Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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361 FXUS63 KOAX 300428 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1128 PM CDT Sun Jun 29 2025 .KEY MESSAGES... - A few isolated showers and storms are possible along a weak front left over in northeast Nebraska from the morning storms (30% chance). - A stronger complex of storms is expected to move in from the west overnight, with strong winds and hail being the primary hazards alongside heavy rains after 2 AM. - Much of Monday and Tuesday will be dry, with temperatures heating back up by late in the week. - Chances are increasing for an active holiday weekend, as a frontal system arrives from the west Friday into the weekend. && .DISCUSSION... Issued at 357 PM CDT Sun Jun 29 2025 Today: Water vapor imagery this afternoon depicts a messy patter that we find ourselves in, with widespread debris from previous and current convection while an arm of forcing associated with a mid/upper shortwave trough starting to grow initial convection up the High Plains. That morning convection that swept through eastern Nebraska and southwest Iowa has complicated the forecast for today, tanking temperatures and overturning the airmass in place, delaying robust convection into the late evening/overnight hours. Taking a look at a recent surface analysis, a surface low was placed over southeast Colorado, with a surface boundary extending northeast from it across northern Kansas, where it runs into the convectively turned over airmass across eastern Kansas and Nebraska. A narrow corridor of surface moisture extends along the northern side of the boundary across much of south-central and into eastern Nebraska, with a largely flat field of cumulus extending from northeast Kansas to Grand Island. Across north-central Nebraska, an impinging cold front has resulted in another narrow field of cumulus that stretches from northwest Nebraska east-northeastward into southeast South Dakota. As the forecast sits right now, we`re carrying a 20% chance that convergence becomes strong enough along either of those boundaries for an isolated shower or storm to form along them through the evening hours. If one would form, it would likely struggle to reach severe levels, though it could provide a nuisance for those outside. What is anticipated to be the main player for storm chances late this evening into the overnight hours will come in the form of a cluster of storms, swept off the High Plains by the incoming front/shortwave, then likely riding the theta-e gradient draped near the NE/KS border. There still is quite a bit of divergence in CAM solutions for the location and orientation of that gradient, with the latest runs of the CAMs suggesting that the forecast area is in play for at least a portion of the MCS as it moves eastward; especially the southern half. Taking a look at ingredients that the MCS will be driving into, low-level wind fields look rather flat, with shear values of less than 25 kts to go along with steep mid/upper lapse rates with poor nocturnal lapse rates at the surface taking away from overall CAPE values. Sub-severe storms look most probable at this time for the overnight hours, with a stronger section of the system looking to track across northern Kansas, where potentially very strong winds of 75 mph or more are possible. Our primary hazards will be associated with marginally severe winds of up to 60 mph, and quarter-sized hail as the front edge of the cluster`s updrafts pulse up before weakening. In addition, we could see heavy rain rates create localized flooding if sufficient back- building occurs (which is possible with the WNW orientation of 0-1 km shear vectors). This area has taken less water than points to the northwest, making increased coverage of flooding difficult. Timing this out based on the latest convective model trends, we`ll see clusters of storms across west-central Nebraska and western Kansas by midnight, that push into the forecast area between 2-4 AM before exiting the area 8-10 AM. Monday Afternoon through Thursday: Northwesterly winds will be left in place for the afternoon hours Monday, as portions of the increasing pronounced shortwave trough traveling through the area swing southward and bring low-end (~10%) chances for a sprinkle/light rain during the afternoon and evening hours. Highs will feel the cooler winds, with highs expected to only top out in the low 80s, making a beautiful start to the work week. From there, a cutoff low over the California Coast is poised to amplify the ridging pattern over the western half of the CONUS, helping to drive highs upwards through the week. Low chances of precipitation are forecast, with a decaying MCS being our only hope for seeing rain before the end of the week. Friday and Beyond: The latest runs of the global deterministic models suggest that the aforementioned cutoff low will begin sweeping up with the mid/upper flow and help transition increased forcing for ascent into the Central Great Plains for Friday afternoon and evening. The position and timing of the front/forcing that comes with this system will be of much interest for those wanting to enjoy the holiday weekend, which is looking increasingly active. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
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Issued at 1128 PM CDT Sun Jun 29 2025 As winds have weakened this evening, we`ve seen wind directions become more variable across the area as subtle boundaries flux across the area. This will likely continue through the next several hours as storms over northwest Nebraska track southeast into central Nebraska. We`re watching showers around Oneill for potential storms that could move through KOFK around 06-08Z tonight. If this can solidify into a solid line of storms, we may see storms make it all the way across to KOMA, but right now just not confident enough to keep storms in the TAF for KOMA right now. KLNK has the highest chance of seeing storms, but more towards daybreak as the storms in central Nebraska continue southeast clipping KLNK to the north. Once this boundary pushes through, expect predominantly north-northwesterly winds for the remainder of the day, increasing this afternoon with gusts to 20-25 kt, then relaxing again Monday evening. Quiet weather expected Monday night.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Petersen AVIATION...McCoy