textproduct: Aberdeen

KEY MESSAGES

- After a brief break today, the active weather pattern continues, starting again Tuesday. Chances for showers and thunderstorms are in place through the end of the work week.

- There is a Slight Risk (Level 2 of 5) for severe weather Tuesday, mainly along and west of the Missouri River. There is a Marginal Risk Level 1 out of 5) for severe storms for locations between the Missouri and James River. Large hail of 1-2" in diameter is the main threat. Wind gusts of 60 mph and tornadoes cannot be ruled out as possible threats either.

- Another Slight Risk (Level 2 of 5) for severe weather is in place for Wednesday for parts of north central and northeastern South Dakota. Large hail of 1-2" in diameter and wind gusts of 60 mph are the main threats. Areas west of the Missouri River and east of the James River Valley are under a Marginal Risk (Level 1 of 5).

DISCUSSION

Issued at 246 AM CDT Mon Jun 1 2026

Storms are moving out of the area early this morning, and are not expected to produce any additional severe wind or hail. An upper- level low over the western CONUS will remain in place over the next couple of days, but will begin to wobble slightly to the north through the day today. This wobble will bring the vorticity maximum that is supporting current showers up to the north along with the low, giving the area a bit of a break from showers and storms today until another jet streak and vorticity maximum will move into the area and bring the return of showers and storms late this evening. Hi-res model guidance does not keep storms around for very long this evening, due to poor mid-level lapse rates (barely above the moist adiabatic lapse rate) leading to a poor CAPE environment. Therefore, confidence is low on thunderstorms development, and even lower on chances for severe weather chances.

A Slight to Marginal Risk for storms returns Tuesday, mainly over central and north central South Dakota. The environment Tuesday evening appears favorable for hail development due to a CAPE/Shear combo of ~2000 J/kg and 30-40 knots respectively. Decent mid-level lapse rates of 7 C/km will also be present, supporting hail growth aloft. A little lower confidence on the wind threat, but some DCAPE as high as 1500 J/kg will likely be present. The potential drawback is that this DCAPE is expected over central South Dakota, while the beset potential severe threat is over north central South Dakota, so it will depend on how things line up. There does appear to be a tornado threat in the evening, as 0-1km shear of >20 knots, low- level helicity of 200 m2/s2, and LCLs below 1000m all appear to line up over north central South Dakota. Future forecast shifts will likely be able to provide more clarity on the specific timing and location of this possible tornado threat as high-resolution guidance comes more into focus, as there is still a bit of disagreement among them at this time.

One commonality between hi-res models Tuesday evening is that storm motion is likely going to be from southwest to northeast, with the potential for training storms to develop if storms don't progress eastward quickly enough. At the moment corfidi upshear vectors and mean cloud layer wind appear to be high enough to help alleviate concerns (both around 30 knots). However should training storms develop, conditions will be favorable for flooding. PWATs around 1.3=1.4", warm cloud layer >10k feet, moist mid-levels, and a long, skinny CAPE profile are all possible. North central South Dakota does not have very saturated soils currently, which may also help alleviate concern, but that was also the thought process ahead of yesterday evening's convection before flooding was observed over eastern McPherson county. A notable difference however is that the ABR observed sounding had a corfidi upshear vector of 10 knots, which made things much more favorable for training storms to develop than what is being forecast for Tuesday evening. All that to say, can't rule anything out just yet, but nothing widespread is currently anticipated in terms of the flooding threat.

By mid-week, the upper-level low over the western CONUS begins to break down, and the Northern Plains will see the return to more zonal flow aloft. Precipitation chances will continue, in part due to the potential for a couple of shortwaves to move over the area during this zonal flow regime. Additional chances for severe weather will exist through the end of the week with these shortwave supported storms, and most medium range machine learning models place at least a 5% chance (equivalent to a Marginal Risk from SPC) over part of the Aberdeen forecast area. Beyond that point, there is fairly strong consensus in the ensembles in another trough developing over the western CONUS and potentially continuing the rain chances and severe potential for the weekend.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1213 AM CDT Mon Jun 1 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail though KMBG, KABR and KATY may see a few hours of MVFR/IFR cigs/visbies this morning.

ABR WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None.