Special Weather Statement, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
133 PM EDT Mon Apr 8 2019

.SYNOPSIS...
An upper trough, surface front, and sufficient moisture will
promote thunderstorms, possibly severe, this afternoon into the
evening. The main surface low will move into the forecast area
Tuesday bringing another threat of severe thunderstorms in the
afternoon. Drier air with fair weather expected Wednesday into
Thursday. Increasing moisture and a weak surface boundary will
provide a chance of showers and possibly thunderstorms Friday
and Saturday with a better chance on Sunday. Above normal temps
through most of the period.

&&

.NEAR TERM /THROUGH TONIGHT/...
The main concern is a threat of severe thunderstorms this
afternoon and tonight. Convective line at 17z seen developing
on radar in central Ga moving northeast toward the CSRA...The
HRRR and other high resolution models have been consistent with
intensification of this convective line as it approaches the
CSRA/AGS area around 20z. The models indicate enough
instability and shear for organized thunderstorms with a
potential for damaging wind and hail...

At the moment (17z)...Slightly drier air has mixed down across
central SC and the CSRA early this afternoon with general
downward vertical motion behind departing short wave trough
earlier. Temperatures have risen into the low to mid 80s. Meso-
analysis indicating enhance DCAPE along the SAV river.
Satellite also showing cloud streets across the area and winds
have been gusty near 20 mph. Air mass is becoming moderately
unstable with CAPE near 1000 J/kg and LI around -5. Deep layer
shear is relatively strong...strongest to the north and west
across the Upstate and North Carolina. Low level moisture
advection will increase this afternoon ahead of upper trough
around ridge offshore. It will be relatively cold aloft with h5
temperatures around -12C. The models indicate further cooling
mainly late tonight to -13 to
-14 C as the upper trough gets closer. The greatest coverage
expected late this afternoon and early evening with an increased
h85 jet and a time near maximum heating.

There may also be increased convective coverage again late
tonight with lowering h5 temperatures but nocturnal timing and
possibly widespread previous convection diminishes confidence.
However, raised pops after midnight based on latest Blended
guidance. Min Temperatures overnight in the 60s.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
The threat of severe weather continues Tuesday as the main
surface low moves across the forecast area.

An upper level low will move across the Southeast on Tuesday. The
surface low will move into the forecast area in the late afternoon
or evening with a cold front trailing to the south. Sufficient
moisture coupled with indications of moderate instability and shear
leads to some severe concerns. Cold air aloft, along with some mid
level dry air will lead to high DCAPE values and low wet bulb
zero heights. This increases the threat of large hail and strong
downburst winds. Instability may be hampered some by cloud
cover and some shower activity early in the day. Long awaited
drier air will finally enter the region late Tuesday night
behind the front.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
There will be a brief period of warm, dry weather on Wednesday and
Thursday. Fair weather Wednesday with weak surface high pressure
building into the Mid Atlantic, and upper ridge shifting overhead.
The surface high and upper ridge axis will shift to our east by
Thursday allowing southerly low level flow to develop. This pattern
supports a warming trend into the weekend. A weak surface boundary
will move into the Southeast Friday and linger in the vicinity
through Saturday. This along with sufficient moisture and some weak
upper impulses may provide a chance of showers and possibly thunderstorms
Fri/Sat. The best chance for rain/thunder appears to be Sunday
or Sunday night. There is potential for severe weather with the
Sunday system.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Some drier air has mixed down across the area early this
afternoon and satellite showing just scattered cumulus streets
at the moment. Deeper moisture southwest of the area will be
advecting into the region late this afternoon and evening.
Southwest winds 10 to 15 knots with gusts to 20 knots through
the afternoon and early evening then diminishing winds. Line of
convection on radar over central Ga. moving northeast toward
the CSRA. High resolution models have been consistent moving
this convection through the area between 20z- 23z. Elevated risk
of severe thunderstorms near terminals as air mass moderately
unstable, strong low level jet around or > 30 kts and relatively
strong 0-1km shear. Broken cumulus expected with brief MVFR or
IFR conditions due to heavy rain and lower ceilings.

Additional convection possible late tonight but confidence low.
Due expect stratus resulting in IFR or LIFR toward morning with
slow improvement after 12z.

For the AGS and DNL terminals... High confidence for
thunderstorms moving through the area around 20z. Potential for
damaging winds gusts. expect at least 30kt southwest wind as
convection moves through. Brief ceiling and visibility
restrictions. More widespread IFR or LIFR conditions developing
after midnight as stratus develops across the area.

EXTENDED AVIATION OUTLOOK...A frontal system in the area will
bring numerous showers and thunderstorms through Tuesday. There
will also be periods of widespread stratus and fog through
Tuesday.

&&

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

&&

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