Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 291756

Area Forecast Discussion
National Weather Service Columbia SC
156 PM EDT Sat Apr 29 2017

High pressure ridging into the forecast area from the Atlantic
will dominate through Sunday and help keep any thunderstorms
mainly associated with heating isolated. The next cold front
will bring showers and thunderstorms Monday. Mainly dry weather
is forecast behind this front Tuesday and Wednesday. Another
significant weather system will impact the region Thursday and


Low cloudiness persists across the CSRA and south central
Midlands early this afternoon. Latest HRRR suggests clouds will
decrease somewhat but temperatures slower to rise than forecast.
Cut max temperatures slightly based on a little more cloudiness
this afternoon. may see a few gusts near 20 mph as cloud
streets on satellite.

Ridging extending into the area from the east will dominate
through tonight. The NAM and GFS display moderate to strong
instability with surface- based LI values -5 to -8 today with
the greater instability in the west section where the upper
ridging will be slightly weaker. The thunderstorm chance should
remain low because of shallow moisture and mid-level capping.
However, we did forecast slight chance pops in the west section
because of the strong instability plus high-resolution models
displays a few storms in that area. If thunderstorms do develop
then damaging wind and hail would be possible because of the
strong instability.

Low cloudiness may re-develop late tonight. Overnight lows near
70...slightly above guidance and well above climatology for this
time of year.


The upper ridge will weaken a bit Sunday as a cold front
approaches from the west, but temperatures will remain warm with
highs in the mid 80s to lower 90s. Heating may help support
showers or thunderstorms Sunday afternoon. The moisture increase
and convergence ahead of the front may also help cause
thunderstorms late Sunday night. However, the chance should be
limited because of shallow moisture Sunday and nocturnal cooling
Sunday night. Kept slight chance pops through 5 AM Monday
morning, then increased chances from west to east through the
early morning as the front moves closer to the area.

A deep closed upper low will lift north into the Great Lakes
region Monday with an associated cold front pushing into the
forecast area Monday afternoon and evening bringing
thunderstorms and moderate rain. Some storms could be severe
given lifted indices -6 to -8, and shear of 35 to 40 kts. NAM
precipitable water values have increased to almost 2 inches.
Strong winds, large hail and heavy rain will be the biggest
threats. South-southwest surface winds will also be breezy
during the day, and a Lake Wind Advisory may need to be issued.


Stable and dry conditions return behind the front 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. The models diverge beyond this point. The 00Z ECMWF
lifts another low from the southern Plains northward through
the Ohio Valley and into the eastern Great Lakes on Thursday and
Friday. The 12Z GFS takes the low through the lower Mississippi
Valley and eventually into the southern Appalachians. The 12Z
Canadian is somewhere between the EC and GFS solutions. There is
a conses though that Thursday will see another round of
thunderstorms and moderate to heavy rain. Friday and Saturday
are much more uncertain depending on the track of that low, so
kept a chance of showers and thunderstorms Friday, and a slight
chance on Saturday. With deep troughing over the eastern U.S.
during this period, temperatures will be near to below normal
with highs in the mid 70s to low 80s on Thursday and then only
in the low to mid 70s going into next weekend.


MVFR ceilings continue across much of the area early this
afternoon. With mixing and heating expect VFR conditions to
develop around 18z. Winds mainly south or southeast around 10
knots with a few gusts above 15 knots. Cumulus may dissipate
during the early evening with mainly clear sky then low clouds
expected late tonight again with restrictions...MVFR or
possibly IFR around 12z into the mid morning.

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




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