FXUS62 KCAE 240101
Area Forecast Discussion
National Weather Service Columbia SC
901 PM 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.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Showers have begun diminishing with loss of heating with a few
cells developing along intersecting outflow boundaries.
Overnight a boundary currently generating thunderstorms across
central NC will drift southward and into the forecast area.
Expect some showers and possibly a thunderstorm to develop
overnight along the boundary as well as the southern CSRA where
outflows will persist from current convection. Other concern
will again be potential for early morning fog. Have included
patchy fog in the forecast as uncertainty remains with the
boundary moving into the northern Midlands and outflow in the
southern Midlands and CSRA. Overnight lows will be around 70.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
A weak front and drier air aloft will move into the forecast area
(FA) from the north Thursday. Deep, moist flow from the SE and
surface-based forcing along the boundary will result in moderate
instability and trigger showers and thunderstorms in the afternoon.
Expect slow storm movement given weak mean wind speeds, increasing
the threat for localized heavy rainfall and flooding. Particularly
in areas that have already received heavy rainfall in the past few
days. Small hail will also be possible with drier mid level air
impinging from the north. Max temperatures will be in in the low to
mid 80s and lows in the upper 60s and near 70.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A moist airmass will remain over the region, with similar conditions
as previous few days. Convection will mainly be diurnally driven
through Saturday with moderate rain from scattered showers and
thunderstorms likely each afternoon. Sunday through Wednesday,
models are in good agreement that there will be a 500 mb trough to
the west, driving a tropical plume of moisture into the Southeast.
PWAT values in the GFS and ECMWF are well above normal or near
record during the time period. There is at least a high chance of
moderate rainfall during the period with heavy rainfall possible at
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
The moist air mass will remain through the TAF period. The high
moisture combined with nocturnal cooling and convergence
associated with a weak front sinking southward should result in
widespread IFR development tonight as indicated by most of the
guidance. Followed the GFS LAMP for the timing. The high
moisture and convergence may help support showers or thunderstorms
overnight but expect little coverage because of nocturnal
cooling. The HRRR displayed little coverage. The chance was too
low to include in the terminal forecasts. The front in the
region will slow improvement Thursday morning but expect diurnal
heating and mixing will eventually lead to MVFR conditions
later in the morning. Heating combined with high moisture and
the front in the region should result in widespread showers and
scattered thunderstorms later during the day and expect mainly
MVFR conditions as indicated by the NAM MOS. IFR conditions will
likely occur at times in heavy showers and possible thunderstorms.
However, did not include the more pessimistic conditions in the
terminal forecasts at this time because of timing uncertainty.
EXTENDED AVIATION OUTLOOK...Late night and early morning IFR to
MVFR ceilings and visibilities along with mainly diurnal
showers and thunderstorms through early next week as a very
moist air mass remains over the region.
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