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Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota
1256 am CDT Thursday may 7 2015

issued at 1252 am CDT Thursday may 7 2015

06z aviation discussion updated below.

Update issued at 639 PM CDT Wednesday may 6 2015

No major changes planned to the current forecast. Added a mention
of gusty winds for this evening as showers and the occasional
tstorm have kicked out gusts of 35 to 50 miles per hour.


Short term...(this evening through Friday night)
issued at 244 PM CDT Wednesday may 6 2015

Forecast challenges continue to revolve around precipitation timing/amounts
over the next 36 hours.

Currently...with overcast skies and winds from the southeast at 10
to 20 miles per hour...temperatures are holding in the 60s while a complex
pattern of showers and thunderstorms continues to develop and lift
north-northwest. For the first time this year...surface dewpoints
are in the 60s over this County Warning Area. The precipitation over the eastern half of
the County Warning Area seems to be a couple of warm air advection-forced bands of rain
showers...while character of precipitation developing across the
western half of the County Warning Area appears more convective in
numerous discrete showers and weak thunderstorms. Mixed-layer cape
remains rather low given all the cloud cover around. Most unstable
convective available potential energy have increased to between 500-1000j/kg.

The main upper circulation within the longwave trough is located over
western Nebraska...and is forecast to open and lift up toward
northern Minnesota tonight and Thursday. It's probable that the
western or northwestern zones in this County Warning Area will continue to be
influenced over the next 24 hours by deformation-zone forced light
banded rain shower precipitation /perhaps a few rumbles of thunder
through late this evening/. However...short range hi-res and rapid
refresh model output is suggesting it's even more probable that a
cluster or complex of thunderstorms...possibly the convection
getting going now in north central Kansas/south central
Nebraska...will continue to develop or expand north-northeast later
this evening and spread some heavier rainfall amounts up through the
eastern forecast zones...mainly along and east of the I-29 corridor.
While there may continue to be some low-end cape around
overnight...deep layer shear is currently and will likely remain
less than 30 knots as all this convective potential lifts
north-northeast overnight tonight.

There may be some remnant trowal-forced or cold air instability-
induced showers/thunderstorms around on Thursday. Otherwise...much
of the rest of the short term forecast period through Friday night
should be dry while cooler...more stable surface high pressure
builds south out of Canada...drying out the low level moisture...and
turning temperatures a touch cooler than the past few days.

Long term...(saturday through wednesday)
issued at 244 PM CDT Wednesday may 6 2015

There is a reasonable agreement between the GFS/European model (ecmwf) with regards
to precipitation chances through the period. An area of low pressure over the
Front Range of The Rockies in Colorado on Saturday will track
northeastward through Monday. This system will bring a decent amount
of rainfall to the County Warning Area on Sunday and Sunday night. Total rainfall
amounts around a third of an inch is higher likely with this event.
There is a potential for higher rainfall amounts. Temperatures will
be very cool with highs only warming into the 50s on Saturday
through Monday. Sunday will likely be the coldest day with highs
only in the upper 40s for the western County Warning Area. While thermal profiles
support an all rain event...would not be too surprised if the far
western portion of the County Warning Area sees light snow by Monday morning.


Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1252 am CDT Thursday may 7 2015

Upper level low pressure area spinning over the region will make
its way northeast through tonight and Thursday. Still expect some
showers near or at all locations tonight with VFR ceilings
becoming MVFR/IFR. The showers could reduce the visibility to 3
to 5 miles at times. There may still be some scattered light
showers across the region on Thursday with MVFR ceilings becoming
VFR along with breezy northwest winds.


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


short term...dorn
long term...South Dakota

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