Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 261144 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 644 AM CDT Thu Apr 26 2018 .SHORT TERM...(Today through Saturday) Issued at 310 AM CDT Thu Apr 26 2018 A short-wave trough from southern Manitoba to the northern High Plains early this morning will translate through the mid Missouri Valley today in tandem with a surface cold front. Current satellite-derived PW data and 00z regional soundings indicate the presence of a very dry air mass ahead of this weather system with the prospect for measurable precipitation seemingly quite small. Short-term model guidance does hint at a narrow band of light precipitation developing across portions northeast NE later this morning. However, forecast soundings indicate a dry low-level air mass with most if not all of any falling hydrometeors evaporating before reaching the ground. Nonetheless, we will maintain slight- chance PoPs across portions of northeast NE. With the passage of the front, steepening low-level lapse rates and a unidirectional wind profile will yield gusty northwest winds of 25 to 40 mph, namely during the afternoon hours. The winds coupled with the dry air mass and temperatures in the 60s will result in very high fire danger generally north of U.S. 30. Another weak front will move through the area on Friday with gusty northwest winds developing over far eastern NE into western IA. Afternoon temperatures are expected to be warmer than today (i.e. upper 60s to lower 70s), and when combined with the wind and low relative humidity, another day of very high fire danger is expected. On Saturday, a mid-level ridge will shift east from the Rockies into the High Plains ahead of a strong storm system moving into the northwestern CONUS. This will induce the development of a lee trough over the High Plains with our winds gradually becoming southeast. Low-level trajectories originating from Canadian high pressure to our east will temper daytime highs with readings in the lower to mid 60s. .LONG TERM...(Saturday night through Wednesday) Issued at 310 AM CDT Thu Apr 26 2018 On Saturday night into Sunday, a strong low-level jet (LLJ) will develop across the Great Plains in response to the slow eastward progression of the aforementioned upper-air system across the northwestern CONUS. Increasing heat and moisture fluxes along the LLJ axis will yield decreasing static stability and the potential for isolated showers Sunday morning. Downward momentum transfer along the LLJ will also create breezy to windy conditions Sunday afternoon. By Sunday night, there is some evidence in model guidance that a weak short-wave trough will eject from the High Plains into the mid MO Valley, supporting an increasing chance of showers and thunderstorms. From Monday into Wednesday, medium-range guidance is now in better agreement in the evolution of the large-scale pattern. On Monday, it appears that another short-wave trough will emerge from the Rockies into the central Plains, contributing to the development of thunderstorms along a cold front and attendant dryline to our west. The continued northeastward progression of the mid-level impulse and nocturnal strengthening of the LLJ will likely maintain clusters of thunderstorms that would affect portions of our area Monday night. Some severe weather is possible. On Tuesday, it appears that the above-mentioned cold front will settle into southeast NE and southwest IA by afternoon where it will serve as a focus for another round of thunderstorms, some of which could be severe. By Wednesday, a stronger short-wave trough translate from the southern Rockies into the central and southern High Plains, driving the deepening of a surface low over western KS. This setup appears supportive of a more widespread severe weather episode to from the southern Plains through KS potentially into the southern part of our forecast area. The northern extent of the severe weather threat will be contingent on the movement of the associated warm front. Excessive rainfall could also become a concern by Wednesday night. Of course, the above scenario is based on current model guidance which is likely to change between now and early next week. Nonetheless, it does appear that the weather will become more active and springlike. && .AVIATION...
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(For the 12Z TAFS through 12Z Friday morning) Issued at 630 AM CDT Thu Apr 26 2018 A cold front will turn winds around to the southwest at 10 to 15kts today then the northwest 14-22ktsG25-35kts. The winds will decrease then back to under 12kts this evening. VFR conditions with a period of lower ceilings fl080-120 and some sprinkles 15-17Z and possibly around 20Z at KOMA/KLNK.
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&& .CLIMATE...
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Issued at 630 AM CDT Thu Apr 26 2018 With the rain yesterday, Omaha has dropped to third driest April on record. With five days left, rain is now possible both Sunday and Monday before the end of the month. April Precipitation Records Location April to Date Record Year Lincoln 0.67" 0.02" 1910 to remain in top 10 0.67" Omaha 0.27" 0.23" 1936 to remain in top 5 0.38" Norfolk 1.32" 0.11" 1928 to remain in top 35 1.46"
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Mead LONG TERM...Mead AVIATION...Zapotocny CLIMATE...Zapotocny

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