Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 280848

Area Forecast Discussion
National Weather Service Columbia SC
448 AM EDT Fri Apr 28 2017

High pressure will ridge in from the Atlantic bringing fair and
warm conditions today through Sunday. The next cold front with
increasing chances of showers and thunderstorms will arrive
Monday. Generally fair with seasonal temperatures expected
Tuesday and Wednesday. Another significant weather system will
affect the region next Thursday.


Evening convection has diminished with the loss of daytime
heating and atmospheric stabilization. The weak front that was
approaching the region remains west of the forecast area and
likely will stall out before reaching the Midlands and become

Upper ridge over the eastern Gulf of mexico will build
northward over the southeastern states today with significant
500mb height rises. 850mb temperatures will also warm
significantly resulting in max temperatures about 2 categories
higher than yesterday in the upper 80s to around 90 degrees.
Dewpoints will be well into the 60s today and tonight making it
feel more like summer than spring. Well above normal
temperatures with highs 10-15 degrees above normal and lows in
the upper 60s to lower 70s, nearly 15-20 degrees above normal.
Low temperatures may be warm enough to tie or break the record
warmest minimum temperature.

Latest models and forecast soundings suggest moderate to strong
instability with CAPE values over 3000 J/kg and Lifted Index
values around -7C to -8C. However, little confidence that this
instability will be realized due to building upper ridge
resulting in significant warming aloft associated with a
subsidence inversion. Therefore will continue to carry a dry
forecast today and tonight.


Upper ridge will continue to dominate over the southeastern
states through the weekend while at the surface moist southerly
flow will continue to circulate into the region around a
surface ridge located offshore. Strong instability is again
forecast with CAPE values over 2500 J/kg and Lifted Index
values around -6C to -7C. Precipitable water values will be a
bit lower than Friday around 1.1 inches and shear is weak.
Forecast soundings indicate lingering subsidence inversion and
in the absence of any upper forcing and surface boundaries to
initiate convection do not expect much in the way of storms,
although an isolated shower or two cannot be ruled out.

The upper ridge will weaken a bit late Sunday and Sunday night
as a deep upper trough and associated front approaches from the
west. Will carry a slight chance of showers late Sunday night
in the far western Midlands and upper CSRA to account for any
lingering convection approaching from the west.

Temperatures during this period will remain well above normal
with highs in the upper 80s to lower 90s and lows in the upper
60s to lower 70s.


A couple of periods of active weather expected during the
extended forecast period with a pair of troughs and associated
cold front moving into the forecast area.

Despite slight timing differences between the GFS/ECMWF both
are showing a deep closed upper low lifting north into the
Great Lakes region on Monday with a cold front pushing into the
forecast area Monday afternoon and evening bringing the chance
for convection and possible severe weather. Several ingredients
come together Monday including precipitable water values rising
to near 1.7 inches with strong moisture advection into the
region with southerly 850mb winds 45-50 knots with upper
dynamics in the form of forced ascent associated with the right
entrance region of the upper jet. Will continue to advertise
likely pops across the western half of the forecast area where
confidence is higher and high chance pops elsewhere.

Dry and cooler weather expected on Tue/Wed behind the cold
front with surface high pressure over the forecast area and
generally zonal 500mb flow. Another amplifying upper trough
will dive into the Mississippi/Tennessee Valleys Wednesday
night into Thursday as moisture quickly returns with a wide
open tap from the Gulf of Mexico bringing precipitable water
values back up around 1.5 inches. There are some timing issues
between the GFS/ECMWF regarding this system leading to lower
confidence so will not make much change to the going forecast
right now.

Temperatures during this period will remain above normal
throughout, although cooler temperatures are expected Mon/Tue
with highs in the lower 80s then warm back to the mid to upper
80s on Wednesday followed by a cool down on Thursday with
clouds and precipitation moving into the region.


Latest HRRR as well as the latest satellite loop indicating lower
clouds beginning to move into the area from the SW early this
morning. Have continued MVFR or lower conditions mainly 10z-
13z...though lingering through late morning at AGS/DNL. By
18Z...expect VFR all TAF sites with southerly winds 8 to 10
knots. More restrictions possible early Saturday morning, but
not enough confidence to mention in the TAFs at this time.

EXTENDED AVIATION OUTLOOK...Late night/early morning fog/stratus
expected to bring MVFR or lower conditions to the area Saturday and
Sunday. Gusty winds and restrictions in thunderstorms may be an
issue with the front Monday.




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