Weather

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fxus63 kabr 102048 
afdabr 


Area forecast discussion 
National Weather Service Aberdeen South Dakota 
348 PM CDT Friday Oct 10 2008 


Short term...through Monday am 


Broad area of precipitation and areas of thunder/sleet associated with broad 
upglide/baroclinicity/entrance region of departing upper jet has all 
but departed the County Warning Area. Therefore highlights for discussion is on 
continued influences of digging upper trough over the Rocky 
Mountains. 


This system is responsible for the redeveloping light precipitation 
across western counties. Enhancement anticipated overnight as 
isentropic upglide reestablishes ahead of strengthening 
southwesterly middle/low level flow. Focus is north and west of 
inverted trough/warm front situated overhead. Precipitable water anomalies 
exceed 2 Standard deviations overnight...with elevated cape 
situated over eastern counties Saturday am. NAM/GFS profiles for 
western counties marginal for rain/snow mix...but no 
accumulation. 


Little to suggest precipitation chances diminish Saturday as 
region remains under broad upper level difulence/upglide...enhanced 
by shortwave passage. Strengthening low level flow Saturday 
afternoon results in precipitable water anomalies increase between +4/+5 with 
formation of low level jet. Elevated instability on nose of 60kt 
jet...with MUCAPE values nearing 500 j/kg...so thunder possible Sunday 
am. May need a Wind Advisory for Coteau counties due to strength 
of low level jet...which exceeds 2 Standard deviation...particularly 
late Sunday am if southeast counties manage peeks of sun. This also 
makes for difficult temperature forecast. Mav guidance captures diminished 
low level thermal advection/cloud covers limiting of diurnal 
trends...however as low level jet establishes...will see dramatic 
temperature gradient set up across the region Sunday. Any sun and mixing 
will cause temperatures to rebound drastically...so increased the 
maximum temperature to better account for Coteau topography. 


As system wraps up Monday...dry slot/cold front will pass through 
the region. Coolest 850 mb air will remain associated with stacked 
low across the western Dakotas...and low level flow remains 
primarily from the west/southwest. 




Long term...Monday through Friday 


The main focus this period is on the remnants of the large upper 
low that is currently moving through the area. Some model 
difference is noticeable early Monday with the GFS moving a weaker 
upper center through eastern Montana while the European model (ecmwf) has a 
slightly stronger center in southern Manitoba Canada. Th European model (ecmwf) 
also depicts a trough extending southwest in Arizona. The ensemble 
shows pretty good agreement between members on this so GFS seems 
the better solution. By late Monday the frontal boundary moves 
east of this area and in effect dry slots the eastern Dakotas. The 
low then picks up speed as it moves northeast and the wrap around 
precipitation area brushes to the north of here. As the low moves 
through some very cold air moves into the region with 850 mb 
temperatures approaching -5c early Tuesday. This will give 
overnight low temperatures around 30f Tuesday morning before the 
low moves past and 850 mb temperatures climb again. Flow becomes 
zonal behind the low and temperatures return to near seasonal 
normals with no precipitation mentioned. 


&& 


Aviation... 
a large area of rainfall has moved through the area. Some light 
rain continues to fall in scattered location. The moisture left 
behind is fostering large areas of MVFR or IFR ceilings. This 
evening expect visibility to also fall to MVFR or lower as fog 
forms across the area. 


&& 


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


$$ 
Short term...Connelly 
long term...Keefe 
aviation...Keefe 


Weather.Gov/Aberdeen