833 
fxus63 kabr 220121 
afdabr 


Area forecast discussion 
National Weather Service Aberdeen South Dakota 
721 PM CST Friday Nov 21 2008 


Update... 
forecast coming to fruiton with high liquid to snow ratios in 
leading banding features...though these have thinned/diminished in 
intensity due to advecting into drier air/away from main 
baroclinic forcing. Intermediate snowfall estimates range between 
a dusting to 2 inches. Now seeing secondary low development in 
western South Dakota with rapidly expanding returns in Rapid City County Warning Area. 
Temperatures on southern periphery look warm enough for 
rain...though Faith is 32/30 and supporting snow most likely. Snow 
ratios with this expected to be closer to 10:1...so another 
inch/two possible still. 


New aviation below. 


&& 
Previous discussion... 
short term...tonight through Sunday night 
determining how exactly tnts system is gonna evolve is the challenge 
for the short range. Current indication is that initial comma 
cloud stretches from southwest North Dakota east into northeast 
South Dakota. Some accumulation is occurring across north central 
South Dakota now...but there is still some dry air to overcome in 
the northeast County Warning Area. Suspect this comma head will lift north and 
then be replaced by another one during the evening that will bring 
more snow to mainly the western half of the County Warning Area. The good news is 
that winds should be on the decrease through the evening and that 
would help with any visibility issues that might be encountered over 
areas east of the advisory. South around Pierre warmer than 
expected ll air has filtered into the region ahead of surface low. 
This should help negate much accumulation into the evening and 
thus snow amounts there should be lower than for areas north and 
east of pir. Speaking of snow amounts...there could be a few spots 
of advisory criteria snow but feel that the majority of the 
snowfall will be in the 1 to 3 inch range and stretch from 
Corson/Dewey County southeast toward Huron and Redfield or 
approximately under the track of the middle and upper low and in the 
most favored region of left exit region of the 300 mb jet. Most of the 
synoptic scale lift trails off after 6z and so should the 
snowfall. The rest of the short range should feature mainly dry 
conditions with some warming this weekend. Temperatures were a mix 
of met/mav guidance and local WRF 2m temperatures. 


Long term...Monday through Friday 
in northwest flow from Monday through Tuesday night...not much to write 
home about. Wednesday and Wednesday night...the upper level ridge 
out west finally shifts east over this area...before the flow 
pattern tries to split into two separate flow patterns. The 
northern stream branch of the polar jet stream looks to steer an 
upper level shortwave trough southeastward into the northern plains states by 
Friday morning...perhaps signaling the next onset of Continental 
cold polar airmass across the Dakotas by the start of next 
weekend. Temperatures about normal for late November will start 
off the extended...with a steady warm up to above normal temperatures by 
Wednesday. A cold front prognosticated for late Wednesday night/Thursday 
appears to signal the transition back to cold air advection and temperatures 
cooling back down to around to slightly below normal Thursday and 
Friday. 


&& 


Aviation... 
visby across the region is IFR to MVFR. Banded snowfall has moved 
east of kabr terminal and over Katy. The result is for the 1/2 to 
1 mile visby at these two locations to improve through 02z. 
As for kmbg...upper low rotation is nearly overhead and given 
improving trend in visby...expect it will continue. Focus for short 
term aviation is now on the broader area of snow...with a 
rain/snow mix on the southern periphery moving out of western South Dakota. 
This appears headed towards kpir terminal...will adjust taf for 
lower visby. 


Ceilings remain MVFR...generally just above 1kft. Not expecting much 
improvement in ceilings through Saturday am. During the day Saturday...wind 
trajectory becomes southwest which will help mix out MVFR cloud 
deck. 


&& 


Abr watches/warnings/advisories... 
South Dakota...Winter Weather Advisory until midnight CST /11 PM MST/ tonight 
for Campbell-Corson-Dewey-Walworth. 


Minnesota...none. 
&& 


$$ 
Update...Connelly 
short term...tdk 
long term...dorn 
aviation...Connelly 


Weather.Gov/Aberdeen