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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Tuesday
• 
• High: 84 °
• Low: 61 °
• Partly Cloudy

• Wednesday
• 
• High: 81 °
• Low: 59 °
• T-Storms

• Thursday
• 
• High: 68 °
• Low: 54 °
• T-Storms

• Friday
• 
• High: 68 °
• Low: 54 °
• Partly Cloudy

• Saturday
• 
• High: 84 °
• Low: 61 °
• Chance of T-Storms

Area forecast discussion for southeast South Dakota/southwest Minnesota/northwest Iowa 
National Weather Service Sioux Falls South Dakota 
647 PM CDT Tuesday may 22 2012 


Discussion.../issued at 330 PM CDT/ 
strong southerly flow continues across the area ahead of a cold 
front that has pushed into far northwest corner of South Dakota. 
With gradient continuing to strengthen aloft...will continue Wind 
Advisory across the area through the evening hours as the front 
works east this evening...could see thunderstorms develop but expect 
the focus to be further north closer to the middle level wave. As 
such...have not made many adjustments to probability of precipitation with focus mainly 
north of I-90. With Stout winds continuing ahead of the 
front...kept forecast lows quite mild closer to cons raw and west model. 


Boundary is expected to enter the forecast area after 06z Wednesday 
and slowly push east. Not a lot in terms of upper level support 
until Wednesday evening as upper wave lifts into the region...and 
weak capping inversion looks to hold for the better part of the 
day. Kept chance probability of precipitation going in the vicinity of the front through 
the day...but focus will certainly be Wednesday night. Highs will 
generally be in the 70s to lower 80s with 850 hpa temperatures in the middle 
teens. 


Continues to look like a potential heavy rain event Wednesday night 
into early Thursday morning as front stalls across far southeast County Warning Area 
Wednesday night into Thursday morning while wave ejects northeast out 
of Nebraska. Initially could see some severe weather during the 
evening across northwest Iowa...but main concern would be the heavy 
rains. Models do differ on placement with GFS and ec a little 
further south than NAM/Gem. Prefer the GFS/ec solution with best 
chance closer to front where deep moisture will pool and where 
highest precipitable waters  near 1.50 inches expected. So activity that develops 
in the afternoon should really get going Wednesday evening and 
persist through the night with local rainfall amounts over 3 inches 
likely especially near the front and then dropping off dramatically 
across far northwest County Warning Area. So highest probability of precipitation will be across southeast 
County Warning Area Wednesday night into Thursday morning...and then a lingering 
smaller chance Thursday afternoon in early evening. Will hold off 
any Flood Watch for Wednesday night...due to uncertainty on exact 
location of heaviest rain...but will mention heavy rain in grids 
across southeast County Warning Area and also mentioned in severe weather potential statement. 


On Friday...boundary across southern Nebraska and southern Iowa will 
begin to lift slowly north Friday night into Saturday...reaching i90 
on Saturday. So as this front lifts north would expect at least 
scattered thunderstorms to develop on edge of middle level cap as low 
level jet increases during the night and wave lifts northeast out of 
western Nebraska. Could see elevated severe storms later in the 
night as this front lifts north. 


With front along i90 on Saturday...best chance for thunderstorms 
will continue north of i90 through Saturday...with potential for 
more heavy rain...this time across northern County Warning Area Saturday night. Will 
highly depend on location of middle level cap and front and heaviest 
rain could fall north of County Warning Area. So will have highest probability of precipitation across 
northern County Warning Area and far southern County Warning Area may not see anything after 
convection lifts north Saturday morning. Very high convective available potential energy south of 
boundary in capped air over northwest Iowa...but definately 
something to watch north of boundary late Saturday afternoon and 
evening for a round of severe weather. 


As we head into Sunday...cold front will push east across County Warning Area Sunday 
afternoon and night with yet another round of thunderstorms. If middle 
level cap can break ahead of this front which GFS and ec hinting 
at...could see some severe weather in the afternoon and evening 
across the eastern County Warning Area. 


Memorial Day looks to be quiet and dry and will continue that trend 
into Tuesday. 


Temperatures will be on a roller coaster Thursday through 
Sunday...with cooler temperatures in the upper 60s to middle 70s 
Thursday and Friday and then as front lifts north...highs on 
Saturday will likely vary from near 70 across the far north to near 
90 far southeast. Should be warmer across all of County Warning Area on Sunday ahead 
of front with highs in the 80s...and then cooling back into 70s 
Monday and Tuesday. 


&& 


Aviation.../for the 00z taf issuance/ 
mainly VFR conditions expected through the taf period. Strong 
southerly wind gusts around 30-35kts expected to persist through 
early part of taf period...though even after 03z gusts around 25kt 
will remain likely until cold front approaches from the west later 
tonight...allowing for weakening surface gradient/further decrease 
in winds. Models continue to show 50-60kt low level jet above 1500ft 
above ground level...leading to concerns of low level wind shear. Although winds 
remain somewhat gusty at the surface...with low level jet of this 
magnitude and direction slightly veered from dominant surface wind 
direction...will continue mention of low level wind shear for all taf locations 
tonight. Confidence in elevated thunderstorms affecting taf sites 
overnight is waning...as upper level support seems to focus more to 
the north of this area. Will hang onto a small window of possible 
thunderstorms and rain for khon 06z-08z as secondary middle level wave moves into the 
area. Otherwise keeping the tafs free of precipitation through 
Wednesday. Chances will increase late in the period along and east 
of I-29 corridor as cold front pushes slowly east. However...think 
capping inversion ahead of the cold front could suppress convection 
until after the end of this taf period and opted to leave potential 
late afternoon thunderstorms and rain out of this issuance. 


&& 


Fsd watches/warnings/advisories... 
Iowa...Wind Advisory from 10 am to 8 PM CDT Tuesday for iaz001>003- 
012>014-020>022-031-032. 


Minnesota...Wind Advisory from 10 am to 8 PM CDT Tuesday for mnz071-072-080- 
081-089-090-097-098. 


NE...Wind Advisory from 10 am to 8 PM CDT Tuesday for nez013-014. 


South Dakota...Wind Advisory from 10 am to 8 PM CDT Tuesday for sdz038>040-050- 
052>071. 


&& 


$$