Marine Weather and Tide Forecast for Landfall, MN

DISCUSSION
Issued at 318 AM CDT Tue May 20 2025

Very strong synoptic scale lift from a negatively-tilted trough over the central CONUS is causing cyclogenesis over IA. In turn, a large stratiform precipitation shield is currently forming north and northeast of the low. Mosaic radar imagery shows this process occurring now as rain fills in over the southern half of MN and western WI from moisture streaming in from the south. All of our MN counties and most of our WI counties (aside from perhaps our extreme northeast) will see continuous rain starting by sunrise and lasting into this afternoon. CAMs then show the rain shield lifting northward into central MN later this afternoon and evening while wrap-around precip re-enters southwest MN again as the surface low occludes. The heaviest rainfall will occur this morning, with south- central MN looking to bear the brunt of the rainfall rates. While we shouldn't have any really high rainfall rates (due to little convection), rates of 0.25-0.5" per hour are likely. Also during this morning, easterly winds are expected to be strong as the surface low deepens and a LLJ moves overhead. Strongest winds are expected over southeastern MN and western WI where gusts could reach or exceed 40 MPH. The HRRR continues to insist that we will have Wind Advisory criteria in this region this morning. However, ongoing rain should dampen gusts slightly. Ended up increasing winds and gusts but kept them just below Wind Advisory criteria.

Areal coverage and intensity of the rain (and winds) should wane a bit going into this evening as the surface low fills and moves east.
By Wednesday morning, the low will be in the Lower Great Lakes region. Meanwhile, guidance shows the band of rain (originally associated with the low) being left over MN/WI. This rain will be oriented in a northwest to southeast direction stretching from western MN into western WI along what is seemingly a stationary front. Forecast soundings show at least light rain persisting Wednesday into Wednesday night before moisture profiles finally dry significantly. Storm total QPF from most guidance is eye-popping and we can be glad that this event isn't occurring on a much shorter time-scale. The highest rainfall amounts within the guidance is mostly centered over south-central MN. Here, the HRRR 24-hr LPMM QPF is on the order of 2-3" with localized areas potentially approaching 4"! Outside of this region, most of our MN counties should at least see another 1-1.5" by the time rain finishes Wednesday night. Expect ponding to occur in low-lying areas.

Upper-level northwesterly flow will prevail over the Upper Midwest Thursday into Saturday. This will allow us to dry out and experience some sun and warmer temperatures again. Highs are forecast to be in the low to mid 60s to end the week with a gradual warming trend occurring early next week. Rain chances also return early next week as forecast models show a couple of shortwaves moving through the Northern Plains. Though, spread between models for these features is pretty high at the moment.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
Issued at 1218 AM CDT Tue May 20 2025

Kept much of the 00z TAF intact with MVFR bcmg IFR with -RA throughout the period. Winds will gust at 30-35kts from 060-090 throughout, dwindling below 25kt gusts by the end of the period.
There could be a gap between rounds of showers from TAF start to 12z where we briefly return to high MVFR/VFR visibility, however showers are expected to fill in these gaps shortly after sunrise and persist throughout the day. Expect predominantly IFR once the showers remain continuous at 3-4sm and CIGS around 1000ft.

KMSP...Compared to the 00z TAF, any mention of TSRA has been removed with thunder absent for the rest of this system. Did opt to include IFR cigs as confidence in 800-1000ft CIGS is higher than with the 00z issuance. Winds are once again the wild card, with gusts frequent to 30-35kts with an occasional higher gust possible.

/OUTLOOK FOR KMSP/ WED.. MVFR/-SHRA early, then VFR. Wind NE 10-15kts.
THU...VFR. Wind N 10-15kts.
FRI...VFR. Wind NE 5-10kts.

MPX WATCHES/WARNINGS/ADVISORIES
MN...None.
WI...None.