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FXUS62 KCAE 230549
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
Issued by National Weather Service Greenville-Spartanburg SC
1249 AM EST Wed Jan 23 2019

.SYNOPSIS...
Moisture will increase tonight and Wednesday as winds veer from east
to south on the backside of surface high off the east coast. There
will be increased cloudiness and spotty areas of light rain late
tonight and Wednesday. A cold front will approach from the west late
Wednesday and will move across the region early on Thursday. Dry and
fair conditions will prevail behind the front Thursday and Friday.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1240 am Wednesday...Only noticeable change to the going
forecast was to push back pop onset a few hours, per obs and
hi-res model guidance. A lowering cloud deck has moved in from
the south as mid to low-level moisture increases through the
overnight hours.

Otherwise...Winds become more southerly today and a moist warm
front moves northward across the CWA. Increased moisture has
dewpoints rising back up into the upper 40s today, and will
bring a chance for light showers this morning, with a possible
lull in scattered, light showers this afternoon prior to main
brunt of advancing cold front that brings more rain tonight.

Warm front brings with it some chance for freezing precipitation in
the very early morning hours in any areas with surface
temperatures cold enough. This looks limited at this time.
Currently have a slight chance for -ZR in Northern Lancaster
County from 7 to 10 Zulu. Depending onprecise minimum surface
temperature, there is some chance for a sprinkle or two of
freezing rain or drizzle along the northern edge of the CWA for
a few hours around the early morning time of minimum
temperature. This might warrant a Special Weather Statement
should it look like it will become a reality. Warm nose is
pretty strong, so that snow is unlikely and precipitation will
be either rain or freezing rain, with rain predominate in most
places. QPF amounts are also very light, with .01 to .02 inches
of -ZR maximum in the few locations that might see some.

Aside from rain chances, today's highs will warm significantly,
thanks to the warm front, back into the low to upper 60s.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
Active weather will be ongoing at the start of the period as a cold
front moves in from the west Wednesday night. Strong deep layer
forcing is expected as a deep trough and strong short wave move over
the area driving the cold front. Good low level isentropic lift and
upper divergence expected as well. This will lead to increasing
shower coverage Wednesday evening and widespread coverage after
midnight. Some weak elevated instability is possible late Wednesday
night or early Thursday morning. However, lapse rates are shallow so
thunderstorm threat is minimal and have left out of the forecast for
now. That said, with the deep forcing and moisture, precip rates
will be high with heavy rainfall possible. With the quick movement
of this system, widespread flood threat is low, but given antecedent
conditions and upstream rainfall, river flooding may continue or
return. Very gusty winds are also expected ahead of the front and
behind it on Thursday. Showers quickly diminish through the day
Thursday as the front moves east with clearing for the afternoon.
Lows Wednesday night will be up to 20 degrees above normal while
highs Thursday will be up to 5 degrees above normal, but cooling a
little faster than normal diurnal trend during the afternoon.

A deep, broad upper trough remains over the eastern CONUS through
Friday. A series of weak short waves move through the trough and
across the area. These waves push a dry secondary cold front across
the area Friday. Winds will pick back up a little with this front,
but much lower than on Thursday. Lows Thursday night will be near
normal with highs Friday nearly 5 degrees below normal.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Guidance remains in good agreement during much of the medium range
forecast. The broad, deep upper trough remains over the eastern
CONUS through much of the period. The guidance continues to show
little to no phasing over the northern and southern stream short
waves moving through the trough Saturday night and Sunday with the
southern stream short wave remaining well south into the Gulf of
Mexico and Florida on Monday. At the surface, this means yet another
dry cold front for Sunday with the surface low over the Gulf also
remaining well south of the area. This means a dry forecast with
highs around 5 degrees below normal for Saturday slowly rising to
near normal by Monday. Lows follow a similar trend.

For Tuesday, better phasing is progged for new northern and southern
stream short waves dropping through the trough and into the area by
late in the day. The associated cold front moves in late the day,
but the guidance disagrees on the amount and strength of the
moisture return ahead of the front. Therefore, will limit PoP to
slight chance for now as this has the potential to change as the
event moves closer in time. Lows Tuesday will be a little above
normal with highs near normal.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Low cloud deck has settled in across much of SC, with all TAF
sites now featuring MVFR cigs and slowly dropping. As the
moisture continues to increase overnight, ceilings will keep
falling into the lower part of the MVFR range in the early
morning hours. Guidance still indicates that cigs will drop
down into IFR range before the start of operations on this morning
and that was kept in the fcst, as well as slight drops to MVFR
vis as light showers develop. Once established, IFR cigs will
likely be slow to improve and will probably take the passage of
a weak warm front in the mid/late afternoon to see some
improvement from S to N. LLWS could also be a
problem with the models forecasting winds in excess of 50 knots
as low as 2K feet near the front, so have a mention of LLWS at
all TAF sites. Some scattered light showers, along with reduced
ceilings and visibility, are expected to persist during the day
today with a brief lull possible in the late afternoon before
the larger slug of deeper moisture and substantial rain arrive
tonight. Wind should come around quickly and increase from the
SSE to S with the warm frontal passage, and cigs should improve
to at least MVFR before potentially falling to IFR again once
the heavier precip starts.

EXTENDED AVIATION OUTLOOK...

Late tonight/early Thursday AM as the front moves through,
expect IFR conditions in clouds/rain. Thursday conditions will
be improving from west to east as the front moves away, with VFR
conditions likely at all terminals by some time during the
afternoon. VFR conditions are then expected to continue into the
weekend.

&&

.HYDROLOGY...
Minor flooding will continue on the Congaree River due to recent
rainfall and upstream reservoir releases within the Broad and
Saluda River basins.

&&

.EQUIPMENT...
The Columbia, SC (KCAE) WSR-88D is out of service due to a
faulty voltage regulator. The part will be ordered but an
estimated time of arrival is unknown at this time.

&&

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

&&

$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
HYDROLOGY...
EQUIPMENT...
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