632 
fxus63 kfsd 072140 
afdfsd 


Area forecast discussion for southeast South Dakota/southwest Minnesota/northwest Iowa 
National Weather Service Sioux Falls South Dakota 
330 PM CST Wednesday Jan 7 2009 


Discussion... 
tonight looks relatively benign after we shake off some of the low 
cloudiness that is lingering around this afternoon. Areas to the 
west of a Hon to Tyndall line will likely stay in cloud cover most 
of the night. Otherwise...weak high pressure at the surface will 
build south tonight and some of the colder...drier air in place over 
eastern ND and northeast South Dakota will leak southward. Because cloud cover 
will be limited in the east...will drop lows into the 5 above to 5 
below range with 10 to 15 above over SC South Dakota where cloud cover will 
likely linger all night. Middle level thermal band will stall and 
slowly begin to lift northeast late tonight. Will include a low pop 
for SC South Dakota to accommodate this. 


Thursday should also start out relatively quiet with clouds increasing across 
the County Warning Area. Low level southeasterly flow north or warm front will keep temperatures cold across 
most of County Warning Area and will lower highs most places. The only exception will be 
across far SW where fnt may actually move north of that area. Could easily 
see highs in 40s if fnt moves north early in the day. For now will hedge 
that it will occur later in the day and will only go for highs near 40. 


Could also see patchy S- across northwest County Warning Area during the day in are of weak 
fntlgen...but will take time to saturate low levels. Looks like main 
action will occur Thursday night...espec across SW Minnesota as strong warm air advection kicks in with 
fairly decent fntlgen from h9 to 700 mb across SW Minnesota during the night. Will up 
probability of precipitation to likely across portions of SW Minnesota...tapering off to chance towards 
i29 in the evening. Next question is precipitation type. Feel with strong 
warm air advection...precipitation across southeastern South Dakota into northwest Iowa will pbly be freezing rain- if it occurs at 
all. Across SW Minnesota...precipitation will pbly start of S...and if snow becomes 
more convective...then column likely will remain below freezing and 
never change over to freezing rain- until late when lift shifts east and then just 
zl-. For now will go likely S with chance freezing rain- across SW Minnesota Thursday night. Will go 
with around 2 inches of snow in mml area with 1 to 2 inches across 
rest of SW Minnesota. If lift is not as strong...then could more likely see a 
tenth of an inch of freezing rain across SW Minnesota. Will definately need to worry about 
advisory with later forecast there. Further west towards i29 and James 
Valley...best chance for any precipitation will be in the evening...followed by chance 
of zl- as lift and forcing shifts northeastward. Temperatures likely will not fall Thursday 
night and will pbly remain steady through the night. 


Friday will see highs in early morning with falling temperatures from west to east during 
day as surface trough shifts eastward during the day. Digging short wave will bring a 
chance of S- to County Warning Area with best chance along and east of i29. This short wave could also 
produce an inch or so of accumulate across SW Minnesota. Also gusty northwest winds will 
develop as inverted trough shifts east with gusts to 35 to 40 miles per hour. 


Linger S- possibly early Friday evening...followed by clearing skies and surface 
high builds in. Lows Sat morning should fall to near or slightly below zero 
northestern County Warning Area with single digits SW. 


Looks Lile it will be warmer on Sat as south-southwest flow develop and will bump up 
temperatures a few degree. Should be a few degree warmer on sun ahead of next short wave 
in northwest flow aloft. Strong track should remain north of County Warning Area Sun night...but 
still could produce a little S- eastern County Warning Area. Colder air will filter into County Warning Area 
Monday with main surge Tuesday and persisting into Wednesday. Will struggle to get 
out of single digits Tuesday and Wednesday northestern County Warning Area...and if latest GFS is 
correct may not get above zero. Models have not been all that good 
that far out but trend is for colder temperatures as Hudson Bay low 
deepens. 


&& 


Aviation... 
expect MVFR ceilings to slowly scour out this evening as a cold dry 
high pressure works south. Not a real strong high pressure so we 
could see shards of low clouds in and out until late evening. After 
this...VFR through the afternoon...except increasing MVFR ceilings 
from west to east between about 16z and 20z Thursday afternoon. Will 
likely see a snow and freezing rain event near the taf sites...but 
the main effects will be across northeast South Dakota into west central and 
southwest Minnesota. 


&& 


Fsd watches/warnings/advisories... 
South Dakota...none. 
Minnesota...none. 
Iowa...none. 
NE...none. 


&& 


$$ 


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