Marine Weather and Tide Forecast for Des Moines, IA

DISCUSSION
Issued at 246 PM CDT Tue Apr 29 2025

Height rises and a surface high kept weather fair today. Winds will continue to slow through the afternoon as the high's influence increases. Highs will be in the low to mid 60s with some places in the north remaining in the upper 50s. Main change this forecast was leaning on the lower end of guidance solutions for temperatures across the north tonight. A mixture of subsidence, calm winds and mostly clear skies will already allow lows to underperform, but add to it the dry low-levels (surface dew point depressions are on average around 15 degrees) from the high pressure and temperatures will be able to sink into the mid 30s. Have lowered temperatures only as far south as the Highway 20 corridor as midlevel clouds will begin their snow northward progression after midnight, keeping southern Iowa warmer, in comparison.

Some notable changes in the synoptic pattern for the rest of the work week. The closed low in the SW US will now arrive in the region before the northern stream trough does, deepening as it does. This feature will lock in most of the low-level moisture fetch and redirect it into the Ohio River Valley. The more southerly trend of the system has taken the instability gradient with it, with MUCAPE values remaining under 500 J/kg in the far south. There will be some possible thunderstorms with this much instability, but activity won't be severe. Rainfall amounts will be largely under an inch, but convection in the far southeast could lead to locally higher amounts. Have lowered temperatures to reflect the cloudy, wet conditions. The northern stream system dives in for Thursday, bringing with it an reinforcing shot of Pacific moisture to keep precipitation going. Finally, another shortwave pivots from the northwest for additional light rain chances on Friday.

An Omega block pattern takes shape over the weekend with Iowa being in proximity of the influence of the ridge. Temperatures will respond by returning into the 70s. Active spring weather won't be far away as the influence from the closed low in the SW US will churn in PVA and Gulf Moisture, hence the rain chances in the west towards the end of the period.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
Issued at 632 PM CDT Tue Apr 29 2025

VFR conditions prevail this evening as northwesterly winds overnight become light and variable, steadily transitioning to an east southeasterly direction by tomorrow morning. Clouds will increase from south to north tomorrow as scattered rain chances move north into the area. There is some uncertainty on the initial arrival of these showers as they move fall into dry air currently overhead. However, as they saturate through the day, expect light rain and low cloud cover to develop. Widespread MVFR conditions are likely, with the chance for IFR conditions at times in the late afternoon/evening.

DMX WATCHES/WARNINGS/ADVISORIES
None.