Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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094 FXUS63 KOAX 201758 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1258 PM CDT Tue Mar 20 2018 .SHORT TERM...(Today through Thursday) Issued at 318 AM CDT Tue Mar 20 2018 A weak mid-level vorticity lobe and attendant precipitation band will translate through the area this morning with light rain temporarily mixing with or changing to light snow before ending or transitioning to drizzle as the stronger forcing for ascent shifts east. The radar presentation as of 0800z is rather unimpressive with highest precipitation rates (~0.02-0.05/hr) associated with rain per surface observations. Based on current radar trends and latest short-term model guidance, any snow accumulation should remain low and generally less than a half an inch. Lingering cloud cover and light precipitation (especially across the eastern part of the CWA) will once again limit daytime heating with highs today mainly in the lower to mid 40s. However by Wednesday, decreasing clouds coupled with building mid-level heights will yield warmer temperatures with afternoon readings in the upper 40s to upper 50s. Wednesday night into Thursday, model guidance suggests that warm advection and isentropic upglide within the exit region of a low- level jet will foster a swath of light rain across portions of western into central IA, to the immediate north/northeast of a weak surface warm front. Our southwest IA counties will be on the western periphery of that precipitation where we will indicate slight-chance PoPs. To the west of the front, south to southwest low-level winds will allow temperatures to warm into the 60s with mid to upper 50s forecast along and to the east/northeast of the boundary from northeast NE into west-central IA. .LONG TERM...(Thursday night through Monday) Issued at 318 AM CDT Tue Mar 20 2018 Latest medium-range guidance continues to indicate an active pattern over the mid-MO Valley through much of the extended forecast period. These data suggest that an amplified ridge will overspread the Great Plains Thursday night into Friday ahead of a low-amplitude perturbation moving from the Rockies into the High Plains. Strengthening warm advection ahead of that disturbance will support a chance of light rain on Friday. By Friday night into Saturday, it appears that the High-Plains disturbance will amplify as it moves through the region, driving the deepening of a surface low which is forecast to track to our south. Nonetheless, steepening lapse rates and increasing moisture content will support scattered showers and a few thunderstorms as the synoptic system moves through the area. On Sunday, a short-wave trough will traverse the northern Plains with an associated surface cold front focusing precipitation chances over the mid-MO Valley. By early next week, the GFS progresses a low-amplitude trough through the central U.S., whereas the ECMWF and Canadian models depict broader troughing lagging west over the Rockies. As such, forecast confidence is low during that time frame. && .AVIATION...
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(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1246 PM CDT Tue Mar 20 2018 Conditions will continue to improve to MVFR levels this afternoon, as mixed precip moves east of the TAF sites. Some light drizzle or rain will still be possible at KOMA through 20Z. Light northwesterly winds will become variable, briefly, before shifting to the south late Wednesday morning. Light winds in addition to moist conditions near the surface will create the potential for fog late tonight and into Wednesday morning, however left mention out of the TAFs for now, until confidence improves.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Mead LONG TERM...Mead AVIATION...KG is the U.S. government's official web portal to all federal, state and local government web resources and services.