Scientific Forecaster Discussion
fxus63 kunr 251804
Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
1204 PM MDT Thu may 25 2017
Discussion...(today through wednesday)
issued at 209 am MDT Thu may 25 2017
Closed low will linger over the northern plains through the
weekend, supporting a long period of unsettled cyclonic flow
aloft. Sfc cold front is in the process of pushing through the fa,
with a prefrontal trough supporting convection east of the fa.
Southern periphery impulse supported a weak mesoscale convective system over Wyoming earlier,
with the remnants of this feature continuing to support showers
over central Wyoming. This feature will continue to progress east this
morning, possibly clipping the far southern forecast area with showers.
Otherwise, dry conds expected today most areas with windy conds northwest
South Dakota where near adv winds are forecast. There is a very small
chance for a shower over the far northwest third as lower heights spread
into the region and support some week instability. Did not include
a pop mention for this given very dry profiles, with sprinkles
expected at best.
Closed low will slowly shift east with several weak impulses
rotating around the low, advecting through the region. This will
support cool and unsettled conds through the weekend, with near
daily chances for shra/ts. Southern stream impulse will phase with
the northern Continental U.S. Trough Fri night/Sat, resulting in a decent
fgen response coupled with pos Theta-E adv. Forecast models
continue to favor the South Dakota/NE border area attm for a decent rain
event (save for the outlier 00z NAM which is biased well north).
However, further track adjustment is likely per this feature as
convective feedback and closed flow aloft introduce model
limitations. Upper low will finally shift east by Mon-Tue of next
week as the western Continental U.S. Ridge trends east. This will support a
warming and drying trend by mid next week, although warmer temps
and fair conds looks short-lived as the next deep upper trough
approaches in European model (ecmwf) and GFS solutions.
Aviation...(for the 18z tafs through 18z friday)
issued at 1202 PM MDT Thu may 25 2017
VFR conditions are expected through the forecast period. Breezy
northwest winds mainly across northwest South Dakota will decrease this