Marine Weather and Tide Forecast for Rochester, MN

DISCUSSION
Issued at 220 PM CDT Fri Apr 25 2025

Weekend Outlook: Sunny Saturday, Scattered Showers Sunday

Clouds clear overnight as today's rainfall departs to the east, setting the stage for a beautiful start to the weekend. Cannot fully rule out the possibility of localized fog towards sunrise, but with modestly strong winds just off surface, did not feel confident to mention fog in the forecast at this time.

Despite weak cold air advection on Saturday, ample sunshine will result in temperatures topping out near seasonal norms for this time of year in the low to mid-60s. Mid to high clouds increase in the afternoon and evening as the 500-mb ridge slides off to the east with a mix of sun and clouds for Sunday.
Southerly flow deepens for Sunday with steadily increasing theta-e advection in the lower to mid troposphere possibly fueling isolated to scattered showers, primarily north of I-90 where saturation in the 900-700-mb layer looks to be more likely, though mid-level lapse rates do not seem conducive to anything outside of showers and possibly a rumble of thunder.

Monday Afternoon/Evening: Severe Weather Threat

Moving past the weekend, all eyes remain fixed on the severe weather potential for Monday afternoon and evening. A deep longwave trough carves out the western CONUS by Sunday midday before ejecting northeastward across the central High Plains by midday Monday. At the surface, a broad warm sector becomes established across the central CONUS with a surface low tracking from the Colorado Front Range northeastward to the MN/ND/SD border by midday Monday. A dryline/pre-frontal trough will march into southwest Minnesota and western Iowa for Monday afternoon and serve as the focus for convective initiation during the late afternoon and evening hours.

As is typical at this time range from the event, fine scale details with the thermodynamic and kinematic fields will play a large role in how the severe weather threat evolves Monday afternoon and evening. There still exists appreciable variability (on the mesoscale) in the timing/position of the dryline, how quickly the warm sector destabilizes, and the wind profiles in the lower to mid-troposphere. Barring open warm sector convective initiation, storms are likely to develop along the dryline in southern Minnesota and advance eastward, congealing into a QLCS through the evening. How quickly this takes place will hinge on the orientation of the deep shear vector and the degree of inhibition in the warm sector. A very subjective view would favor discrete cells west of the Mississippi River with a QLCS mode more likely east of the river.

It is worth noting the strong consensus in the EPS and GEFS- based AI aggregate severe weather probabilities that have only been increasing over the last 24-48 hours. The latest 12Z probabilities are all highlighting a 30-60 percent corridor for the potential of severe weather (within 25 miles of a point) across Iowa into southern MN, which is an exceptionally strong signal for being 4 days out. The top 5 analogs from the CIPS guidance are all large severe weather outbreaks over the Upper Midwest, including several that produced longer tracked tornadoes (May 17, 1992, June 7, 2007, April 18, 2004, and April 10, 2011).

The details with this event will continue to be refined over the next few days. Please continue to check for forecast updates through the weekend.

Tuesday - Thursday: Seasonal Temps, Dry Midweek

The flow pattern quickly moderates in the wake of the trough passage Monday night into Tuesday, resulting in temperatures not straying too far below seasonal norms for midweek. Low- amplitude ridging ripples along the Canadian border late Tuesday into Wednesday, bringing a stretch of drier weather for this period. By Thursday, the next northern stream wave approaches, and while Gulf moisture is progged to remain south of the region, scattered showers cannot be ruled out with this trough passage.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
Issued at 1044 PM CDT Fri Apr 25 2025

VFR conditions are expected through the TAF period with very little cloud cover. Winds will remain under 10 kts and will shift from northerly to southeasterly throughout the TAF period.

ARX WATCHES/WARNINGS/ADVISORIES
WI...None.
MN...None.
IA...None.