Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 260845
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
345 AM CDT THU MAY 26 2016

.SHORT TERM...(Today and Tonight)
Issued at 340 AM CDT Thu May 26 2016

An MCS exiting the far eastern cwa very early this morning with more
energy not too far away. While most of the morning and afternoon
hours will likely be fairly quiet, there will be a small chance for
showers and thunderstorms over mainly the Missouri River corridor
into northwest Iowa. This is in response to upper level energy
lifting northeast from Colorado and New Mexico. Some effects from
this are being seen in western and central Nebraska with scattered
showers and isolated thunderstorms. While this activity is likely to
wane as it lifts northeast, the upper level support will gradually
increase through the afternoon and may spark some showers and
thunderstorms. However with the deeper moisture and instability
bottled up to the south the better threat for thunderstorms will
likely hold off until the main upper level support moves north from
late evening into the overnight hours. While there will be some
potentially better instability in the afternoon the chance for
thunderstorms will be a bit more conditional as thunderstorm
development is more in question. Will keep mainly chance pops south
of Interstate 90 through the afternoon.

Went ahead an increased the chance for rain and thunderstorms as
well as QPF overnight as the models hinting that while the better
instability and severe threat will be to the south in the afternoon
and early evening, as the main wave lifts north overnight the low
level jet will increase substantially with the main focus looking to
take place along and west of Interstate 29. This was the reason for
increasing QPF in these locations as PWAT values might be close to
1.25" to 1.50".

Otherwise another warm day without too much wind...highs mainly
upper 70s to lower 80s. Lows Thursday night not too different from
this morning with mid 50s to lower 60s.


.LONG TERM...(Friday through Wednesday)
Issued at 340 AM CDT Thu May 26 2016

Active pattern continues into the extended.  Short wave train is
expected to lift from southwest to northeast on Friday.  Leading
wave is focused across central South Dakota during the daytime
hours...and have concentrated highest pops across the western
portions of the forecast area.  Still have chance pops across the
east for potential for scattered activity.  Not an overly strong
capping inversion, but very steep lapse rates from 750-500 mb leads
to moderate instability aloft.  Marginal severe threat on SPC seems
fairly accurate with bulk shear values of 30-45 knots.

Fairly strong short wave is expected to lift northeast across the
eastern half of the forecast area Friday night.  Have maintained
likely pops for this feature, and increased qpf closer to WPC
guidance over allblend.

Not a lot of wind shear across the region on Saturday, especially in
the low levels, but with upper low hanging across the eastern half
of the forecast area, could still see scattered showers and
thunderstorms.  With precipitable water values climbing above
an inch throughout the day across the east, have raise qpf
values closer to WPC guidance. Still steep lapse rates at and just
below the hail growth zone, so could see some marginal hail with any
activity that develops.

Upper level ridging across the area on Sunday leads to a potential
break in convection. The steep mid level lapse rates continue to
result in instability aloft, but void of a trigger across the region
beyond diurnal heating.  As such, undercut pop guidance.

Low level jet on Sunday night does not appear to be as strong as
previous runs have suggest, and have begun to cut pops across the
area Sunday night into Monday morning.

Active pattern returns to the area on Monday as a series of short
waves begin to train across the area Monday afternoon into Monday
evening.  Have raised pops over guidance Monday night into Tuesday
as those appear to be particularly favorable times for
precipitation.

Active patter looks to continue into late next week, when large
upper level low moves through the area.  Still some timing
differences on that whether it will be Thursday or Friday of next
week.


&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1202 AM CDT Thu May 26 2016

Line of thunderstorms should exit northwest Iowa and northeast
Nebraska by about 8z or 9z. After this mainly vfr conditions
through the period. However thunderstorms will likely develop
again late Thursday afternoon into Thursday evening bringing more
widespread coverage.


&&

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

$$

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


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