Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 222143
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
543 PM EDT Mon May 22 2017

.SYNOPSIS...
A frontal boundary will stall near the forecast area through
Tuesday, with showers and thunderstorms likely in advance of the
front. The cold front will finally be moving east of the region
by Thursday, with drier and cooler air taking hold for the end
of the week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Showers and thunderstorms continue to move through the area
with additional cells across eastern and central GA. Main threat
from thunderstorms remains heavy rainfall. Portions of the area
have seen around 2 inches of rain so far today in addition to
rains yesterday and last night. With the locally heavy rainfall
continuing the ground to become saturated and result in ponding
of water in low lying and flood prone areas. Rainfall rates of 2
inches per hour via radar have been noted across the forecast
area today with some locally higher rates around 3 inches per
hour.

PWAT values will remain around 2 inches overnight allowing for
widespread moderate rain, with locally heavy rain possible.
Several Flash Flood Warnings and Advisories have already been
issued and with heavy rain can be expected through the night the
Flash Flood Watch will remain in effect for the entire area
through Wednesday night.

Overnight lows will generally be in the upper 60s to around 70s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Flash flood watch posted due to increased threat for heavy rain
associated with stalled frontal boundary and anomalously high
precipitable water. There is also a marginal risk of severe
thunderstorms especially in the south Midlands and CSRA
associated with strengthening low level jet 40 to 50 kts early
in the day and possible weak meso-low tracking northeast along
the front through the afternoon...

Upper trough over the upper Midwest diving southeast into the
lower Mississippi valley during the period. Several short wave
troughs will rotate through the base of the trough and track
northeast into the Carolinas and Georgia. The surface frontal
boundary will move into central SC and east central Georgia
early Tuesday. The models appear to suggest a surge of moisture
early in the day with precipitable water near 2 inches. Short
wave trough moving through the area along with a weak surface
low/meso low should lead to numerous showers and a few
thunderstorms in the morning through early afternoon. A few of
these storms may be severe...especially south of the front in
the south Midlands and CSRA. Concern with enhanced 0-1 km SR
Helicity southeast through the afternoon. But the main threat
remains heavy rain due to training of storms near stalled front.
WPC has region in slight risk of excessive rainfall. There may
be a lull late in the day as stronger short waves move to the
north and east. However...air mass will be moderately unstable
and front remains in the area focusing low level convergence.
The front may move north to near the SC/NC border during the
overnight and the rain may diminish somewhat as short waves move
to the northeast...but air mass remains moist and unstable.

Another surge of moisture on Wednesday ahead of cold front and
the flash flood threat continues along with marginal severe
weather threat. Mos guidance consensus used for temperatures.

QPF amounts through Wednesday night of 2.5 to 3 inches with
locally higher amounts.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The front should be east of the area Thursday, but with cold
temperatures aloft the area may still see isolated showers
through the afternoon. Drier and cooler air should then spread
over the region for the end of the week but warming again by
weekend. A front to the north may move south into the area late
in the weekend resulting in isolated afternoon convection.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
Restrictions expected to dominate the TAF period.

Showers and thunderstorms to continue move through the terminals
with additional cells developing across eastern and central GA.
Main concern is heavy rainfall...which will be possible through
Wednesday. With localized rainfall thus far nearing 2 inches the
ground is becoming saturated and resulting in water not draining
from paved surfaces quickly. Convection expected to continue
overnight which will result in further runoff issues.
Restrictions will dominate the period with mainly MVFR...and high
end IFR at times in moderate to heavy rain. Winds will be
southerly at 9 knots or less with gusty and erratic winds around
thunderstorms.

EXTENDED AVIATION OUTLOOK...Restrictions expected in scattered
to widespread convection Tuesday through Thursday.

&&

.HYDROLOGY...
Showers and thunderstorms continue producing heavy rain across
the area with localized flooding...mainly in urban areas at this
point. Heavy rain potential will continue over the next couple
of days and with ground becoming more saturated potential for
flooding will increase. With heavy rain also across the Upstate
will also see rises in rivers and stream during the next 24-36
hrs with moderate rises expected on the area rivers. This may
lead to river flooding and will be monitored closely.

&&

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

&&

$$


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