Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 191729
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1229 PM CDT THU MAY 19 2016

.SHORT TERM...(Today and Tonight)
Issued at 259 AM CDT Thu May 19 2016

Models all show advection of mid level moisture today with this
effect shifting a little more into the eastern part of the area,
around Interstate 90 and east, for this afternoon. Skies today will
go partly cloudy. Model soundings on BUFKIT show a very unstable
layer with the heating, but this does not go much above 10k feet.
This is not too much different than the situation we had a few days
ago, and today as well, I expect at most light showers to be very
spotty, at least as far as precipitation reaching the surface. The
HRRR, as one might expect, shows the development of myriad very
weak returns. Will keep chances just barely at the mention level at
most, and will not extend the mention all the way over northwest IA
after coordination. Overall, with mild high temperatures at or a
bit above 70, it will be a pleasant Spring day, warm enough for
breezy southerly winds in our SD area not to add any real chill.

The marginal light shower possibility should be gone by the start
of the evening, though it looks like some mid level moisture and
clouds will continue to drift over the area tonight. Will keep low
temperatures mostly 50 to 55, with a continuing southerly breeze
helping to put a limit to the cooling.

.LONG TERM...(Friday through Wednesday)
Issued at 259 AM CDT Thu May 19 2016

Friday through early Saturday will be marked spotty precip chances
at best, with moisture remaining limited as surface ridge axis holds
in place from east Texas into the Great Lakes. For this reason will
continue to favor lower end of dew point guidance into Saturday,
especially for eastern portions of the forecast area. Difficult to
really pin down more favored locations for any isolated shower or
thunderstorm development through this period. However, continue to
see northern stream upper level wave dropping through the eastern
Dakotas and Minnesota through this period. This could provide enough
weak lift to trigger spotty showers or an isolated thunderstorm from
east central SD into southwest MN/northwest IA Friday afternoon,
though a little concerned about lack of moisture as discussed above.
As the wave continues to slip southward Friday night, some models
pointing to interaction with eastern fringe of low level jet/warm
advection, resulting in elevated convection developing late Friday
night through portions of the Missouri River Valley. Keeping this
activity a little more isolated and farther west than NAM/GEM at
this time, closer to the low level jet support and axis of elevated
instability, with the chance that isolated showers could drift east
into the Sioux City area after daybreak Saturday. Temperatures on
Friday expected to be similar to slightly warmer than today, with
Saturday marking the start of above normal temperatures which should
persist through the end of this forecast period.

Gulf begins to open up for better moisture transport Saturday night,
but at this time appears deeper moisture will remain west of our
forecast area through daybreak Sunday and will keep the dry forecast
going through Saturday night. Models do seem to be pushing the upper
ridge east a little faster now than was seen the past couple of days
though, and with strong surge of low level moisture Sunday, followed
by dry line and increasing deep layer shear possibly pushing close
to Missouri River in central SD by 23/00Z, may have to watch for
isolated strong to severe storms west of the James River by Sunday
evening.

Mid-upper level trough then slides through the forecast area Sunday
night and Monday and will maintain highest pops through this period,
especially Sunday night with both GFS and ECMWF indicating potential
for isolated rainfall amounts in excess of an inch. Still a few days
for timing/location to be ironed out, but depending on where the
heavier rain falls, may have to watch for renewed flooding issues on
some of our northwest IA rivers.

Area remains in somewhat unsettled west-southwest flow pattern
through the middle of next week. As is often seen, models disagree
on timing/location of short waves moving through the flow, resulting
in spotty rain chances lingering for Tuesday and Wednesday. Should
remain on the mild side, with highs in the 70s and lows in the 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1228 PM CDT Thu May 19 2016

VFR through the period. Diurnally driven VFR ceilings through
sunset, then increasing clouds late tomorrow morning.

&&

.FSD Watches/Warnings/Advisories...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...
LONG TERM...JH
AVIATION...08


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