Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 221151 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 551 AM CST Sun Jan 22 2017 .SHORT TERM...(tonight through Tuesday) Issued at 343 AM CST Sat Jan 21 2017 ...The primary forecast concern is the potential for accumulating snow Tuesday into Wednesday... Manual 00z upper-air analysis and early-morning water vapor imagery indicate a potent subtropical-branch short-wave trough over the southern Plains with a weaker, polar-branch system over the upper Great Lakes. The former will evolve into an intense trough and associated closed low as it translates through the southeastern States today. In it`s wake, a mid-level ridge will build over the Rockies today before shifting east into the Great Plains tonight into Monday. In the low levels, winds will become decidedly northerly today, allowing for some low clouds and a cooler air mass to settle into the area, especially along and east of the MO River. Areas of dense fog present over our western Iowa counties should dissipate this morning with some light drizzle possible at these same locations later today. Afternoon highs should range from around 40 east to lower 40s west. A weak surface high will build southeast through the mid MO Valley tonight into Monday while a lee cyclone deepens over the central High Plains. Strengthening low-level warm advection on the backside of the high should allow for slight warming of the air mass with Monday`s highs rebounding into the 40s. Attention then turns to the evolution of a vigorous mid-level trough which will shift from the Interior West into the Great Plains Monday night into Tuesday. There continues to be model differences in the amplitude and track of this system, particularly at the surface. The 00z deterministic GFS remains the most progressive solution with the track of the surface low. The Canadian/GEM remains the slowest solution, while the ECMWF is a compromise of the two. With respect to QPF, the GFS indicates the primary deformation band of precipitation remaining to our north across SD into west- central MN. In contrast, the SREF and GEFS mean QPF fields are more consistent with the ECMWF in suggesting the a swath of higher precipitation potential over northeast NE/southeast SD/northwest IA, which is consistent with our conceptual model. Under this scenario, light snow chances will increase Monday night into early Tuesday over our northern counties. Precipitation chances will increase areawide on Tuesday into Tuesday night as large-scale forcing for ascent strengthens and deepens. Low-level temperature profiles in forecast soundings indicate all rain or a rain-snow mix during the day, before a change over to all snow occurs Tuesday night. .LONG TERM...(Tuesday night through Saturday) Issued at 343 AM CST Sat Jan 21 2017 It still appears that several inches of snow will be possible across northeast Nebraska into west-central Iowa Tuesday night into Wednesday with lesser amounts with southward extent. Winds will strengthen from the north Tuesday night with the passage of the surface low to the east with areas of blowing snow possible. We will remain in north or northwest flow aloft which will maintain near or slightly below normal temperatures through the remainder of the work week. A slight warming trend is anticipated by next weekend. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) Issued at 551 AM CST Sun Jan 22 2017 IFR/LIFR ceilings enveloped KOFK AND KOMA and look on track to spread into KLNK by 13z. Brief period of LIFR visibilities may precede IFR/LIFR ceilings, but in general visibilities settle out have trended to MVFR category after ceilings established. NAMNest/RUC/HRRR maintain IFR ceilings through at least mid-morning, with diurnal mixing allowing ceilings to raise into low-end MVFR categories by late morning. Short term models differing on how quickly western edge of stratus erodes, with NAMNest/RUC keeping stratus entrenched at KLNK and KOMA most of the day. Decided to be somewhat conservative, and maintained MVFR ceilings until late afternoon. Skies should clear most locations by evening. Enough residual moisture lingers such that MVFR fof may redevelop early Monday morning. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Mead LONG TERM...Mead AVIATION...Fortin

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