Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 200448 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1148 PM CDT FRI AUG 19 2016 .SHORT TERM...(tonight through Monday) Issued at 201 PM CDT FRI AUG 19 2016 Early afternoon surface analysis indicated a cold front from northern IA into northern KS. Modifying the 12Z KOAX sounding for afternoon conditions indicates that the atmosphere has become moderately unstable with around 1000-1500 J/kg of MLCAPE. This generally agrees with objective analysis as well, with the MLCIN decreasing. The 12Z upper air analysis indicated broad west and southwest flow across the central and northern Plains with a stronger upstream shortwave trough associated with 40-50 m H5 height falls over the northern Rockies. Forcing for ascent this afternoon and into the evening will generally be weak, but the height falls do cross the boundary this afternoon. The combination of the weakening MLCIN, frontal boundary, and height falls will likely lead to increasing convection over the central and southern CWA through the afternoon and into the evening. The upper air analysis did indicate that the better flow was trailing the cold front limiting effective shear, and the orientation of the cold from northeast to southwest along the deep-layer shear vector suggest any organization to the thunderstorms will likely be linear. Mid-level lapse rates are poor, but given the CAPE some small hail to near severe criteria and wind appear to be the main threat into early evening over mainly the southern CWA. By late evening the storms should move east of the area, but by this time the larger-scale forcing for ascent associated with the CPVA will be moving across the area. Thus will continue with some pops through the night for showers. We will also see a stronger cold front associated with the stronger trough that will bring in much cooler and drier air, along with gusty northwest winds overnight. The rest of the weekend we will see little in the way of sensible weather, but very pleasant conditions. Highs on Saturday, with mixing to around 850 mb, should remain in the 70s. With the deep mixing and steep low-level lapse rates coupled with residual low- level moisture we could see an isolated light shower or sprinkle in the afternoon, but did not include in this forecast. A touch of fall is likely on Saturday night with some upper 40s possible in the better radiational cooling locations, but everyone should see overnight temperatures drop into at least the lower to mid 50s. Return flow develops on Sunday as the surface high pressure moves off to the east, and as temperatures warm aloft we should see highs back at or above 80. The warming trend will continue into Monday with gusty south and southwest winds. .LONG TERM...(Monday night through Friday) Issued at 201 PM CDT FRI AUG 19 2016 The next weather system to impact the CWA will start to move into the Plains on Tuesday as moisture returns to the area ahead a cold front. This front will sweep through the area on Wednesday associated with a stronger upper-level trough moving through the northern Plains. Will maintain some low chance pops for Tuesday associated with the WAA pattern. The chances for precipitation will increase on Tuesday night and Wednesday associated with the cold front. We will leave the second half of the extended dry for now. Monday and Tuesday look like the warmest days with highs climbing well into the 80s before the front knocks things down for the end of the work week. && .AVIATION...(06Z TAFS for KOFK...KLNK and KOMA.) Issued at 1148 PM CDT FRI AUG 19 2016 As of 04z, a band of mainly rain showers stretched from west- central Iowa into southeast Nebraska, behind the initial surface cold front, and likely along the elevated frontal surface (near 850 mb). This activity will likely continue to impact KOMA through about 20/07z with temporary MVFR ceilings. A secondary, stronger cold front currently from eastern South Dakota to central Nebraska will move through the area late tonight into early Saturday. The best precipitation chances associated with this boundary will likely remain north of KOFK, though there could be a period of MVFR ceilings toward 20/12z. Expect winds to become gusty from the northwest by late morning/early afternoon Saturday as the boundary layer deepens and mixes down higher-momentum flow aloft. && .OAX Watches/Warnings/Advisories... NE...None. IA...None. && $$ SHORT TERM...Boustead LONG TERM...Boustead AVIATION...Mead

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