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Area forecast discussion...updated 
National Weather Service Columbia SC
1108 am EST Sat Dec 20 2014

a frontal zone will remain near the southeast coast
through Tuesday. A series of low pressure systems will move
northeastward along the front. A strong cold front approaching
from the west will move through the forecast area Wednesday.


Near term /until 6 PM this evening/...
shortwave energy moving through the area at this time has been
responsible for the widespread light rain observed across the
region. Regional radar showing the back edge of the rain pushing
into the western midlands at this time and rain should end from
west to east by 2 PM. Visible satellite shows extensive low clouds
extending back through Alabama so do not foresee much sunshine
today and that will help keep temperatures in the 40s to lower 50s
this afternoon.

Have updated probability of precipitation to show improvement from west to east over the
next few hours then dry by late afternoon.


Short term /6 PM this evening through Sunday night/...
high low-level moisture will continue through tonight. There may
be areas of fog as indicated by the GFS MOS. Little temperature
recovery should occur today because of cloudiness. The high
temperature guidance is likely too warm. Leaned toward the more
consistent GFS MOS for the temperature tonight.

Weak isentropic lift supports a rain chance Sunday mainly late as
moisture becomes deeper ahead of another middle-level shortwave
trough. The guidance consensus supports probability of precipitation of 20 to 30 percent
for mainly late in the day. The models are consistent displaying
significant moisture and isentropic lift Sunday night into Monday
especially in the southeast part of the forecast area. The models
indicate moisture becoming shallow late Monday behind the
associated middle-level shortwave trough. Used the guidance consensus
for the pop forecast. The guidance high temperatures are likely
too warm because of cloudiness and a low-level northeast flow. The
guidance low temperature were close. The models have been
consistent indicating all-liquid precipitation.


Long term /Monday through Friday/...
high moisture should continue Monday night through Tuesday ahead
of a warm front and deepening upper-level trough. The GFS and
European model (ecmwf) models have trended slower with the passage of a strong
cold front and now display frontal passage Wednesday. The warm
front may lift northward ahead of the cold front.

If the forecast area gets into the warm sector there may be
enough instability for thunderstorms ahead of the cold front Tuesday
night or Wednesday. The GFS and European model (ecmwf) display 850 mb winds of 40 to
60 knots. The shear and potential for sufficient instability
indicates a possibility of severe thunderstorms.

Expect a diminished shower chance Wednesday night behind the
front with breezy conditions. The models have been consistent
showing a dry west flow between high pressure near the Gulf Coast
and low pressure lifting north of the Great Lake region for
Christmas day. Breezy conditions may continue during the day...but
the model trend has been to show the ridge farther northward with
less of a pressure gradient in the forecast area.

Moisture may increase ahead of another cold front approaching
Friday. The GFS shows less moisture compared to the European model (ecmwf). The
European model (ecmwf) keeps much of the forcing associated with the front west of
the forecast area through Friday. The GFS...ECMWF...and ekd MOS
probability of precipitation are just 10 to 20 percent.


Aviation /16z Saturday through Wednesday/...
MVFR and possibly IFR ceilings through late afternoon with possible
brief improvement early evening...before dropping back to MVFR/IFR
this evening.

Shortwave and associated precipitation continue to move across the
Carolinas and rain should end from west to east between 12pm-2pm.
MVFR/IFR ceilings have developed all terminals and likely to continue
through the afternoon but should be a brief period of improvement
late afternoon into early evening before lower ceilings return for the
remainder of the period. Winds generally light and variable with a
prevailing east-northeasterly direction.

Extended aviation outlook...widespread low clouds and precipitation
expected Sunday night into Monday with another Gulf Coast system
crossing the region. Yet another system will affect the area
Tuesday night bringing possible restrictions with windy conditions
expected Wednesday.


Cae watches/warnings/advisories...


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