Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 230133

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

A low pressure system over the lower MS River Valley will
slowly lift northeast spreading widespread rainfall across the
area through Monday night. This storm system will finally move
out of the area Wednesday.


Low pressure will be moving through the Gulf Coast states.
Low-level winds will continue pushing both Gulf and Atlantic
moisture into the forecast area overnight. Pwat values area
already over an inch across the entire cwa, and those values
will continue to increase through the night.

Initial rainfall has been scattered and relatively light.
However as the night progresses, coverage will continue to
increase across the region as additional rainfall moves in from
the west. Expecting mostly categorical pops by morning across
the CSRA and Central Midlands, with likely pops across the
Northern Midlands.

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, lows
tonight will be in the mid 50s north to around 60 south.


Vertically stacked cyclone centered over western TN Monday will
slowly move eastward reaching central TN by 12Z Tuesday.
Primary surface low associated with this system will remain
beneath the upper cyclone but a secondary low at the triple
point will move across GA and into SC on Tuesday.

Strong isentropic ascent will result in significant rainfall
Monday into Monday night. Models also indicating more
instability from the central Midlands on south with capes around
2500 J/kg and lifted indices of minus 2C to minus 4C. Could see
isolated storms during the afternoon capable of damaging gusts
and perhaps marginally severe hail.

Pwat amounts expected 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.
There still exist the 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.

Kept highs on Monday on the cool side of guidance...ranging from
the lower 60s north to lower 70s south. Lows Monday night will
range from the upper 50s to lower 60s. Warmer readings in the
70s expected Tuesday.


Broad upper troughing will remain over the eastern CONUS through
next weekend.

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.

Have based the extended forecast primarily on the GFS model...
indicating a moisture limited front crossing the region Friday
and dry surface high pressure building next weekend. Should see
highs in the 70s with overnight lows in the upper 40s to lower


VFR conditions still expected through portions of tonight, then
ceilings begin lowering after Midnight as moisture advection
develops ahead of warm front.

A low pressure system is approaching from the west. Ceilings
expected to continue to lower tonight and should be at least
MVFR by sunrise Monday morning. Light showers are currently
spreading into the region from south to north. Southeast winds
are generally light, but are expected to become gusty as heavier
rain moves in in the morning. LLWS is also possible beginning
early morning, and could last through much of the day. Rain will
continue through the day Monday with MVFR and probably IFR
cigs. Visibility restrictions are also likely in heavier rain.
Additionally, cannot rule possible isolated thunder during the
day Monday, but confidence is too low to mention in the TAFs at
this time.

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




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