130 
fxus63 kabr 101457 
afdabr 


Area forecast discussion 
National Weather Service Aberdeen South Dakota 
857 am CST Wednesday Mar 10 2010 


Update... 
most locations to the east are showing visibility up to 1/2 to 1 
mile...area webcams support removal of dense fog advisory. 
In the near term...also adjusted eastern County Warning Area probability of precipitation and 
temperatures. Guidance continues to advertise main area of 
reflectivity moving along the fsd/abr County Warning Area boundary...however 
regional radar summary shows widespread rain/drizzle occurring 
across the eastern County Warning Area...so have increased probability of precipitation in that area. 
Northeast flow is advecting slightly warmer temperatures into the 
eastern County Warning Area as well...so have increased maximum temperatures to 36-38 
degrees in that area. 




&& 
Previous discussion... 
short term...today through 00z Saturday. 
Main forecast challenge facing the near term is ongoing precipitation 
event...trying to nail down precipitation type/duration/amounts/timing 
along with dealing with current winter weather advry that is in 
effect. 


Currently Sat pictures show closed 500hpa system spinning over 
Nebraska...with models in good agreement on posn. Models also show 
500hpa vorticity across southern Nebraska/northern Missouri rotating back into 
eastern Dakotas later today. Meanwhile...dry slotting taking place 
across County Warning Area continues to dry precipitation from east to west as returns on kabr 
88d are diminishing. 08z surface observation indicate only fog across much of 
the region...with some 6sm up reported at kmbg. Anticipate that 
fog/light drizzle/mist will continue across the eastern County Warning Area until that 
next wave impacts the eastern County Warning Area later this morning/aftn. Further 
west...bufr soundings indicate that any precipitation that begins to fall 
should be snow. Not out of the question to see a bit of freezing 
precipitation/drizzle this morning as soundings don't saturate to -10c 
until later this morning...but am going to remain simple in the 
weather grids as any mixed precipitation shouldn't last more than an hour 
or so. Also...given dry slotting now taking place...am beginning 
to worry about winter weather advry that is in place across the 
west. Have backpeddled a bit on snowfall totals as forcing isn't 
all that great...and westward snowfall amounts have also backed 
off...and refocused more southeast interestingly enough. Kbis is 
reporting slushy roads due to freezing precipitation. Am going to let 
winter weather advry ride through the morning and let day shift 
evaluate during the morning when calls can be placed to determine 
extent...if any...of snowfall and accums. 


Precipitation should turn over to all snow across the County Warning Area later this 
evening into Thursday as cooler 850hpa temperatures slowly advect in. 
850hpa-700hpa q-vector convergence lifts north out of area as 
well. Some concern that surface wet bulb temperatures at or above freezing will keep 
precipitation liquid longer than anticipated...especially across the east. 


Precipitation should kick over to snow though Thursday night across all the 
County Warning Area...with some heavier banding possible further south in kfsd's 
area of concern...although not out of the question across southern 
Spink and eastern hand counties. Critical thickness values and low 
level temperature forecasts all support snow development. However...current 
500hpa wave digging across SW Continental U.S. Is expected to get wrapped up 
into central Continental U.S. 500hpa closed low...with strong warm air advection returning 
back into the eastern County Warning Area Friday morning. Timing of the return of the 
warm air advection will also play into how much the snow accumulates Thursday 
night. 


Temperature wise...don't expect much more than a 3 to 4 degree diurnal 
temperature range through the period. 




Long term...Friday night through Tuesday 
temperatures and precipitation chances are the main issue through the time 
period. Active split-flow pattern is prognosticated and expected to 
continue across the Continental U.S. Through the long term. Middle Mississippi 
Valley upper low is expected to move/wobble east during the time 
period. A couple waves are forecast to rotate around the north side of 
the low and potentially bring some precipitation to the northern plains. 
However most guidance Post Friday night suggests this precipitation will 
be east and southeast of the abr County Warning Area. So will keep the majority of 
the weekend dry for the time being. Meanwhile another system crosses 
The Rockies and then dives into the far southern High Plains early 
next week. For now it looks like any ill effects from this system 
will remain south and west of the abr County Warning Area. Temperatures should 
continue to rebound through next week as the snow gradually melts 
across the County Warning Area and heights rise. However felt MOS/HPC guidance 
might be a touch too high during the day due to abundant clouds 
and moisture...thus backed off those guidance numbers by a few 
degrees. 


&& 


Aviation... 
widespread low IFR ceilings will continue across the region through 
today. Meanwhile patchy precipitation will gradually become more widespread 
this afternoon. Visibilities will generally range from MVFR to IFR 
depending upon the light precipitation and fog. 




&& 


Abr watches/warnings/advisories... 
South Dakota...Winter Weather Advisory until 6 am CST /5 am MST/ Thursday for 
Campbell-Corson-Dewey-Hughes-Potter-Stanley-Sully-Walworth. 


Minnesota...none. 
&& 


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


Weather.Gov/Aberdeen