Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 051442
Area Forecast Discussion
National Weather Service Tallahassee FL
942 AM EST Mon Dec 5 2016
.NEAR TERM [Through Today]...
Southwesterly flow prevails above 850mb this morning, ahead of a
strengthening shortwave centered near the TX/Mexico border. Below
850mb southerly flow prevails and will strengthen today as an area
of low pressure in the western Gulf moves gradually eastward. A
well defined frontal boundary extends northeast from this low
across the northern Gulf through Destin, Bainbridge, and Tifton.
Based on satellite data, models seem to be correctly initializing
a large plume of moisture moving north through the eastern Gulf
this morning. The increasing southerly flow, increasing moisture,
and increasingly sloped surfaces at the aforementioned frontal
boundary are all highly favorable for a widespread isentropically
induced rainfall event across the region today. Further, satellite
derived PWAT values match model forecasts which show a plume of
2"+ PWATS spreading inland across the Tri-State region today, this
anomalously high moisture would indicate the potential for heavy
rain. This will be further exacerbated by the fact that deep layer
steering flow is forecast to remain boundary parallel today,
resulting in at least a potential for some southwest to northeast
training of cells. Though heavy rain will be the main threat this
afternoon, modest deep layer shear and decent instability (south
of the front) could allow for a couple strong to severe storms to
develop with the main threat being damaging winds. The main threat
for severe weather will begin late tonight as low and deep layer
shear start to ramp up.
As far as the evolution of storms is concerned, light rain will
continue across south Georgia this morning while rain in the Gulf
continues to become more widespread. By the noon hour, rain should
be fairly widespread along at least the north Florida coast. The
large area of rain will spread across all of Florida, Alabama, and
Georgia with just about all of the Tri-State region under a 100%
chance for rain today. Widespread rain amounts today are expected
to be between 1-3", with isolated amounts up to 5".
It will remain quite cool north of the frontal boundary today,
with highs peaking out around the low 60s in southeast Alabama and
southwest Georgia. Elsewhere, highs should reach the middle to
.AVIATION [Through 12Z Tuesday]...
IFR visibilities are still rather widespread this morning, though
gradually improving. Expect no vis restrictions (outside of rain)
by 18z. Solid IFR ceilings should prevail at DHN and ABY today,
with IFR possibly lifting to MVFR or even temporarily low-end VFR
at TLH, ECP, and VLD later this afternoon. Heavy rain is expected
today and should result in LIFR/minimum conditions should a storm
impact a terminal.
.PREV DISCUSSION [551 AM EST]...
.SHORT TERM [Tonight Through Wednesday]...
The short wave trough will lift from East Texas at 00Z Tuesday to
the Tennessee Valley by Tuesday morning. The attendant surface low
will lift from the coast of Louisiana to Kentucky during this time.
Forcing for ascent will increase overnight as the front lifts back
northward as a warm front. Low level dew points will remain around
70 across our Florida zones and increase back to the upper 60s
further north. A 40-55 knot low level jet will move into the central
Gulf Coast region and low level shear will increase. As storm
relative helicity increases, the threat for damaging wind and a few
tornadoes will build, especially during the pre-dawn hours. SPC has
increased the size of the slight risk area, expanding it to include
all areas from Tallahassee westward through 12Z Tuesday. A marginal
risk covers the remainder of the forecast area. The slight risk
shifts to include most of our Georgia and Florida Big Bend zones
from daybreak through midday Tuesday as temperatures soar into the
upper 70s. Drier air will quickly invade the forecast area ending
the severe threat in the afternoon. This front will bring cooler
temperatures to the region for Tuesday night and Wednesday, but they
will still be well above normal.
.LONG TERM [Wednesday Night Through Monday]...
A stronger cold front will push across the area late Thursday and
Thursday night with a brief light freeze possible across our
northwestern zones by Friday morning. Highs on Friday will only be
in the upper 40s to lower 50s and that will set the stage for a
longer-duration freeze Friday night. Lows by daybreak Saturday will
range from the mid 20s north to the upper 20s across our inland
Florida zones. Coastal areas will bottom out in the 30s.
Temperatures will then moderate over the weekend as high pressure
moves east of the area.
Southerly winds will increase this evening and overnight as low
pressure along the northwest Gulf Coast lifts rapidly to the north
of the local waters. Cautionary conditions are likely and advisory
conditions cannot be ruled out. Winds and seas will gradually
decrease on Tuesday as they shift to the west and eventually
northwest behind a cold front. A stronger cold front will sweep
across the waters on Thursday with offshore winds easily increasing
to advisory levels from Thursday night into Friday.
Other than low dispersion values today, there are no fire weather
concerns as a moist airmass and periods of rain are expected over
the next few days.
Radar estimates 3-4 inches of rain has fallen across portions of the
Florida Panhandle north of I-10 and into extreme Southeast Alabama.
Another couple of inches could fall in these areas with 3-4 inch
totals expected from this morning through Tuesday afternoon further
east across South Central Georgia to the central and western Big
Bend. The rainfall so far has been beneficial as it has fallen
across drought-stricken areas. We are seeing rises on some area
rivers, but with flows so low, flooding is not a concern at this
time. About the only exception would be the Shoal river which is
predicted to approach flood stage on Tuesday near Crestview.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 76 70 78 52 71 / 100 70 50 0 0
Panama City 76 69 73 54 66 / 100 60 40 0 0
Dothan 63 61 73 50 66 / 100 80 40 0 0
Albany 62 60 77 51 67 / 100 90 60 0 0
Valdosta 77 68 79 51 70 / 100 80 50 0 0
Cross City 78 69 78 53 72 / 80 60 50 0 0
Apalachicola 75 69 74 55 68 / 100 60 40 0 0