Marine Weather and Tide Forecast for Nevada, IA

DISCUSSION
Issued at 238 PM CDT Sun Apr 20 2025

Broad stratiform rain has spread across the area today, resulting in rainfall totals by early afternoon around 0.25-0.75" over most of the area. Meanwhile, further south in Missouri early storms have already developed on the boundary there. This is anticipated to lift towards southeast Iowa later this afternoon and into the early evening. The low track remains very near, but just southeast, of putting the DMX county warning area in the cross hairs, but it will be close. CAM runs through today continue to develop helicity tracks that into southeast Iowa, clipping near our far southeast counties Davis and Wapello. The environmental space includes an area of 100+ J/kg 0-3 CAPE with 30+ kts of deep layer shear. Helicity swaths are evident in nearly all CAMs into southeast Iowa in the roughly 4- 8pm window so the main question now is where exactly the storms that develop will track.

Rain tapers off across the area overnight and a widespread 1-2" is anticipated by that time, with locally heavier amounts of 3+".
River will see within bank rises with a few forecast to reach action stage, however the prolonged period over which this rain is falling negates most hydrologic concerns. Guidance has changed little from that discussed in the previous hydrologic discussion, which has been maintained below.

Temperatures warm Monday into the 60s and will remain in the upper 60s to mid 70s through out the upcoming week. The week remain active, however, with several chances for showers and thunderstorms. The next window will be Tuesday as a quick shortwave moves across the upper midwest. As it does, a ribbon of 500-1000 J/kg MLCAPE and 30+ kts of 0-6km shear will be in place. Soundings are fairly dry in the the low levels with GFS soundings showing an inverted-v shape with dry air in place. A few stronger or perhaps severe storms may be possible in this environment, capable at least of stronger wind gusts and small hail. This coincides nicely with the freshly issued SPC day 3 Marginal Risk (level 1 of 5) for Tuesday. Behind this wave the synoptic pattern becomes messy with poor agreement amongst models. This has made it difficult to pin down a more defined timeframe for future rounds of convection and resulted in rather prolonged periods of precipitation chances. This will need to be fine tuned in the days to come.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
Issued at 639 PM CDT Sun Apr 20 2025

Widespread IFR to MVFR aviation conditions across the state early this evening with pockets of LIFR. Rain showers continue over the southeast to east with activity lifting northward into portions of central and northern Iowa still over the next several hours. In areas where rain has lessened, drizzle or fog continues keeping visibilities and ceilings lower. Rain ends by 6-9Z in most of the area with gradually improving aviation conditions into midday Monday with VFR expected to return everywhere by the afternoon. Winds gradually shift to be out of the northwest into Monday morning remaining gusty through the overnight with gusts up to around 25 knots, but winds too will decrease again on Monday afternoon.

HYDROLOGY
Issued at 351 AM CDT Sun Apr 20 2025

Mainly within back rises are anticipated with this precipitation based on RFC contingency forecasts whose median and expected QPF values are Action Stage or below. HEFS output is similar with median/50% exceedance probabilities noting all responses below Action Stage, and 30% exceedance showing Action Stage or less responses. The flood potential is non-zero however if the high end of ensemble QPF is realized with max contingency QPF and HEFS 10% exceedance noting a few spots just reaching Flood Stage in the Shell Rock and Cedar Basins later this week. The most expected impacts will be reduced visibilities in rain, standing water on roads, fields, and ditches.

DMX WATCHES/WARNINGS/ADVISORIES
None.