Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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924
FXUS63 KFSD 271735
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1235 PM CDT FRI MAY 27 2016

.SHORT TERM...(Today and Tonight)
Issued at 418 AM CDT Fri May 27 2016

A fairly quiet night across the area with just some spotty
thunderstorms west of the James River Valley. Air in central
Nebraska stabilizing overnight as any shower and thunderstorm
activity associated with the MCV drifting north dissipates. Lift
associated with this MCV and an associated wave may be enough to
spark an isolated to scattered shower or thunderstorm this morning,
but the better chance should be in the afternoon in central South
Dakota closer to the stronger forcing and just west of the low level
boundary. Instability and shear not too impressive so at best an
isolated threat for quarter sized hail. Temperatures will likely be
a bit limited with cloud cover and spotty precipitation chances so
will aim for highs mainly in the mid 70s with some upper 70s in
northwest Iowa.

By tonight the threat for showers and thunderstorms will increase,
but the threat for severe will still remain limited. Instability
still looks to remain bottled up to the south so if storms can get
going there again, the chances farther north may decrease a bit. But
with a strong wave suspect that at least after midnight we will see
an increase in coverage, especially in northwest Iowa and far
southeast South Dakota. Low temperatures will mainly be in the mid
to upper 50s.

.LONG TERM...(Saturday through Thursday)
Issued at 418 AM CDT Fri May 27 2016

Saturday has the larger scale appearance of a soggy day over much of
the CWA, as a fairly consistent signal of the upper level low
pressure lifting from Nebraska to Minnesota.  Always the wild card
that convection remains much more significant toward I-80 and
interferes with more widespread migration/development within
deformation zone north and west of the upper low track.  Proportion
of thunder to showers will be much greater in the southeast half of
the CWA vs. the northwest half of the CWA. With fairly widespread
precipitation, there is concern that highs will be quite restrained.
Would not be shocked to see some areas struggle to reach 70 degrees
based on expected 850-925 hPa temperatures, but for now the chance
for any breaks in precipitation would mean a less extreme change and
have kept mainly lower to mid 70s. On Saturday night, wave will be
pulling away with precipitation chances gradually dwindling through
the evening.  Potential for a half inch to inch rainfall across
areas southeast of a Yankton to Windom line.

Sunday appears as we will be able to squeak out a more pleasant day
with winds fairly light, and enough sunshine to push temperatures
back closer to 80 degrees for much of the area as broad ridging
aloft spreads across the northern plains. There will be a weak
boundary settling southward toward the northern CWA, and despite
likelihood that the broad GFS rendition of widespread convective
instability by afternoon, far northern areas may be able to overcome
a lack of larger scale forcing to generate an isolated shower or
late day storm. Generally not very enthusiastic with precip chances
through Sunday night, with only potential development of some
steeper mid level lapse rates and the later night push for a weaker
theta-e advection spurring any interest in mentioning a precip
threat.  Again in and around a mild 80 degrees, as long as more
widespread precipitation holds off most of Monday.

Period primarily from later Monday through Tuesday night should
again become more active as strong wave in Pacific northwest pushes
eastward into the northern Plains. ECMWF is almost a state quicker
over 12 hours with eastward progression, and likely will be a shade
slower toward other solutions. Should allow plenty of time to plenty
of moisture to return. Again have the challenge that bulk of more
significant instability could get hung up closer to the synoptic
front toward far southern Nebraska, and allow a break between former
features precip and that associated more with the upper low and
frontal boundary. May have to keep an eye on timing of features for
Tuesday, as the increase westerly/southwesterly flow aloft will
enhance deep layer shear to values suggesting a potential severe
threat with modest instability.

Following feature, appears as if temps will cool back to a bit below
normal for a couple of days, and generally the precipitation chances
should be meager by Wednesday night and Thursday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1232 PM CDT Fri May 27 2016

The near term will be highlighted by lower end VFR to MVFR
ceilings. There is a risk of an isolated thunderstorm near KHON
into early this afternoon. By late this afternoon and this
evening, the various nam and gfs moisture fields are suggesting
primarily VFR conditions. However beginning at midnight, a
disturbance will move northward, likely producing a round of
thunderstorms at KSUX and KFSD for a few hours. This could
certainly bring conditions down into the MVFR category with
pockets of moderate to heavy rainfall. For now, left this kind of
activity out of the KHON TAF site as it appears it may remain east
of there. From 12Z to 18Z Saturday, stability begins to increase.
Most of the rainfall should be north of KSUX, impacting the KFSD
and KHON taf sites. However left TSRA out of these two sites for
Saturday morning but with plenty of MVFR conditions.

&&

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

$$

SHORT TERM...08
LONG TERM...Chapman
AVIATION...MJ



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