textproduct: Twin Cities

KEY MESSAGES

- Much warmer air begins arriving today. Stratus and fog are possible through early Friday as the milder air interacts with the snowpack. Temperatures through Saturday will be dependent on cloud cover/fog and lingering snow depth.

DISCUSSION

Issued at 403 AM CDT Wed Mar 18 2026

Clouds and a few flurries are lingering east of the Mississippi River early this morning. The eastward progression of the clearing line has slowed due to its NW-SE orientation and the bank's movement toward the ESE. Western WI should be cloudy most of the morning, but eastern MN is still expected to clear for a time. High clouds across the Dakotas will arrive this afternoon. A weak shortwave in the northwest flow will pass to the north this evening and bring a low chance for rain north of I-94.

The main concern for the next couple days will be the potential for low clouds and fog. The snowpack is quite cold currently from the past couple days in the single digits and teens. As ridging from the Plains works east, much warmer air aloft arrives beginning today and an inversion around 2 kft will develop. Surface dew points also rise well into the 30s atop the cold snowpack. This should at a minimum result in some low clouds below the inversion, and possibly widespread dense fog, as surface temperatures cool to the dew point tonight, both of which may remain above freezing. Forecast soundings from the NAM and GFS are showing extensive low clouds and fog for the next couple days, but the RAP is quite a bit drier in the boundary layer tonight. More fog was introduced to the weather grids tonight. Should fog indeed develop, light winds in the boundary layer and the inversion aloft will make it difficult to bring improving conditions until perhaps Thursday afternoon. Even then, it's not likely we'll lose the low stratus entirely. In this scenario, current forecast high temperatures tomorrow would be too warm. The process may repeat again Thursday night into Friday if the snowpack hasn't already taken a significant hit. By Friday afternoon the snow will likely be gone across southern and western MN, and stronger low level winds and a stronger late March sun angle should be able to mix out any morning stratus. Highs in the 60s are currently expected there, with 40s and 50s lingering farther northeast where the deeper snow may still be hanging on.

A thermal ridge moves in Saturday ahead of a cold front. By this point, a couple days of fog and temperatures continuously above freezing should have taken care of the rest of the snow. 925 mb temps of +18 to +20C signal highs as warm as the mid to upper 70s across southern MN. There are still timing questions with the cold front, but the ECMWF and AIFS have slowed down its arrival from yesterday, now bringing it in Saturday evening. Therefore the temp forecast has increased, but is still a little modest with a lot of spread remaining. Cooler temperatures return behind the front, but remaining near normal into early next week.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1228 PM CDT Wed Mar 18 2026

MVFR stratus continues to clear very slowly from northwest to southeast across western Wisconsin. Given the orientation of the clearing line, it may be another few hours before for KRNH and KEAU. Mid/high clouds will increase this afternoon. Low clouds and fog appear likely to develop area wide tonight, but overall confidence isn't particularly high given the increased mid level cloud cover. I have added & increased the likelihood of BR/FG in this set of TAFs. While mid-level cloud cover could slow the process, light & variable winds combined with snow melt moisture trapped beneath the inversion should support fog. Fog will be slow to burn off, but should improve Thursday AM. Low stratus likely remains on Thursday given the feedback loop with snowmelt & light winds.

KMSP...IFR (or worse) conditions return overnight with fog/mist. Confidence isn't particularly high on the timing of when vsby improves tomorrow morning, but current guidance supports by late morning.

/OUTLOOK FOR KMSP/ FRI...VFR. Wind SW to NW 5-10kts. SAT...VFR. Wind SW 10-15kts. SUN...VFR. Wind N 10-15kts.

MPX WATCHES/WARNINGS/ADVISORIES

MN...None. WI...None.