Area Forecast Discussion
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744
FXUS62 KTAE 141444
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1044 AM EDT Mon Apr 14 2014

...Strong to Severe Storms and Heavy Rainfall Possible from Late
Tonight through Midday Tuesday...

.Near Term [Through Today]...

An overnight squall line over Mississippi and western Alabama is
in the process of weakening as it encounters stable air over
central and eastern Alabama. The weakening storms and trailing
stratiform rain has set up a large arcing outflow boundary from NE
LA - S MS - WC/N AL. There is also a well established cold pool
and mesoscale high pressure behind this, centered roughly on
Tuscaloosa at 14z. Nevertheless, there is still a thin band of
convection on the downshear side of the cold pool that has been
advancing steadily toward southeast Alabama. Extrapolation of
recent trends would take it into our forecast area around 1630Z.
Therefore, we maintained PoPs in the western part of our area
during the daytime hours, although only "isolated thunderstorms"
were mentioned due to the meager instability. Isolated showers
continue to be advertised in the far eastern part of our area
mainly between 16-21Z by a variety of convection-allowing models.

It should be noted that existing CAM runs (and even global models)
have not handled well the eastward progression of the convective
line in Alabama. This may introduce a previously unforeseen
mesoscale boundary into the area this evening that could provide
an additional focusing mechanism for convective development. The
next several hours should give us a better idea of whether or not
this outflow boundary will play a role in shaping tonight`s
weather.

Looking ahead to tonight, recent model runs - particularly CAM -
have increased QPF across our area. Therefore, look for an
increase in the rainfall forecast later today. Depending on 12z
guidance, a Flash Flood Watch may be considered for parts of the
area as well, especially the Florida Panhandle west of the
Apalachicola River.


.Long Term [Wednesday Night Through Monday]...

With the first low pressure system long gone by the beginning of the
extended period, we should at least experience a 2 day break in the
unsettled weather on Wed. and Thu. with an initial shot of
unseasonably cold air moderating back towards climo levels. By the
end of the week and through next weekend, however, the fcst will
once again become quite difficult as the conditions are leaning
heavily towards yet another very unsettled period. While the details
on timing, potential rainfall totals, and the possibility of any
severe weather have been very inconsistent from run to run in both
the GFS and ECMWF, the chances of another significant rainfall event
during this time frame are clearly increasing. This is definitely
not welcomed news for our area rivers and streams, many of which
remain elevated from previous rainfall events, and will be primed
yet again by the initial rainfall event early in this week.
Furthermore, until a more significant change in the synoptic pattern
becomes evident across the CONUS, these anomalous digging shortwaves
and potential heavy rainfall producers will continue to threaten the
Southeast U.S.

&&

.Hydrology...

Rainfall forecasts for tonight and early Tuesday are expected to
be increased from previous expectations, especially in parts of
the lower Choctawhatchee, Chipola, Apalachicola, and Ochlockonee
River basins. In general, the additional rainfall tonight and
Tuesday should slow the falling trend on area rivers and possibly
lead to increases on some - particularly smaller basins.
Therefore, we can say that at the very least flooding may be more
protracted this week along some area rivers. However, given
uncertainty on where localized heavy bands of rain set up, it`s
difficult to say which rivers may see more notable rises.

For real-time detailed river stage monitoring refer to this page:
http:/water.weather.gov/ahps2/index.php?wfo=tae

&&

.Prev Discussion [337 AM EDT]...

.Short Term [Tonight Through Wednesday]...
The long wave trough over the center of North America will shift
eastward during this period with a potent short wave rotating
through its base as it crosses the forecast area on Tuesday. The
associated cold front will sweep across the area from northwest to
southeast from 09-21z Tuesday. Showers and thunderstorms will
precede the front. At this time, it appears a squall line will enter
the area around 02-04z and bring a threat for damaging wind gusts.
The hail threat will be primarily north of the region, but our
northwestern zones could get some hail. There is also a non-zero
tornado threat of tornadoes, particularly in any discrete cells out
ahead of the main line and closer to the greater instability near
the Gulf Coast. By sunrise, the main band of convection is expected
to be over the FL Big Bend and South Central GA. There still appears
to be sufficient shear and instability in place at that time for a
marginal severe threat in these areas before 18z. Most convection
will exit east of the area by sunset.

An unseasonably cold airmass will arrive behind the cold front with
highs on Tuesday struggling to reach 60 degrees over Coffee County
AL Tuesday afternoon. South Central GA and the FL Big Bend will peak
in the lower 70s. Strong cold advection Tuesday night will drive
temperatures down into the 30s for all but our southeastern FL Big
Bend counties and coastal areas. This is about 15 degrees below
normal. It does not appear that any records are in jeopardy, but
wind chill reading will drop to around 30 degrees give or take a
few. That winter coat may have to come out of the closet one more
time. Highs on Wednesday will rebound to the upper 60s north to
mid 70s southeast.


.Aviation...
[Through 06Z Tuesday] A patchy MVFR to IFR fog/ceiling mixture
will be possible at ECP later this morning, though confidence is
low due to the substantial coverage of high cloudiness. The only
other restrictions through this afternoon could affect VLD late in
the afternoon as showers and possibly isolated thunderstorms
accompanied by low ceilings pass from south to north across the
Suwannee Valley. Overnight a line of storms will move from west to
east across the Tri-State region, likely bringing IFR (or lower)
restrictions to terminals along and west of a line from ABY to
TLH.


.Marine...
Onshore winds will pick up to cautionary levels tonight ahead of a
cold front. After frontal passage, offshore winds will quickly
increase to small craft advisory levels for Tuesday and Tuesday
night before veering to the east and dropping to cautionary levels
from Wednesday into Friday morning.


.Fire Weather...
Relative humidity levels will remain well above critical thresholds
for the next couple of days as flow veers southerly ahead of an
approaching frontal system that is expected to bring a decent amount
of rainfall across the Tri-State region tonight through Tuesday. In
it`s wake, the lowest relative humidities will be on Wednesday, but
it is unclear whether durations or fuel moisture criteria will be
met to warrant Red Flag conditions.

&&

.Preliminary Point Temps/PoPs...

Tallahassee   83  64  72  37  72 /  10  70  80  10   0
Panama City   76  61  66  42  70 /  20  80  70  10   0
Dothan        82  57  63  36  69 /  30  90  60  10   0
Albany        82  62  68  36  70 /  10  80  80  10   0
Valdosta      86  63  74  38  73 /  20  60  80  20   0
Cross City    83  65  75  42  75 /  20  40  70  20  10
Apalachicola  77  64  69  42  69 /  10  70  80  10   0

&&

.TAE Watches/Warnings/Advisories...

FL...High Rip Current Risk until 6 PM CDT this evening for Coastal
     Bay-South Walton.

GA...None.
AL...None.
GM...None.

&&

$$

NEAR TERM...LAMERS
SHORT TERM...WOOL
LONG TERM...GOULD
AVIATION...HARRIGAN
MARINE...WOOL
FIRE WEATHER...HARRIGAN
HYDROLOGY...LAMERS






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