textproduct: Aberdeen

KEY MESSAGES

- Record or near record warm temperatures in the upper 80s to lower 90s are expected Wednesday. Winds out of the south will gust 30 to 40 mph and relative humidity will fall into the 15 to 30 percent range. The strong winds and warm/dry conditions will combine to create very high grassland fire danger index values.

- There is a 30-70 percent chance of showers and thunderstorms Wednesday night into Thursday, mainly throughout central and north central South Dakota.

- Strong sustained west winds 25 to 35 mph with gusts up to 50 mph are expected on Thursday. These windy conditions may last all the way through Friday into Friday night, especially along and north of U.S. Highway 212.

- After a warm start to the day Thursday, cold air will establish control of the temperature forecast from Thursday afternoon through the end of the weekend. High temperatures Friday through next Monday are expected to be near to around 5 degrees below normal; low temperatures 5 to 10 degrees below normal (below 32F).

UPDATE

Issued at 819 PM CDT Mon Apr 20 2026

The Red Flag Warning for far northeastern South Dakota and west central Minnesota has been allowed to expire. No significant changes are anticipated to the near-term forecast for the rest of the evening.

DISCUSSION

Issued at 120 PM CDT Mon Apr 20 2026

At 1 PM CDT, skies are sunny/mostly sunny and temperatures are warming into the 60s and 70s (20 to 25 degrees warmer than this hour yesterday). Winds are south at 15 to 25 mph with gusts up to 40 mph at times. Relative humidity values are falling through the 20 to 30 percent range as well.

Northwest flow aloft is forecast to persist through Wednesday. A cold front will pass southward through the forecast area tonight, but there will not be much of a cool down expected on Tuesday given the rather limited time for low level CAA tonight into Tuesday morning. Today's really dry airmass gets shunted down into far southern South Dakota/Nebraska on Tuesday, and by peak heating/mixing on Tuesday, the I-90 corridor of this CWA could be dealing with relative humidity as low as 15 to 20 percent, although the east-southeast wind expected in that area on Tuesday is not expected to gust to 25+mph.

A strong low level jet develops Tuesday night and persists into Wednesday night in response to the strong low level WAA expected over the central/northern plains heading into Wednesday. Presently, there is no notable tongue of Gulf moisture surging up into the CWA on Wednesday. With 925hpa and 850hpa temp progs supporting upper 80s to mid 90s (which are record or near record high temps) on Wednesday, and a dry airmass advecting back into the CWA on strong (20 to 35+mph sustained/40-45 mph gusts) southerly winds, the CWA is primed for very high or higher Grassland Fire Danger indexes. Circling Wednesday as a potential Fire Weather Watch day once today's Red Flag Warning event is over.

The upper level steering flow will switch around to the west/southwest Wednesday night as a large/cold upper level low/longwave trough heads east across the nation's mid-section. Both the NAM and GFS in BUFKIT showcase more than enough mid-level moisture (at or above 2km) availability Wednesday night into Thursday morning to support thunderstorm mention (Elevated CAPE at or above 750J/kg). At times, deep layer (cloud bearing) shear appears to produce straight-line hodographs at or above 35 knots. So, there is that potential for updrafts to rotate/split. Wouldn't be surprised if some hail is produced Wednesday night into Thursday morning. Still fairly cold aloft, too, in April, when convection happens, adding to the favorability of updrafts to be able to make hail. The probability of one quarter inch or more of rainfall occurring Wednesday afternoon through Wednesday night is 20 to 35 percent and is presently centered on Sully, Hughes and Hyde Counties.

Still looks like the upper low will run up against an upper level steering flow blockade as it makes its way through Montana/the Dakotas into southern Canada. A rather blocky steering flow pattern is set for the end of the week into the weekend, which should stall this upper low's progression across NOAM. There continues to be a signal in both the deterministic GSM's and all the various ensemble model camps for rather strong westerly- component winds to develop on Thursday, at least across the northern two-thirds of the CWA, continuing through Friday night before diminishing.

Becoming anomalously cold Friday and Saturday in the wake of this large upper low, while the strong westerly-component winds are occurring. Thursday is expected to be the transition day from warm at the start of the day to getting cold at the end of the day. Beyond that, the rest of the 7-day forecast boasts of high temperatures only reaching the 50s (so long as post-system stratus/strato-cu isn't widespread over the region), with night-time temperatures falling below the freezing mark Thursday night through Sunday night.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 620 PM CDT Mon Apr 20 2026

Terminals KABR,KATY,KPIR,KMBG

Expect VFR conditions to continue over the next 24 hours with winds around 15kts or less.

ABR WATCHES/WARNINGS/ADVISORIES

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