Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 290026

Area Forecast Discussion
National Weather Service Columbia SC
826 PM EDT Fri Apr 28 2017

High pressure will ridge in from the Atlantic bringing fair and
warm conditions through Sunday. The next cold front will bring
showers and thunderstorms to the area Monday. Generally fair
with seasonal temperatures expected Tuesday and Wednesday.
Another significant weather system will impact the region for
next Thursday and Friday.


Ridging at the surface and aloft will dominate the region
overnight. Cumulus which had formed have dissipated with loss of
heating with satellite imagery showing some upper level clouds
moving northward from the Gulf Coast. The upper clouds will
begin moving over the forecast area during the early morning
hours with winds remaining southerly at 5 to 7 mph. Although
dewpoints will remain in the mid 60s to around 70 overnight the
combination of wind and increasing clouds will limit fog
development. Overnight lows will be in the upper 60s to around


High pressure will persist off the southeast coast this weekend
with a moist southwesterly surface flow. It will be warm with
high temperatures in the mid 80s to lower 90s. Strong
instability is forecast with CAPE values over 2500 J/kg and
Lifted Index values around -5C to -7C. However, moisture is
lacking on Saturday with precipitable water values only around
1.1 inches and shear is weak. Additionally, forecast soundings
indicate a lingering subsidence inversion, and in the absence
of any upper forcing or 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. Have included a slight chance of showers and
thunderstorms during the day, but confidence is low due to
persistent subsidence and dry air aloft.


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 possibly 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 and upper
dynamics in the form of forced ascent in the right entrance
region of the upper jet. Breezy south-southwest winds and areas
of heavy rain can also be expected.

Stable and dry conditions return behind the front for Tuesday,
and temperatures will be slightly cooler with highs only in the
mid 70s to low 80s. There is a slight chance of showers and
thunderstorms late Wednesday with a warm front ahead of the
next system. As a deep low digs south, ample Gulf of Mexico
moisture will be advected into the region on Thursday and
Friday, and there will be a good chance for moderate rain, as
well as another round of potentially severe thunderstorms.


VFR conditions will continue through the evening with mainly
clear skies and southeast to south winds 5 to 10 knots.

Most of the models continue to indicate MVFR or lower cigs
developing after 06Z as low level moistures advects into the TAF
sites from the east. Given improving confidence...have
indicated a period of IFR/MVFR conditions 08Z-15Z. Restrictions
will be mainly due to cigs given a 30 knot low level jet which
will inhibit widespread fog development. Should see conditions
improving to VFR mid to late Saturday morning as bounday layer
mixing commences. Will once again see afternoon cumulus
development with bases 5kft to 6kft and southerly winds around
10 knots.

EXTENDED AVIATION OUTLOOK...Early morning fog/stratus expected
to bring MVFR or lower conditions Sunday and Monday. Gusty winds
and restrictions in thunderstorms expected Monday as a cold
front moves through the region.




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