Marine Weather and Tide Forecast for Nevada, IA

DISCUSSION
Issued at 218 PM CDT Thu May 15 2025

Today's weather has unfolded largely as forecast, with a large cyclone stacking and deepening over the Dakotas and moving quickly north northeastward toward the North Dakota/Minnesota border. A dryline trailing from the system is sparking strong thunderstorms over Minnesota, but the boundary has already moved northeast of our forecast area. An area of scattered light showers is moving across northwestern Iowa and may just clip areas around Estherville this afternoon, but with no impact and other than this the forecast is dry through tonight and into Friday morning. However, with a tightening pressure gradient and deep mixing we are seeing strong and gusty winds spreading across our area and these will continue until sunset when they should diminish somewhat as mixing decreases. The current advisory remains in effect, and while a couple of reporting sites outside the advisory have occasionally reached criteria, it has not been consistent or widespread enough to warrant expansion.

Overnight tonight, while surface winds diminish somewhat, some short-range models are tracking a very subtle shortwave impulse moving over central Iowa and producing spotty light QPF.
However, forecast soundings are quite dry and most solutions remain dry, so have maintained POPs below 10% accordingly. On Friday the stacked and slowly filling low will drift eastward across northern Minnesota, with an expanding shield of stratus and showers advancing around its southern flank and into our area from the northwest. Have maintained POPs in that area, diminishing from likelies (60-70% chance of rain) in our northwestern corner to lower chances (20-30%) near the Highway 30 corridor and just sprinkles south of that. In any event, no significant rainfall or thunder is anticipated with this precipitation. Of greater consequence is another surge of strong and gusty winds during the day, this time from the west northwest. While forecast soundings indicate notably shallower and less efficient mixing beneath the low cloud deck, stronger winds just off the deck and moderate cold air advection will aid in momentum transport and we should see advisory level winds once again, perhaps even over a slightly larger area than today.
In light of this, and with winds expected to reach criteria in our northwestern counties just after sunrise, have elected to go ahead and issue another Wind Advisory now for Friday, encompassing the same area as today's advisory plus several more of our southwestern counties. This may need to be expanded or time-adjusted a bit tonight as more data comes in.

On Friday night, as the large storm system moves away over the Great Lakes, winds should gradually diminish and clouds and any lingering sprinkles will move out. This will give way to a brief spell of quiet and relatively cool weather as a surface high pressure ridge slides across the Upper Midwest around Saturday and into Sunday. High temperatures Saturday afternoon will only range in the 60s to lower 70s south, and lows Sunday morning are forecast in the upper 30s northeast to upper 40s south; a notable change from our long recent spell of unseasonable warmth.

By Sunday morning the next storm system will be taking shape as a 500 mb trough digs down over the western U.S. and Rockies. A reinforcing vorticity maximum will move from around Seattle down into the larger trough during the day on Sunday, and the entire system will then move eastward toward the Midwest and Iowa in the early part of next week. However, the interaction between the two vorticity maxima wobbling around the larger cyclonic flow is not being well-resolved by the long range models, resulting in differences between solutions that could have significant implications for hazardous weather potential in our service area. It is likely that an initial surge of theta-e and moisture advection, along the inflection zone where 500 mb flow turns to southwesterly in advance of the approaching system, will produce a swath of rain moving across Iowa from southwest to northeast on Sunday night or Monday. However, potential for heavy rain or severe weather is unclear at this time, as is the timing of this progression. After that confidence steadily decreases as the large, discombobulated trough approaches. Long range models have been trending slowly but steadily southward with heavy rain and thunderstorm chances since yesterday, but still keep these over or just south of southern Iowa and have maintained high (70-80%) POPs Monday night and Tuesday for now, tapering off thereafter as the large system moves away to the east. Despite the maintenance of high POPs in a desire for forecast consistency, overall confidence in the evolution of this system has faded, and will need to wait for better resolution of this scenario before additional details can be sussed out. Nevertheless, certainly the potential for severe thunderstorms and/or heavy rain remains for our area early next week, and should be monitored over the next several days.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
Issued at 725 PM CDT Thu May 15 2025

Skies will gradually clear this evening as fair weather cu erodes. West winds stay up for a time through 02-03z; generally in the 30-40 knot range. Winds will subside overnight, before increasing again after 12z Friday. In fact winds will be nearly as gusty during the day on Friday as they were today - gusts of 30-40 knots. Clouds will be on the increase after 06z as well, becoming bkn-ovc after 15-18z. Additionally, have added -SHRA mention to KFOD and KMCW after 18z. Any rain amounts will remain on the light side.

DMX WATCHES/WARNINGS/ADVISORIES
Wind Advisory until 9 PM CDT this evening for IAZ004>007- 015>017-023>026-033>037-044>048.
Wind Advisory from 7 AM to 9 PM CDT Friday for IAZ004>007- 015>017-023>026-033>037-044>048-057>059-070-071.