth to keep surface winds up in the mixed shallow
Arctic layer. A Wind Chill Advisory for early Monday will likely
be issued on Sunday for areas along and north of I-40.

After clear calm and cold Tuesday morning, temps should gradually
moderate as the Arctic pressure ridge center lifts to the mid-
Atlantic coast. Weak low level southerly flow will return modified
maritime air on Wednesday, ahead of a fast moving midlevel shortwave.
Rainfall chances will remain limited over the Midsouth, better
focused to the south and east toward the coast in the vicinity of
richer low level moisture.

12Z GFS and ECMWF models dig a deeper trof over the southern
plains late in the week, but with significant timing differences
developing by Christmas day. The ECMWF is the more progressive of
the two and more in line with previous model consensus. In any
case, milder temps and a return of rain chances appear on order
late in the week.

PWB

&&

.AVIATION...
18Z TAF cycle

Winds, ceilings, weather all a problem this cycle. Strong and gusty
southerly winds to continue this afternoon. Winds will veer to
northwesterly and blustery early this evening. Rain and
thunderstorms could come in this afternoon and last into the
evening. Then freezing drizzle possible at Jonesboro and Memphis.
Ceilings to drop below 1000 feet after frontal passage.

WER

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Winter Weather Advisory until 3 AM CST Sunday for Clay-Craighead-
     Greene-Lawrence-Mississippi-Poinsett-Randolph.

     Winter Weather Advisory until 3 AM CST Sunday for Crittenden-
     Cross-St. Francis.

MO...Winter Weather Advisory until 3 AM CST Sunday for Dunklin-
     Pemiscot.

MS...Winter Weather Advisory until 6 AM CST Sunday for Alcorn-Benton
     MS-DeSoto-Marshall-Prentiss-Tippah-Tishomingo.

TN...Winter Weather Advisory until 6 AM CST Sunday for Benton TN-
     Carroll-Crockett-Dyer-Gibson-Henry-Lake-Lauderdale-Obion-
     Weakley.

     Winter Weather Advisory until 6 AM CST Sunday for Chester-
     Decatur-Fayette-Hardeman-Hardin-Haywood-Henderson-Madison-
     McNairy-Shelby-Tipton.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MEMPHIS TN
953 PM CST SAT DEC 17 2016

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>022-048>055-088>092-190600-
ALCORN-BENTON MS-BENTON TN-CALHOUN-CARROLL-CHESTER-CHICKASAW-CLAY-
COAHOMA-CRAIGHEAD-CRITTENDEN-CROCKETT-CROSS-DESOTO-DECATUR-
DUNKLIN-DYER-FAYETTE-GIBSON-GREENE-HARDEMAN-HARDIN-HAYWOOD-
HENDERSON-HENRY-ITAWAMBA-LAFAYETTE-LAKE-LAUDERDALE-LAWRENCE-
LEE AR-LEE MS-MADISON-MARSHALL-MCNAIRY-MISSISSIPPI-MONROE-OBION-
PANOLA-PEMISCOT-PHILLIPS-POINSETT-PONTOTOC-PRENTISS-QUITMAN-
RANDOLPH-SHELBY-ST. FRANCIS-TALLAHATCHIE-TATE-TIPPAH-TIPTON-
TISHOMINGO-TUNICA-UNION-WEAKLEY-YALOBUSHA-
953 PM CST SAT DEC 17 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST ARKANSAS...
THE MISSOURI BOOTHEEL...NORTH MISSISSIPPI...AND WEST TENNESSEE.

.DAY ONE...TONIGHT

THERE IS AN ENHANCED RISK FOR SEVERE THUNDERSTORMS ACROSS SOUTHERN
PORTIONS OF WEST TENNESSEE...NEAR THE TENNESSEE RIVER...AND NORTH
MISSISSIPPI THROUGH LATE TONIGHT. THE THREAT WILL EXIST FOR
DAMAGING WINDS AND A FEW TORNADOES WITH THUNDERSTORMS ALONG A
STRONG ARCTIC COLD FRONT.

