Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 300323 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1023 PM CDT MON AUG 29 2016 .UPDATE...
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Issued at 1005 PM CDT MON AUG 29 2016 A north to south area of heavy rain fell across parts of the forecast area this evening. Reports of 1.5 inches in Lincoln, almost 2 inches near Chalco, another 1.31 inches at Kennard, and 1 to 3 inches were estimated per dual pol across parts of Pottawattamie Co. Additional storms continue to develop as shortwave trough energy slowly moves across Kansas and Nebraska the rest of tonight and Tuesday. The moisture plume with 1.88 inches of PWAT on the 00Z OAX sounding remains in place and gradually is pushed south later Wednesday. Upper level divergence remains in place and h5 moisture increases with 80 to 90 percent rh over a broad area through Tuesday. The low level forcing signal is weaker, thus more difficult to define threat area and have a general flash flood risk. Expanded the flash flood watch to included areas that received locally heavy rains again tonight and will be prone to flash flood should these highly efficient storms develop as the h5 trough slowly swings through Tuesday. The FFA may need to be extended in time, however later shifts can asses this.
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&& .SHORT TERM...(tonight through Thursday) Issued at 241 PM CDT MON AUG 29 2016 Conditions are primed in some areas for additional flash flooding tonight, primarily for those areas that received from 1 to 5 inches of rain last night in slow moving thunderstorms. Thus a flash flood watch was issued for portions of southeast NE and southwest IA where flash flood guidance was lowered as a result. Environmentally, things are not that different from last night. The atmosphere remains tropically moist being fed by a moist water vapor plume that can be traced to the western coast of Mexico. PW values this morning were around 1.8", which climatologically is right at the maximum moving average for this time of year. This moisture is also 1-2 standard deviations above normal based on NAEFS climatological means, thus we have a lot of water to work with. The upper low across the central Rockies will continue to very slowly fill then lift across the plains through Tuesday. The main westerlies are well north of the region, thus storm motions are quite slow, only 10-15 mph at times. Due to the abundant moisture, rainfall rates could easily reach 1-2" per hour. Storms have begun to fire with the heat of the day with surface based CAPE ranging 2000-3500 J/kg. Effective shear is very marginal though, generally less than 20 knots. While freezing levels around 13300 could be conducive for hail, wet bulb zero levels are extremely high around 12650. With the lack of higher storm scale rotation and very marginal mid level lapse rates, hail will be a struggle, but there does appear some wet microburst potential for any storms that can develop a cold pool. The wet pattern continues into Tuesday with conditions nearly identical, but perhaps more coverage of storms as the upper trough axis remains in place across the region, then slowly drifts south of the area by early Wednesday. Will maintain likely Pops along/south of I80 late tonight into Tuesday, then end precip from north to south Wednesday morning, then go dry and mild for Thursday. .LONG TERM...(Thursday night through Monday) Issued at 241 PM CDT MON AUG 29 2016 Dry conditions continue Friday with an upper ridge remaining in place across the central US, but rain chances return for the holiday weekend as the ridge shifts east, and a series of upper level weather disturbances move into the area Saturday and Sunday, along with a cold front on Labor Day. && .AVIATION...(00Z TAFS for KOFK...KLNK and KOMA.) Issued at 636 PM CDT MON AUG 29 2016 Intermittant showers and thunderstorms expected at KLNK/KOMA and also possible at KOFK this evening with favorable deep moisture in place/theta-e advection in the area through 06z. VFR cigs outside of showers/thunderstorms...however with precipitation...conditions may range from vfr to LIFR/MVFR with heavy rain reducing visibilities. Some gusty winds possible; generally 30kts or less in the vicinity of storms. Coverage uncertain later tonight, thus mention vcsh/shra. Favorable stormy pattern continues Tuesdayand again due to low confidence in coverage left as vcts && .OAX Watches/Warnings/Advisories...
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NE...Flash Flood Watch through Tuesday afternoon for NEZ045-052-053- 066>068-078-088>093. IA...Flash Flood Watch through Tuesday afternoon for IAZ069-079-080- 090-091.
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&& $$ UPDATE...Zapotocny SHORT TERM...DeWald LONG TERM...DeWald AVIATION...Zapotocny

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