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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
1236 PM CDT Tuesday Apr 28 2015

Short term...(today and tonight)
issued at 416 am CDT Tuesday Apr 28 2015

Current surface observations show the wind shift line aligned from
Marshall Minnesota...to Sioux Falls to just east of Yankton. 10 to 15 miles per hour
winds behind the wind shift have allowed temperatures to remain in
the middle and upper 40s across our western zones coupled with
substantially higher dew point temperatures also. Both the NAM and
GFS do point to a lowering of the current middle and upper cloud deck
as the short wave crosses our forecast area. Therefore left the
mention of isolated sprinkles or light showers in for now...
especially across the eastern half of our forecast area by midday
and afternoon. But honestly measurable rainfall will likely be very
tough to find. Concerning highs today...looks like little change is
needed from the previous forecast. The mixed layer gives readings
mainly in the upper 60s and lower 70s...with Sioux City probably
topping out in the middle 70s.

As the surface winds go light tonight coupled with clear or clearing
skies...lowered lows to below guidance readings in the low lying
areas. Actually the bias corrected European model (ecmwf) and Gem regional looked in
The Ball park and picked up on this idea.

Long term...(wednesday through monday)
issued at 416 am CDT Tuesday Apr 28 2015

Mixy and dry conditions are expected on Wednesday as high pressure
moves over the area. With dry atmosphere...have sided with warmer
bias corrected guidance values.

Similar story on Thursday as return flow starts to set up. With
increasing southerly winds could see an elevated fire danger
especially in the east where the dry air aloft is more pronounced.
Have relative humidity values forecast to fall into the 20-30 percent range
throughout the afternoon hours.

Cold front moves through the area Thursday night into Friday
morning. Very little moisture available with the Gulf shut
down....so have kept probability of precipitation in the slight chance to low chance range.
Have slightly higher probability of precipitation in the north closer to the middle level wave
which leads to slightly more instability aloft.

Any lingering convection shifts east of the east on Friday leading
to another mild day across the area. Have raised forecast highs
closer to British Columbia numbers...especially across central and eastern South
Dakota where cloud cover won't be an issue.

Over the weekend...looks like a relatively quiet start to the
weekend...but with increasing southerly flow and a warm front
lifting through the area...should see enough moisture return with
the low level jet Saturday night that elevated thunderstorms will be
possible. Cold front is expected to move through the area Sunday
night...leading to the chance of a second round of convection.

Have removed guidance probability of precipitation from the forecast for Monday...as cooler
drier air returns to the region. Have increased winds Saturday
through Monday over cons all values based on winds aloft.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1230 PM CDT Tuesday Apr 28 2015

Narrow band of low end VFR stratus with a few patches of MVFR
ceilings will continue to sink south and east through around 00z.
With clearing now working in behind the band in east central South
Dakota. A few sprinkles will be possible in the stratus but will
not impact visibility. Winds are averaging 10 to 15 knots with some
higher gusts to 20 knots but will decrease around sunset to around 5
knots.

&&

Fsd watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
Iowa...none.
NE...none.
&&

$$

Short term...mj
long term...
aviation...

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