Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 011707

Area Forecast Discussion
National Weather Service Sioux Falls SD
1207 PM CDT Sat Oct 1 2016

.SHORT TERM...(Today and Tonight)
Issued at 326 AM CDT Sat Oct 1 2016

Low level moisture and clouds were stalling earlier in the night but
have made a strong push to the east during the pre dawn hours. All
model guidance still indicates this push will run out of steam a
little west of Interstate 29, further away from the large upper low
to the southeast. However, the low clouds look to hold their own
much of the day with some breaks. Further west of Interstate 29,
only high clouds will be seen. Temperatures still look targeted for
highs in the upper 60s east to the mid 70s west.

Guidance very slowly but steadily decreases the low cloud deck
tonight, and this makes sense given the upper low starts to slowly
weaken and recede, with the flow of deep moisture also slowly
decreasing. The concern however is that more shallow moisture can
still stratify into a lingering or redeveloping semi solid cloud
deck tonight. For now will go for the slow decrease indicated, but
the shallow layers have been known to cross up the models.  Lows
tonight look to be mostly a tad above 50.

.LONG TERM...(Sunday through Friday)
Issued at 326 AM CDT Sat Oct 1 2016

No major changes in the medium or extended portions of the forecast
this morning.  Model guidance continues to focus on the next
incoming rain chance early next week, but minor timing issues linger.

Sunday-Monday: A very pleasant Sunday is anticipated as mid-lvl
ridge axis slides east of the CWA. The resultant increase in
southerly sfc flow will bring temperatures into the 70s and even a
few 80s in central SD. Gradient winds really increase on Monday as
upper troughing begins to cross the Northern Rockies. Would not
be surprised to see persistent 20 to 30 mph sustained winds with
gusts 40 mph or higher at times. With increasing mid-upr cloud cover
through the day, temperatures will still end up in the middle to
upper 70s in most areas.

Monday Night: Showers and thunderstorms that build over western
Nebraska and South Dakota Monday evening will slide eastward Monday
night, bringing likely rain chances to areas west of I-29 by
daybreak Tuesday.  Additional scattered warm advection rain may
develop ahead of the primary band of rain.

Tuesday - Wednesday: ECMWF/GFS/NAM all in agreement that a frontal
boundary will bisect the CWA by mid-day Tuesday. Thunderstorm
redevelopment may quickly take place Tuesday afternoon along the
H850 moisture axis from Yankton to Sioux Falls and Marshall.
Thunderstorms will press eastward by daybreak Wednesday. Given the
deep influx of moisture and parallel flow to the frontal boundary,
would anticipate an increased potential that a marginal risk for
excessive rainfall is issued for Tuesday afternoon into
Wednesday. A bit more uncertainty develops on Wednesday regarding
the southeast push to the H850 trough and sfc front, and potential
for redevelopment along this boundary Wednesday afternoon. ECMWF
is a bit slower, while GFS/GEM are much more progressive in
bringing drier air into the region.

Thursday - Saturday: High pressure is expected to settle into the
region for the end of the week and next weekend. With the sfc trough
axis bisecting the CWA from NW to SE, temperatures have the
potential to drop into the 30s. That said, there could be several
bouts with stratus through this time period that may influence
overnight temperatures.  Daytime highs will remain below normal into
the lower 60s.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1207 PM CDT Sat Oct 1 2016

VFR conditions through the period. Scattered to possibly briefly
broken MVFR clouds closer to Spencer and Storm Lake Iowa.




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