Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 261948
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
248 PM CDT THU MAY 26 2016

.SHORT TERM...(This evening through Friday)
Issued at 247 PM CDT Thu May 26 2016

Warm front remains well south of the region, extending from the
surface low in southwest Kansas to the northeast near the Iowa and
Missouri border. A more diffuse frontal boundary has sagged just
south of the forecast area, but has allowed mid and high clouds to
blanket much of the forecast area. Instability is quite low,
especially heading north of the Missouri River, and is well capped.
Shower and thunderstorms activity has already fired in the I-70 and
I-80 corridor This will make it more difficult to get increased
moisture/instability into our forecast area, making thunderstorms
development problematic across our forecast area until the low level
jet and shortwave lift into the region late this evening and
overnight. Effective shear is moderate across far southeast SD into
northwest Iowa. Instability is highest in the Highway 20 corridor,
where capping is also weakest, so expect that this area has the best
potential to see severe activity this evening...if any develops this
far north. Large hail to 2 inches and gusts to 65 mph will be
possible if any storms do creep into our southern border, the
highway 20 corridor, this evening. But given the more southerly
track of convection seen in the CAMS, and qpf trends in the
operational models, think that the vast majority of any evening
convection remains south of the forecast area.

Heading towards midnight and the early morning hours Friday, the
approach of the shortwave and the arrival of the low level jet may
lift shower and thunderstorm activity into the forecast area. Either
way, severe hail threat would be minimal overnight, however a few
strong wind gusts could approach severe levels through the overnight
hours.

Energy from the shortwave splits off to the north on Friday while
the main upper low wobbles over eastern Colorado. Think that there
will be at least some breaks in the showers and thunderstorms during
the day Friday, however we maintain our moist and unsettled air into
the afternoon, so do not think that we will be entirely dry in the
afternoon. Scattered showers and thunderstorms seem the best bet for
now. Shear looks marginal for any severe storms, however afternoon
heating and increasing mid level lapse rates could allow for enough
instability for an isolated severe storm in the afternoon.


.LONG TERM...(Friday night through Thursday)
Issued at 247 PM CDT Thu May 26 2016

Wave coming up from the south southwest Friday night and Saturday is
depicted by the models as a little weaker and not getting as far
north as in earlier runs. The system still will have plenty of
moisture, but it no longer looks like there is strong enough lift to
present the heavy rain threat we were looking at, and not a good
enough boundary or thermal gradient to support storms which would
produce heavy rain. Will keep likely pops for showers and storms,
which should wane Saturday afternoon and night as the system turns
more easterly and pulls slowly east of the area.

Sunday could be a dry day, but some instability redeveloping by
afternoon under a westerly flow aloft leads me to keep a slight
chance mention for storms.

Shower and storm chances should increase again early in the coming
week ahead of a trough digging in to the northern Rockies. It looks
like this system will eventually dig more east of the plains,
leaving our area in a dry northwesterly flow. This is shown to
happen by midweek on the new EC, but happens in a much slower/longer
time frame on the 12Z GFS. Therefore, will keep the extended shower
chances loaded for Wednesday and Thursday, for now. Should the
faster EC pan out, we can make those days dry in future forecasts.

Temperatures will be mild to modestly warm through the period. the
warmest days with some lower 80s will probably be Sunday and Monday
with mainly 70s highs otherwise. Those two days appear to have the
best sunshine and heating between the clouds of Saturday and a
slight cooling trend later next week. Should the latest EC come
into reality, the start of June could be on the cool side.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1237 PM CDT Thu May 26 2016

Active weather pattern continues, with thunderstorms lifting into
the southeastern half of the region mid to late evening and
through the remainder of the forecast area after 06z. Expect mvfr
and ifr ceilings and/or visibility in the heavier storms. Models
suggest that mvfr and patchy ifr ceilings will become more
widespread late tonight - after 09z - mainly along and east of
I-29.


&&

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

$$

SHORT TERM...
LONG TERM...
AVIATION...



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