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Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota 
1036 am CDT Monday Mar 15 2010 


Update... 
stratus continues to be entrenched across the region. Increased 
sky cover through tonight to 100% as abundant low level moisture 
remains in place. The shortwave moving down the side of the upper 
ridge today is a little farther east than prognosticated and a bit weaker 
in its lift potential. Therefore decreased probability of precipitation in the east for 
the rest of the day though did leave slight chance across the far 
eastern counties into west central Minnesota. 


Hydrological update...river gauges indicate a rapid rise in water 
levels possibly caused by an ice jam at the Elm River near 
Frederick. Issued an areal Flood Warning for northwest Brown County to 
account for the potential of an ice jam moving down the river. 
Other rivers and creeks continue a slow rise. 


See updated aviation discussion below. 






&& 
Previous discussion... 
short term...today through Wednesday 
two separate vorticity lobes still evident on water vapor imagery early 
this morning over the eastern Dakotas. These pieces of energy are 
helping to maintain areas of light rain over the eastern County Warning Area. Will 
hold on to light rain mention in the forecast through the morning 
but a gradual waning in areal coverage/activity is expected by 
late morning and into the afternoon hours. Skies will remain 
mostly cloudy but could see a few breaks developing this 
afternoon. Soundings show the moist layer is not as deep as 
previous days and stronger March sun may be able to get some 
breaks going in the stratus. Although...later tonight any breaks 
will more than likely fill in as low level moisture remains in 
place. Fog also a possibility tonight as the high settles in and 
winds go light. May be tough to get rid of the clouds across the 
County Warning Area on Tuesday but a gradual clearing is expected from west to 
east across the County Warning Area. Clouds look to finally clear out on Wednesday 
as upper ridge moves overhead and drier air works into the region. 
Warmer air also moves in and southwest winds develop at the surface. 
Rather good pattern for decent warming in this area and should see 
highs in the 40s and 50s. With snow cover going away...temperatures will 
be able to climb a little easier. 




Long term...Wednesday night through Sunday 
main challenge in the extended period is precipitation chances and 
types. An upper level ridge will be over the plains to start the 
period...then gets dampened southward as a shortwave tracks across 
central Canada. A trough begins to dig over the Pacific northwest 
on Thursday...then tracks to The Rockies/western High Plains 
Thursday night. The trough strengthens as it becomes centered over 
the plains on Friday...then slides east of the region as a ridge 
builds over the western United States over the weekend. 


At the surface...a cold front will track across the state 
Wednesday night. Low pressure strengthens over eastern 
Colorado/western Kansas on Thursday with both the GFS and European model (ecmwf) 
indicating precipitation developing on the north side of the low 
over South Dakota. The low elongates and track north and east to 
become situated from the Great Lakes to western Texas on 
Friday...then strong high pressure drops over The Rockies Friday 
night and becomes dominant over the plains Saturday and Sunday. 
Will keep a schc to chance pop Thursday through the day Friday over 
the entire County Warning Area. Temperatures look to fall enough Thursday night 
that there may be some snow mixed in with the rain at times. 


Temperatures will start off above normal with highs in the 40s on 
Thursday...then the cooler air begins to move in behind the 
exiting cold front...with highs back to near normal Friday through 
Sunday. Nighttime lows will be highly dependent on cloud 
cover...so expect them to remain above normal early in the 
period...then around normal later in the period when the surface 
high becomes dominant. 






&& 


Aviation... 
sub-VFR flight category flying weather to continue over the next 
24 hours at all four terminals. Kabr and Katy will see a gradual 
end to the drizzle/very light rain by early this morning. There 
may also be some breaks this afternoon/early evening in the cloud 
cover...but difficult to tell at the moment if any of those breaks 
would occur at or near a terminal. Look for fog and low clouds to 
redevelop/persist later tonight...right on into Tuesday. 






&& 


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


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


Weather.Gov/Aberdeen