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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
419 am CDT sun may 24 2015

Short term...(today and tonight)
issued at 419 am CDT sun may 24 2015

Strong moisture transport combined with isentropic lift above 850 mb
leading to showers across the region this morning. Middle level lift
weakens some throughout the day as short waves currently across the
area lift north. The net result will be decreasing precipitation chances
west of I-29. Further to the east...warm conveyor across the
Central Plains continues to feed moisture into the region resulting
in scattered showers as warm front lifts north across the area.
Believe there will be a break in the activity across the west in the
late morning and early afternoon hours...leading to a small amount
of instaibilty developing before additional thunderstorms develop in
the middle to latitude afternoon hours. Unless there is pretty good not expect severe weather today. Have lowered forecast
highs in the east with the expectation of showers through much of
the today.

Messy pattern tonight with upper level low weakening to the west and
secondary low developing and lifting northeast across the area. Precipitable water
values by this evening climb to nearly 1.3 inches...greater than two
Standard dieviations from the norm. This leads to an efficient
atmosphere to produce moderate to heavy rain across the area.
Raised pop and quantitative precipitation forecast values through the night...and have also raised
lows slightly with relatively soupy atmosphere.

Long term...(monday through saturday)
issued at 419 am CDT sun may 24 2015

The overall upper air pattern for the upcoming week is very
chaotic...and thus very difficult to latch onto any one strong
feature. Therefore with this type of scenario had a tendency to
blend many model solutions together. On Memorial Day...large upper
low continues it very slow track into the central and northern
plains and begins to weaken. In response...a rather strong surface
low generates then lifts northeastward along a track which is mainly
southeast of our forecast area. It still looks like the last
remnants of the upper low is on target to move across our area on
Tuesday. So needless the weather remains unsettled but rainfall
chances generally wane through the early week.

On appears the highest probability of precipitation are warranted in our eastern
zones early in the morning as one short wave exits. After that...
rain chances get pretty spotty. Drier air begins to entrain into our
northern zones Monday night...continuing to nudge southward through
the day on Tuesday. Therefore most of the chances for showers will
be bottled up across our southern zones Monday night and Tuesday
before going dry over the entire forecast area Tuesday night. Things
could change as confidence in the precipitation pattern is not at
all high due to the run to run variance in the model solutions from
day to day. A little more confident on the temperature regime...with
rather seasonable highs in the upper 60s and 70s Memorial Day and
Tuesday...with lows Monday night and Tuesday night in the 50s.

A quasi zonal and wavy pattern returns by middle week...with another
upper low forming by Thursday throughout the intermountain west. One
large discrepancy between the GFS and European model (ecmwf) is that the GFS is
quicker with a northern stream trough moving across southern Canada
and northern Minnesota by early Friday. If this verifies...are moisture
supply will be cutoff more quickly than what the European model (ecmwf) is showing.
At any rate...a decent short wave moves through Wednesday night and
Thursday which will give another chance for showers and
thunderstorms. Beginning Friday...predicting rainfall chances gets
trickier due to the discrepancies mentioned above. For now am siding
with the slower European model (ecmwf) so kept chance probability of precipitation in Friday and Friday
night...then pushing across our southern zones on Saturday. If the
current trends continue...would not be surprised if all of the
various medium range models dry things out across our entire
forecast area by Saturday so we may have to eliminate those probability of precipitation in
future forecasts. Highs remain the upper 60s and 70s.


Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1036 PM CDT Sat may 23 2015

Scattered rain will continue to lift northward overnight. Ceilings
will gradually lower to MVFR and eventually IFR through Sunday
morning. Some uncertainty on when shower activity will end...but
likely middle-late morning.

Latest guidance suggests easterly flow may remain in place well
into the afternoon...which may prolong sub-VFR conditions in the
terminals. Quite a bit of uncertainty on any potential afternoon
redevelopment...and have chosen to not mention any precipitation at this


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


Short term...
long term...mj

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