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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
639 am CDT Sat Apr 19 2014

Short term...(today and tonight)
issued at 342 am CDT Sat Apr 19 2014

Once again dry sub-cloud layer preventing any attempt at precipitation from
really reaching the surface early this morning...and with middle level
wave shearing off to the northeast resulting in continued weakening
support...have pulled any measurable probability of precipitation from the morning. Will
carry a few sprinkles for now...but may even be able to pull all
precipitation mention for the morning hours if current trends continue.
Otherwise today should be quite mild with decent mixing expected in
southwest flow ahead of approaching trough axis...poised just west
of the County Warning Area at 08z. Even behind the boundary...which is expected to
be near a kmml-kfsd-kykn line by late afternoon...models indicate
little significant low level cooling. With fair mixing in the west
to northwest well as greater amount of sunshine and drier
low levels...should still see very mild temperatures and will again
favor warmer rap and bias-corrected raw model temperatures for highs this
afternoon. Expect most areas to climb into the 70s...and would not
be surprised to see an 80+ degree reading in our far south though
keeping highs just shy for now. Mixy southwest flow and warm temperatures
east of the boundary lead to very high fire danger east of Highway
60 corridor in northwest Iowa/southwest Minnesota...though with the
winds expected to diminish with approach of boundary...and low level
moisture beginning to pool near/south of the boundary...conditions
should actually improve as the afternoon progresses.

Will hang onto low probability of precipitation in our southeast this afternoon as weak middle
level wave lifts northeast along the boundary...though instability
pretty weak so will have only isolated thunder mention. Boundary
sags slightly farther southeast and stalls across our far southeast
tonight. With continued southerly low level moisture transport into
the boundary...and another weak wave getting kicked out of southern
rockies trough...will gradually ramp up probability of precipitation through the overnight
hours...though boundary forecast to push a little farther southeast
than previously probability of precipitation likewise a little farther south
and expect any nighttime showers to remain south of kfsd. American
models quite a bit more bullish on precipitation amounts than Gem/ECMWF...
which also decreases confidence in potential for more widespread
showers...and thus trimmed highest probability of precipitation back into likely range.
Pooled moisture along the boundary as well as extensive cloud cover
should hold lows tonight in the lower to middle 50s across southeast
County Warning Area...while drier air/light winds in our northwest allow readings to
fall into the lower 40s.

Long term...(sunday through friday)
issued at 342 am CDT Sat Apr 19 2014

The frontal boundary will remain stalled across our southeast on
Sunday and Sunday night...keeping the focus for showers and
thunderstorms over that area during the period as a southern stream
wave begins to lift up into the region. While there may be a break
in the activity on Sunday morning...expect chances to increase on
Sunday afternoon and evening as the aforementioned shortwave begins
to exert more influence and better instability nudges into our
south. Will see some locally heavy rain possible in heavier activity
with precipitable water values running around an inch and a quarter. Areas farther
to the north and west will actually have a decent day on Sunday as
afternoon temperatures mix out into the lower to middle 70s...while
areas affected by cloud cover/showers will only make it up into the
middle and upper 60s. By late Sunday night the boundary finally
begins to sag to the south as the upper level trough pulls to the
east...with and showers and isolated thunderstorms diminishing
toward early Monday morning. Lows will remain relatively
mild...dropping into the lower 40s through the western and central
Highway corridor to the lower 50s through the Sioux City to Storm
Lake area.

Surface ridging then slides across the region for Monday and Tuesday
with temperatures dropping back a bit in a cold air advection regime.
Looking at highs in the 60s to near 70 both days. It will be breezy
on Monday with good mixing and winds running around 25 to 30 kts at
the top of the mixed layer.

Into the extended...more significant system for the middle of the
upcoming week as an upper level trough over the western U.S nudges
eastward. Model consensus would put the bullseye for best
precipitation chances across the area in the Wednesday night to
Thursday timeframe as the main upper level forcing and lower level
frontal dynamics come together. Does appear to be fairly windy
through the Wednesday to Friday timeframe...with temperatures
trending downward by the end of the week with the passage of the


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 639 am CDT Sat Apr 19 2014

Southerly wind gusts of 20-30kt still likely along and east of I-29
corridor into this afternoon...but should gradually diminish west to
east as surface trough pushes east. Western parts of the area should
generally see lighter winds through the period...though brief gusts
of 25-30kt possible as sprinkles or light showers slide east across
the region this morning.

As the boundary moves into Minnesota/Iowa this afternoon/tonight...could see a
few showers or even an isolated thunderstorm...though threat at taf
locations too low to feel confident in mentioning prior to 06z. After
06z...coverage expected to increase near and south of the boundary in
northwest Iowa...and have added -shra into ksux taf for the pre-dawn
hours Sunday. Isolated thunderstorms and rain possible with this activity...but again
with low confidence in thunderstorms and rain coverage...opted to just stick with rain showers
for now. Ceilings/visibility expected to remain VFR.


Fsd watches/warnings/advisories...
South Dakota...none.


Short term...jh