Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 241008
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
608 AM EDT Wed May 24 2017

.SYNOPSIS...
Several waves of low pressure moving along a frontal boundary
stalled near the forecast area will bring periods of showers and
thunderstorms to the region through tonight. A cold front will
finally be moving east of the region Wednesday night, with drier
and cooler air taking hold by the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early morning analysis reveals surface low pressure over
southern Indiana with a cold front extending southwestward
through the Tennessee Valley to the western Gulf coast. Another
weaker nearly stationary boundary was located near the forecast
area but is subtle and diffuse. Sounding analysis indicates the
mid levels have dried a bit since Tuesday afternoon but abundant
low level moisture remains in place. Regional radar showing some
scattered convection lifting northeastward from central Georgia
into the forecast area ahead of a weak northeastward lifting
shortwave trough.

Expect scattered convection to continue lifting into the
forecast area through the early morning hours but then may see a
bit of a lull for a few hours in the wake of the passing
shortwave. More widespread convection is expected this afternoon
and evening as another surge of deep moisture moves over the
area with backed south to southeasterly low level flow in
response to deepening surface low pressure over the
Tennessee/Ohio Valleys. Precipitable water values will push back
up close to 1.75 inches and warm layer cloud depth will be
greater than 10kft supporting efficient rain processes and
continuing the flood threat. Therefore will continue to carry
the Flash Flood Watch already in effect through 8pm tonight.

Severe weather is also possible with strengthening mid level
flow and the nose of a 130 knot upper jet pushing into the
region during peak heating this afternoon. Diffluent 500mb flow
will also provide large scale lift combined with moderate to
strong instability leading to possible damaging wind and hail
threat, and tornadoes cannot be ruled out although that risk is
lower. Expect convection to develop over central GA and spread
northeastward into the forecast area this afternoon and continue
through the evening until a cold front off to the west pushes
into the region and shifts the deeper moisture to the east
overnight. SPC has expanded the slight risk area to encompass
all of the Carolinas and most of Georgia into Florida and MOS
guidance severe pops are quite high, over 50 percent.

Will carry categorical pops across most of the area
this afternoon into early evening with pops decreasing overnight
from southwest to northeast behind the front. Temperatures today
will be highly dependent on cloud cover and therefore confidence
is low but think the eastern Midlands could see some temps
around 80 to lower 80s while the remainder of the region remains
in the 70s. Overnight lows tonight will be dictated by cool
advection behind the front and we should see lows ranging from
the upper 50s western Midlands and upper CSRA to lower 60s
eastern Midlands.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
The upper trough axis will swing through the forecast area on
Thursday with a pocket of very cold 500mb temperatures at -20C
which is quite cold for late May. Expect the cold temperatures
aloft will result in scattered showers with steep mid level
lapse rates and could even see a bit of graupel with some of the
stronger cells. By late afternoon the cold pool will have
shifted east of the forecast area and precipitation chances
should diminish along with cooler, drier air building into the
region. Highs on Thursday will be limited by cloud cover and
weak cool advection. Overnight lows Thursday night will fall
into the 50s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Dry and fair weather expected to close out the week with surface
high pressure building over the area with generally zonal
westerly or northwesterly flow at 500mb. Temperatures will be
slightly below normal on Friday in the lower 80s but will
quickly warm back above normal on Sat/Sun with southerly flow
returning and weak upper ridging building over the area.

The next weather system will impact the forecast area on Sun/Mon
as a deep trough dives southeastward into the middle of the
country and 500mb flow veers to the southwest allowing moisture
to increase again over the area. The combination of weak
shortwave energy and increasing moisture will warrant small
chance pops Sunday into Monday.

&&

.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
Widespread stratus in place, with IFR CIGs. Will expect IFR CIGs to
continue into mid morning, then a gradual diurnal CIG improvement
during the day. Otherwise, main focus will then shift to shower and
scattered thunderstorm activity this afternoon and early evening,
some possibly severe. Bulk of moisture to shift out of the region
tonight, with drier air filtering in along with some wind expected
to preclude restrictions.

EXTENDED AVIATION OUTLOOK...Scattered showers and a few
thunderstorms possible Thursday afternoon, mainly north. Breezy
conditions expected Thu.

&&

.HYDROLOGY...
Significant rainfall over the past few days has resulted in
runoff into the mainstem rivers. Additional rainfall is expected
today and tonight, therefore over the next several days we will
see rises in rivers and streams across the area which could
result in river flooding. Additional rainfall and flood
potential will continue to be closely monitored.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...Flash Flood Watch through this evening for GAZ040-063>065-077.
SC...Flash Flood Watch through this evening for SCZ015-016-018-
     020>022-025>031-035>038-041.

&&

$$


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