Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 230547

Area Forecast Discussion
National Weather Service Columbia SC
147 AM EDT Wed May 23 2018

The region will remain moist and unstable the next few days
between a ridge offshore and weak low pressure to the west.
Scattered to numerous showers and thunderstorms mainly during
the afternoon and evening expected over the next few days.


Current radar indicates convective activity over the CSRA
moving east. Will expect the activity to gradually dissipate as
it moves east into the central and southern Midlands. Lower
cloud cover expected to develop later tonight with diurnal
cooling, along with patchy fog mainly in areas where rain
occurred previously, depending on extent of lingering mid/upper
level cloud cover.

Otherwise, weak upper troughiness will remain over our forecast
area (FA), as upper trough digs some over the NE and Mid
Atlantic coast. Slow moving upper disturbance will remain near
the CSRA. Weak surface ridge axis to remain to our south and
east. Weak surface boundary to approach the FA from the north
late today into tonight. A moist atmosphere to remain over the
FA with PW values progged around 1.9 inches.

Will expect combination of diurnal heating and any convergence
along boundaries such as differential heating, old outflows, sea
breeze, etc to provide at least scattered convective coverage
to develop this afternoon. Latest high resolution models
generally indicate activity developing by 17/18Z and appearing
to favor the southern half of the FA. Some model discrepancy on
timing and impact of surface boundary approaching from the
north. This may act as an additional focusing mechanism for
convection for the northern FA late today into tonight.

Will accept model blend of chance to likely POPs. Weak to
moderate instability provides an isolated severe threat but main
threat will be locally heavy rain/flooding due to high
atmospheric moisture coupled with slow storm movement or any
merging/training cells provides a localized heavy rain/flooding

Used model blend on most weather elements.


Bermuda ridge remains anchored offshore of the Carolinas with
weak low pressure over Georgia. A frontal boundary appears to
become nearly stationary across North Carolina early in the
period. Air mass across SC/GA remains moist and unstable as
tropical moisture flux continues from the Florida peninsula.
Moisture appears to be a little deeper over the next couple of
days. With weak low level convergence across the area and
occasional weak upper level support from short wave troughs
associated with low pressure over Georgia, expect scattered to
numerous showers and thunderstorms mainly diurnally driven in
the afternoon and evening. Continued with persistence forecast
for temperatures. Max temperatures in the low to mid 80s and
lows in the upper 60s and near 70.


With weak upper low still off to the west of the area, a
southerly flow aloft will persist through the period. Generally
continued with diurnally driven showers/storms through the end
of the work week. Much uncertainty to the forecast entering the
weekend and into early next week although trending toward
increasing tropical moisture across the southeast and Gulf
coast regions. The medium range models trending toward possible
tropical low pressure development in the Gulf of Mexico. The 12z
GFS has trended west more in line with latest GEM. The bottom
line regardless of the evolution of low pressure development in
the Gulf of Mexico or Florida is a continued somewhat wet
pattern with mainly diurnally driven convection and near normal


Convective activity currently near DNL/AGS moving east.  Will
expect this activity to gradually dissipate as it moves east in
the near term, though recent radar loops indicate the activity
will impact CAE/CUB.

Otherwise, will expect lower cloud, and patchy fog, development
later tonight given a moist atmosphere and diurnal cooling.
Expect gradual diurnal improvement by late morning to midday.

Diurnal heating and a moist atmosphere expected to provide at
least scattered convective coverage this afternoon/evening.
Latest high resolution models generally indicate activity
developing by 17/18Z, and appearing to favor the southern FA.
For now, will handle with VCSH/TS and tempo SHRA.

EXTENDED AVIATION OUTLOOK...Late night and early morning IFR to
MVFR ceilings and visibilities along with mainly diurnal showers
and thunderstorms through Sunday as a very moist air mass
remains over the region.




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