Tornado and Damaging Wind in Alabama, December 16, 2019

Area Forecast Discussion
National Weather Service Mobile AL
545 PM CST Mon Dec 16 2019

.DISCUSSION...Updated for latest aviation discussion below.

&&

.AVIATION...
17/00Z Issuance...Expect at least MVFR cigs through most of the
forecast period, with periods of IFR (or lower) in and around
showers and thunderstorms from around 17/03z to 17/09z, and then
a more dominant period of IFR in the wake of the precipitation
with low stratus and fog as the actual front moves through between
17/12-17/17z. After about 17/18z-17/21z ceilings/vsbys improve to
high end MVFR to VFR. Light southerly winds early this evening
increase to moderate with stronger gusts by late this evening,
then shift to the northwest toward sunrise and into Tuesday
morning, when northwesterly winds gusting to 20 to 25 knots will
be possible.  /12

&&

.PREV DISCUSSION... /issued 405 PM CST Mon Dec 16 2019/

NEAR TERM /Now Through Tuesday/...Main upper trof, with vigorous
embedded short waves within the mean sw flow well east of the
main upper system, will continue to dig south over the central and
lower Plains States tonight and early Tue reaching the mid MS
River Valley and east Tx by late Wed afternoon. With the enhanced
lift aloft combined with strong vertical sheared, 0-1km helicity
values climbing to 200 to 300 m2/s2 in the boundary layer, along
with surface temps and dewpt temps in the 70s strong to severe
thunderstorms have formed over large parts of lower LA and MS this
morning and afternoon moving mostly to the northeast. These
thunderstorms are forming well out ahead of a strong cold front
where 850 winds are also ranging from 35 to 45 knots helping to
enhanced the severe threat well east of the front for the
remainder of the this afternoon continuing through tonight.
Thunderstorms will reach extreme western sections of the forecast
area by late this afternoon or early this evening spreading
further east over remaining areas of the forecast area late this
evening and overnight. Most of the hi res data continues to
support this reasoning with the biggest threat for severe weather
remaining over extreme northwestern sections of the forecast area
where a moderate risk for severe storms is plotted for late today
through about 1 AM CST tonight. Further east a slight risk for
severe weather continues for tonight or through about 9 AM CST Tue
morning. As mentioned earlier damaging winds, large hail and
tornadoes will be possible with the stronger thunderstorms.
Confirmed sitings of tornadoes and damage to the west over MS and
LA continues this afternoon. A tornado watch is now in effect for
parts of inland SE MS and northern parts of Southwest AL until 11
PM CST tonight. Stay tuned for further updates on this developing
severe weather situation.

In the wake of the front skies will clear slowly on Tue generally
from west to east with gusty northwest to northerly winds Tue
into Tue evening. Will have to monitor this situation closely for
possible wind advisories during the day on Tue. Lows temps by
early Tue morning will be 5 to 10 degrees above seasonal norms
then gradually warm to 4 to 6 degree below seasonal norms later in
the day. Lows tonight will range from the middle 40s to lower 50s
generally along and west of the I-65 corridor and the lower to
middle 50s to the east and south stretching to the immediate
coast. Highs Tue will range from the lower to middle 50s generally
west of the I-65 including coastal AL and the middle to upper 60s
to the east, basically ahead of the cold front. 32/ee

SHORT TERM /Tuesday night Through Thursday night/...The short term
period will begin as an upper level, positively-tilted trough
over the the Ohio Valley extending down through the ARKLATEX
region continues to make its way towards the east coast.
Meanwhile, a surface cold front will have moved over the
southeast, eventually ending up over the east coast of the
Carolinas and Georgia as well as northern FL. Also, surface high
pressure, located over Texas, will build eastward into the region.
By Wednesday evening, zonal flow will take hold aloft over the
northern Gulf coast as an upper level ridge over the Plains
advances towards the eastern CONUS. The surface high pressure and
upper level ridge will maintain their hold over the region through
early Friday, leading to dry and mostly clear conditions for the
area during this time.

Low temperatures Wednesday morning will be chilly, due to CAA
from the northwest from FROPA earlier in the day Tuesday. Lows are
expected to range from the lower 30s inland to the mid 30s along
the coast. Highs Wednesday afternoon will also be a bit chilly,
likely only reaching the lower to mid 50s. Lows Thursday morning
will be a touch colder than Wednesday morning. Lows are likely to
be in the upper 20s inland and in the lower 30s near the coast.
Conversely, highs Thursday will be slightly warmer than Wednesday,
with temperatures around the mid 50s. /26

LONG TERM /Friday Through Monday/...Surface high pressure will
begin to move off to the northeast Friday morning.
Simultaneously, a shortwave trough will advance towards the
eastern CONUS. A cold front is also expected to move over the
Plains and up into the Ohio and Tennessee Valleys for late week.
This will increase chances of showers to our area Friday and into
the weekend. The models are in decent agreement with the upper
level features through about Saturday afternoon, when then they
begin to diverge in solution. This is particularly true in regards
to the timing and amplitude of the shortwave trough expected to
advance towards the southeast late Friday into early Saturday.
Therefore, have maintained slight to chance PoPs through the
weekend given by the blended guidance. By Sunday morning, another
area of surface high pressure will develop over Texas and build
over the eastern CONUS. For the northern Gulf, this will lead to
dry and mostly clear conditions for early next week.

