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fxus62 kcae 220228 
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Area forecast discussion 
National Weather Service Columbia SC 
928 PM EST Friday Nov 21 2008 


Synopsis... 
cold...dry high pressure will build down into our region through 
Sunday. A front will bring a chance of showers Monday 
afternoon and Monday night...followed by cool but dry weather. 


&& 


Near term /until 7 am Saturday morning/... 
update as of 925 pm: wind speeds still up a bit over the area 
lakes late this evening...so will continue lake Wind Advisory 
until 1 am. Will lower wind speeds just a bit in the zones for the 
overnight period. Otherwise...ongoing forecast looks good as cold 
high pressure centered over the Ohio Valley builds over the area. 


Previous discussion: cold...dry high pressure will continue to 
build into the region overnight leading to very cold overnight 
lows. Cold advection will become neutral late tonight as winds 
relax and if there is even just a hour or two of near calm 
winds...temperatures could bottom out as record lows. Expect clear 
skies through the night and have gone below MOS guidance for lows. 


&& 


Short term /7 am Saturday morning through Monday night/... 
relatively tranquil weather is expected Saturday and Sunday with 
continued below normal temperatures. High pressure will settle over 
the area on Saturday with light winds up to around 700 mb...which 
will prevent good mixing...which will keep temperatures cooler. 
Despite full sunshine on Saturday...have gone below MOS guidance for 
highs given the cool dry airmass and a very cold start to the day 
with minimal mixing expected. 


Saturday night could very well be as cold or colder than tonight as 
the surface high will be overhead and nearly ideal radiational 
cooling conditions are expected. The one problem that could affect 
this scenario is a fast moving...dampening shortwave that will cross 
the Ohio Valley into the middle Atlantic Saturday night. This feature 
could bring thicker middle/high level clouds which would effectively 
insulate the surface layer and prevent temperatures from dropping 
off too much. At this point...it is figured that most of these 
clouds will remain north of the forecast area...more in North 
Carolina...but the northern counties would be most likely to be 
affected. Expect record lows to be met or exceeded Saturday night 
if the clouds do not play a factor. 


Weak upper level shortwave ridging will occur on Sunday in the wake 
of the exiting shortwave...coinciding with weak southerly flow at 
the surface as the surface high shifts off the coast. This will 
allow for a slight warm up of temperatures with highs expected to 
reach the middle 50s. 


Sunday night into Monday a strong...digging shortwave will move into 
the Ohio Valley and into the northeastern states...which will bring 
increased clouds and a chance for precipitation to the midlands. 
Moisture looks to be quite limited...precipitable water values only 
reaching around 0.75 inches...and will carry slight chance probability of precipitation. 
Increased southerly flow on Monday should allow temperatures to rise 
into the 60s ahead of an approaching cold front which will sweep 
through the area sometime Monday night. 


&& 


Long term /Tuesday through Friday/... 
continued cool and dry weather is expected through much of the 
extended periods. A deep closed cyclone is prognosticated to be over the 
northeastern states from Tuesday through Friday...with a general 
northwesterly flow aloft...becoming more westerly by the end of the 
period. 


High pressure will be in control at the surface over much of the 
upper Midwest into the Ohio Valley and southeastern states through 
the extended. Temperatures should remain slightly below normal to 
near normal in the lower 60s. 


A digging trough in the western United States will push into the 
Southern Plains by Friday as a warm front develops to the east into 
the Tennessee Valley and southeastern states. This will bring a 
chance for precipitation to the area on Friday...as a warm advection 
pattern develops. There remains some uncertainty with the details 
among the medium range models concerning the timing and exact 
location of the front and best warm advection. Therefore will opt to 
keep minimal probability of precipitation...slight chance...for day 7. 


&& 


Aviation /03z Saturday through Wednesday/... 
expect VFR sky and visibility conditions to continue through the taf 
period. Northwest winds 5 to 10 kts through 05z...then becoming 
variable less than 5 kts after 05z. 


Extended outlook...a cold front will move through the area Monday 
with possible showers and ceiling/visibility restrictions. 


&& 


Cae watches/warnings/advisories... 
SC...lake Wind Advisory until 1 am EST Saturday for scz015-016-018- 
020>022-025>031-035>038-041. 
Georgia...Lake Wind Advisory until 1 am EST Saturday for gaz040-063>065- 
077. 


&& 


$$