Area Forecast Discussion
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991
FXUS62 KTAE 221127
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
627 AM EST Sun Feb 22 2015

.Update...

The eastward spread of light isentropic showers was missed by
pretty much all of the available hires guidance. Have expanded
PoPs eastward and weighted the forecast towards the HRRR for the
next several hours. Still expect the isentropic rain to weaken
and become more sparse through the early afternoon as discussed
below. At this time the remainder of the forecast remains valid,
though temperature trends will have to be monitored across the Big
Bend and southern GA should rain continue longer than expected.
This could result in lower temps than currently advertised.

&&

.Prev Discussion [342 AM EST]...

.Near Term [Through Today]...
Zonal flow aloft will dominate the Southeast today, with a broad
northern stream trough in the northeastern quadrant of the
country, and an upper low cutting off over the Central Great
Basin and west coast. At the surface, a regional subjective
analysis depicts a cold front draped southwest to northeast from
the southern Mississippi Valley into northern Alabama. Extending
east-northeast from northern Alabama is a quasi-stationary
boundary draped up the lee side of the Appalachians. The large
area of light to moderate rain was being forced out ahead of the
surface front, associated with a weak southern stream anomaly.
Another area of light rain along near the Tri-State intersection
is being forced in the near surface 290-295K window.

As warming begins across the Southeast today, the slope of the
isentropes will dampen and the aforementioned area of rain should
come to an end by mid-afternoon. Though, not before spreading an
area of light rain primarily along and west of the Apalachicola
and Chattahoochee rivers. The larger area of precip across the
Southeast this morning will lift northeast with the upper-level
shortwave and the focus for the majority of rainfall across the
Southeast will shift back to the surface front. The front is
expected to just barely reach our southeast Alabama and extreme
western Georgia counties late this afternoon as surface high
pressure builds south. This will yield the best chance for rain
later this afternoon along and northwest of a line from Ben Hill
county to Walton county. Total rain accumulations through today
shouldn`t top a half an inch across southeast Alabama, and a
quarter of an inch elsewhere.

With the sharp precip gradient, a similar temperature gradient is
also expected. Low 70s should be anticipated in aforementioned
areas impacted by rain, while middle to even upper 70s (across
the Suwannee Valley) should be expected elsewhere.


.Short Term [Tonight Through Tuesday]...
The cold front mentioned above will push through the forecast area
tonight into Monday. The best chance of rain will be across the
northwest half of the area as the front will be weakening as it
moves through. Model disagreements become apparent by Tuesday as
the NAM and ECMWF spread additional light rain into the area with
a weak upper level shortwave while the GFS is drier. The official
forecast went with a compromise and shows 30-50% PoPs. With an
increase in cloud cover expected on Tuesday, high temperatures
will be held down somewhat with lower 50s expected across the
north and mid 50s to near 60 across the southeast big bend.


.Long Term [Tuesday Night Through Sunday]...
A more significant system is possible on Wednesday with both the
GFS and ECMWF indicating a fairly vigorous upper level shortwave
with a surface low moving along the coast. With the 00z models in
general agreement on the timing, PoPs were bumped up to 70% for
Wednesday. This looks like a decent rainfall producer with a
couple of inches possible across the area. With the surface low
expected to track south of the area, the airmass currently looks
too stable for thunderstorms across our area. After the Wednesday
system, another system is possible for next weekend. Overall, high
temperatures are expected to be a bit below average with lows
near average.


.Aviation...
[Through 12z Monday] MVFR to IFR ceilings should be expected in
and around areas of rainfall through mid-morning. Thereafter, VFR
ceilings should be expected at all terminals but DHN and ABY where
MVFR will prevail with light to moderate rain.


.Marine...
Southerly winds will be subsiding today. However by late tonight
into Monday, a cold front will move through the coastal waters,
bringing an increase in northerly winds possibly to cautionary
levels mainly west of Apalachicola. Winds are then expected to be
light for Tuesday before increasing again on Wednesday to near
advisory levels as an area of low pressure moves along the coast.


.Fire Weather...
Hazardous fire weather conditions are not expected over the next
several days.


.Hydrology...
Several rounds of rainfall are possible this week with the best
chance for an areawide moderate to possibly heavy rainfall event
expected on Wednesday. Total rainfall is generally expected to be
in the 2-3 inch range with isolated higher totals possible. This
will cause rises on area rivers and may bring a few of our sites
back up to action stage. At this time, flooding is not expected,
although if widespread rainfall amounts were to increase above 3
inches, then the Kinchafoonee Creek as well as the Ochlockonee and
Aucilla Rivers could come close to minor flood stage.

&&

.Preliminary Point Temps/PoPs...

Tallahassee   71  55  69  49  57 /  70  20  20  40  50
Panama City   65  57  63  48  54 /  70  20  20  40  50
Dothan        71  49  59  41  51 /  70  50  20  40  50
Albany        73  51  61  40  51 /  70  50  20  30  40
Valdosta      76  55  68  45  53 /  60  20  20  40  50
Cross City    76  54  72  50  60 /  30  10  20  30  50
Apalachicola  66  58  68  51  57 /  70  10  20  40  50

&&

.TAE Watches/Warnings/Advisories...

FL...RIP CURRENT RISK through this evening for Coastal Bay-Coastal
     Gulf-South Walton.

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

&&

$$

NEAR TERM...HARRIGAN
SHORT TERM...DVD
LONG TERM...DVD
AVIATION...HARRIGAN
MARINE...DVD
FIRE WEATHER...HARRIGAN
HYDROLOGY...DVD






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