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FXUS63 KFSD 270919

Area Forecast Discussion
National Weather Service Sioux Falls SD
419 AM 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 06Z TAFS through 06Z Friday night)
Issued at 1022 PM CDT Thu May 26 2016

Scattered thunderstorm chances will continue through the taf
period...with the greater chances through the lower Missouri
River corridor into northwestern Iowa very late tonight.
Conditions will lower into the IFR/MVFR range in heavier
thunderstorm activity.


.FSD Watches/Warnings/Advisories...


LONG TERM...Chapman

FXUS63 KFSD 261048

Area Forecast Discussion
National Weather Service Sioux Falls SD
548 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

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


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 547 AM CDT Thu May 26 2016

While some patchy river valley fog will be possible through about
14z, mainly VFR conditions are expected through about 0z. After
this thunderstorms will become an increasing threat with a few
severe storms possible south of Interstate 90 this evening.


.FSD Watches/Warnings/Advisories...



FXUS63 KFSD 252051

Area Forecast Discussion
National Weather Service Sioux Falls SD
351 PM CDT WED MAY 25 2016

.SHORT TERM...(This evening through Thursday)
Issued at 351 PM CDT Wed May 25 2016

Instability still looks sufficient for severe storms late this
afternoon and evening with modest 1500 or so CAPE, but shear is
looking a little less supportive than it did earlier with
directional wind profiles dampened by veering of lower level winds.
Of course the doubt remains in both initiation and coverage of
storms with heating dampened somewhat by lingering low level
moisture and clouds, apparently partly related to the storms that
west through in the early morning, and somewhat of a cap to be
broken. It seems best to keep coverage isolated. The HRRR has been
tracking a few storms across the area during the coming evening
hours, with the strongest activity south of Interstate 90. This
activity may be a reflection of an impulse that seems apparent in
current activity over western nebraska. The HRRR also brings a
couple cells across further north. Will keep pops low given the
unfavorable parameters for convection to become even remotely

As the low level flow brings in more stable air, and with nocturnal
cooling, any activity should die off later tonight without a decent
low level jet to support our patented nocturnal storms. Skies should
be clear to partly cloudy with lows in the mid 50s to low 60s.

The quiet weather should continue well into Thursday, until the
backing of the upper flow ahead of an approaching southern plains
wave induces an increase in low level moisture and overall
instability from the south and southeast. This will bring a threat
of storms to the southeast half of the area in the afternoon,
mainly in northwest Iowa and extreme northeast Nebraska, with some
severe threat. Temperatures should warm into the lower 80s east and
the upper 70s west.

.LONG TERM...(Thursday night through Wednesday)
Issued at 351 PM CDT Wed May 25 2016

A very active and wet pattern persists into early next week as a
series of shortwaves lift northeast through Great Plains. Upper
level trough over the central and southern Rockies arrives in the
high plains Thursday night, and slowly wobbles north northeast
across our forecast area through Saturday night. With low level
moisture continuing to tap into gulf moisture and several impulses
traversing the mid level flow, showers and thunderstorms will remain
likely each forecast period through Saturday. There is a low chance
for severe weather Thursday evening into the overnight hours, with
moderate instability and marginal shear values as the warm front
noses into central or northern Nebraska. Friday`s severe chances
will hinge on how overnight convection will impact the airmass and
where any boundaries set up across the region. Shear is a little
less favorable on Friday and cloud cover may impede instability

The upper low lifts out of the region Saturday night, with weak
ridging/subsidence keeping shower and thunderstorm chances to a
minimum on Sunday. The drier conditions are short lived as the upper
level southwest flow directs yet another series of shortwaves into
the central Plains. Models still a bit uncertain in the timing of
waves, but high chance pops Monday into Wednesday seem warranted for


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1230 PM CDT Wed May 25 2016



.FSD Watches/Warnings/Advisories...



FXUS63 KFSD 242355

Area Forecast Discussion
National Weather Service Sioux Falls SD
655 PM CDT TUE MAY 24 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 313 PM CDT Tue May 24 2016

A warm and pleasant evening is expected across the region with a
weak bit of subsidence shifting across the area. Southwest upper
level flow however will direct yet another shortwave into the
Missouri Valley a little after midnight and lift it northeast
through the forecast area overnight into Wednesday morning. Weak
surface boundary remains stalled across central SD and another
boundary parked across southern Kansas. As the surface low in
Colorado lifts northeast this evening and the low level jet kicks
in...the boundary to our south lifts northward. Convection is
expected to develop across Nebraska later this afternoon and evening
and push into south central SD and the Mo Valley region late evening
into the early morning hours.

