textproduct: Sioux Falls

KEY MESSAGES

- Isolated small hail up to quarter size could be possible in northwest Iowa through mid-morning. Similar conditions this afternoon to early evening, with slightly higher potential for 50 mph winds.

- Rain/Drizzle will transition to a wintry mix then snow from west to east today through this evening. A glaze to over 0.10" of ice (greatest in southwest Minnesota), flash freeze, and areas of 1-3" of snow (greatest in south-central South Dakota.

- Above normal temperatures will dominate the week ahead with occasional low precipitation chances.

UPDATE

Issued at 330 AM CST Fri Mar 6 2026

As of 3 AM, cold front has progressed into our far western counties, currently located near to just east of Huron to Platte SD line. This is a little quicker with temperatures dropping more sharply behind the front than previously forecast. HRRR seems to have the best handle on this and have blended more of the HRRR into temperatures going forward into this afternoon.

There have been no changes to the severe weather outlook this morning, though a faster frontal timing may temper the northwest extent of any risk, so please monitor for updates through the day.

Previous shift had already accounted for somewhat faster frontal timing with adjustments to precipitation types/expansion of the Winter Weather Advisory for today/tonight, and made only minor tweaks to p-type transitions/amounts this morning. Although these updates resulted in some light ice accumulation in our far southeast, confidence in this icing potential for Sioux City to Storm Lake remains low and no adjustments to the Winter Weather Advisory are planned early this morning. Next shift will want to look closely at latest guidance to determine whether a short advisory for icing will be needed in these areas. Fortunately, the overall air mass remains relatively mild with even the 10th percentile NBM showing temperatures climbing above freezing by Saturday afternoon with many areas in the upper 30s to mid 40s. So aside from potential impacts of more substantial snow cover (2-3" possible in south-central South Dakota), travel impacts from overnight icing may ease by the latter half of Saturday.

Issued at 821 PM CST Thu Mar 5 2026

We're continuing to see low-mid level moisture surge northward across Nebraska and western Iowa this evening.The OAX/UEX/FSD VWP show the LLJ increasing towards the 35 to 40 knot range. Short term CAMs continue to increase scattered shower and thunderstorm coverage by midnight along the MO river valley and into NW Iowa. While there is considerable effective shear, a fairly thin and tall MUCAPE profile only approaching 800 J/KG may limit strong storm potential. Freezing level AOA 10K FT are also seasonally high. That said the greatest potential will develop after 3am and may continue through 8am. Mostly small hail will be likely, but a very isolated storm could produce quarter size hail.

Further west we're already seeing the cold front expected to move southeast late Friday, stretching across central South Dakota. One big change from guidance earlier today is surging colder air much faster to the Southeast. After initial rain moves northeast through Iowa this morning, we should see development of drizzle followed by renewed showers along and west of the James River by mid-morning as a tightening frontal circulation develops. A slight low-lvl ridge may actually back the baroclinic zone westward in the morning, leaving a greater risk of freezing drizzle/rain to develop west of the James River by mid-morning.

Once deeper troughing ejects northeast into the Plains, we'll again see redevelopment of convection along the advancing cold front, likely just along the far southeastern edge of the CWA. Further west, forcing along the low-lvl frontal zone will increase further, inducing fairly widespread wintry mix that will turn to snow into the late evening and overnight.

Given the soundings, and likely faster surge of colder air southeast, have increased ice coverage over most areas to a glaze to tenth of an inch. Have also increased snowfall amounts slightly and increased the potential for sleet (and a non-zero risk for thundersleet in the evening). Adjusting these elements has led to advisory expansion and adjustments in timing for Friday.

One thing to note is that if we see a quick 1-3" of snow, then temperatures on Saturday may also trend lower.

DISCUSSION

Issued at 337 PM CST Thu Mar 5 2026

Mid to upper clouds are building in ahead of an approaching wave this afternoon. Breezy southerly winds will gradually decrease through the evening. Lows for tonight will fall into the low 30s to mid 40s, with the warmest temperatures over northwestern Iowa. Tonight WAA and an increasing LLJ may be enough to trigger showers and thunderstorms, most likely beginning after midnight. Some of these could be strong to severe with 500-1000 J/kg of tall and thin MUCAPE, and 40+ kts of 0-6 km bulk shear. ESAT tables indicate precipitable water to be at >99% for climatology from 06.06Z through 07.06Z. Considering this, rainfall could be heavy at times under stronger thunderstorms. By Friday morning rain totals of 0.2" to 0.4" are possible for eastern South Dakota with the highest as you move east. Areas in southwestern Minnesota and northwestern Iowa may see 0.5 to 0.75" in total. As far as the severe threat is concerned, despite some convective parameters being on the favorable side the weak instability may limit severe storms to just one or two isolated thunderstorms. The main threat with any that do become severe will be heavy rain, hail up to the size of a quarter (1 inch), and possibly wind gusts in excess of 60 mph. The main area of concern is for areas east of I-29 in northwestern Iowa and eastern Nebraska. Severe risks diminish around daybreak Friday.

