Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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317 FXUS63 KOAX 050857 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 357 AM CDT Sun May 5 2024 .KEY MESSAGES... - Slightly warmer and dry today, with highs in the upper 60s. - Potentially strong storms are expected Monday afternoon, primarily from 4 to 10 PM as a line of storms moves thought the area. Damaging wind, hail, and an embedded tornado are possible. - Light showers and a few rumbles of thunder linger through the end of the work week, with drier conditions and highs in the 70s returning for the weekend. && .DISCUSSION... Issued at 353 AM CDT Sun May 5 2024 Today: Water vapor imagery this morning features an eye-catching and deep trough entering the far western CONUS, with a broad arm of mid-level moisture and ascent stretching from Arizona northward into Idaho/western Montana, while the weakening shortwave exiting to the north of the Great Lakes region continues to leave the far eastern CONUS with continued cloudcover. Looking at a recent surface analysis, the aforementioned trough is carrying with it a frontal zone an impressive distance east past the Pacific Coast into eastern Nevada, where many other systems see theirs washed out. Drilling down to the forecast area, surface high pressure is seated near Fort Dodge, Iowa with weak winds at the surface extending well into eastern Nebraska. Clear skies above have aided nocturnal cooling to help develop very patchy fog despite relatively dewpoints in the upper 30s to low 40s, primarily in river valleys. By sunrise, any leftover fog should dissipate, and leave southeasterly winds in place alongside sunny skies. Highs are expected to reach into the upper 60s, with areas of northeast Nebraska seeing gusts to 20-25 mph before diminishing around sunset. Warm southerly flow should keep overnight lows from getting to cool, preventing another foggy morning (patchy or not). Monday: The primary focus of the forecast period continues to be the strong storm system that will make its way to the forecast area Monday. In the mid/upper levels, the aforementioned trough out west will have translated eastward, becoming negatively-tilted as it prepares to eject into the Central Plains. As it is arriving, a strong pressure gradient and overall mass response will develop, resulting in strong moisture transport and gusty winds that develop early Monday across much of central and western Nebraska and spreads eastward throughout the morning. Wind gusts in the 35 to 45 mph range will be possible out of the southeast, while dewpoints of just over 60 degrees spread northward to the NE/SD border by the afternoon. Ample shear and sufficient instability supportive of severe storms will be present, with all forms of severe weather expected to be present. As far as additional details go for Monday`s severe potential, initial runs of the extended CAMs during the afternoon hours continue to jive with an arrival time to eastern Nebraska in the 3-4 PM time range. Low-level shear vectors continue to combine with the strong forcing for ascent to quickly grow any convection upscale into a long bowing structure, that will move eastward across the area before exiting to the east by 10 PM. Areas with the highest surface moisture in southeast Nebraska continue to show the greatest potential for severe weather, which is reflected by the Enhanced Risk from the SPC (with the rest of the forecast area in a Slight Risk). One sticking point that could make the afternoon more tricky would be the presence of a convergent zone joining warm air advection out ahead of the main front that could kick start scattered shower and storm activity early. This activity would then interact with the bow/QLCS, and locally enhance tornadic potential as the prefrontal cells are ingested. Nonetheless, continued attention is due as we approach Monday afternoon (though the strongest of the storms will stay well to the south of the forecast area). Tuesday and Beyond: With Monday`s storm system in the rear view mirror, the main mid/upper trough is expected to cut off and drift northward, with a center near the MT/ND border region. A strong zonal to slightly southwesterly mid/upper jet will be settled over the area and will provide no shortage of shortwaves and embedded impulses that will keep light showers and a few rumbles of thunder in to the forecast for the remainder of the week. Highs will take a slight hit and fall into the 60s for much of the remaining work week before highs return to the 70s for Saturday and Sunday. By that point the influence from the Monday system will have finally left the area in favor of increasing heights and northwesterly flow as a couple of days settle in for the weekend. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1136 PM CDT Sat May 4 2024 VFR conditions are expected to prevail throughout the forecast period. Calm and variable winds will shift to southeasterly early this morning. Patchy fog is possible this morning but confidence is low that this will be widespread. Winds will remain southeasterly and increase in speeds above 12 kts at all terminals by 17-22Z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Petersen AVIATION...Wood