Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 231809
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
109 PM CDT MON MAY 23 2016

.SHORT TERM...(Today and Tonight)
Issued at 347 AM CDT Mon May 23 2016

Line of storms has weakened as anticipated, as it moved east away
from more favorable shear overnight. Leading edge should move east
of Highway 71 on the eastern edge of the forecast area by daybreak
or before, but trailing more stratiform rain will likely continue
along and east of I-29 corridor into mid morning. Primary question
for the remainder of the day will be how far east the main boundary,
currently west of the James River as of 08Z, will push through the
day, as additional development most likely near or east of this
boundary. Greatest model consensus shows this boundary moving near
an Ivanhoe-Sioux Falls-Vermillion line by 18z, then stalling as
another wave lifts northeast out of the Central Plains. This wave
should trigger redevelopment toward midday in areas east of the
boundary. Most recent runs of RAP/HRRR show a decrease in areal
coverage of ongoing precip between 12Z-15Z, followed by this
redevelopment across northwest Iowa and southwest Minnesota after
17z-18z.

What does this mean for severe potential today? Slight mid-upper
level cooling in response to the wave will bring an increase in
instability this afternoon, despite a fair amount of cloud cover
limiting the heating across the area of concern today. However,
shear needed to sustain storms is on the weaker side in areas east
of the boundary. Thus thinking that isolated severe storms with
marginal hail could develop as the wave moves across the area, but
do not anticipate an organized severe weather event this afternoon.

Expect any showers/storms to wind down through the evening as the
northern stream wave kicks east through the western Great Lakes,
leaving dry conditions through the overnight hours. With the low
level boundary stalling, moisture along/east of I-29 never really
gets scoured out through the day, and with light surface flow and
partial clearing, could see some fog develop early Tuesday morning.
Confidence not high enough to introduce into the forecast at this
time, but something to consider as later shifts watch how things
evolve through the day.

.LONG TERM...(Tuesday through Sunday)
Issued at 347 AM CDT Mon May 23 2016

Tuesday appears to be mainly dry across the region.  With drier air
mixing down from aloft, should see dew points fall through the day
limiting the amount of instability. However, warm front is expected
to lift north across the plains approaching the southern fringes of
the forecast area in the late afternoon hours.  Increasing moisture
south of the boundary along with convergence along the front will be
nearly enough to tip the scales in terms of convective development.
In addition, low level jet will increase south of the front.  With
the forecast area located on the nose of the low level jet as works
north, as strong shortwave approaches from the southwest, expect
convection to become more widespread through the evening hours.
fairly straight hodographs favor splitting supercells. In terms of
severe, expect hail and winds to be the primary threats as storms
will be elevated.

Wednesday looks to be characterized by very steep lapse rates from
around 700 mb.  This results in relatively large amounts of CAPE by
mid to late afternoon.  Capping inversion is weaker across the
north, and have kept pops higher up there.  Still can not rule out a
wave triggering more widespread activity, but hard to pin point at
this time.

Cold front sweeps through the area wednesday night into thursday
morning. PWAT values ahead of the front surge to 1.1-1.2 inches. At
this point, appears that the front movement will be fast enough to
limit flooding potential, but will need to keep an eye onthis. There
is the potential of seeing convection with this front, so kept pops
in the chance range ahead of the boundary.

Drier filters into the region on Thursday behind the front.  With
the drier atmosphere in place, have lowered pops especially in the
west where the chance of lingering rain looks low.

Warm front along with a fairly strong short wave are expected to
move across the area on Thursday night into Friday.  Have raised
pops into the high chance to likely range.

Dirty west to southwest flow at the mid levels continues through the
weekend into early next week. this results in convective chances
continuing through the extended, though the details are difficult to
ascertain at this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 106 PM CDT Mon May 23 2016

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP EAST
OF YANKTON TO LUVERNE TO WINDOM LINE EARLY AFTERNOON THROUGH EARLY
EVENING. MVFR CEILINGS WILL CONTINUE IN THIS REGION...WITH
OCCASIONAL IMPROVEMENTS IN THE AFTERNOON...HOWEVER CEILINGS AND
VISIBILITY SHOULD DROP BACK TO MVFR AND IFR IN THUNDERSTORM
ACTIVITY. THERE MAY ALSO BE THE POTENTIAL FOR PATCHY FOG MAINLY
EAST OF I29 LATE TONIGHT.

&&

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

$$

SHORT TERM...JH
LONG TERM...BT
AVIATION...


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