Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 221728
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
128 PM EDT Sun Apr 22 2018

.SYNOPSIS...
High pressure continues to slide through the New England states
as low pressure moves into the western Gulf Coast states. The
low will move toward the forecast area today pushing Atlantic
and Gulf moisture into the area. Tonight the low pressure will
move into the central Gulf States then slowly move eastward,
finally crossing the forecast area Tuesday night. This will
result in widespread rainfall this evening through Tuesday with
unsettled weather through Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure will remain well north of the forecast area today
and tonight as low pressure moves eastward through the Gulf
Coast states. As the low moves eastward through the day Atlantic
and Gulf moisture will overspread the region with increasing
chances of showers. Current WSR-88D returns indicate some light
rain developing over central and eastern GA and expect
scattered rain to move into the CSRA this afternoon and
spreading into the southern Midlands later in the afternoon.
Rain will slowly work northward through the day however is not
expected to begin in the northern Midlands and Pee Dee until
this evening. Overnight easterly winds will continue pushing
moisture into the forecast area with pwat values increasing to
over an inch and rain becoming likely across the entire area.
Rainfall amounts through tonight will range from one quarter
inch or less in the northern Midlands to around an inch in the
northern CSRA. With increasing clouds and rain today afternoon
high temperatures will be in the low 70s with lows tonight in
the low 50s north to around 60 south.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Low pressure will continue moving eastward along the southern
boundary of TN with isentropic ascent increasing over the
forecast area. This will result in rainfall increasing with
potential for significant amounts Monday and Monday night. On
Tuesday and Tuesday night models have made some adjustments to
the track of the low with the current track expected along the
western side of the Appalachians. This will result in slightly
drier air over the area Tuesday and Tuesday night. Pwat amounts
expected continue between 1.5 and 1.75 inches which is nearly
double seasonal normals and will create potential for moderate
to heavy rainfall. Rainfall amounts through Tuesday night are
currently expected mainly between 2 and 2.5 inches. Along with
the shift in the low movement models have also increased
instability for Monday and Tuesday. Instability will be weak and
best instability does not occur with the best shear so
confidence in coverage of thunderstorms is low...however there
is potential for a few thunderstorms. Secondary concern will be
on potential for flooding due to rainfall across the area as
well as heavier amounts in the Upstate. Will continue to monitor
and expect significant rises in lake and river levels from
Monday through much of the week.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Upper level trough will remain over the eastern US through the
long term with unsettled weather for the forecast area. While
the low pressure tracks northward away from the area Wednesday
the next upper level disturbance will drop through the lower MS
River Valley. Models differ with the progression of this feature
with the GFS aggressively pushing the feature eastward with the
ECMWF takes a weaker approach. Both models indicate moisture
will remain over the area with low chances of rain Wednesday and
Thursday. Confidence in models remains low beyond Thursday as
models differ with handling of the systems through the weekend
with the GFS developing a significant upper level low over the
Great Lakes and the ECMWF maintaining the remains of a frontal
boundary over the region. Have made few changes to the forecast
beyond Thursday due to low confidence. Temperatures through the
long term will be near normal.

&&

.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
VFR conditions expected through today. Ceilings lowering this
evening as moisture advection develops ahead of warm front.

Pressure ridge extending into the region from the Mid Atlantic
region. Ceilings expected to slowly lower today but remain VFR.
MVFR ceilings more likely by early evening as low level
moisture flux/warm advection increases and showers spread into
the region from south to north. Southeast winds will increase
later today, becoming gusty in the evening with the arrival of
precipitation. LLWS possible early Monday morning. Periods of
rain will continue after sunrise Monday with MVFR cigs. Cannot
rule possible isolated thunder during the day Monday but
confidence is too low to mention in the TAFs at this time.

.EXTENDED AVIATION OUTLOOK...
Widespread showers, possibly heavy, and associated restrictions
Monday/Monday night, with thunderstorms possible. Conditions
improving by Tuesday afternoon.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.

&&

$$



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