Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 161129

National Weather Service Sioux Falls SD
629 AM CDT Fri Apr 16 2021

.SHORT TERM...(Today and Tonight)
Issued at 316 AM CDT Fri Apr 16 2021

Forecast Highlights:

1. Cloudy with occasional very light precipitation into Saturday

2. Above normal temperatures on Sunday

3. Increasing potential for accumulating snow Sunday night into

Today: A myriad of very weak forcing mechanisms will continue to
produce low end risks for light rain, drizzle, or flurries through
most of the next 24 hours. Early this morning, we`re beginning to
see the redevelopment of patchy drizzle and flurries as far east
as southwest Minnesota as very weak warm advection within the
850:800 mb layer moves through. Slightly deeper moisture is
centered over central SD and into Nebraska where legitimate light
rain may develop. The challenge for today is really picking up on
where and when you could see this extremely light precipitation.
The large scale picture would continue to support the highest
probabilities for measurable QPF along and south of the Missouri
River corridor, but given continued weak low-lvl convergence and
warm advection can`t rule out very brief periods of drizzle
further into the Tri-State area through the afternoon.
Temperatures will warm into the 40s in most locations. Any
afternoon breaks could force highs closer to 50 degrees.

Tonight: One PV anomaly meanders through southwestern Iowa, while
a second upper wave begins to move into the central Dakotas later
tonight. Once again, I`d look for the potential of very light
spits of rain, drizzle, or flurries focused mostly west of I-29
and into central South Dakota.

.LONG TERM...(Saturday through Thursday)
Issued at 316 AM CDT Fri Apr 16 2021

Saturday: Clouds will be very slow to clear from north to south on
Saturday, but should scatter some in the afternoon. I`ve extended
a low PoP into Saturday morning, as there should be lingering
low-lvl lift and enough low-lvl moisture to continue to produce
light drizzle at times. These PoPs may need to be extended through
Saturday morning. If clouds can scatter some in the afternoon,
then high may climb into the 50s, but it`s possible highs may
trend lower.

Sunday: Rising mid-lvl heights ahead of a much deeper positively
tilted trough moving through southern Canada will induce a period of
strong warm advection and favorable southwesterly winds on Sunday.
Barring impacts of increasing mid-upper cloud cover, expectations
are that temperatures should climb into the 60s.  Have bumped up
temperatures above populated guidance.

Sunday Night-Monday: A strong cold front will plow through the Upper
Midwest Sunday night into Monday morning, with a 20 to 30 degree
temperatures drop by Monday.  Model guidance remains consistent
bringing an intense but narrow zone of frontogenesis through the
area behind the passage of the surface front into Monday morning.
The NAM is the slowest of all solutions, with good agreement
between the GFS/ECMWF/CMC. EC/CMC remain the wettest solutions,
with the GFS showing some split nature to the forcing mechanisms.
Based on ensemble guidance, probabilities of measurable QPF have
increased, and have bumped up PoPs and QPF accordingly. Still a
few days off, but this event is certainly one that could bring
some minor snow accumulations into Monday morning. Temperatures
will rebound slightly on Monday, but still only looking for highs
in the lower 40s.

Tuesday-Wednesday:  A large upper trough moving through the Upper
Midwest will keep temperatures below normal through Wednesday.  In
fact, fairly confident that highs on Tuesday may struggle to reach
40 degrees with abundant clouds after the southward advection of
colder air.  Have lowered highs 1-3 degrees in most locations. We`ll
begin to see temperatures rise a bit on Wednesday, but still remain
below normal in most locations.

Thursday: The upper pattern remains quite variable and unsettled
through the end of next week.  No major weather systems, but a
general warmup in temperatures followed by potential for another
frontal boundary arriving by next weekend.&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1047 PM CDT Thu Apr 15 2021

Low VFR to MVFR stratus and north winds below 10 kts will prevail
through the period. MVFR ceilings should spread across the region
tonight. There is a small chance of light rain or snow near HON
tonight through mid morning Friday, but chance was too small to
mention in TAF at this time. MVFR vsby develops with light rain
spreading into the Missouri River Valley Friday morning,
gradually spreading east toward FSD and SUX mid day or later. Rain
is more likely at SUX than FSD Friday afternoon. Patchy IFR
ceilings may develop heading into Friday as well, especially
across southwest MN and southeast SD.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 625 AM CDT Fri Apr 16 2021

Difficult forecast this morning, as latest guidance suggests that
MVFR and lower ceilings may linger through much of the daytime
hours. Patchy drizzle or sprinkles may be possible at times
through the day, but any visibility restrictions will be brief if
they take place. The area with the greatest restriction potential
will be from Marshall to Madison to Mitchell and Lake Andes.

Guidance is a bit mixed into the overnight hours, as some hints of
lower ceilings remaining confined to areas west of the James River
valley, and some potential for ceilings to rise back to VFR levels
in Sioux Falls and Sioux City and points eastward. Still stay more
optimistic with the forecast beyond 00z and allow for additional
changes to be made at a later TAF issuance.




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