Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 180443 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1143 PM CDT Mon Jul 17 2017 .SHORT TERM...(Tonight through Thursday) Issued at 315 PM CDT Mon Jul 17 2017 Forecast concerns in the short term will be the chance for thunderstorms tonight through Tuesday night and temperatures and excessive heat headlines through the work week. Our 12Z OAX sounding had dried out a little with pwat of 0.90". The h3 jet extended from northern CA into the Northern Plains and southern Canada. Ht falls over 100m were noted over Manitoba and these trailed southward to around 20m toward KLBF. Water vapor satellite imagery and h7 dewpoints showed mid level moisture with the weakening h5 low pressure system. The latest surface map hat temperatures in the 90s across the local area with most dewpoints in the 60s with a few in the 70s. Any cool air was northeast east of the boundary in central Iowa and north of the front in North Dakota. The WSR-88D radar mosaic showed a cluster of storms in west central Nebraska...lifting to the northeast. Through the afternoon...the RAP/HRRR develop showers and thunderstorms mostly in central Nebraska with the weak h5 wave and some weak upper level support. The main storm track in the short term remains to our north across the Dakotas into MN/IA/MN...however the is some chance that the southwest extent of an MCS could affect parts of our area Tuesday night. Tonight...the low level jet increases to 40kts into central Nebraska and is more in the 20 to 25kt range as it spreads east into the local forecast area. By 12Z the weak h5 wave is over eastern Nebraska shifts into northern Missouri by Tuesday night. The clouds are forecast to increase with the chance for isolated to scattered thunderstorms into parts of northeast/east central Nebraska tonight and toward the Missouri River Tuesday morning. There should be a diurnal lull and then the coverage increases in the afternoon. The slips southward into northeast Nebraska Tuesday afternoon and this could provide an additional focus. Due to the limited coverage isolated to scattered pops...however these can be refined per radar trends Tuesday. Highs Tuesday will again be in the 90s and with higher dewpoints the highest heat indices should be 98 to 105. A heat advisory may be need for parts of the area Tuesday depending of the clouds/precip/resultant temps. The effects of any MCSs in the area Tuesday night could affect temperatures for Wednesday or delay /modify the warm up. At this time with highs in the 90s and a few 100 or higher with higher dewpoints expected will issue and excessive heat watch for Wednesday through Friday for all but northeast Nebraska. It is uncertain how far south the front will make it, however this seemed like a good starting point. More broad 105 to 112 heat index values are forecast across the area for these days and have a cumulative effect with the mild low temperatures and little relief overnight. .LONG TERM...(Thursday night through Monday) Issued at 315 PM CDT Mon Jul 17 2017 Thursday night into Friday convection will be ongoing mainly from the Dakotas into MN and northern Iowa. The GFS is hinting that some storms from the Black Hills could make it into the forecast Friday night and a weak shortwave in the flow aloft/front could move in Friday night. The trend for the weekend is cooler. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1138 PM CDT Mon Jul 17 2017 Mainly VFR conditions are forecast through Tuesday night. Broken to overcast mid and high clouds will remain over eastern Nebraska TAF sites through 18Z before scattering out. Showers and isolated thunderstorms are possible at all sites between 06Z and 14Z, but extent of thunder and coverage of precipitation are both expected to be low enough to keep out of TAFs for now except for a mention of VCSH at KLNK. Otherwise light south to southeast winds early in the TAF period will kick up to between 10 and 20kt after 18Z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Excessive Heat Watch from Wednesday afternoon through Friday evening for NEZ015-033-034-042>045-050>053-065>068-078- 088>093. IA...Excessive Heat Watch from Wednesday afternoon through Friday evening for IAZ043-055-056-069-079-080-090-091. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Dergan

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