The big question will be whether convection can get going this
evening ahead of the main wave. The HRRR and GFS develops scattered
convection by mid evening in southeast SD to the south of
I90...likely triggering off of the diffuse boundary in south central
SD. Convergence is very weak here and a bit more defined in central
Nebraska. Modest instability has developed along with steep lapse
rates, however effective shear is pretty marginal and some weak
capping exists. If elevated thunderstorms do manage to develop in
south central or near the Missouri Valley this evening, a few storms
could become strong to severe with half dollar hail and gusts up to
60 mph. Did leave an isolated to scattered thunderstorm mention in
the forecast near the Missouri Valley. The experimental HRRR,
NAMDNG, NAM, and ECMWF however, keeps the region dry through the

Tonight, showers and thunderstorms will become likely as the wave
lifts through the region. Storms will track northeast and while the
severe threat wanes quickly after midnight with effective shear
values dropping quickly, fairly high precipitable water values above
1.25 inches will keep the threat for heavy rainfall going.
Fortunately, it does look like activity will be moving fairly
quickly. Still, with recent heavy rainfall in northwest Iowa and
southwest Minnesota, will need to watch for flash flooding concerns.

Wednesday`s forecast is a tricky one. Ongoing convection in the
morning will lift to the northeast by mid/late morning. With clouds
becoming scattered to broken and potentially allowing temperatures
to heat back into the low to mid 80s with dewpoints in the low 60s,
we potentially become moderately unstable. Without much in the way of
lift, temperatures will need to heat out fully, so any thunderstorm
development will be quite conditional on how early morning
convection impacts the airmass in its wake. This will also make it
difficult to go above chance pops given the uncertainty.  Severe
storms will again be possible in the afternoon if anything manages
to form. Shear looks a little better than this evening, but still
somewhat marginal.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 313 PM CDT Tue May 24 2016

Wednesday evening thunderstorms are expected to wane steadily later
in the night with the exit of the short wave and the inflow from the
west and northwest of somewhat drier and more stable air. After
coordinating it looks like we can go for no mention of storms in
the area for Thursday morning, then a threat Thursday afternoon and
night, as that moisture and instability increase from the southeast.
Meanwhile, an upper low moving from the four corners area into the
southern plains will begin to move north northeast and amplify the
moisture availability as it approaches SD and IA. This will likely
bring widespread showers and storms to the area for parts of the
Friday through Saturday time frame. Will hold pops to the loaded
extended values of likely at most for now because of the usual
timing issues that far ahead, but one or two periods in that time
frame should have rain affecting most of the area.

Some severe storm threat seems possible with late Thursday and
Thursday evening storms, given the recovering instability and likely
good heating. Friday through Saturday severe threat is uncertain,
with modest shear ahead of the approaching upper low, but possibly
weak heating in the broadly increasing moisture field.

The Friday and Saturday system should pull northeast and leave a
mostly rain free Sunday, but will leave some fairly small chance
mainly in southwest MN for Sunday in case the upper low is slow to
pull out. Monday is uncertain, with a strong wave digging into the
Pacific Northwest area suggesting plains ridging and not much
convection. However, instability should also start to increase
again, so a chance of storms seems appropriate.

Modestly warm and humid conditions, certainly not really worthy of
summer yet, will keep high temperatures well into the 70s or low
80s, with lows in the 50s to low 60s. The cooler days will be the
cloudiest, such as Friday and Saturday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 645 PM CDT Tue May 24 2016

VFR conditions are expected to persist through early Wednesday
morning. Convection may try to develop later this evening ahead of
a larger complex of storms anticipated to move eastward overnight.

While the widespread severe weather risk is low. A stronger wind
gust or marginal hail producing storm is possible as these storms
move through. Convection will push east of the Interstate 29
terminals by mid-morning and expectations are that stratus will
move in through mid-day.

Depending on how overnight storms progress, we`ll again have a
risk for more thunderstorms Wednesday afternoon.


.FSD Watches/Warnings/Advisories...