SIGNIFICANTLY COLDER AIR CONTINUES TO SURGE INTO THE MID SOUTH
BEHIND THE ARCTIC COLD FRONT. AS TEMPERATURES RAPIDLY DROP BELOW
FREEZING FROM NORTHWEST TO SOUTHEAST...LIGHT RAIN WILL TRANSITION
TO LIGHT FREEZING RAIN AND SLEET. ICE ACCUMULATION OF ONE TENTH OF
AN INCH OR LESS ALONG WITH MINOR SLEET ACCUMULATIONS CAN BE
EXPECTED ACROSS THE NORTHERN HALF OF THE REGION. A WINTER WEATHER
ADVISORY CONTINUES FOR IMPACTED AREAS WHERE ICY CONDITIONS SHOULD
DEVELOP ON BRIDGES AND OVERPASSES.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

EARLY MORNING ICY CONDITIONS ON AREA ROADWAYS WILL CONTINUE INTO
SUNDAY MORNING EVEN AFTER PRECIPITATION COMES TO AN END.

IN ADDITION...SUBFREEZING WIND CHILLS WILL BE POSSIBLE EARLY
MONDAY MORNING ALONG AND NORTH OF THE INTERSTATE 40
CORRIDOR...INCLUDING THE MEMPHIS METRO AREA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE NEEDED TONIGHT ACROSS THE ENHANCED RISK
AREA. PLEASE CONTINUE TO PASS ALONG ANY REPORTS OF WIND
DAMAGE...TORNADOES...OR WINTER WEATHER ACCUMULATIONS TO THE
NATIONAL WEATHER SERVICE IN MEMPHIS TENNESSEE.

JLH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEMPHIS TN
946 PM CST SAT DEC 17 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0930 PM     TORNADO          2 E BARR                34.61N 89.74W
12/17/2016                   TATE               MS   TRAINED SPOTTER

            TORNADO ON THE GROUND REPORTED BY TRAINED SPOTTER.

&&

WLC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEMPHIS TN
1010 PM CST SAT DEC 17 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0950 PM     TORNADO          WATERFORD               34.65N 89.46W
12/17/2016                   MARSHALL           MS   AMATEUR RADIO

            TREES DOWN IN WATERFORD, POSSIBLE TORNADO. TIME BASED ON
            RADAR ESTIMATES.

&&

WLC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEMPHIS TN
1012 PM CST SAT DEC 17 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1002 PM     TORNADO          2 WNW HOLLY SPRINGS     34.78N 89.48W
12/17/2016                   MARSHALL           MS   FIRE DEPT/RESCUE

            TORNADO REPORTED ON THE GROUND BY MARSHALL COUNTY FD
            DISPATCH.

&&

WLC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEMPHIS TN
1025 PM CST SAT DEC 17 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1015 PM     SLEET            KENTON                  36.20N 89.01W
12/17/2016  E0.00 INCH       GIBSON             TN   PUBLIC

            SLEET REPORTED IN KENTON.

&&

WLC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEMPHIS TN
1026 PM CST SAT DEC 17 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1021 PM     FREEZING RAIN    REELFOOT LAKE STATE PAR 36.36N 89.43W
12/17/2016  E0.00 INCH       LAKE               TN   PUBLIC

            REPORT OF FREEZING RAIN/SLEET MIX.

&&

WLC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEMPHIS TN
1032 PM CST SAT DEC 17 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1028 PM     FUNNEL CLOUD     5 WNW THEO              34.96N 88.78W
12/17/2016                   ALCORN             MS   TRAINED SPOTTER

            SPOTTER REPORTS VISUAL OF FUNNEL, BUT NOTHING ON THE
            GROUND. WINDS MEASURED AT 59 MPH.

&&

WLC