Severe Thunderstorm Warning 60, NWS Huntsville, AL

Area Forecast Discussion
National Weather Service Huntsville AL
533 PM CST Tue Nov 29 2016

.UPDATE...
For 00Z TAFS.

&&

.NEAR TERM...(Tonight)
Issued at 136 PM CST Tue Nov 29 2016

Latest surface analysis shows a low across the western Great Lakes
with a trailing cold front extending through central Missouri through
central Red River Valley. A stationary/warm front was situated
generally south of I-20 across AL/MS. The airmass along and south of
the warm front was quite juicy this afternoon with dewpoints well
into the 60s.

For tonight, the initial question is how quickly/how far north the
warm front progresses. Given the limited convective activity along
the gulf and southerly flow in place across the state, expect the
airmass to recover by late afternoon/early evening. The HRRR
continues to indicate isolated/scattered convective development
within the warm sector between 00z-03z and this seems reasonable
given little in the way of capping.

Hodographs become a bit more favorable for sustained rotating cells
within a (perhaps slow progressing) QLCS that will move across during
the late evening and overnight hours. Unlike normal cool season
events, if moisture does indeed recover as expected CAPE values
should easily reach the 500-750 j/kg range ahead of this line. Given
the combination of instability and sufficient shear, storms will
certainly have to be monitored for at least a brief tornado threat.

Based on the models trends toward more parallel (sw to ne) flow in
the mid levels, have beefed up QPF just a touch. This is also in line
with the latest projections from WPC. Temperatures will move very
little tonight with most areas not seeing a true FROPA until 12z or
thereafter.

.SHORT TERM...(Wednesday through Thursday)
Issued at 136 PM CST Tue Nov 29 2016

Convection, perhaps near-severe in sports or slowly diminishing,
will still be ongoing across our eastern counties at 12z on
Wednesday. The upper trough axis will push across by early afternoon
ushering in the "cooler" air. Will taper pops from west to east and
also temporally with all areas rain free by afternoon.

Weak surface high will build across the region Wednesday night into
Thursday with sunny and slightly below normal temperatures
anticipated.

.LONG TERM...(Thursday night through Monday)
Issued at 136 PM CST Tue Nov 29 2016

Fairly strong cold air advection will continue to advect drier air
into the area Thursday/Thursday night, via northwesterly flow. In
addition, light winds will continue over the Tennessee Valley, as
the surface high will not have moved much. This will allow for a
very good radiational cooling event by Friday morning. It should
allow lows to drop to near dewpoints to around 30 degrees.
Temperatures should rebound to near normal highs during the day on
Friday.

Models all develop a more zonal flow aloft originating from Texas,
as the high pressure remains over the area through Friday night. This
will be in response to a cut-off low that develops over the
southwestern U.S. This should keep highs and lows through Friday
night near normal/slightly above normal (normal highs mid to upper
50s/normal lows mid to upper 30s).

Models do advect deeper moisture eastward into the Tennessee Valley
ahead of it Saturday through Sunday. How far north the deeper
moisture gets and thus rainfall is the difference in the model
forecasts. At this point, including a blend for the forecast.
Saturday night through Sunday are keeping a 30 to 60 percent chance
of rain in the forecast. This likely will be the best time for more
widespread precipitation, but how much greatly depends on which model
solution is correct.

Early next week remains active, as the cut-off low kicks northeast
along the jetstream into Arkansas and into Kentucky. There could be
some stronger thunderstorm potential with this system, but too far
off to address at this point.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 525 PM CST Tue Nov 29 2016

A warm front will move north across the cwa tonight while a slow
moving cold front will finally push across the TN valley by
Wednesday aftn. This wx scenario will produce a good chc of shra and
tsra over the taf sites tonight thru much of Wednesday mrng. The best
chc of strong to severe tsra will be tonight. The shra and tsra
activity will begin to taper off by Wednesday aftn. Otherwise vfr
conditions until 02z...after 02z expect mainly ifr conditions thru
18z with vfr conditions after 81z.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

NEAR TERM...15
SHORT TERM...15
LONG TERM...KTW
AVIATION...007

For more information please visit our website
at weather.gov/huntsville.

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
410 PM CST TUE NOV 29 2016

ALZ001>010-016-TNZ076-096-097-301130-
LAUDERDALE-COLBERT-FRANKLIN AL-LAWRENCE-LIMESTONE-MADISON-MORGAN-
MARSHALL-JACKSON-DE KALB-CULLMAN-MOORE-LINCOLN-FRANKLIN TN-
410 PM CST TUE NOV 29 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH ALABAMA AND PORTIONS OF
SOUTHERN MIDDLE TENNESSEE.

.DAY ONE...REMAINDER OF TODAY AND TONIGHT...

A WARM FRONT WILL LIFT NORTHWARD ACROSS THE REGION LATE THIS
AFTERNOON BRINGING THE THREAT FOR STRONG TO SEVERE THUNDERSTORMS.
THE PRIMARY THREATS WITH THESE STORMS WILL BE LARGE HAIL, DAMAGING
WIND GUSTS, AND BRIEF TORNADOES. A TORNADO WATCH IS IN EFFECT FOR
PORTIONS OF NORTHWEST ALABAMA UNTIL 11 PM CST.

A MORE WIDESPREAD THREAT OF STRONG TO SEVERE STORMS IS EXPECTED LATE
EARLY WEDNESDAY AHEAD OF A SLOW MOVING COLD FRONT. ALL MODES OF
SEVERE WEATHER INCLUDING DAMAGING WINDS, LARGE HAIL AND A FEW
TORNADOES WILL BE POSSIBLE WITH THESE STORMS. VERY HEAVY DOWNPOURS OR
LOCALLY HEAVY RAINFALL MAY RESULT IN LOCALIZED FLASH FLOODING. THE
HIGHEST THREAT FOR SEVERE WEATHER EXISTS ACROSS NORTHWEST ALABAMA
THOUGH STORMS WILL BE SLOW TO WEAKEN AS THEY MOVE ACROSS THE
REMAINDER OF THE AREA OVERNIGHT.

AN ADDITIONAL CONCERN WITH THIS EVENT IS THAT IT WILL BE OCCURRING
MAINLY IN THE OVERNIGHT HOURS TONIGHT INTO WEDNESDAY.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY...

THUNDERSTORMS REMAIN POSSIBLE DURING THE MID TO LATE MORNING HOURS ON
WEDNESDAY BUT MAINLY FOR THE EASTERN HALF OF THE AREA AS THE LINE
OF SHOWERS AND THUNDERSTORMS EXITS TO OUR EAST.

THERE IS A SLIGHT CHANCE FOR THUNDERSTORMS STARTING SUNDAY NIGHT AND
CONTINUING THROUGH TUESDAY MORNING.

.SPOTTER CALL TO ACTION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL IS
LIKELY THROUGH WEDNESDAY MORNING.

70/DD