Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kfsd 180451 

Area forecast discussion
National Weather Service Sioux Falls South Dakota
1051 PM CST sun Nov 17 2019

issued at 1039 PM CST sun Nov 17 2019

The main forecast change has been in precipitation chances as the
weak/disorganized wave moves through. Forcing remains very weak
and low-level moisture is limited. In fact, hi-res models are
coming in weaker/drier for our region. With that said, have
decreased precipitation chances tonight into early Monday morning.
The primary p-type continues to be rain. While confidence is low,
a brief window of patchy freezing drizzle is possible towards
daybreak along and east of I-29.


Short term...(this evening through monday)
issued at 257 PM CST sun Nov 17 2019

Certainly different conditions compared to yesterday with a stratus
deck well entrenched across much of the area, slowly eroding from
west to east. This has kept temperatures about 10 degree cooler,
with mid 30s to mid 40s for most locations.

Overnight, we will be watching a quick moving fractured wave sliding
down in the northwest flow. High res guidance confirming this wave
will likely result in at least a chance of some very light
precipitation late tonight into Monday morning. A warm layer aloft
should keep any precipitation in the form of liquid with surface
temperatures providing the primary determination of impacts. With
overnight lows likely staying above freezing west of I-29, should
see any light precipitation stay rain but things get a little more
tricky along and east of I-29. At this time, it appears most
locations will see temperatures moderate above the freezing mark
prior the arrival of any precipitation. However, it may be a close
call in some locations (especially along the Buffalo ridge) with
the NAM and its influenced derivatives precariously close to a
brief period of freezing rain. This has also pushed some
probabilities in the href for very light freezing rain for
locations just east of a Brookings to Sioux Falls to Cherokee
line. Given the recent performance of the previously mentioned
guidance, as well as known biases, have hedged more towards the
rain vs freezing rain solution but certainly a non-zero chance of
a brief period of freezing rain. Will be something for evening and
overnight shifts to monitor as even with the very light nature of
any precipitation, could still cause some minor issues,
particularly on elevated surfaces.

Any remaining precipitation should fizzle prior to mid day Monday,
although clouds will be slow to clear, especially east of I-29.
Warmer mid level temperatures will be streaming into central and
eastern South Dakota and should help warm afternoon temperatures back into the
50s despite a northwesterly component to the winds. Previously
mentioned cloud cover east of I-29 will hold temperatures in the 40s
and wouldn't even rule out a sprinkle over SW Minnesota as another vort lobe
scrapes the area.

Long term...(monday night through sunday)
issued at 257 PM CST sun Nov 17 2019

Mid and upper level height rises commence Tuesday as ridge axis
shifts east later in the day. Surface winds will be rather light
which may limit mixing and thus temper the overall warming
potential. With this said, still feel temperatures will end up
closer to the 75th percentile of guidance and thus have continued to
trend things this direction.

Next forecast concern will revolve around the trough that will work
into the western US. Mid level warm advection overnight Tuesday into
early Wednesday will bring increasing cloud cover and perhaps an
outside chance at some very light precipitation. More significant
precipitation arrives late Wednesday into early Thursday as a piece
of energy rides up in the southwest flow with favorable jet dynamics
aloft. While model consensus keeps the crux of the energy just to
our south, trends have favored a northward tint with the vast
majority of ensemble members having some form of quantitative precipitation forecast across our southeast
half. Have coordinated with neighboring offices to raise pops with
the blended guidance very near the 25th percentile and likely too
low. Forecast soundings point toward a precipitation type of rain to
start with an eventual switch to snow prior to precipitation ending.
At this time, any snow amounts look to remain non-significant but
will continue to evolve as the event nears. Winds will also likely
be on the breezy side with the systems passage.

Late week into the weekend should be on the quiet side with
temperatures in the upper 30s and 40s.


Aviation...(for the 06z tafs through 06z Monday night)
issued at 1039 PM CST sun Nov 17 2019

Light rain showers are possible tonight into early Monday
morning. Confidence in timing is low-moderate given that this is a
very unorganized system. As for now, the best chances look
possible after 09z Monday. Some patchy freezing drizzle is
possible at kfsd/ksux; however, did not mention -fzdz in tafs due
to low confidence. Overall, VFR conditions are expected through
the period at all sites.


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


National Weather Service Glossary of Abbreviations