area forecast discussion 
National Weather Service Columbia SC 
622 am EDT Thursday may 23 2013 


Synopsis... 
an approaching cold front will move through the forecast area 
tonight. The dry air mass behind the front will dominate during 
the weekend. 


&& 


Near term /until 6 PM this evening/... 
moisture and instability ahead of a middle-level shortwave trough 
was supporting scattered showers early this morning. Satellite 
trends and the models indicate deeper moisture associated with 
the shortwave trough will shift east of the forecast area early 
this afternoon. A pre-frontal trough will be in the forecast area 
through today. Convergence associated with this feature plus 
diurnal heating should support thunderstorms but expect limited 
coverage because of diminished moisture behind the middle-level 
shortwave trough this afternoon. Maintained chance probability of precipitation with 
the greater values in the northeast part closer to the deeper 
moisture and more convergence associated with the surface trough. 
Moderate instability may support damaging wind with a few of the 
thunderstorms. Wet-bulb zero heights also support hail. The 
temperature guidance was close. 


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Short term /6 PM this evening through 6 PM Friday/... 
convergence associated with the cold front may support 
thunderstorms early. Coverage should still be limited with deeper 
moisture east of the area. Drying behind the front should dominate 
late tonight through Friday night. Mixing associated with the 
front supported the warmer temperature guidance tonight. We will 
get off to a relatively warm start so the warmer guidance appeared 
better Friday. Used the guidance consensus for the temperature 
Friday night. 


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Long term /Friday night through Wednesday/... 
the dry air mass behind the cold front should dominate during the 
weekend. Expect some increase in moisture beginning Monday. The 
GFS and European model (ecmwf) display a warm front developing near the area. The 
GFS is farther northward with the placement of the front. The GFS 
also shows less moisture in the forecast area. Both models show 
an increase in 500 mb ridging which should limit thunderstorms. 
Believe the best forecast for now is an average of the GFS and 
European model (ecmwf) MOS. Forecasted slight chance probability of precipitation Tuesday and Wednesday. 


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Aviation /10z Thursday through Tuesday/... 
convection continues to diminish as it moves east-northeast across the area. 
Showers should end by around 12z-13z. Some IFR/MVFR ceilings will linger 
until around 13z. Upper impulse and surface trough will move through 
later today...possibly leading to scattered shra/tsra. Due to the 
scattered nature of the convection...will not mention precipitation 
at any of the taf sites for the afternoon hours. By late this 
evening...skies should begin to clear as drier air moves into the 
area from the west. 


Extended aviation outlook...drier air moving in behind a front will 
preclude any impacts to aviation...other than breezy conditions 
possible Friday/Friday nt. 


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Cae watches/warnings/advisories... 
SC...none. 
Georgia...none. 
&& 


$$