Area Forecast Discussion
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FXUS62 KTAE 131048
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
642 AM EDT Sat Sep 13 2014
.Near Term [Through Today]...
The 11 pm EDT regional surface analysis showed a cold front from the
Piedmont of SC through southeast LA, with a weak frontal wave near
Columbus, GA. A trough/convergence zone extended south of this low
through Apalachicola, where scattered showers and thunderstorms were
developing this early morning. The weak 1014 mb low pressure system
that tracked across South FL Friday had emerged off the Naples
coast, with no signs of tropical cyclone development. Vapor imagery
and upper air data showed a narrow ridge over portions of the
Southeast. A band of warm, dry, sinking area (associated with a PV
anomaly) was spreading westward across North FL and southeast GA.
We expect the showers & thunderstorms (ongoing as of 230 am) to
diminish somewhat over the next several hours, but there is enough
moisture, instability, & forcing for at least a few to survive into
this morning. Though the details differ, there was relatively good
agreement among the various MOS and ECAM with regards to how today`s
showers and thunderstorms will develop. After a morning lull, we
expect numerous thunderstorms to develop in the FL Panhandle,
southeast AL, and southwest GA, as the aforementioned cold front
enters our northwest zones and stalls. Across the FL Big Bend and
south central GA, the PoP is lower due to the approaching drier air
aloft. Our PoP ranges from 60% around Dothan and Panama City, to
20-30% to the east. With plentiful deep layer moisture, especially
north and west of Tallahassee, some of the slow-moving storms will
produce very heavy rain amounts (isolated 2-4 inches). However, the
threat appears isolated enough so that a Flash Flood Watch is not
needed at this time. With weak forcing, rather light winds aloft,
and unspectacular 700-500mb lapse rates, we`re not anticipating
organized or numerous severe storms today; though a "pulse" severe
storm can`t be ruled out.
.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
.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.
-- Changed Discussion --[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.
-- End Changed Discussion --
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
Red Flag conditions are not expected through at least this weekend.
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 93 73 93 72 92 / 30 20 40 20 50
Panama City 90 76 89 76 89 / 50 30 40 20 50
Dothan 92 72 92 72 92 / 60 50 50 30 50
Albany 92 72 92 73 92 / 50 40 50 30 50
Valdosta 93 71 94 71 93 / 20 20 40 30 50
Cross City 93 72 92 71 92 / 20 30 40 20 50
Apalachicola 89 77 89 76 88 / 20 20 40 20 40