Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 200515 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1115 PM CST Sun Feb 19 2017 .SHORT TERM...(Tonight through Wednesday) Issued at 307 PM CST Sun Feb 19 2017 A low-latitude short-wave trough over the southern Rockies and northwest Mexico this afternoon will phase with a polar-branch disturbance over the High Plains tonight with an elongated vorticity ribbon translating through the central and northern Plains Monday into Monday night. In the low levels, strengthening south winds ahead of a deepening lee trough over the High Plains have hastened the poleward flux of an increasingly moist boundary-layer into the mid MO Valley with 20z dewpoints commonly in the upper 40s to lower 50s. Latest short-term convection-allowing model guidance suggests that initial thunderstorm development will occur across the southern Plains this afternoon into evening with activity spreading north through central and east KS into portions of east NE and southwest IA after 08-09z. Steepening mid-level lapse rates coupled with the continued moistening of the environment and strengthening dynamic forcing for ascent will be supportive of isolated thunderstorms embedded within the broader precipitation shield. The showers and thunderstorms are expected to shift to the east of the area by late morning or early afternoon with no additional convective activity anticipated along the trailing wind shift/weak cold front which will advance across the area during the afternoon. Skies should clear from west to east Monday afternoon, allowing temperatures to warm to near or above record values for the day (see the Climatology section below). The mid-level pattern will transition to quasi-zonal in the Tuesday-Wednesday time frame with an unseasonably warm and moist low-level air mass residing across the mid MO Valley ahead of a cold front which will move into the area on Wednesday. A number of temperature records could be challenged through the first half of the work work (again, see the Climatology section below) before a cooler air mass filters into the region from the north by Thursday. .LONG TERM...(Wednesday night through Sunday) Issued at 307 PM CST Sun Feb 19 2017 The primary feature of interest in the extended range is a vigorous short-wave trough and associated surface low which will track from the central High Plains through the mid and lower MO Valleys Thursday into early Friday. We continue to see model fluctuations in track and amplitude of this synoptic system. The ECMWF has remained the most consistent of the available data, indicating the surface low developing from southeast CO Thursday morning to north-central or northeast Kansas by Thursday evening, prior to undergoing occlusion over central or eastern IA by 12z/Friday. The deterministic GFS and GEFS mean depict similar (albeit slightly farther south) evolutions, while the 12z Canadian model has now become the outlier with a farther north and slower solution. Under a scenario similar to the ECMWF, the chance of rain will increase from northwest to southeast across the area on Thursday. By Thursday night into early Friday, intense dynamic forcing for ascent coupled with rapidly deepening cold air on the backside of the surface cyclone will yield a change over to snow within the evolving deformation precipitation band. While exact amounts remain uncertain, current model trends suggest the potential for several inches of snow across parts of east-central and northeast NE into west-central IA. In addition to the snowfall, winds will strengthen considerably from the north Thursday night into Friday with areas of blowing and drifting snow possible. The snow is currently expected to taper off Friday evening with additional chances for light snow on Saturday into Sunday. Temperatures late this week into next weekend will be notably colder with afternoon readings generally in the 30s north and central with 40s southeast. && .AVIATION...
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(For the 06Z TAFS through 06Z Monday night) Issued at 1115 PM CST Sun Feb 19 2017 Low clouds are slower to move into the area, but should still move in overnight. Showers and isolated thunder should spread up over southeast Nebraska and into western Iowa late tonight. The MVFR ceilings should continue into Monday morning, then conditions will improve to VFR. Winds will shift to the northwest as a front moves through, but had too many groups to include all details of wind shift for KOMA and KLNK.
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&& .CLIMATE... Issued at 307 PM CST Sun Feb 19 2017 Given the unseasonably warm conditions expected, the following are the record high and maximum low temperatures: Monday/20th: Omaha - 67/1930, 50/1930 Lincoln - 71/1991, 51/1930 Norfolk - 66/1930, 37/1996 Tuesday/21st: Omaha - 72/1977, 53/1930 Lincoln - 74/1991, 51/1930 Norfolk - 74/1995, 40/1930 Wednesday/22nd: Omaha - 71/1982, 42/1933 Lincoln - 74/1982, 46/1896 Norfolk - 72/1995, 37/1998 && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Mead LONG TERM...Mead AVIATION...Miller CLIMATE...Mead

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