Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 230354
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1054 PM CDT THU SEP 22 2016

.SHORT TERM...(This evening through Friday)
Issued at 259 PM CDT Thu Sep 22 2016

Shortwave ridging has moved in behind a departing mid-lvl
disturbance over southwest Wisconsin.  We`re finally beginning to
see stratus clear across portions of NW Iowa and SW Minnesota as we
approach mid-afternoon. With a few weak convergence boundaries and
convective temperatures slowly being met, wouldn`t be surprised to
see scattered showers or even a few thunderstorms into the early
evening hours primarily across NW Iowa and SW Minnesota.

By this evening, models suggesting stratus should begin to expand
once again as warm frontal boundary reforms to the south of the CWA.
Already low stratus over south central SD could lead to dense fog
quickly this evening. Elsewhere, patchy to even areas of fog look
possible. Patchy drizzle may also form, but at this point have held
off from including in the forecast due to low coverage and
confidence in occurrence.

By Friday, the aforementioned warm front will begin to surge
northward as an upper trough pivots into the Central Rockies. With a
return of broad warm advection ahead of this trough, we may begin to
see scattered showers and thunderstorms after midnight and into mid-
morning Friday. The primary limiting fact is a wedge of dry air also
rotating northward into the region. Otherwise, the real question for
Friday will be just how far the front can reach by the late
afternoon hours. South of this boundary, temperatures have the
potential to jump towards 90 degrees once stratus lifts north,
especially over the MO River Valley. On the other side of this
front, where stratus and lingering showers may prevail well into the
afternoon, temperatures may only reach the lower 70s.

.LONG TERM...(Friday night through Thursday)
Issued at 259 PM CDT Thu Sep 22 2016

Friday evening looks to be mostly clear across the area, with the
exception across southwest Minnesota along the Buffalo Ridge.  It
appears that low level moisture will have a hard time scouring out,
and may have some low level moisture that results in low clouds and
fog through the evening hours.  However, as gradient winds increase,
expect conditions to gradually improve.  Fairly strong low level jet
develops with a very solid 30 knots at 925 hpa across much of the
area by 06z. Cold front approaches from the west bringing the chance
of showers and thunderstorms.  As the front moves across, chance for
showers and thunderstorms shifts east across the forecast area. Cold
air lags behind the front, so should see fairly mild temperatures on
Saturday.

Sunday is a different story however as cold air advection combines
with stronger winds developing behind the front resulting in a
breezy fall day across the region. with again 30 knots developing at
925 hpa early Sunday morning, have raised winds throughout the day
on Sunday.  Should be a fairly mixy environment, with dry atmosphere
and unidirectional flow.

Thereafter the forecast becomes muddy as models are still waffling
on details of the southern half of the trough over the weekend.
Ensembles really don`t offer a clear picture of what solution to
follow.  GFS keeps the upper trough together, but strengthens the
southern half of the trough during the day on Monday.  The EC and to
some degree the NAM, break off the southern edge of the upper trough
and leave it as a cut off low across the Southwestern US before
ejecting it back into the mid section of the country sometime late
next week. The Canadian is somewhat of a blend of the two (if that
is possible), with upper trough remaining as one system, but
becoming cutoff across the central portion of the country and
remaining semi-stationary through much of next week.  While the
devil is in the details- which remain uncertain at this point,
stuck closer to model blend for now.  It is fairly certain that this
will be a slowly evolving pattern, so will likely not see
temperature fluctuations like we have seen this week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1044 PM CDT Thu Sep 22 2016

Main concerns through the TAF period are stratus and potential
fog overnight through Friday morning. Stratus will bring IFR
ceilings to HON, FSD, and SUX with LIFR ceilings possible at HON.
Showers and storms are possible, but low confidence precluded a
mention in the TAF. Conditions will improve following sunrise as
southerly winds clear the region out by early afternoon.

&&

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

$$

SHORT TERM...Dux
LONG TERM...BT
AVIATION...08



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