A surface low pressure will move through the region dragging a cold front with it early Friday morning. Strong CAA in the 925-850 mb layer rapidly decrease temperatures there 10-15 degrees C. This will help to bolster gusty northerly winds behind the front. Areas along and west of the James River Valley will experience the strongest gusts of 30-40 mph. Through the day stronger winds push east of I-29 but will be slightly lower at 20-30 mph. In addition rain showers and weak thunderstorms will become scattered to numerous through the day as the main vorticity lobe of the wave moves northeast. With this comes an increase in instability and renewed chances for strong to severe thunderstorms for areas east of I-29 in northwestern Iowa. The main threats will once again be brief heavy downpours, hail to the size of a quarter, and to a lesser extend damaging wind gusts of 60+ mph. An additional 0.1 to 0.25" are possible with the highest again being east of the SD/MN/IA border. Eventually rain will change over to freezing rain/drizzle or sleet to a wintry mix before becoming all snow overnight.

The timing of the change over remains uncertain due to timing differences in the cold front passage in the short term guidance. About half of the guidance has the front over central South Dakota around to shortly after midnight tonight. While the other half indicate a slower passage around or shortly after 6 am Friday. This 6 hour difference continues as the front progresses through eastern South Dakota and into western Minnesota and Iowa. This leaves uncertainty in ice and snow totals very high at this time. One thing that does appear more certain at this time is an area of prolonged freezing rain and drizzle for portions of east central South Dakota, southwestern Minnesota, and northwestern Iowa. Here there may be between 0.1 to 0.2 inches of ice accumulations before switching over to snow. For this reason, a Winter Weather Advisory has been issued from 3 pm Friday through 9 am Saturday morning. Snow moves clear of the area by late morning Saturday.

Saturday afternoon skies will clear and we will warm into the 40s to 50s. Sunday a high pressure skirts to our south, turning winds southwesterly and increasing WAA. Highs will warm into the 60s and winds will be diurnally breezy gusting 20-25 mph. Flow aloft becomes slightly more zonal for Monday. A short wave passes along the US/CAN border which will give a weak push of CAA that cools highs to the 50s for areas north of I-90, 60s to the south both Monday and Tuesday. Wednesday brings another chance for rain with cooler highs in the 40s. Then things dry out and warm again into the 50s and 60s for the remainder of the week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 557 AM CST Fri Mar 6 2026

Complex forecast this morning with a variety of weather expected over the next 24 hours. Beginning the day with thunderstorms and brief heavy rain in portions of northwest Iowa, mainly from KSUX to KSLB, but could lift slightly farther north before exiting to the east by 15Z.

Farther west, a cold front has pushed east of Highway 281 and will continue to progress east through this afternoon. While not much precipitation across this area currently, have seen reports of -DZ increasing along with LIFR-VLIFR ceilings/visibility in fog.

As the cold front pushes east and surface temperatures fall below freezing, will see increasing potential for icing with freezing rain/drizzle, with a transition to snow expected later in the afternoon and tonight as colder air aloft moves in. The low stratus is expected to clear KHON-KAGZ by late in this TAF period; otherwise low MVFR-IFR ceilings will persist.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Winter Weather Advisory from 6 PM this evening to 9 AM CST Saturday for SDZ062-066-067-069>071. Winter Weather Advisory from noon today to 9 AM CST Saturday for SDZ040-055-056-060-061-065-068. Winter Weather Advisory from 9 AM this morning to 3 AM CST Saturday for SDZ038-039-050-052>054-057>059-063-064. MN...Winter Weather Advisory from 6 PM this evening to 9 AM CST Saturday for MNZ081-089-090-098. Winter Weather Advisory from noon today to 9 AM CST Saturday for MNZ071-072-080-097. IA...Winter Weather Advisory from 6 PM this evening to 9 AM CST Saturday for IAZ001>003-012>014. NE...None.