textproduct: Aberdeen

KEY MESSAGES

- Above normal high temperatures in the 80s today. A sharp cooldown is expected Saturday through early next week with highs in the 60s to low 70s. These temperatures are about 5 to 10 degrees below normal.

- A Red Flag Warning is in effect for parts of south central South Dakota. A combination of dry fuels, wind gusts up to 40 miles per hour, and afternoon humidity around 20 percent will create critical fire weather conditions. Grassland Fire Danger will reach High for all counties west of Brown and Spink Counties and Very High west of the Missouri River.

- There is a Slight (Level 2 of 5) to Marginal (Level 1 of 5) risk for severe storms late this afternoon into this evening over northeastern South Dakota and western Minnesota. Main severe threats include hail up to 2 inches in diameter and wind gusts of 60 to 75 miles per hour. A tornado cannot be ruled out either.

UPDATE

Issued at 649 AM CDT Fri Sep 11 2026

See below for an aviation forecast discussion for the 12Z TAFs.

DISCUSSION

Issued at 211 AM CDT Fri Sep 11 2026

A cold front is set to pass through the region this afternoon, turning winds to the northwest. Under the cold air advection regime, wind gusts may reach as high as 40 miles per hour, with perhaps a stray gust up to 45 miles per hour. Confidence on gusts reaching 45 miles per hour (Wind Advisory criteria) is somewhat low at this point. HREF and REFS both do not give much credence to the possibility (<10% this afternoon) but NBM probabilities show a couple of hours of 10-20% chances to hit 45 miles per hour over north central South Dakota. Regardless of the exact probability, confidence is not high enough to issue a Wind Advisory today. The headline with a bit higher confidence is a Red Flag Warning, which is being issued with this forecast package for Jones, Lyman, and Buffalo counties. This are will see a period of humidity below 20 percent this afternoon, which when combined with winds will create critical fire weather conditions. Further north humidity increases to 20-40%, which is still enough for elevated fire weather concerns and High to Very High Grassland Fire Danger this afternoon.

The other point of concern with the cold front passing through will be convection over northeastern South Dakota and western Minnesota this afternoon. The latest model guidance trends towards storms firing over this area sometime between 20-22Z before quickly progressing eastward and out of the Aberdeen CWA as they intensify. This will leave a fairly short window in which severe weather could impact the area. Should storms fully develop within the Aberdeen forecast area, hail and wind will be the most likely severe threats. Hail in particular could prove to be significant, with a CAPE/Shear combo of roughly 3000+ J/kg and 30-40 knots in place. Also supporting the hail threat are mid-level lapse rates around 7.0-7.5 C/km in the area. On the wind side of things, much of the area out ahead of the front will have upwards of 1000 J/kg of DCAPE in place and low-level lapse rates near dry-adiabatic to aid in gusts reaching the surface. Also can't quite rule out the potential for a tornado with these storms. Favorable ingredients include strong MLCAPE, helicity as high as 200 m2/s2, and low-level turning within the hodographs. The actual value of low-level shear leaves something to be desired (only about 20 to 25 knots, with perhaps some small pockets of a more ideal environment of 30 knots), but the main limiting factor to tornado potential will be LCLs over 1000m in most locations. However despite these limitations, it is not out of the question for these ingredients to line up in such a way that allows for tornadic development, but confidence is not high. It should be noted as well that a number of CAMs keep convection out of the Aberdeen CWA entirely. This is likely due to the limiting factor of a cap in place. The Potential Temperature difference between the surface and the warm layer is only about 5K at best, and there seems to be a bit of a spread in model confidence on the ability of that cap to be overcome or worn down through the day. All this to say that while this would definitely be a less likely outcome, it would not be entirely out of the question for the cap to hold and the Aberdeen area sees little to no convection today. The latest severe outlook from the Storm Prediction Center covers the areas east of the James River in a Slight to Marginal Risk.

Temperatures behind the cold front will drop, with highs in the 60s across the forecast area expected over the weekend. These highs 5-10 degrees below mid-September normals are expected to persist through at least the start of next week. The departing upper-level trough's right entrance region will move over the Northern Plains early Sunday, bringing a jet streak overhead. This will lead to some potential for rain showers Sunday morning across much of the forecast area. By Sunday afternoon, a brief ridge and surface high pressure center will build into the region, but both are expected to be fairly short-lived.

Chances for rain return early next week as another upper-level trough moves over the Northern Plains. Divergence aloft from a jet streak will be the driving force for this system, as well as some help from an associated cold front. The below normal temperatures already in place out ahead of the front will help to form a fairly strong cap in place and likely significantly limiting deep convection through the profile. This in turn will all but eliminate chances for severe weather during this period, an assessment that mid-range severe probability models agree with. Still, non severe showers to perhaps a stray thunderstorm will be possible due to the divergence aloft (~50-60 knots of speed shear from roughly 700mb to 300mb). Latest NBM probabilities of seeing half an inch of rain or greater still range from 30-50% through 00Z Tuesday, which is a slight downward trend from 24 hours ago. Other long range ensembles trend more towards the 10-30% range for that same half inch threshold.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 649 AM CDT Fri Sep 11 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions forecast for all terminals. Winds from the south southwest shift to northerly with a frontal passage today. KATY could continue to see some LLWS for a couple more hours this morning.

ABR WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning from 10 AM this morning to 7 PM CDT this evening for SDZ045-048-051. MN...None.