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fxus63 kabr 070144 aaa 
afdabr 


Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota 
844 PM CDT Monday Oct 6 2008 


Update... 
overall the forecast looks to be in okay shape. Did expand fog 
back further west where it appears that low level moisture may not 
get scoured out as much as previously thought. Meanwhile upper 
wave over eastern Nebraska continues to track northeast and is 
keeping a moist feed into the eastern County Warning Area...but most of the rain 
should push into Minnesota during the very early morning hours. 
Temperatures appear on track. Updates already issued. 


&& 
Previous discussion... 
short term...tonight through Wednesday night 
surface trough continues to move slowly east across the 
area...with most of the precipitation having shifted east of an 
Ellendale to Presho line. Shortwave trough across Montana and the 
western Dakotas continues to move eastward with drier air 
associated with it. Dewpoints upstream are in the upper 20s to low 
30s with some of this air making it into central South Dakota by late this 
afternoon and early evening. Rather large moisture gradient across 
the state with Wheaton reporting a 64 degree dewpoint and Buffalo 
at 27 degrees. 


As everything shifts east overnight...precipitation will gradually 
come to an end from west to east. Constructed weather/pop grids to 
match this so that by 12z Tuesday...everyone should be dry. As for 
clouds...eastern half of the state will remain cloudy for a good 
portion of the night but clearing is expected from west to east 
late tonight. Fog potential was examined today and believe there 
is a chance for some patchy fog but there are many things working 
against it. First off...it appears most locations west of the 
Sisseton hills will maintain a 5 to 10 miles per hour wind later tonight. 
Also...the drier air out west will continue to advect into the 
area overnight making it much for difficult for the temperature to drop 
to its dewpoint. Soundings are also not overly supportive of fog. 
Although...do believe there is an opportunity for fog formation 
across the eastern County Warning Area closest to the trough axis where lighter 
winds will be. Think fog is possible just west of wherever the 
back edge of the clouds set up. In this area...if rapid cooling 
occurs and temperatures fall to the dewpoint before the drier air advects 
in...then there could be fog. Have therefore added patchy fog 
wording across portions of the eastern County Warning Area. 


Dry conditions are expected on Tuesday and Wednesday...with a 
brief surface ridge moving across the area on Tuesday. Frontal 
boundary works across the area on Wednesday and breezy conditions 
will develop behind this front. Temperatures look to be seasonable 
both Tuesday and Wednesday with highs generally in the 60s to low 
70s. 


Long term...12z Thursday through Monday 
main forecast challenge facing the extended deals with precipitation potential 
heading into next weekend. 


Models continue to differ across a wide spectrum of solutions for the 
upcoming weekend. The GFS continues to be the most progressive of all 
the models...along with being the most inconsistent in its 
solution. For today...the GFS brings the longwave 500 mb trough into the 
intermountain region at the beginning of the weekend...then closes 
off a fairly potent low by Saturday across the 4 corners 
area...lifting this feature into the Midwest for the weekend where 
it advertises it stalling out. With this stalled system to the 
south...the GFS also remains rather aggressive with the cold 
air...with much of the County Warning Area remaining below zero at 850 mb starting 
Friday and continuing throughout the period. With the moisture the 
closed system draws northward...potential early October snowstorm 
could be in the offing. 


However...the ec...which is the most consistent of all the models 
so far...also shows the 500 mb longwave dropping into the western 
Continental U.S....closing off the 500 mb low much further west...more toward 
California/Nevada region. It then lifts this low quickly to the NE...keeping 
much of the County Warning Area in the warm sector as it does. Opposite of the GFS 
solution...the County Warning Area remains well above zero at 850 mb...with sections 
of the eastern County Warning Area reaching the teens above zero at 850 mb by the end of 
the weekend. This would spell more of a rain event for the County Warning Area. 


The Canadian 500 mb ensemble plots show more members closer in 
appearance to the ec versus the GFS...and HPC also favors a more 
amplified solution offered by the ec. With this in mind...have gone 
with a more middle of the Road forecast...and did warm up temperatures a bit 
for the weekend to keep all mention of precipitation as rain. With such 
uncertainity...didn't bother to mess too much with the weather 
grids...as very low confidence exists within this extended 
forecast package. 


&& 
Aviation... 
for the most part it should be VFR for the rest of the night at 
all terminals. However...as the rain and clouds gradually move off 
into Minnesota overnight...patchy fog could occur at kabr and 
Katy. 
&& 


Abr watches/warnings/advisories... 
South Dakota...none. 
Minnesota...none. 
&& 


$$ 
Update...tdk 
short term...tmt 
long term...Hintz 
aviation...tdk 


Weather.Gov/Aberdeen