Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Aberdeen South Dakota
552 am CST Sat Dec 20 2014
aviation discussion has been updated.
short term...through Monday
Stratus stuck across the east yet again this morning. To the
west...might get some daytime heating before the next weak wave.
H925 temperatures warm to between -1 and +4c...though its uncertain
whether this will be realized at the surface without mixing. A
narrow ribbon of middle level clouds/very light quantitative precipitation forecast will result from
the warm advection push. Thermal profile suggests ptype as
rain/freezing rain...depending on surface temperatures which are
around freezing. Model quantitative precipitation forecast is negligible...so only spotty impacts
to travel expected.
Focus shifts to Sunday night/Monday. Confidence is very low for
impacts to the region...thanks to the variety of model solutions
and a track generally favoring lower end quantitative precipitation forecast. With mild middle
level temperatures in place...a rain/freezing rain ptype is the
most likely outcome as the system moves across the County Warning Area during the
overnight hours and surface temperatures run a few degrees either
side of freezing. Generally light quantitative precipitation forecast early Monday morning given
warm advection/isentropic upglide as the main source of
lift...but if the timing coincides with the am commute/travel and
school...this could potentially have a greater impact.
Cold advection will result in a change over to snow on Monday. As
the system deepens over Minnesota...wrap around/trowal precipitation may
extend back into the County Warning Area for accumulating snow...though guidance
is not unanimous in this outcome. The gradient does increase
however...so anticipate gusty winds for the Missouri Valley west.
Long term...Monday night through Friday
There is still a lot of uncertainty in the long term forecast.
The period starts of with an upper trough/low over the northern
plains...and perhaps even some trowal induced light snow over the
eastern County Warning Area. However...that trough gets shunted east as more energy
moves southeast across The Rockies. This energy is handled
somewhat differently by the models...but the result is a band of
wintry precipitation somewhere over the central/northern plains late in the
week. Forecast confidence in the latter part of the period is low
based on the varying model solutions. Temperatures for now look to
be right around normal for most of the period.
12z tafs for the kabr...Katy...kpir and kmbg terminals
IFR ceilings will likely improve some at Katy/kabr during the day.
Meanwhile visibilities should also improve to VFR by afternoon. A weak
system may bring light precipitation to both terminals this afternoon or evening.
After some patchy early morning fog both kpir and kmbg should be
mostly VFR today. A weak system could bring early and middle
afternoon light precipitation to kmbg. Precipitation type could initially be freezing rain
but then transition to -ra as temperatures warm.