Area Forecast Discussion
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FXUS62 KTAE 171731

Area Forecast Discussion
National Weather Service Tallahassee FL
131 PM EDT Sat Mar 17 2018

.AVIATION [Through 18Z Sunday]...

CIGS continue to gradually lower at this hour, with ECP, DHN, and
ABY reporting low end VFR/high end MVFR conditions. Expect this
trend to continue at all sites through tonight. SCT SHRA/TSRA is
developing W of ECP/DHN/ABY at this hour and moving ENE toward
DHN and ABY. Brief reductions in vsby and CIGS are possible with
this activity thru this evening. Prevailing SW winds around 10
kts, with gusts to 20kts at DHN/ABY this afternoon. LIFR
conditions likely tonight due to low CIGS and reduced vsbys.



.NEAR TERM [Through Today]...

Strong quasi-zonal upper level flow will persist today, while at the
surface a front remains nearly stationary well to our north. After
some patchy fog in the FL Big Bend region dissipates shortly after
sunrise, deep layer moisture will continue to increase across our
area under southwesterly flow. While frontal forcing will not impact
our area, isentropic ascent will remain present throughout the day.
Combined with ample moisture and increasing instability, especially
across our northern and western areas during the afternoon,
scattered showers and thunderstorms will be possible. In fact,
latest CAM guidance has shown the potential for isolated
strong/severe thunderstorms across our far northern areas. SBCAPE
could exceed 1000 J/kg during the late afternoon and early evening,
along with 0-6 km bulk shear around 40 kts in our northern tier of
counties in SW Georgia and SE Alabama. As a result, isolated
damaging wind gusts and/or hail will be possible with the strongest
thunderstorms during the afternoon and early evening.

After morning lows ranging from the upper 40s and lower 50s east to
lower 60s along the FL Panhandle coast, temperatures will warm up
quickly under southwesterly flow. Highs will range from the upper
70s to lower 80s across inland areas and mid 70s along the Gulf

.SHORT TERM [Tonight Through Monday]...

A somewhat complex forecast scenario looks to evolve over the
short term period. After lingering convection from Saturday
diminishes, focus will shift to the west where model guidance
shows a trough moving out of the Four Corners on Sunday afternoon.
This will induce surface cyclogenesis across the OK Panhandle and
lift a warm front northward across the Central Gulf of Mexico and
into our region. With relatively fast flow aloft, sufficient wind
shear will be present for storms Sunday afternoon/evening
developing along and near this frontal boundary to become strong
to severe with the primary threat being large hail, though given
the orientation of the low level flow, an isolated tornado is also
possible especially if the low level flow is stronger than
currently indicated in the model guidance. The severe threat with
this event will be focused more across Southeast Alabama and into
Southwestern Georgia.

Once the warm front retreats well north of the region on Sunday
night, our region will be in a bit of a lull as the main
trough/surface low begins to approach by daybreak Monday. There`s
a good chance of strong to severe storms on Monday and into Monday
night, but the details are a bit uncertain at this time frame.
Deep layer shear throughout the day is certainly sufficient for
severe storms /50-55 kt ocnl near 60 kt/ and surface-based
instability impressive /1700-2500 J/kg/. But unlike on Sunday, the
models suggest the flow will be nearly unidirectional, which
supports damaging winds as the dominant severe threat - though
large hail and an isolated tornado is also possible. Model
guidance is split on storm mode on Monday. It`s possible that a
large MCS could move through the region late Monday morning and
into the afternoon well ahead of the surface cold front, which
most of the models still have well west of our region at 18z

Beyond Monday evening, while still having some potential for
severe weather, the threat is more conditional and uncertain as
prior convective activity could stabilize the airmass coupled
with the loss of daytime heating. Model soundings show surface
instability becoming negligible, but lapse rates begin to steepen
aloft ahead of the main trough. While the GFS shows little or no
activity with the cold front Monday night, the NAM and Euro both
show fair good development across our region Monday night as the
cold front moves through. Again, much like on Monday, the dominant
severe threat would be damaging winds.

Event Summary/Key Points...

1. A stretch of unsettled weather is expected over the next three
days bringing multiple chances for severe storms.

2. The initial focus for strong storms will be across Southeast
Alabama and Southwest Georgia this afternoon where hail and
damaging winds are possible.

3. The threat for severe weather increases Sunday afternoon and
evening, especially across Southeastern Alabama and Southwest
Georgia. Large hail, damaging winds, and isolated tornadoes will
be possible with this event.

4. By Monday, severe storms are possible region-wide - with two
distinct waves of impact weather. One during the daytime hours
and the other late Monday night. With both, damaging winds is the
primary threat, though there is a risk of an isolated tornado.

.LONG TERM [Tuesday Through Saturday]...
At the start of the period, model guidance has a cold front moving
across the forecast area, with potentially strong to severe storms
immediately ahead of the boundary. This front is expected to clear
the forecast area by Tuesday afternoon.

The departing storm system is expected to intensify over the
Western Atlantic and move quickly out to sea, leaving behind
another cool and dry airmass. From Wednesday through Friday the
models have been alternating between a stretch of especially cool
temperatures or a less intense cool snap. This cycle, with the
Eastern CONUS trough remaining more off the New England Coast,
the bulk of the chilly air, seems to stay to our north.
Accordingly, both Euro and GFS-based MOS products have warmed 4-8
degrees for overnight lows Wed Night and Thurs Night. Stayed a
couple of degrees cooler than the latest guidance in the event
things flip back on the next cycle. In any event, Wed-Fri will
feature below normal temperatures, but also dry conditions.

By Saturday, high pressure sets up east of the Florida Peninsula,
returning Gulf moisture to the region and leading to a warming
trend with temperatures rising above normal.


Moderate southwesterly winds are expected throughout the weekend
and into Monday well ahead of an approaching storm system. Winds
will increase to cautionary levels by Monday night as a cold front
nears the marine area. After the cold front crosses the waters by
Tuesday, winds will shift to an offshore direction and increase to
advisory levels potentially through Thursday morning.


Moisture will continue to increase across our area this weekend,
with minimum RH values remaining well above critical thresholds each
day. As a result, no fire weather concerns are anticipated.


An unsettled stretch of weather is expected over the next 3 days.
The rainfall on Saturday and Sunday should be more isolated, and
generally focused across Southeast Alabama and into Southwestern
Georgia. More widespread activity is expected on Monday.
Throughout the event, storm total rainfall amounts should average
between 1 and 3 inches. As a result, flooding is not anticipated
at this time.


Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.



Tallahassee   61  81  64  79  65 /  10  60  40  60  50
Panama City   65  75  67  75  65 /  10  50  60  50  50
Dothan        61  79  64  80  61 /  10  80  60  80  50
Albany        61  80  63  79  63 /  10  30  70  80  60
Valdosta      58  80  64  77  66 /  10  40  60  70  50
Cross City    57  79  62  77  66 /   0  20  20  40  50
Apalachicola  64  76  66  75  67 /  10  40  50  40  50




NEAR TERM...Pullin
LONG TERM...Godsey
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