Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 260448 CCA

Area Forecast Discussion
National Weather Service Sioux Falls SD
1047 PM CST Fri Nov 25 2016

.SHORT TERM...(This evening through Saturday)
Issued at 302 PM CST Fri Nov 25 2016

Band of high clouds will work into the area tonight insulating the
surface from radiating efficiently.  Model soundings and satellite
suggest cloud cover would be fairly thick, and have therefore sided
with a blend of forecast lows overnight.  Potential for a little bit
of fog where melting snow has saturated the near surface layer.  Hi-
res CAMs suggest best potential for this to occur will be across
central Minnesota.  With low level surface flow out of the
southeast, could see fog spread as far west as the Buffalo Ridge,
but cams keep it east of there for now.  Will need to monitor though
to potentially add mention to Marshall and Windom.

Mild southwest flow keeps temperatures aloft quite mild.  Will not
come anywhere close to mixing out with low single this time of
year, but have raised forecast highs into the upper 40s and 50s with
925 hpa temps of 4-6 C.

.LONG TERM...(Saturday night through Friday)
Issued at 302 PM CST Fri Nov 25 2016

Saturday night should be a dry and quiet night with light winds and
cool conditions. Very light southerly flow will begin to respond at
the surface as low pressure begins to deepen to the southwest.
Clouds should not increase too much just yet which will allow
temperatures to fall into the 20s.

By Sunday a strong upper level low pressure will spread into
Nebraska. Ahead of this wave, strong moisture return will set up in
northern Nebraska in the morning and spread north through early
afternoon. Instability not really there in this initial surge of
moisture, but the moisture will be deep enough to allow a band of
rain to develop and quickly spread north. Late in the afternoon and
into the evening the dry slow will spread north and with it there
could be a little instability that could allow a few non severe
thunderstorms to develop and again quickly race north. The exception
will be parts of central SD in the mid and upper James Valley where
lift may hang around and allow precipitation to linger longer.
Thermally expecting all rain, maybe mixing with a little snow in
central SD if the cold air can get in before the lift weakens. But,
similar to this past storm, the source for cold air just is not
there so will need to rely on drying aloft to force the thermal
field down. So confidence in winter weather precipitation is not
very high.

This low pressure will cut of from the main jet and spin to the
north, bringing small chance for rain or snow Monday into Wednesday.
Chances not great but the better chances should be north of
Interstate 90 where saturation in the ice bearing layer is more
probable. If temperatures aloft can cool a bit more some convective
showers would be possible each day across the entire area, but
confidence not high enough to include just yet. Do not doubt that
forecast highs Tuesday and Wednesday will be warmer than currently
forecast given likely deeper mixing with a westerly component.

Made no changes to Thursday and Friday as cooler air looks to filter


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1047 PM CST Fri Nov 25 2016

Main aviation concern will be the potential for patchy fog to
develop late tonight. The NMM and to a lesser extent, the HRRR
indicate that patchy fog will be possible mainly along and east of
the James River, as winds become light overnight. However, with
a greater amount of cirrus blanketing the entire forecast area,
have decided to continue leaving out mention of any fog from the




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