Area Forecast Discussion
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743
FXUS62 KTAE 131430
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1030 AM EDT Sat Sep 13 2014

.Near Term [Rest of Today]...

The previous forecast remains largely on track, so only minor
tweaks were made. The leading edge of an expansive stratus deck,
roughly marking the location of a quasi-stationary front, extended
from near Mobile to near Atlanta this morning. When combined with
14Z objective MSAS analysis of MSLP and observed winds, this
places the front very close to the northwest corner of our
forecast area. The environment along and immediately southeast of
the front is characterized by mid-70s surface dewpoints and PWATs
around 2" (per GOES sounder). Meanwhile, some drier air was
encroaching on the southeast part of the forecast area based on
the latest water vapor loops and objective RAP analysis.
Tallahassee appeared to be on the cusp of the drier air, with a
PWAT of 1.9" on the 12Z sounding. Therefore, the higher rain
chances that were already included in the northwest half of the
forecast area seem on track at this time. Convection-allowing
models (CAM) almost unanimously show fairly widespread
thunderstorm activity just ahead of the front in our SE Alabama
and western Florida Panhandle zones after about 19-20Z. They also
agree that the storms are likely to linger until a few hours after
sunset again, particularly in the Florida Panhandle. PoPs were
bumped up in the Florida Panhandle for the evening hours. With
less convective coverage in the Florida Big Bend and south-central
Georgia, those areas could see highs in the mid-90s again. To the
north and west, highs should be from around 90 to the lower 90s.

The 12Z Tallahassee sounding did indicate stronger E-NE flow than
yesterday, likely due to the influence of the passing tropical
wave to the south of the area. However, radar VWPs and RAP
analysis place the axis of the deep mid-upper level ridge near
the northwest corner of our forecast area with a notable weakness
in the flow. This will likely lead to slow storm motions in the
region with the highest PoPs. Slow storm motions, storm-scale
interactions, and the moist environment will provide adequate
ingredients for localized heavy rainfall. The heavy rain wording
was maintained in the forecast. Some CAMs indicate rainfall rates
as high as 4-5" in just under 2 hours, so isolated flash flooding
will be possible. However, the threat is expected to be isolated
enough to preclude the issuance of a Flash Flood Watch.

&&

.Prev Discussion [642 AM EDT]...

.Short Term [Tonight Through Monday]...

Although weak upper level ridging will continue to dominate the
northern Gulf Coast and SE U.S during the remainder of the weekend
and into early next week (before it is eventually replaced by a trof
towards mid week), plenty of deep layer tropical moisture will
continue to flow into the region from the Gulf of Mexico and western
Atlantic. This will keep PoPs above climo through the short term
period with daytime rain chances generally in the 40-50% range, with
decent PoPs continuing well into the evening hours, especially
tonight over NW portions of the CWA. Temps are expected to remain
above normal as well, with highs mainly in the lower to a few mid
90s away from the coast, with overnight lows in the lower to middle
70s.


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

The main uncertainty for the extended forecast is to what extent
the weak system moving westward into the Gulf will impact our
area. The collaborated NHC/WPC forecast takes the system westward
to a position south of Houston by mid-week and keeps it weak. Deep
moisture will continue to increase across the area with a stalled
frontal boundary also in the vicinity. These ingredients point to
an unsettled period coming up with an above average chance of rain
by mid-week. Some locally heavy rain is possible given the weak
boundary and deep tropical moisture expected to be in place. This
could be further enhanced by the Gulf system depending on its
evolution, but that evolution is much more uncertain. Daytime
highs are expected to be held down in the mid 80s from Tuesday
through most of the week given the expected cloud cover and
increased rain coverage.


.Aviation...

[through 12z Sunday] Other than brief patchy fog early, generally
VFR conditions are expected. Scattered to numerous SHRA/TSRA will
develop this afternoon & evening across southeast AL, the FL
Panhandle, & southwest GA, affecting KDHN, KABY, & KECP with
occasional gusty winds, low cigs, and poor vis. Elsewhere VFR
conditions will continue. SHRA/TSRA should slowly diminish around
midnight or shortly after.


.Marine...

Winds and seas will be slightly elevated this weekend as a weak
tropical disturbance passes well to the south of the coastal waters.
Thereafter, a very weak surface pressure pattern will return to the
marine area, with typically low summertime winds and seas expected
once again.


.Fire Weather...

Red Flag conditions are not expected through at least this weekend.


.Hydrology...

As mentioned above, some locally heavy rainfall (with up to 2" to 4"
amounts) will be possible today in some of the slow moving storms to
the north and west of Tallahassee, but any heavy amounts should be
isolated in nature and not have much of a hydrological impact
through early next week. By the middle of the week, however, an
upper level trof will replace the current ridge which will be
retreating westward, and before the cooler and drier air is allowed
to seep into the region by late in the week or next weekend, more
widespread heavy rainfall could fall over the CWA. Should this
occur, some more significant rises along area rivers and streams
could take place, so this situation will be worth monitoring.

&&

.Preliminary Point Temps/PoPs...

Tallahassee   96  73  93  72  92 /  20  30  40  20  50
Panama City   90  76  89  76  89 /  40  60  40  20  50
Dothan        91  72  92  72  92 /  70  60  50  30  50
Albany        92  72  92  73  92 /  50  50  50  30  50
Valdosta      95  71  94  71  93 /  20  30  40  30  50
Cross City    93  72  92  71  92 /  30  40  40  20  50
Apalachicola  90  77  89  76  88 /  20  20  40  20  40

&&

.TAE Watches/Warnings/Advisories...

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

&&

$$

NEAR TERM...LAMERS
SHORT TERM...GOULD
LONG TERM...DVD
AVIATION...FOURNIER
MARINE...GOULD
FIRE WEATHER...FOURNIER
HYDROLOGY...GOULD






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