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Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota 
954 am CST Sat Nov 21 2009 


Update... 
just some high cirrus associated with a 250hpa jet-streak streaming 
into the region from the southwest. The only changes made to the 
today period forecast were to increase cloud cover a bit for some 
of this thicker cirrus expected to be around today...and to 
increase the southerly surface winds to ensure 20 to 30 miles per hour with 
gust to 40 miles per hour wording showed up...since the RUC shows 35 to 40 
knot winds at appx 1000ft off the surface. Would think that 
daytime mixing and the formidable pressure gradient across the 
area would begin tapping into some of those strong winds by early 
this afternoon. 




&& 
Previous discussion... 
short term...today through Monday 
today will be breezy/windy across much of the County Warning Area as pressure 
gradient tightens ahead of an approaching cold front. 925/850 
winds on the order of 40-50 knots but do not expect wind gusts to 
be this high. The cold front tracks east across the County Warning Area 
tonight...bringing cooler temperatures for Sunday. After much 
above normal temperatures in the 50s today...highs will drop back down 
into the 40s for Sunday. Weak shortwave moves through the area on 
Sunday but best moisture availability remains east of the region 
in Minnesota so will keep forecast dry. Attention then turns to the 
approaching storm system which begins to affect the region late 
Sunday night and Monday. GFS remains the furthest north of all 
models and is quicker...but has shown a noticeable trend to the 
south...trying to come in line more with the more consistent ec 
and Canadian solutions...which have always been further south. The 
new 00z ec is even a tad further south than its previous run but 
whats interesting is that it has developed a more pronounced 
inverted trough which noses northward along the South Dakota/Minnesota border. This 
could spell out decent precipitation chances this far north...even though 
main surface low is well south of the area. Will have to keep an eye 
on this development. Thermal profiles still suggest mostly rain to 
start off...then changing over to snow from west to east towards 
the end of the event. Have not made real significant changes to 
weather/probability of precipitation during the short term period. 




Long term...Monday night through Friday 
a somewhat active pattern still appears on tap for the first part 
of the long term. All models still produce a decent looking yet 
progressive upper low over the central/northern plains through middle 
week. The European model (ecmwf) remains the slowest and furthest south of all 
deterministic 00z runs. Meanwhile the Gem has trended toward the 
GFS. With some uncertainty in the forecast...felt that the best 
policy was to stay somewhat close to the inherited solution. Rain 
and snow will be possible into Tuesday before becoming mostly snow 
by Tuesday night. It appears the highest precipitation probabilities will 
exist over the big Sioux Valley/Sisseton hills where an inverted 
trough may hang out for 24 hours or more. Temperatures were only 
modified slightly after looking at the latest long range temperature forecasts. 




&& 


Aviation... 
VFR conditions will prevail today with scattered-broken high clouds at or above 15k 
feet streaming across the region. Southerly winds of 15 to 30 miles per hour 
will be common during the daylight hours...then will diminish to 
less than 10 miles per hour after sunset. 




&& 


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


$$ 
Update...dorn 
short term...tmt 
long term...tdk 
aviation...Parkin 


Weather.Gov/Aberdeen