Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 201502
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1002 AM EST Sat Dec 20 2014
.Near Term [Through Today]...
The morning analysis shows a weakening upper trough passing just
north of the area and a stationary frontal boundary just offshore
of the northern Gulf coast. We are on the cool side of this
boundary with northeast flow, cloudy skies, and areas of light
rain. Forcing for light rain will continue to decrease through the
day today with coverage diminishing. Even with the rain
decreasing, clouds will likely persist through the day, especially
across western areas, resulting in cool high temperatures ranging
from the upper 50s in southeast Alabama to the upper 60s in the SE
Florida Big Bend.
.Prev Discussion [428 AM EST]...
.Short Term [Tonight Through Monday]...
The aforementioned surface low, separated from its mid-level
counterpart, will meander slowly into our northeast Gulf waters
overnight. Surface high pressure will strengthen over the eastern
half of the country in the wake of a passing shortwave. This will
set up a weak CAD pattern with low-level cool air spilling into
the Tri-State region from the northeast. Although the approaching
surface low will be weak, the southerly low-layer flow will glide
over a cool near-surface dome generated primarily by the cool
shelf waters along the northeast Gulf coast. This rain will
gradually spread inland through the night, initially impacting the
Florida Big Bend region. Through the first part of the day on
Sunday, rain will spread north into south Georgia as the
aforementioned wedge of cool air keeps isentropic surfaces sloped
in the lowest layers. Late Sunday afternoon, into Sunday night a
shortwave will roll into the Southeast and link up with the
ongoing low-level forcing to create a period of more widespread
heavy rainfall. As the shortwave moves into the Mid-Atlantic on
Monday, it will pull the surface low through north-central Florida
focusing much of the heavier rain in this region on Monday. In its
wake, the cold wedge will strengthen once again with another round
of low-level isentropic rain is expected late Monday afternoon
through Monday night.
.Long Term [Monday Night Through Saturday]...
Although rain will continue throughout the night Monday into
Tuesday morning, a strong low pressure system moving through the
Plains into the Mississippi Valley will weaken the cool wedge of
high pressure and allow for the more "tropical" airmass to spread
inland on Tuesday. Dewpoints are forecast to surge into the middle
60s, with PWATs between 1.5"-2" (>+2 sigma) accompanying. When the
upper-level low pressure links up with the low-level forcing on
Tuesday afternoon the potential for some very heavy rainfall will
exist. Furthermore, the strong low and mid level wind fields
generated by the prolonged stratiform rain will combine with a
destabilizing airmass on Tuesday afternoon to yield the potential
for some strong to severe thunderstorms as well. Confidence in
severe weather remains low at this time, but should be monitored
closely over the next few days.
Finally, on Wednesday we`ll clear out the rain and the clouds and
usher in a burst of cold air for Christmas Eve. At this time,
temperatures appear as though they`ll be a few degrees below
average, in the middle 30s area-wide. Near average to slightly
below afternoon highs and overnight lows are expected to finish
[Through 12Z Sunday]
Conditions will gradually change to MVFR at ECP/ABY/DHN overnight
along with periods of light rain. Ceilings may lower to IFR at DHN
before sunrise. Expect a period of MVFR conditions to last until
early afternoon at these sites when all terminals should return to
VFR. After 00z Sunday, a large area of at least MVFR ceilings will
move back in from the east affecting all terminals.
Easterly winds will near cautionary levels this afternoon,
primarily west of Apalachicola. Thereafter, sub-headline easterly
winds will continue through the weekend before veering southerly
on Monday ahead of an approaching low pressure system. A strong
cold front will increase winds to advisory levels beginning
Tuesday night, with an increase to Gale conditions possible on
Wednesday. By Thursday, winds will fall to below headline levels
once again with seas lagging about 12 hours behind.
Moist conditions through at least Wednesday will prevent any red
flag criteria from being met.
Rain will continue on-and-off for the next several days. A couple
rounds of heavy rain will be possible Sunday night and Tuesday, with
the heaviest expected on Tuesday. 7-day rainfall totals range from
3 inches across southeast Alabama to 5 inches across the southeast
Big Bend of Florida. These totals are expected to be widespread
averages, with isolated higher amounts possible. The potential for
river flooding exists primarily early next week when the heaviest
rain will fall on well primed basins.
.Preliminary Point Temps/PoPs...
Tallahassee 65 54 60 56 67 / 30 30 70 90 50
Panama City 63 56 61 58 68 / 40 30 80 100 50
Dothan 57 47 57 53 64 / 100 20 60 80 40
Albany 59 47 57 51 62 / 90 20 60 80 50
Valdosta 65 52 60 56 67 / 20 30 70 90 70
Cross City 70 58 66 61 67 / 20 40 70 90 70
Apalachicola 66 58 63 61 69 / 20 40 80 100 50