Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 281954

Area Forecast Discussion
National Weather Service Sioux Falls SD
254 PM CDT TUE JUN 28 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 246 PM CDT Tue Jun 28 2016

Tricky forecast for tonight and Wednesday, with quite a bit of
uncertainty in the convective pattern. Northwest flow aloft
prevails, while low level southeast flow has set up and upslope
situation to our west. For this evening and tonight, models continue
to suggest that a cluster of thunderstorms will form in southwestern
South Dakota and northwest Nebraska, and track southeast through the
overnight hours. The question will be how much of our forecast area
will be impacted. The NAM and HRRR keep these storms mainly outside
of the forecast area this evening, then form additional weaker
showers and storms through southeast SD and northwest IA in the
early morning hours. The GFS and GEM however a much more aggressive
in bringing the evening convection to our west across the bulk of
the forecast area through the overnight hours. The GEM in particular
paints some very heavy QPF values. ECMWF delays nearly all evening
storm development until a mid level wave drops through the center of
our forecast area late tonight. Will go with chance to low end
likely pops mainly across our IA, SD, and NE counties after midnight
where the isentropic lift is best and the greatest model consensus
lies. Instability is pretty meager throughout the region while shear
is somewhat marginal. Overall think that the severe threat is
minimal, but thunderstorms with small hail and locally heavy
rainfall is possible.

Any overnight convection will weaken and slide southeast through
midday on Wednesday. The question will be how the convection earlier
in the day will impact instability in the afternoon. With potential
clouds and a question of where any boundaries may set up, not much
confidence in where and afternoon convection forms. Instability will
likely not be great, but cannot rule out some scattered showers and
storms forming, especially mid to late afternoon. Highs will reach
the upper 70s to mid 80s.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 246 PM CDT Tue Jun 28 2016

Model guidance continues to shift PoPs southward Wednesday evening and
overnight as shortwave energy edges away from the area. Highest
PoPs remain south of the I-90 corridor through midnight. A
stronger upper trough is expected to drop southeast into the Great
Lakes on Thursday, and this trough will push a frontal boundary
through the CWA during the day. A linear axis of showers and
thunderstorms will move from north to south across the CWA through
the day, but coverage of activity is in question. This front will
quickly push southward in the afternoon with dry conditions by
Thursday evening in most locations.

High pressure will dominate the region on Friday and continue to
influence the weather conditions through the upcoming holiday
weekend. Guidance continues to show a prevailing mid-lvl ridge over
the CONUS, with disorganized energy moving through the Southern
Plains and a series of waves cresting the top of the ridge in
southern Canada.

This pattern should keep the majority of hours dry through early
next week, with temperatures moderating back towards and above
seasonal normals by Sunday. The 4th of July continues to look
relatively quiet, but will need to watch the potential for a weak
sfc trough to form over central SD/NE, serving potentially as a
focal point for scattered convection during the afternoon and
evening hours. At this time, this is a very low PoP.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1218 PM CDT Tue Jun 28 2016

VFR conditions are expected through the TAF period.
Isolated high based showers or thunderstorms will track southeast
through around 21z, but potential to hit TAF sites is too low fore
mention in TAFs at the moment. Thunderstorms may clip south
central SD in the late afternoon or evening, however the bulk of
this activity will be south of the forecast area. Additional
isolated to scattered high based showers and storms will again
become possible late tonight, after 06z into the mid morning
hours. Again, this activity will be too spotty for mention in the
TAFs at this time.


.FSD Watches/Warnings/Advisories...


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