Damaging Winds in Alabama, March 24, 2016

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
138 PM EDT THU MAR 24 2016

.Aviation...

[Through 18Z Friday] A line of thunderstorms was taking shape to
the west of the area at 1730Z, and stretched from near MOB to the
southwest. At its current pace, it would arrive near DHN and ECP
terminals around 22-23Z, and at ABY and TLH terminals around
00-01Z. These storms could bring LIFR-IFR visibilities and gusty
winds to 30 knots or more. Otherwise, tonight we expect a mixture
of cloud layers with occasional periods of MVFR or IFR CIGS, and a
gradual improvement after sunrise on Friday. Additional showers
are possible overnight and may linger near TLH and VLD into
tomorrow. An additional round of thunderstorms will be possible
tomorrow at TLH and VLD, but confidence was not high enough to
mention TSRA in the TAFs yet.

&&

.Prev Discussion [1029 AM EDT]...

.Near Term [Rest of Today]...

Although the air mass over our forecast area at 13-14Z was fairly
dry with dewpoints in the 50s (other than along the coast), models
continue to indicate the northward advection of higher dewpoints
through the day today. Coupled with the arrival of some steeper
mid-level lapse rates from the west, and at least some mixed
sunshine today, the ingredients are in place for steady
destabilization - particularly across western parts of the area.

Convection-allowing models have been keen on developing some
showers and storms in the western parts of our area late this
afternoon as the atmosphere destabilizes and warm-air advection
gradually ramps up.

There is currently (14Z) a band of convection stretching from near
Tuscaloosa to near New Orleans, and stretching further SW
offshore. This was making steady progress east, and was generally
not depicted well in many models - even those that initialized
less than 12 hours ago. Recent runs of the HRRR have depicted this
band of convection ahead of the (now-decaying) primary MCS along
the Gulf coast, and those HRRR runs push clusters or lines of
thunderstorms into the western parts of our forecast area around
21Z to 22Z. Whether or not this specific scenario pans out remains
to be seen, but most models do show an increase in convection in
either the late afternoon or early evening. We continue to show
limited PoPs prior to 21Z, with a rapid increase in the western
half of our area between 21-00Z. Some severe wording was added in
those areas as well; given the combination of moderate instability
and shear, some of the storms could be severe from late this
afternoon into this evening.

.Short Term [Friday night Through Saturday]...
A stalled frontal boundary will be in place across Northeast
Florida out into the Gulf of Mexico. A disturbance moving through
the southern stream flow will lead to showers and thunderstorms
developing along the front and lifting northward through the day.
Model guidance continues to remain split regarding the intensity
of this system on Saturday. There seems to be reasonably good
consensus that there will be rain in the area - it's more a
question of how much. The GFS continues to be on the stronger side
with rainfall amounts, with the NAM/Euro lighter. Overall, went
with a north-south PoP gradient with the highest values along and
south of I-10. Extensive cloudiness will keep temperatures during
the afternoon in the mid 70s.

.Long Term [Saturday Night Through Thursday]...
With one wave moving east of the region on Saturday evening, the
frontal zone will remain nearly stationary across the southern
portion of the region. Model guidance shows a second southern
stream advancing across the Central Gulf Sunday morning ahead of a
northern stream trough racing across the Central Plains. This
system should have a good deal more forcing to work with - thus
feel this system Sunday into Monday will present the greatest
heavy rainfall threat. The 24/00z Euro seems to have shifted
toward the GFS with a little greater QPF this cycle. As a result,
have increased PoPs for Sunday into the 70-80 percent range with
noticeably higher QPF.

By Sunday night, the trailing northern stream trough will be
moving across the Tennessee River Valley and should be
sufficiently strong to sweep the frontal zone south of the
forecast area by Monday afternoon. Drier air will begin to arrive
on Tuesday, with a stretch of dry conditions lasting through
Wednesday.

Thursday looks to feature a return to active weather as the next
system nears the region. Still a lot of details to be worked out
at long ranges, but it appears as though Thursday looks wet, with
some potential for another round of heavy rainfall.

Throughout the period, temperatures are expected to be above
climatology, especially with respect to overnight lows early in
the period. Some cooler and drier air will arrive Tue-Wed, but
should only return temperatures to climatology - before warming
again ahead of Thursday's storm system.

.Marine...

In general, winds at all of our marine observation sites have been
running near or over the available model guidance. Buoy 42039 to
the south of Panama City has been around 20 knots for a few hours
and recently spiked to 23 knot sustained winds. For that reason,
we have issued a Small Craft Advisory to the west of Apalachicola
until 21Z. That may need to be extended, as some models show
another increase in winds closer to 00Z. Some models do also
indicate a lull in winds today, but given the persistence of
strong winds in the western portions of our coastal waters early
this morning, we issued the advisory.

.Fire Weather...
Hazardous fire weather conditions are not expected through at
least early next week.

.Hydrology...
Three separate periods of rainfall over the next few days will
lead to the potential for river flooding by the end of the weekend
and into next week. While there's still some uncertainty with
respect to the amounts, it looks at this point like the primary
threat will be more river flooding and less urban flooding. The
most at risk areas for flooding would be our western areas, where
recent rains have stream flows at or just above normal.

Total rainfall from the three systems Thursday evening through
Sunday night could be in the 3 to 5 inch range with isolated
heavier totals possible.

&&

.Preliminary Point Temps/PoPs...

Tallahassee   66  77  64  75  65 /  70  70  50  80  40
Panama City   65  72  62  72  66 /  70  60  50  80  50
Dothan        61  74  55  77  62 /  80  50  20  50  60
Albany        64  73  58  75  62 /  80  70  30  60  50
Valdosta      66  77  64  75  64 /  60  70  50  80  40
Cross City    66  79  67  77  65 /  40  60  60  60  30
Apalachicola  67  74  65  72  67 /  60  60  60  70  40

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until midnight EDT /11 PM CDT/ tonight FOR
     Coastal Bay-South Walton.

GA...NONE.
AL...NONE.
GM...Small Craft Advisory until 5 PM EDT this afternoon FOR Coastal
     waters from Apalachicola to Destin FL out 20 NM-Waters from
     Apalachicola to Destin FL from 20 to 60 NM.

&&

NEAR TERM...LAMERS
SHORT TERM...GODSEY
LONG TERM...GODSEY
AVIATION...LAMERS
MARINE...LAMERS
FIRE WEATHER...MOORE
HYDROLOGY...GODSEY