Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 212251

Area Forecast Discussion
National Weather Service Columbia SC
651 PM EDT Mon Oct 21 2019

Moisture will increase ahead of an approaching cold front. The
front will cross the area Tuesday. Most of the moisture and
rainfall associated with this system will be in the area late
tonight and Tuesday morning. It will be breezy behind the front
Tuesday afternoon. High pressure is forecast to dominate
Wednesday and Thursday followed by a frontal system late in the


Regional radars still showing no rain across the cwa. Currently
the nearest rainfall is across southeastern GA, and is tracking
along the coast. Further west, rainfall is still pushing
through eastern AL and will be entering western GA Shortly.
Ahead of this system moving out of AL, A strong 850mb jet will
be developing, with wind speeds of 30 to 40 kts. At the surface,
models indicate a surface boundary will be slowly lifting
northward in advance of the cold front, mainly after midnight.
In addition, upstream convection/outflow ahead of the cold front
will move into the forecast late tonight and towards the early
morning hours. Although we are currently dry, showers will
become likely later tonight as these surface boundaries push
towards/through the cwa. Can not rule out a brief strong or
severe storm late tonight.

The cold front will cross the area during the day Tuesday.
Showers and a few thunderstorms will continue through the
morning but diminish in coverage as dry air moves in from the
west around mid-day. Expect strong west winds behind the front
Tuesday afternoon, a Lake Wind Advisory may be needed.

Severe threat: There is potential for isolated severe
thunderstorms and weak tornadoes late tonight into Tuesday
morning. When the warm front lifts into the FA after midnight,
there may be enough instability to support thunderstorms and
heavy rain. The thunderstorms will develop in an environment of
strong 0-1 km wind shear and strong helicity along the warm
front. This supports a threat of tornadoes from these isolated
thunderstorms. The threat is highest in the CSRA, Midlands and
the Pee Dee where instability will be greater and will diminish
after 11 am when the warm front exits the FA.


High pressure will build into the area from the west Tuesday
night but expect diminished wind because of less mixing
associated with nocturnal cooling. The pressure ridge is
forecast to extend through the area Wednesday through Thursday
and it should remain dry. Wind is forecast to be relatively
light with the ridge axis close to the area. Used a model blend
for the temperature forecast except did lean toward the lower
temperature guidance Tuesday night because of strong net
radiational cooling.


Forecast confidence is low during the medium-range period. The
GFS and ECMWF have shown little run-to-run consistency with the
placement of a frontal system or deepest moisture. Believe the
best forecast for now is a model blend for the pop and
temperature forecast. Have forecasted chance pops with near
normal temperatures.


VFR through this evening then deteriorating conditions tonight.

A warm front will approach the forecast area from the south tonight,
ahead of which deteriorating CIGs/VSBYs expected, along with some
rainfall, and LLWS. Guidance indicating LIFR conditions. Warm front
to pass through during the early morning hours Tuesday, after which
will expect improvements in VSBYs, and possibly some slight
improvement in CIGs. An isolated severe thunderstorm will also
be possible late tonight and Tuesday morning.

A cold front will move through during the afternoon. Expect
scattered showers along and ahead of the cold front. Winds will
continue to veer through the period as these features move
through. Breezy conditions possible after the cold frontal
passage in the afternoon, along with a return to VFR.

EXTENDED AVIATION OUTLOOK...No significant impacts to aviation
Tuesday night through Thursday. Deteriorating conditions
Thursday night through Saturday with the next weather system.




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