Marine Weather and Tide Forecast for Nevada, IA

DISCUSSION
Issued at 253 AM CDT Wed Apr 23 2025

Showers and thunderstorms occurring over the area late last night and into the early morning hours took advantage of the marginal amounts of instability over the forecast area, producing large amounts of hail up to at least ping pong ball sized over Story and Marshall counties and smaller sized hail in southern Iowa. Showers and storms continue to fester early this morning, but have generally remained below severe limits after midnight. That said, while MUCAPE values are waning, still see a few storms capable of producing gusty winds and small hail.

The aforementioned storms remain loosely correlated with a stationary boundary in place over the southern part of the state, with the southern storms being rooted more to the surface feature and the north central Iowa storms being elevated and along the edge of the MUCAPE gradient. We will see this boundary retreat farther north as warm, moist air continues to stream into the state today. With weak forcing in place aloft and this persistent theta-e advection continuing through the day, expect to see scattered showers and thunderstorms to continue festering in proximity to the boundary. The severe thunderstorm risk isn’t overly high, but the threat for a few stronger storms does still exist through Wednesday. The better 0-6 km shear will be primarily north of the boundary this afternoon and evening, but we do see healthy MLCAPE values around 1000 J/kg to 2000 J/kg in an uncapped environment for a few hours this afternoon.
Therefore, any storms that latch onto the boundary may have the potential to tap into the slightly better shear to the north, becoming organized and introducing the potential for some strong to severe storms. Hail and damaging winds would be the primary threat with the storms this afternoon, especially with a decent inverted-v signature present on forecast soundings. The tornado risk is low, given the weak, unidirectional flow in the low levels. Severe weather risk north of the boundary will be low, given minimal amounts of instability, but warm air overrunning the boundary will still result in scattered shower and isolated thunder chances in northern Iowa.

As we get into the overnight hours Wednesday night and Thursday, our extended period of precipitation continues with another surge of forcing and moisture attached to an approaching upper level shortwave and weak surface height falls. This will maintain the scattered shower and thunderstorm chances through tonight with more widespread chances developing on Thursday as the main wave lifts into the state. This will be accompanied by PWAT values of 1.2” to 1.5”. These values aren’t necessarily high compared to the warm season, but will be 200% of normal PWAT values in Iowa during April. Therefore, not expecting a torrential downpour, but some areas may see a decent soaking rain on Thursday. Ensemble QPF values reflect this, showing mean 24 hr precipitation values nearing an inch of rainfall over roughly the northwest half of Iowa and HRRR local probability matched mean 24 hr precipitation showing a few streaks of 2”+ rainfall through this same area. These higher amounts will likely be in areas where multiple stronger updrafts track through, in addition to the more stratiform-like precipitation.
Fortunately, the environment on Thursday does not look conducive to severe weather, with relatively heavy rain being the main impact.

Precipitation will linger through the night Thursday and into early Friday morning, but will begin to diminish as high pressure brings dry air into the state on Friday. This will give us a break from precipitation through Saturday and early Sunday, with more shower and storm chances returning Sunday into Monday. Our pattern remains fairly active into next week, with SPC maintaining a day 6 15% risk (slight risk) for severe weather Monday into Tuesday as a wound up low pressure lifts into the area. More on this system will be provided in the coming days.



AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
Issued at 1223 AM CDT Wed Apr 23 2025

VFR prevailing conditions over the next 24 hours, but with isolated MVFR thunderstorms and showers likely. Current thunderstorms near OTM should stay to the south so kept VCTS in prevailing, but can't rule out some lightning getting closer so opted for a TEMPO as well. Central Iowa will see another round of thunderstorms early this morning with another, more widespread round this evening. Sustained winds will be light, but variable with higher wind gusts related to possible thunderstorms.

DMX WATCHES/WARNINGS/ADVISORIES
None.