526 FXUS63 KOAX 192329 AFDOAXArea Forecast Discussion National Weather Service Omaha/Valley NE 629 PM CDT Fri Sep 19 2025
.KEY MESSAGES...
- A cluster of showers and thunderstorms is expected to push into the area (50-70% chance) through the evening. Frequent lightning and locally heavy rainfall are the primary hazards.
- Fog is expected to develop overnight into Saturday morning, with patchy areas of dense fog possible.
- High temperatures are expected in the 70s to low 80s through the period. Periodic rain chances (15-40%) are expected into next week.
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.DISCUSSION... Issued at 204 PM CDT Fri Sep 19 2025
Today and Tomorrow...
Water vapor imagery and objective analysis this afternoon depict a somewhat complex mid- to upper-level pattern. Weak riding is noted over both the Four Corners region and the southeastern CONUS, while a 500 mb closed low pivots across eastern SD into IA/MN. An embedded shortwave disturbance and associated speed max are rotating around the back side of the low, pushing into central and eastern Nebraska. This feature, along with an associated weak surface front, has served as the focus for a cluster of thunderstorms that developed over north-central NE earlier this morning and has since progresses east-southeast into eastern NE. As of 2 PM, MRMS composite reflectivity places this line of thunderstorms roughly from Holdrege to Columbus, NE.
Afternoon high temperatures remain dependent on cloud cover and precipitation. Areas south of I-80 will likely climb into the upper 70s, while locations farther north under the thicker cloud shield will likely top out in the low 70s.
CAM guidance is in decent agreement on stalling the front, and associated precipitation this evening into the overnight period (PoPs 50-70%), near or just south of the I-80 corridor, with the exact latitude a remaining question. Instability remains limited (MLCAPE near 500 J/kg) and bulk shear is weak (20-25 kts), keeping the potential for strong to severe storms minimal (below 5%). The primary concern will instead be locally heavy rainfall where showers and storms stall and if training storms develop. Warm cloud depths of around 3500 m and PWAT values between 1.25" and 1.50" (near the 90th percentile of OAX mid- September sounding climatology) suggest efficient rainfall production in heavier cells. CAM guidance highlights a corridor of 0.50-1.50 inches of rainfall with pockets approaching 2.50-3.00 inches, bringing some locally heavy rainfall potential. Current flash flood guidance thresholds are 1.50-1.75" for 1 hour, 2.00- 2.25" for 3 hours, and 2.75-3.25" for 6 hours. Current guidance keeps storms spotty enough to avoid any widespread hydrologic concerns, though this will continued to be monitored into the overnight period.
Another foggy morning is expected on Saturday as residual low-level moisture and light winds near the surface set the stage for foggy/misty conditions, with patchy areas of dense fog possible, especially in northeast Nebraska. Showers and storms will gradually taper off overnight (PoPs 20-40%), clearing from west to east through Saturday morning as the low pulls to the northeast. Behind the departing system, low- to mid-level clouds will be slow to erode, keeping Saturday highs in the low to mid 70s.
Sunday and Beyond...
Sunday into Monday, the region will remain under predominantly zonal flow aloft as subtle disturbances pass by. Temperatures will subtly warm, with highs expected to reach the upper 70s to low 80s on Sunday and widespread low 80s on Monday ahead of a cold front Monday evening. Behind the front, highs through the remainder of the work week will generally hold in the mid 70s, near seasonal average for mid-September. Overnight lows are expected in the 50s.
Forecast confidence decreases with regard to precipitation timing and location as the area remains within a split-flow regime. Long- range guidance shows notable discrepancies in the timing and track of individual disturbances, leading to periodic 15-40% PoPs through the week. However, model agreement favors keeping the most significant precipitation chances displaced to our south and east as a closed mid-level low dips into the Ozark plateau. Confidence is low in the potential for strong to severe storms in our area. While pockets of instability may develop at times, weak shear will be the limiting factor, keeping severe potential minimal. Both GEFS and ECMWF ensemble-based machine learning guidance indicates only modest severe probabilities, periodically peaking in the 5-10% range.
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.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 629 PM CDT Fri Sep 19 2025
KOFK: Clearing skies this evening will lead to fog development starting around 08-10Z and impacting the terminal until around 14Z. Clearing skies after 14Z with light winds out of the southwest.
KOMA: Terminal staying north of the band of showers though high clouds will keep potential for fog low overnight. Instead, expect low clouds around FL015 to drift in and out of the terminal overnight, with guidance showing around a 30% chance of low clouds completely socking in the terminal from 11-14Z. Once low clouds clear around 14Z, expect cigs around FL040 to stay in place through the morning, gradually clearing late in the afternoon.
KLNK: Higher potential for MVFR cigs overnight with cigs gradually lowering to predominantly MVFR by 08Z. Expect predominantly MVFR cigs until around 14Z when low clouds break up and cigs lift to around FL040. This cloud deck will be slow to clear, possibly breaking up by around 20-21Z.
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.OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None.
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DISCUSSION...Wood AVIATION...McCoy
NWS OAX Office Area Forecast Discussion