FXUS63 KFSD 241801

Area Forecast Discussion
National Weather Service Sioux Falls SD
101 PM CDT TUE MAY 24 2016

.SHORT TERM...(Today and Tonight)
Issued at 432 AM CDT Tue May 24 2016

Should be on the quiet side during the daylight hours today, with
areas of fog in areas east of the James River Valley early this
morning in the wake of MCS pulling east through central Iowa. Most
areas will see mostly sunny skies today, though will see some early
morning stratus associated with the aformentioned fog, and a cirrus
shield expanding northward from convection in northern Kansas will
brush through northwest Iowa this morning as well.

This line of convection has pushed main surface boundary well south
of the forecast area this morning, with another boundary/moisture
discontinuity located from north central Nebraska through northeast
South Dakota into the Red River Valley. The latter boundary weakens
as it pushes east through the day, but the greatest model consensus
still depicts the drier low level air behind the boundary expanding
over most of eastern South Dakota/western Minnesota by mid to late
afternoon. With shortwave mid-upper level ridge moving northeast
across eastern South Dakota through 25/00Z, have favored high-res
model solutions which keep any convective redevelopment suppressed
to our south and west in Nebraska and western South Dakota into the
evening. Expected sunshine and fair mixing in the drier air mass
should allow most areas to climb into the lower 80s for highs today.

Concerns for tonight hinge on timing of mid-upper level wave and how
quickly it can drag the low level warm front back into our forecast
area. Wave begins to impact the forecast area during the evening,
but currently appears as though warm front and associated low level
jet convergence will remain focused in Nebraska until after 06Z. As
a result, have trimmed pops back through the evening, but quickly
ramp pops up into high likely range around 06Z as the wave swings
through and elevated warm front attempts to lift toward the Missouri
River Valley later tonight. NAM forecast soundings show decent mid
level lapse rates and modest effective shear in the late afternoon
and evening, and if storms are able to develop prior to 06Z, could
see some hail threat from what should be largely elevated storms.
Greater threat should remain south of our forecast area, however,
closer to the low level boundaries. Strong moisture push from the
south through the evening brings precipitable water values back to
near 1.5 inches, and as low level jet turns more southwesterly in
response to the passing wave, we could see threat of locally heavy
rain become primary concern overnight.

.LONG TERM...(Wednesday through Monday)
Issued at 432 AM CDT Tue May 24 2016

Wednesday is a difficult forecast as there is likely to be ongoing
convection to start.  Corfidi vectors suggest convection should work
east through the morning hours.  As the atmosphere warms in the low
levels, forecast soundings suggest the potential of convection
redeveloping east of the James river with strong enough heating.
Despite searching, could not find a strong trigger mechanism, which
may limit the coverage of any convection that is able to get going.
As such, kept pops mainly in the low chance range.

Cold front is is expected to work across the western half of the
forecast area Wednesday night.  Upper low is passing to the north
across North Dakota, and front across the forecast area is really
suffering from a lack of support aloft.  As such, appears as though
the front will struggle to move completely through the forecast
area.  Have highest pops in the north, but am not convinced large
scale convection will build far enough south into the forecast area.

Airmass ahead of the orphaned boundary becomes unstable throughout
the day on Thursday.  Very steep lapse rates from 700-600 mb leads
to 1500-2500 J/kg of CAPE.  In addition, there is nice directional
and speed shear, potentially leading to bulk shear of 25-30 m/s if
convection is able to become surface based.  The question is whether
convection will be able to become surface based with elevated
inversion.  Model sounding appear to artificially erode the cap too
quick. There is southwest flow aloft, but not a strong wave moving
through the area until Thursday night into Friday. Have continued to
raise pops with this feature. With a fair amount of clouds on Friday
into Saturday, favored cooler guidance values.

Not as much convection is expected through the latter half of the
weekend; however, Sunday night appears to be interesting with
potential low level jet developing across the plains.  Southwest
flow remains aloft across the area with troughiness over the west
coast, so there is the potential of a shortwave or two lifting
through the region. Have maintained chance pops Sunday night and
beyond, but at this time, is too far out to discern the details.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1257 PM CDT Tue May 24 2016

VFR conditions are expected through the bulk of the forecast
period. Late this evening, showers and thunderstorms will start
working northeastward into the Missouri Valley and south central
SD, then expand across the remainder of the forecast area
overnight. Cannot rule out mvfr or ifr ceilings and visibility in
the heavier thunderstorms, so have hinted at lower ceilings late
tonight through mid morning at TAF sites.


.FSD Watches/Warnings/Advisories...



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