Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 152238

Area Forecast Discussion
National Weather Service Columbia SC
638 PM EDT Tue Oct 15 2019

A warm front will be south of the forecast area today then move
northeastward tonight spreading showers across the area. On
Wednesday a cold front will cross the area bringing dry and
seasonable temperatures Wednesday night through Friday. The
next system to impact the region will occur late this weekend
into early next week.


Frontal boundary extending from east-central Ga east into the
Low Country SC early this evening. Rain has been focused near
and south of the front. Dry low-levels (note sfc dew points in
the low to mid 50s...even a few areas mid 40s Pee Dee) in the
Midlands limiting rain at the moment. Models suggest weak
isentropic lift and moisture flux early this evening then
increasing after Midnight. So bulk of rain late tonight into
the early morning across the central Midlands. Rainfall expected
to be light especially in the central and north Midlands. Heavy
rain expected to remain mainly southeast of the the
coastal plain where convergence (weak sfc low) and isentropic
lift will be maximized. Overnight lows tonight will generally be
in the low 60s.


The upper trough axis and cold front will be to our west at 12z
Wednesday with diffluent 500mb flow over the forecast area and
PWAT values around 1.4-1.6 inches. Expect widespread showers
across the area during the early morning hours and gradually
shifting off to the northeast through the morning as the trough
axis and front approach from the west as PWAT`s decrease with
time as deeper moisture shifts eastward. Expect most of the rain
to end by midday although some lingering showers are possible
into early afternoon as atmosphere becomes a little bit unstable
although moisture will be limited by downsloping 850mb flow so
will continue to decrease pops through the day. Temperatures
will be tricky and dependent on how many breaks in the clouds
through the afternoon hours as the cold advection lags well
behind the cold front. Stronger cold advection begins Wednesday

Seasonal Fall weather is expected on Thursday and Friday as
expansive surface high pressure, extending from southern Canada
into Texas/Louisiana, builds into the area from the west. Aloft
the 500mb flow will be northwesterly on Thursday followed by a
large upper ridge moving over the region on Friday and Friday
night. The atmosphere will become quite dry with precipitable
water values dropping to at or below a half inch which is about
50% of normal. The cool high pressure settling over the region
combined with a dry air mass will provide near to slightly below
normal temperatures with highs in the upper 60s to lower 70s
and lows in the 40s.

There is a weak cut off low that drifts underneath the ridge
along the Gulf Coast states during this period and may bring
some rain close to the CSRA late Friday night but think the
atmosphere will be too dry to support any measurable


Active weather returns to the forecast area during this period
as a mean trough develops over the middle of the country and
deep southwesterly flow develops over the forecast area.

Over the weekend Sat/Sun, a series of shortwaves will dive
southeastward into the middle of the country resulting in a
broad upper trough, which will back the 500mb flow to the
southwest over our area. Increasing moisture from the Gulf of
Mexico will provide increased chances of rain in the forecast.
There are some timing differences among the medium range models
handling the individual shortwaves in the larger scale flow
which leads to some uncertainty with when the best chances of
rain will occur. However, it does appears there will be a
couple of periods of rain showers over the weekend into early
next week. Guidance is reasonably consistent showing a cold
front pushing through the forecast area sometime on Tuesday
which will keep chances of rain in the forecast through the
extended period.

Temperatures during this period will be above normal with a
warming trend with highs in the 70s on Saturday, 70s to lower
80s on Sunday and in the 80s on Mon/Tue. Overnight lows will be
warming as well especially with extensive cloud cover expected
as lows will be in the 50s on Saturday night but then warm into
the 60s Sun/Mon nights.


Deteriorating conditions tonight.

Frontal boundary stalled to our south. Upper energy will roll
eastward across the southern tier of states tonight and early
Wednesday, leading to a surface wave developing and moving east
across our region, ahead of which isentropic lift will spread
rain into the area. Latest radar loops and high resolution
models indicate patchy light rain moving in this evening,
becoming heavier and more widespread later tonight. CIGs/VSBYs
will lower in response. Will indicate flight categories falling
to IFR and LIFR later tonight. Widespread rain expected to exit
our forecast area Wednesday morning, with gradually improving
CIGs. Next upper trough and surface front, diving down from the
Midwest, will come through in the afternoon, with some showers
along it, and possibly even an isolated thunderstorm. Winds
expected to veer to W/WNW and increase in the afternoon with
breezy conditions possible.

EXTENDED AVIATION OUTLOOK...No impacts to aviation expected
Wednesday night through Saturday. Chance of rain and associated
restrictions Sat nt/Sun.




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