641 FXUS63 KOAX 091738 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1238 PM CDT Wed Jul 9 2025 .KEY MESSAGES... - A few spotty storms are possible this morning, with a better chance for stronger storms this evening (30-50%), capable of hail (up to 1") and damaging wind gusts (up to 60 mph). - Higher storm chances (50-75%) arrive Thursday evening into the overnight period, with hail and damaging winds again the primary hazards. Locally heavy rainfall will also be a concern. - Storms may linger into Friday, followed by light, on-and-off rain chances through the weekend. && .DISCUSSION... Issued at 233 AM CDT Wed Jul 9 2025 Today and Tonight... Water vapor imagery this morning depicts a mid- to upper-level ridge centered over the Four Corners region, placing our area under predominantly northwesterly flow aloft. Fog, with patchy areas of dense fog, will be possible this morning, primarily in southwest IA and areas near the Missouri River valley. Spotty showers and thunderstorms may develop later this morning (4-7 AM) across north- central and into northeast NE as warm air advection and the nose of a 25-30 kt southwesterly low-level jet briefly points into the region. CAM guidance varies considerably in storm coverage, with the HRRR and Fv3 showing brief, isolated showers, while the NAM Nest and NSSL-WRF suggest a most robust thunderstorm complex. Given modest instability (MUCAPE around 1500 J/kg), weak shear (bulk shear near 20 kts), and limited forcing for ascent, the more subdued solutions appear more probable. PoPs peak at 20-30% through mid-morning, then taper off by noon, allowing for afternoon highs in the upper 80s to low 90s. A better opportunity for strong to severe storms arrives this evening as a shortwave disturbance and associated vorticity maxima rounds the ridge and approaches west-central NE and SD. Storm are expected to initiate in the late afternoon/early evening along a weak stationary front draped from north-central into southeast NE. A few initial discrete storms are possible before convection grows upscale into an MCS. How far east this complex pushes will depend heavily on the outcome of morning convection. Should morning storms remain limited, more robust afternoon destabilization could allow MLCAPE values to climb into the 2500-3000+ J/kg range. However, shear will remain limited, with 0-6 km bulk shear dropping to 20-25 kts as storms move east, likely capping overall organization. That being said, strong instability could support isolated area of hail (up to 1) with any discrete or stronger updrafts before a transition to a damaging wind threat (gusts up to 60 mph) as upscale growth occurs. SPC currently includes the western portion of the CWA in a Marginal Risk (level 1 of 5) for severe weather. PoPs again peak at 30-50% this evening before tapering off overnight. Thursday... Thursday is shaping up to be an active weather day two shortwave troughs moving over the northern Rockies merge into a single, more pronounced disturbance that flattens the ridge and pushes into the northern Plains. In response, a surface low is expected to develop over western NE early in the day and track eastward across the state. Ahead of the low, strong low-level moisture transport will draw in a stream of 70 degree dewpoints, setting the stage for hot and humid conditions. Combined with afternoon highs in the upper 80s to mid 90s, heat index values are expected to peak between 95 and 102 degrees. Scattered showers and isolated storms may develop Thursday morning into early afternoon in response to warm-air advection. These could complicate the forecast by tempering instability, but if coverage remains limited, steep mid-level lapse rates (8-9 deg/km) and afternoon destabilization should allow a corridor of very strong instability to build into the area, with MUCAPE values exceeding 3000 J/kg. Bulk shear in the 30-40 kt range, combined with a strengthening LLJ into the evening, will support long hodographs, bringing a favorable environment for organized convection. There is still some uncertainty in storm mode and associated hazards. The most likely scenario features an initial cluster of supercells developing at peak daytime heating to our west before evolving into an MCS that tracks eastward across the area. Damaging wind gusts and hail appear to be the primary hazards. SPC currently includes the western edge of the CWA in a Slight Risk (level 2 of 5) for severe weather. Heavy rainfall is another concern. PWAT values between 1.75-2.00" (above the 90th percentile of OAX sounding climatology for early July) combined with long, skinny CAPE profiles and warm cloud depths of 3-4 km will promote highly efficient rainfall processes. Although the MCS itself is expected to be somewhat progressive, a favorable overlap of the LLJ and surface boundary could support backbuilding storms behind the main line, increasing the potential for locally heavy rainfall and flash flooding. WPC has placed most of the area under a Slight Risk (level 2 of 4) for excessive rainfall. PoPs currently peak at 50-75% Thursday evening. Friday and Beyond... PoPs of 40-70% continue into Friday as the axis of the shortwave disturbance pivots across the area, keeping highs confined to the 80s. A brief cooldown is expected Saturday as the area remains on the backside of the departing system, with highs falling into the upper 70s to low 80s. Zonal to northwesterly flow aloft will persist through the weekend as the ridge over the southwestern CONUS flattens and retreats towards California. A few weak shortwave disturbances embedded in the flow may bring occasional low-end precipitation chances (PoPs ~15%) through the weekend and into the start of next week. Temperatures will rebound by Sunday and into early next week, with highs returning to the upper 80s to low 90s. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1238 PM CDT Wed Jul 9 2025 VFR conditions expected for this TAF cycle. Sustained winds will remain from the south at 12 kts or less during the period, with gustiness increasing late in the TAF period across all terminals. A period of low level wind shear from a low level jet will occur between 07z and 13z. Main concerns continue to be an organized line of convection moving through sometime after 03z from west to east. Have attempted to time out arrival at terminals with TEMPO groups, but expect further refinements with upcoming issuances. Storms could be strong to severe with damaging wind gusts up to 60 mph and large hail. Could see brief, localized visibility and ceiling reductions at times near convection. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Wood AVIATION...Castillo