Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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527 FXUS63 KOAX 271732 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1232 PM CDT Thu Jun 27 2024 .KEY MESSAGES... - Moderate flooding is ongoing or expected to begin along the Missouri River the next day or two. It`s forecast to last into next week for Omaha and points south. - Low chance of strong to severe storms Thursday night into Friday and a better chance Friday afternoon into Friday night. Both rounds of storms could produce heavy rain and localized flash flooding. - Quiet and cooler for the weekend, with highs in the mid 70s to mid 80s. Then warming back up and becoming more active for the holiday week. && .DISCUSSION... Issued at 256 AM CDT Thu Jun 27 2024 A weak shortwave is generating light showers on radar over northeast Nebraska this morning. Only trace accumulations have been observed so far. More significant showers are out over central Nebraska where the better moisture advection is occurring with the low-level jet. This won`t migrate eastward until this evening as a surface high remains in place over eastern Nebraska through much of today. Expect only isolated to scattered showers through this afternoon with mostly cloudy skies keeping temperatures on the cooler side. Highs today will only peak in the upper 70s to low 80s, though if the sun does peek out we could gain a few extra degrees this afternoon. Tonight we`ll see the low-level jet shift eastward bringing the axis of significant moisture advection into our area which will ramp up shower and storm activity after 7 PM. This will also dampen the environment out ahead of a cluster of stronger storms that develop out over western Nebraska. We expect strong storms to develop out over northeast Colorado or the Nebraska Panhandle this afternoon and evolve into a convective complex that progresses eastward overnight. As these strong storms move toward our area, the worsening environment should weaken the storms leading to a diminishing threat for severe weather. SPC does have us in a Slight Risk for severe storms, but if it were up to me I`d have us closer to 5 percent. CAMs support this as well as the synoptic models. The bigger concern overnight tonight will be for heavy rain as PWAT values in the axis of moisture advection will get up to around 1.8-2 inches. That is near the daily max in sounding climatology for the area. This will mean showers and storms will be very efficient rain producers, so any training of storms could lead to quick accumulations of an inch or more of rainfall. Flash flooding could become a concern. As of right now the CAMs suggest showers should all keep moving, but this should be monitored none-the-less, especially with rivers already running high and the ground being fairly saturated. Most of the shower and storm activity will move off to the east Friday morning, but we`ll remain in unstable mid-level flow regime through the day with warm, moist, unstable air continuing to stream into the region from the south. Highs Friday afternoon will get back up into the mid-to-upper 80s with dew points up around 70 degrees, which will lead to significant afternoon environmental surface-based instability. 35-45 kt of Effective Bulk Shear and sufficient low-level shear will support the development of supercells or strong convective clusters Friday afternoon and evening with the potential for very large hail, damaging winds, flash flooding, and a few tornadoes if we can get a sustained supercell or two. The problem may be lack of any cap which will lead to rapidly developing convective clusters limiting the tornado potential. We`ll get a better idea from the CAMs tomorrow for timing of convective initiation and convective mode, so stay tuned. Friday afternoon-evening is the time period to watch. Saturday and Sunday we get a break in the storm chances just in time for the weekend as high pressure dropping south out of Canada builds across our area. This will bring in mild, dry weather making for very pleasant weather this weekend. Our next chance for rain comes with an upper-level trough bringing a front through during the Sunday night-Monday timeframe. Another stormy pattern looks to set up going into midweek next week just in time for 4th of July celebrations. Lastly, we all should continue to monitor the situation with our ongoing flooding along the Missouri River basin. Additional rainfall with the already swollen rivers may lead to additional flooding on more rivers and/or extended flooding on the Missouri longer than currently forecast. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1232 PM CDT Thu Jun 27 2024 Scattered showers and a few spotty storms will remain possible through the afternoon, but coverage is pretty limited so did not include any mention at the TAF sites. Higher storm chances move in tonight, though confidence remains somewhat low on how they`ll pan out, with some guidance suggesting they almost completely die prior to getting here, leaving the TAF sites dry. Timing is also very subject to change, but tried to give the most likely 2 hour window at each site. Otherwise, expect VFR conditions through much of the period outside of any stronger storms and maybe some potential 1500 to 2500 ft clouds toward the very end of the period. Winds will remain southeasterly to southerly with gusts of 20 to 25 kts. Can`t completely rule out some low level wind shear overnight, but think surface winds will stay strong enough to preclude mention. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...McCoy AVIATION...CA