Marine Weather and Tide Forecast for Newton, IA

UPDATE
Issued at 351 AM CDT Fri May 23 2025

A shortwave is on approach from the Rockies, its influence beginning with the midlevel clouds present this morning in the west. Some southwest fetch, and therefore moisture transport, will reach Iowa today, but will be almost completely absent from instability. There could be a rumble of thunder in the southwest this afternoon as MUCAPE values could get into the low 100s. An elevated reflection of the moisture advection will collect enough moisture to produce showers across the north this afternoon. This activity will slowly wane after sunset as the moisture transport moves southeast. The presence of low level dry air give soundings an inverted-v look. This means that there could be some wind gusts with showers and storms this afternoon, but the lack of environmental winds in the vertical profile will keep these gusts tame. Supporting this is the 00z HRRR which had no members with gusts exceeding 30kts.

Cloud cover will linger into Saturday and the weather will set up not too dissimilarly as Friday, this time more focused in the south rather than southwest. Have increased PoPs Saturday night slightly above NBM in the north to reflect where the elevated boundary will set up. The moisture content in profiles looks less impressive compared to the elevated boundary today, so have withheld categorical mentions for now, but trends will be monitored. Have also preserved posture of lowering high temperatures below guidance due to account for cloud cover during the daytime.

DISCUSSION
Issued at 241 PM CDT Thu May 22 2025

The transition to northerly flow aloft has fully occurred today as an upper low has moved into the western Great Lakes while high pressure ridging is occurring through the Dakotas and Manitoba.
The northerly flow allowed the northern Iowa/Minnesota stratus to move south today and a few areas of light rain occurred south to near Interstate 80 before diminishing. The stratus also transitioned to more cellular clouds with cumulus developing upstream in the clearing which has now moved into northern Iowa.
The main area of stratus that has become cellular will be slower to erode overnight with clearing occurring from north to south overnight. This will allow temperatures to cool overnight as the wind diminishes with surface high pressure arriving.

The upper flow will undergo another transition Great Lakes upper low moves a bit more east allowing for some 500 mb height rises and a pseudo zonal flow. A short wave will pass over the Rockies overnight and will carry Pacific moisture into the region on Friday. Clouds will be on the increase on the lee side of the Rockies as the moisture lifts over the mountains. This process will eventually lead to high to mid-level cloudiness to increase from west to east over Iowa on Friday. Enough saturation will occur during the day for rain chances to increase across parts of central and western Iowa, especially during the afternoon. In addition, the increasing cloud cover will lead to another cool day. Guidance is suggesting highs in the mid 60s which are likely overdone. Little change in the pattern through Sunday which will keep cool weather and some shower/non- severe thunderstorm chances going through Sunday. By Sunday night, an upper low will develop over western South Dakota and this will initially lead to a more southwest flow into Iowa before the upper low moves and settles over Iowa by late Tuesday. This again will lead to cool temperatures and keep precipitation chances going across the state. This setup can also lead to funnel cloud development. Will need to further evaluate the near surface parameter space as this event draws closer. The uncertainly for mid to late next week is how quickly that upper low will move out of the area and western ridging and warmer air arrives. At this time, a more delayed departure is favored but possibly back to warmer weather at the end of next week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
Issued at 1226 PM CDT Fri May 23 2025

VFR conditions prevail through the period with light and variable winds persisting through the afternoon and into the overnight. Scattered to broken cumulus will continue to develop over the area this afternoon, but remain around 5 to 7 kft. Mid to upper level clouds will also stream in from the west today, bringing scattered shower chances this afternoon and evening. No major impacts to aviation are expected with these showers, but may see some brief gusty winds as they pass through.

DMX WATCHES/WARNINGS/ADVISORIES
None.