Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 242025
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
325 PM CDT Tue Apr 24 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 314 PM CDT Tue Apr 24 2018

Positively tilted short wave is continuing to edge slowly
southeastward through the forecast area at this time. Mid and upper
level QG forcing will eventually extend across southeast Nebraska
and northeast KS by 12Z Wednesday. Behind this wave is a pretty
sharp cold front with a northerly fetch of air dominating. In fact
temperatures have been cooling this afternoon over some locations of
the CWA with chilly high pressure moving southward. Many cams and
short range deterministic models are showing rainfall filling in
across our southern zones late this afternoon and evening as the
focus of the QG forcing moves into that area, as well as strong
850mb baroclinicity in the lower levels. Although rainfall will be
light, pops will remain stubbornly high for locations south of I 90
in extreme southeast SD and northwest IA through the late evening
hours. Then overnight and late tonight, rain chances will be on the
decrease as the forcing shifts more into eastern Nebraska.
Concerning temperatures, lowered readings some in our northern zones
where clearing should take place first. Conversely, our far southern
areas may not clear out for quite some time, so raised temperatures
around the Sioux City and Storm Lake locations above consensus
values.

A pleasant day will be in store for Wednesday with plenty of
sunshine and light variable winds as surface high pressure
centered over Nebraska moves south of the CWA. Near to slightly
below normal temperatures are expected, with highs in the upper
50s and 60s.


.LONG TERM...(Wednesday night through Tuesday)
Issued at 314 PM CDT Tue Apr 24 2018

A weak frontal boundary will move through the area on Thursday,
allowing cloud cover to increase from northwest to southeast
through the day. Rain chances with this frontal boundary still
look meager, with only spotty/very light rain. What the boundary
will bring is breezy to windy conditions behind it. Leaned towards
CONSMOS and Superblend to produce north winds of 15 to 25 mph,
with gusts to 35 mph. Skies will be clearing through the afternoon
as the boundary moves outside of the forecast area.

For the end of the week into Monday, temperatures will continue to
be the main impact as an upper ridge settles over the High Plains,
bringing warm southerly winds over the region. Temperatures aloft
warm considerably on Sunday with 850 mb temperatures of around 12-
15+ C. Have increased temperatures a few degrees to produce highs in
the mid to upper 70s.

By Monday into the middle of the week, models show the potential
for a more unsettled pattern as several upper level disturbances
move across the area, breaking down the ridge. Uncertainty arises
in timing, location and QPF as models are not in agreement. The
GFS brings the first period of precipitation early Monday morning
while the ECMWF brings some QPF 12 hours later. Something to point
out is that if showers do develop across the area, thunderstorms
cannot be ruled out due to dewpoints values of 45 to 50+F and
sufficient instability prevailing over the region.


&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1215 PM CDT Tue Apr 24 2018

Although light rain will be in the area this afternoon and
evening, the rain is light enough that we are not overly confident
that it will cause IFR or MVFR visibility. If it does, it likely
will not last very long. That said, MVFR ceilings are definitely a
threat at KHON this afternoon. There is a chance that some MVFR
ceilings could develop also this afternoon and evening at KSUX so
will monitor.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...MJ/05
LONG TERM...05
AVIATION...MJ



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