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Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota
1242 PM CDT Wednesday may 6 2015

issued at 1241 PM CDT Wednesday may 6 2015

18z aviation discussion updated below.

Update issued at 1108 am CDT Wednesday may 6 2015

Only minor modifications needed to timing in the weather/probability of precipitation grids
this morning. Next in several rounds of rain showers /embedded
thunder/ working up into the County Warning Area at this time. Suspect will see
additional coverage later this evening and overnight.


Short term...(today through Friday afternoon)
issued at 345 am CDT Wednesday may 6 2015

The forecast continues to be rather convoluted thanks to the slow
moving/weakening upper system supporting several waves of generally
light precipitation now through Thursday. The first wave has passed
north of the County Warning Area before becoming better organized...while the next
episode of isentropic forcing is now lifting into the County Warning Area from the
south. Unfortunately upstream radar coverage is spotty with light
returns. Sref probabilities point to quantitative precipitation forecast between 0.05 to 0.10
inches. Profiles this afternoon are marginally
unstable...particularly in the eastern County Warning Area where MUCAPE values top
1000 j/kg...however upper level support is focused West River. Best
isentropic forcing shifts towards fsd County Warning Area highest probability of precipitation
migrate into far eastern counties...while the rest of the County Warning Area will
remain under a moist airmass with little upper support. The system
lifts northeast Thursday...with one final period of weak isentropic
forcing during the day. Sref probabilities support generally light
quantitative precipitation forecast both tonight and thinking most areas will only
receive around a quarter to half an inch in total with this

Surface high pressure noses into the region for early Friday but
cold advection generating a light northeast breeze should keep
temperatures from bottoming out.

Long term...(friday evening through tuesday)
issued at 345 am CDT Wednesday may 6 2015

There are now some disagreements in the long term forecast that
would impact the coverage and amount of precipitation across the County Warning Area
from Saturday afternoon into Monday afternoon. The GFS was diverting
in its surface low pressure area track solution from the ec and Gem
models from Saturday night into Monday. On Saturday evening...all
three models show a surface low pressure area in southeast Colorado.
From here...the ec and Gem show the surface low tracking northeast
while the GFS shows it tracking east northeast. The track difference
would affect the northward push of the rainfall shield into our
region. At this time...all three models show our County Warning Area receiving some
rainfall with less northward push and duration with the GFS model.
Therefore...still have in good chances of rainfall for mainly
Saturday night into Monday morning. With the ec track...rainfall
could continue in the east into Monday afternoon. Surface high
pressure will then build in for Monday night and Tuesday with
clearing skies. Highs will be mostly in the 50s and lower 60s for
Saturday through Monday with 60s for Tuesday.


Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1241 PM CDT Wednesday may 6 2015

While MVFR conditions are expected through tonight...widespread
showers could reduce flying conditions to IFR levels at times. IFR
conditions are highly likely for all terminals between 10z-15z
with low clouds and fog. Winds should shift to the northwest
around 15z which will slowly improve flying conditions.


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


short term...Connelly
long term...mohr
aviation...South Dakota

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