Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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733 FXUS63 KOAX 030533 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1133 PM CST Fri Dec 2 2016 .SHORT TERM...(tonight through Monday) Issued at 234 PM CST Fri Dec 2 2016 Main forecast concern is the positively titled trough over the intermountain west this afternoon. The south end of this trough is expected to continue to dive into Mexico while the northern portion should continue to progress eastward through the northern and central Plains over the next 36 hours. Ahead of this trough we will see high level clouds increase tonight, with the deck lowering to mid clouds Saturday morning before deeper saturation occurs on Saturday afternoon. The models are in general agreement that broad isentropic upglide on the 285-295 K surfaces will continue into Saturday night until the axis of the mid-level trough passes. Precipitation type is an issue with initially a cold airmass in place, but warmer air aloft moving in from the south, as well as diurnal warming of the boundary layer. This will likely result in a rain and snow mix across the southern 2/3rd of the forecast area during the day on Saturday, with potentially a more concentrated period of light snow on Saturday evening associated with the strongest large-scale forcing for ascent before the warmer air aloft shifts northeast into the CWA. Precipitation may end on Saturday night as a little light rain/drizzle as we lose the introduction of ice into the column. Snowfall amounts would be light and mainly confined to grassy surfaces, but up to or a bit more than a half inch seems reasonable over west-central IA, with amounts for the OMA/LNK metro areas in the range of a couple tenths. This system exits to the east by Sunday morning with little in the way of sensible weather expected for Sunday through Monday. .LONG TERM...(Monday night through Friday) Issued at 234 PM CST Fri Dec 2 2016 Longer range models continue to struggle with how to handle a strong Pacific jet as it moves into the western US early next week. It appears over the last several days that the EC has been slowly moving toward a more GFS solution, and given the ensemble support this appears more likely. This would generally just mean a strong cold front by mid week with the coldest air of the season descending into the Plains. We will continue to mention some small chance pops associated with the incoming cold air, but chances of a significant winter storms appear very small currently. Once the cold air is in place by mid week we should see well below normal temperatures through the end of the forecast period. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1132 PM CST Fri Dec 2 2016 Mid and high-level clouds will continue to overspread the area tonight in advance of a short-wave trough progressing into the High Plains. The impulse will subsequently track east across the region on Saturday, promoting development of a southwest-to- northeast-oriented precipitation shield across portions of eastern Nebraska and southwest Iowa. While KOFK is expected to remain to the north of this precipitation, it will be impacted by the arrival of MVFR ceilings late Saturday afternoon. At KOMA and KLNK, precipitation is expected to begin by late morning or early afternoon and continue into at least Saturday evening. Model variability in the structure of the low-level thermodynamic profiles yields various precipitation type forecasts. For now, the highest probability scenario is a rain-snow mix with precipitation rates peaking in intensity from mid afternoon into early evening. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM... LONG TERM... AVIATION...Mead

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