Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 200547

Area Forecast Discussion
National Weather Service Columbia SC
147 AM EDT Thu Apr 20 2017

A weak frontal boundary will weaken dissipate as it lifts north
overnight. Warmer temperatures return on Thursday ahead of an
approaching cold front. The cold front will stall across
central NC on Friday and Saturday with a strong cold front
moving into the Midlands on Sunday.


Afternoon convection has waned and the radar is generally clear
late this evening. Hi-res model data indicates little if any
additional convection expected overnight. Abundant low level
moisture in place and only scattered clouds will support
radiational cooling and likely support some fog formation with
no low level jet forecast. Expect low level stratus to develop
once again which may cut down on the potential for dense fog.
High dewpoints in the lower 60s currently will prevent
temperatures from dropping too far and expect overnight lows in
the lower 60s.


Thursday will bring a return to warmer temperatures and more
widespread dry conditions as the old frontal boundary moves
back north of the cwa. A weak upper ridge will build over the
region on Thursday helping to limit any shower/storm
development. Best rain chances should remain closer to the
mountains in the upstate, along the sea-breeze closer to the
coast, and north of the cwa closer to the old front. Dry
conditions will continue Thursday night.

On Friday, any boundaries east of the Appalachians will be
diffuse and hard to identify. The main surface cold front will
be west of the mountains through the day. Best chance for
rainfall through the afternoon hours will be closer to the
mountains in the upstate. Instability remains weak to moderate
with due to the warm temperatures, and can not rule out an
isolated shower or storm across the western cwa during the
afternoon hours. Most activity will dissipate by sunset.

For Saturday, the models have trended drier ahead of the next
approaching cold front. There should be a warm front situated
just off to the north of the cwa early Saturday morning, with
the main surface cold front well west of the area back towards
the Mississippi river valley. The main upper trough that is
expected to be cutting off west of the area will still be moving
southeastward out of the central plains through the day. Upper
flow over the cwa will be out of the southwest, with some weak
ridging still being indicated by the longer term models. This
should limit any widespread rainfall event on Saturday, with the
best rainfall off to the north of the cwa along the warm front.
Saturday night will see the upper trough and surface cold front continue
to push eastward, with the best rain chances through the night
across the western and northern counties.


The main upper trough axis will be pushing east of the
Mississippi river valley on Sunday morning, with the surface low
trying to get organized along the central Appalachians. A cold
front should be across portions of western Georgia and Florida
Panhandle, with a warm front draped across central North
Carolina. This puts the cwa in the warm sector the this system
early in the day Sunday. Models indicating moderate instability
across the area during the day ahead of the cold front. PWAT
values above 1.5 inches. Expecting to see shower and
thunderstorm development during the morning ahead of the cold
front, with a few strong storms being possible by the afternoon.
Heavy rainfall may be possible in the slower storms. The cold
front will be pushing through the cwa Sunday night, with the
main front then being along the coast early Monday morning. The
upper trough passes through the region during the day Monday,
with the cutoff portion of the low passing well south of the
area across northern Florida. For now will hold onto slight
chance to chance pops on Monday associated with the upper
trough moving through. Drier air then returns from Monday night
through Wednesday. Temperatures will be above normal Sunday
with near normal Monday and Tuesday. Readings back above normal
by the middle of the week.


Shallow low-level moisture/light winds and diurnal cooling may
lead to the development of fog toward morning. Latest HRRR and
LAMP Guidance suggesting fog and stratus will spread inland from
the coast during the early morning hours. The latest
observations shows fog developing in the coastal plain and in
the CSRA. Lowered visibility from previous forecast based on
trends and indicated period of IFR ceilings toward
morning...LIFR at AGS visibility. Return to VFR by late morning
with scattered to broken cumulus through the day.

EXTENDED AVIATION OUTLOOK...Patchy fog/low clouds and associated
restrictions probable each morning. Thunderstorms, possibly
severe, Sunday afternoon/evening.




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