959 FXUS63 KOAX 202324 AFDOAXArea Forecast Discussion National Weather Service Omaha/Valley NE 624 PM CDT Sat Sep 20 2025
.KEY MESSAGES...
- Areas of fog again late tonight into Sunday morning.
- Off-and-on precipitation chances Sunday through Wednesday, with the best rain potential (40-70% PoPs) Monday night and Tuesday.
- A few strong to severe storms are possible Sunday evening, and again Monday afternoon into Monday night.
- Near-normal temperatures through much of next week.
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.DISCUSSION... Issued at 308 PM CDT Sat Sep 20 2025
Tonight through Sunday night:
A mid/upper-level low over northern ND this afternoon is forecast to undergo deepening this period as it continues east into northern MN. At the same time, a separate vorticity maximum currently over WY will progress into the central Plains and lower MO Valley on Sunday, contributing to overall trough amplification from the upper MS Valley into Ozarks. At the surface, light and variable winds observed across the region this afternoon are expected to become light south tonight, ahead of an area of low pressure, which will develop across southern SD on Sunday.
The combination of light winds and a relatively moist boundary layer are expected to contribute to fog formation again tonight into Sunday morning, especially across portions of southeast NE into southwest IA. The models suggest that a few warm- advection-related showers and thunderstorms may develop late tonight into Sunday across parts of southeast NE and southwest IA, where 20-30% PoPs have been included. Additional thunderstorm development is possible from late Sunday afternoon through Sunday evening across portions of southeast SD, northwest IA, and perhaps northeast NE, in the vicinity of the above-mentioned surface low. It currently appears that the best storm potential will remain to the northeast of our area, with 15-25% PoPs included in far northeast NE and parts of west- central IA.
Model soundings in the vicinity of the surface low indicate the presence of a modestly sheared and unstable environment, which could support a few strong to severe storms, with the primary hazards being hail and locally strong wind gusts. As mentioned above, the best storm potential and associated severe risk may ultimately remain to the northeast of our area.
Highs on Sunday may end up being a bit warmer than those today, with readings in the mid/upper 70s.
Monday through Wednesday:
The 12z global models are in reasonably good agreement in depicting mid-level trough amplification and subsequent low formation across the northern and central Rockies on Monday. That feature is then expected to gradually weaken as it progresses from the central High Plains into the Ozarks on Tuesday into Wednesday. The surface pattern is more muddled, with indications that a cool front will settle south through the mid MO Valley on Monday night into Tuesday morning.
Increased forcing for ascent associated with the approaching mid-level system will support PoPs increasing from 15-25% on Monday afternoon to 40-70% Monday night through Tuesday. The PoPs subsequent decrease from north-to-south on Tuesday night into Wednesday. A few strong to severe storms appear possible Monday afternoon into Monday night, owing largely to the presence of a steep-lapse-rate, moderately unstable air mass developing within the pre-frontal warm sector.
Highs in the upper 70s to low 80s on Monday are forecast to cool into the 70s on Tuesday and Wednesday, due to widespread clouds and areas of rain.
Thursday and Friday:
A mid-level ridge is forecast to build east from the Rockies into the Great Plains late next week, with drier and slightly warmer weather expected.
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.AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 624 PM CDT Sat Sep 20 2025
VFR conditions this evening with mid-level clouds around FL050 continuing to diminish in coverage. Winds are light, generally out of the south or southeast. Overnight, winds will become nearly calm, allowing for fog development primarily across southeast Nebraska and southwest Iowa, including KLNK and KOMA. This should develop between 10-11Z and remain over the terminals until around 15Z. Once fog burns off, we`ll see winds gradually increase out of the south or southeast to 10-15kt. VFR conditions through the remainder of the TAF period.
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.OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None.
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DISCUSSION...Mead AVIATION...McCoy
NWS OAX Office Area Forecast Discussion