Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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561 FXUS63 KOAX 211647 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1147 AM CDT Wed Jun 21 2017 .UPDATE...
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Issued at 1142 AM CDT Wed Jun 21 2017 An outflow boundary from convection to the north has pushed through the northern 2/3 of the area. Showers and storms have formed along this boundary from Crete to Nebraska City. Wind shear is especially weak, but instability is about 1500 J/kg. This may continue into the early afternoon, but should not be severe. Cooler temps behind the outflow boundary will also temp highs across the northern 2/3 of the area today, thus have backed off temps just a bit there. Regarding severe threat later this afternoon and evening, latest HRRR/RAP models suggest that convection should still develop across northeast NE through south central NE by late afternoon, along the convergence zone with the approaching front. These storms will push east off the boundary through the evening, but without a significant upper level system, they may have a hard time remaining strong the further east they get. Best threats will be in northeast NE late this afternoon, and convection may not reach Lincoln and Omaha until 9 pm or after, and then the strength remains in question the further east the storms get.
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&& .SHORT TERM...(Today through Friday) Issued at 315 AM CDT Wed Jun 21 2017 Forecast concerns in the short term will be thunderstorm potential/evolution through Thursday night and severe weather potential. The h5 pattern during the period has a large high pressure system over the desert southwest U.S. that extends toward Alberta and Saskatchewan. Hot temperatures...127 degrees at Death Valley, CA...and numerous excessive heat warnings and advisories were over the southwest U.S. Meanwhile Tropical Storm Cindy was in the Gulf. Through Thursday night...a broad tough will flatten the ridge with fast flow across the Northern Plains and a couple and closed low pressure over Ontario. This morning, the front will lift north as a warm front and southwest extent of elevated thunderstorms is still questionable. It is common for storms to develop as the low level jet increase and the warm nose returns to the region. Pooled h7/H85 moisture was noted over parts of the Plain and a few storms developed near the KS/Nebraska border near the surface cold front. Warmer h7 air will spread into the forecast area and the h85 low level jet increases to 40 to 50kts. Moisture transport vectors increase this morning and are oriented southwest to northeast across the forecast area, however Corfidi vectors show that elevated storms that form will travel from northwest to southeast. There are accas/mid clouds, therefore will have to monitor...a stronger WAA signal is farther north over the Northern Plains into Iowa. Thunderstorms can develop southwest into the low level jet, especially if the cap is weaker in that region and moisture is adequate. Will maintain pops for these features...especially from northeast Nebraska into Iowa and monitor areas farther south. The cold front will push into central Nebraska by 21Z. 14 to 15 deg C H7 temperatures are in place. Very steep lapse rates over the western High Plains will stretch from southwest Minnesota into eastern South Dakota into southwest Nebraska and western Kansas back toward New Mexico by 18z...shifting into western Iowa by 00Z. Instability increases to 2000 to 4000 J/kg near the front. The forecast soundings maintain a cap...however near the front...isolated strong to severe thunderstorms could develop. SPC has the area outlooked in a slight risk with all modes of severe weather possible including isolated tornadoes and locally heavy rain. Trimmed pop area and focused in northeast Nebraska...although something isolated may try to get going elsewhere. There is some pooling of moisture in southeast Nebraska and southwest Iowa and the cap may be weaker here. The storm coverage with the cap appears limited on the NAM12/EC/GFS...however with the forcing from the shortwave and convergence with the front in the 00-06Z timeframe thought it prudent to include scattered thunderstorms during the evening. The wave pushes east and the surface front tries to lift back north with another round of showers and thunderstorms for thursday afternoon and thursday night and the stronger shortwave pushes the front south. Again we are in the slight risk as temperatures heat up into the 80s and 90s with the area on the southern edge of a belt of stronger winds aloft. There may be some lingering showers Friday, however this would be behind the front. Highs today should top out well into the 90s and more humid with stronger south winds. Highs Thursday will again depend on the frontal position, but have highs in the 80s north and 90s south. Cooler for Friday with highs in the 70s .LONG TERM...(Friday night through Tuesday) Issued at 315 AM CDT Wed Jun 21 2017 Cooler for the extended with highs in the 70s then a return to the 80s Monday and Tuesday. We remain in a general northwest flow aloft pattern. There may be some showers Saturday, however the medium range models have backed off on the coverage; although the EC still has better coverage. Dry weather is forecast for Sunday and Monday with some small rain chances Tuesday. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 627 AM CDT Wed Jun 21 2017 VFR conditions expected through the morning and afternoon hours. Thunderstorms may impact KOFK by 23z and spread southeast thereafter and affect KOMA and KLNK but uncertainty remains high. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ UPDATE...DeWald SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Kern

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