Temperatures will generally be on an upward trend Friday through
early next week, with lows increasing to be in the lower 40s by
Monday morning and highs in the mid to upper 60s Monday afternoon.
/26

MARINE...A moderate southerly wind flow will continue over the
marine area tonight ahead of a cold front approaching from the
west. The cold front will move across the area late tonight
through early Tue morning leading to a strong northwest to
northerly flow Tue through Wed morning. Wind gusts to gale force
will also be possible over the open Gulf waters late Tue afternoon
through early Wed morning. As a result a Gale Watch is in effect
for the open Gulf waters from 20 to 60 nm out Tue night through
early Wed morning. Northerly winds and seas will gradually subside
Wed afternoon through Thu. 32/ee

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through Tuesday afternoon for ALZ265-266.

FL...High Rip Current Risk through Tuesday afternoon for FLZ202-204-
     206.

MS...None.
GM...Small Craft Advisory from 6 AM Tuesday to 8 AM CST Wednesday for
     GMZ630-633>636.

     Small Craft Advisory from 6 AM Tuesday to noon CST Wednesday for
     GMZ631-632-650-655.

     Gale Watch from Tuesday evening through Wednesday morning for
     GMZ670-675.

     Small Craft Advisory from 6 AM to 6 PM CST Tuesday for GMZ670-
     675.

     Small Craft Advisory from 8 AM to noon CST Wednesday for GMZ670-
     675.

&&

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Hazardous Weather Outlook...UPDATED
National Weather Service Mobile AL
730 AM CST Mon Dec 16 2019

ALZ051>060-261>266-FLZ201>206-MSZ067-075-076-078-079-171330-
Choctaw-Washington-Clarke-Wilcox-Monroe-Conecuh-Butler-Crenshaw-
Escambia-Covington-Mobile Inland-Baldwin Inland-Mobile Central-
Baldwin Central-Mobile Coastal-Baldwin Coastal-Escambia Inland-
Escambia Coastal-Santa Rosa Inland-Santa Rosa Coastal-
Okaloosa Inland-Okaloosa Coastal-Wayne-Perry-Greene-Stone-George-
730 AM CST Mon Dec 16 2019

This Hazardous Weather Outlook is for portions of south central
Alabama...southwest Alabama...northwest Florida and southeast
Mississippi.

.DAY ONE...Today and Tonight

A High Rip Current Risk remains in effect for coastal portions of
Alabama and the western Florida panhandle.

A Dense Fog Advisory is in effect for southeast Mississippi and
portions of southwest Alabama until 10 AM CST.

Severe thunderstorms will be possible from late this afternoon
through tonight, with the highest potential for severe storms west
of a line from Butler, Alabama to New Augusta, Mississippi where
the Storm Prediction Center has an Enhanced Risk for severe
storms. A Slight Risk of severe storms exists elsewhere across the
area. The primary severe weather threats will be damaging winds,
hail up to quarter size, and a few tornadoes.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

A High Rip Current Risk remains in effect for coastal portions of
Alabama and the western Florida panhandle Tuesday.

There is a Moderate Rip Current Risk along coastal portions of
Alabama and the western Florida panhandle Tuesday night through
Wednesday night.

.SPOTTER INFORMATION STATEMENT...

Activation of SkyWarn severe spotter networks may be required
late this afternoon into tonight.

GMZ630>636-650-655-670-675-171330-
Northern Mobile Bay-Southern Mobile Bay-Mississippi Sound-
Perdido Bay-Pensacola Bay System-Western Choctawhatchee Bay-
Eastern Choctawhatchee Bay-
Coastal waters from Pensacola FL to Pascagoula MS out 20 NM-
Coastal waters from Okaloosa Walton County Line FL to Pensacola
FL out 20 NM-
Waters from Pensacola FL to Pascagoula MS from 20 to 60 NM-
Waters from Okaloosa Walton County Line FL to Pensacola FL from
20 to 60 NM-
730 AM CST Mon Dec 16 2019

This Hazardous Weather Outlook is for portions of the coastal
waters of Alabama and northwest Florida.

.DAY ONE...Today and Tonight

A Dense Fog Advisory is in effect for the coastal waters from
Pensacola FL to Pascagoula MS out 20 NM, southern Mobile Bay,
Mississippi Sound, northern Mobile Bay until 10 AM CST.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

A Small Craft Advisory is in effect for the Alabama and western
Florida waters out 60 nm, southern Mobile Bay, Mississippi Sound
beginning 6 AM CST Tuesday until 6 PM CST Wednesday.