Community News: Weather update on flood conditions 7:20pm 9-24-16

Short Term Wx Discussion – This afternoon and Tonight – from NWS-C – updated at 1517 9/24/2016

Showers and thunderstorms are developing quickly across eastern South Dakota and southwest Minnesota on southward.  Models have significantly downplayed the convective coverage and intensity all day – possibly because the extensive cloud cover has eroded and temperatures have warmed into the 80s across southern MN.  This has produced energy aloft values of 1500 Joules/kg within the deep moisture layer with precipitable water values of 1.7-2 inches along the front.  Some models seem to be handling this better with widespread showers and thunderstorms pushing through the region tonight.

The main threat from this activity is heavy rain.  Already there are lines of training thunderstorms across southwest MN.  As this activity builds eastward with time, instability will be trending downward but rich moist air will remain intact along the front.  Soil moisture is in excess of 60{b5761be34e80a16b6d0e4dabc1869c131a263f96a745c82bebdd3b8a4330bfa9} and even higher in some areas of south central MN to west central WI.  Any addition heavy rain would bring the potential for flash flooding and possibly exacerbate ongoing long term flooding.  In collaboration with forecast offices in Aberdeen SD and Des Moines IA – have issued a flash flood watch for areas at greatest risk.  However, if the training activity over Sioux Falls SD area continues, the watch may be extended further west.

Most of the activity should be to the east Sunday morning.  A few showers may persist toward Eau Claire WI but the heavy rain threat should be over by mid-morning.  Dry air should bring a period of clearing before wrap around stratus cloud deck arrive by afternoon.

Long term Wx Discussion – Sunday thru Friday – from NWS-C update at 1517 9/24/2016

Things look to turn quiet and dry for the extended period.  In the big picture the upper trough will move through Sunday night and Monday, then work its way into the Great Lakes by Tuesday.  There have been some differences on model guidance as to what happens after, but all guidance takes it sufficiently east to bring high pressure to our area by Wednesday with a fair stout system for Thursday and Friday before we start to get back into some southwest flow by Saturday.  It may be possible there are some showers Sunday night into Monday – particularly across the north and east.  After that things look dry through the remainder of the period.  Temps will slowly moderate by midweek, then look warm in the latter half of the week as warm advection increases across the region.  There is a chance for showers and thunderstorms in the Friday/Saturday time frame particularly across the west.