Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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184 FXUS63 KOAX 202030 CCA AFDOAX Area Forecast Discussion...CORRECTED National Weather Service Omaha/Valley NE 330 PM CDT WED JUL 20 2016 .SHORT TERM...
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(tonight through Saturday) Issued at 1233 PM CDT Wed Jul 20 2016 ...The heat wave continues...with some relief by Sunday... For this update there were no changes in the excessive heat warning. The 19Z MSAS/Satellite data shows virtually clear skies across the area with surface low pressure centered near KPIR. Heat index values today reached warning criteria as dew points soared well into the mid to upper 70s under a southerly surface flow. Weather stations from southwest Iowa even reported a few 81 degree dew points, which is extreme. Of course this humidity is the reason for the misery. Actual air temperatures are rather unimpressive, only in the low to mid 90s. Normal temperatures for this time of year are 88 at Omaha, 89 at Lincoln and 87 at Norfolk. Aloft we are under the influence of strong high pressure. 500mb heights were observed at 596 decameters on the morning sounding and have risen throughout the day. This ridge will strengthen through tomorrow, allowing high temperatures to climb even higher on Thursday. 100 degrees will be common across Nebraska by this time tomorrow, with upper 90s expected in western Iowa. Continued high dew points means the misery will continue for Thursday and likely into Friday if we can keep the clouds and precipitation away. Aside from temperatures, a weak shortwave trough will move into northeast Nebraska late tonight and could spark a few showers across central Nebraska. While these showers could leak into our area, decided to go with a dry forecast tonight given the low probability. A strong shortwave will move over the ridge on Thursday, yielding a better chance of precipitation as the upper ridge begins to slowly break down. Associated with this feature is also a marginal risk for severe weather. Though instability is high given the moisture in place, the environmental shear is negligible and best placed over northeast Nebraska and areas of western Nebraska. The best opportunity for storms will likely be in the evening hours. Beyond Thursday the area remains in a favorable regime for some precipitation as the upper ridge flattens. This will allow more shortwave energy to traverse the area, yielding a slight chance of showers and thunderstorms going into the weekend. .LONG TERM...(Saturday night through Wednesday) Issued at 1233 PM CDT Wed Jul 20 2016 A stronger cold front will push through the Central Plains on Saturday night. Temperatures behind this feature should drop a bit, but not substantially. The latest guidance points to high temperatures on Sunday in the upper 80s, this coupled with dew points in the 60s should feel better than days past but still not great. We do however expect an increased potential for precipitation associated with this front. This feature is slow moving and may even stall as it traverses the forecast area, thus have opted to keep showers and thunderstorms through Sunday and Monday associated with it. By Tuesday a potent shortwave is progged to move out of Wyoming and Colorado on its way to eastern Nebraska by Tuesday night. This feature looks to drag a lot of moisture into it as precipitable water values skyrocket well above two inches. This system will be a significant precipitation producer if it comes to fruition. Long-range guidance differs enough on placement and timing to not get too excited yet. This feature exits the region on Wednesday allowing drier conditions to prevail by later in the day.
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&& .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1221 PM CDT Wed Jul 20 2016 VFR conditions through the period. Southerly winds at 14 to 24 knots, with gusts diminishing by 23-01z. Non convective LLWS develops 05-06z...then diminishes by 14-15z. && .OAX Watches/Warnings/Advisories... NE...Excessive Heat Warning until 8 PM CDT Friday for NEZ011-012- 015>018-030>034-042>045-050>053-065>068-078-088>093. IA...Excessive Heat Warning until 8 PM CDT Friday for IAZ043-055-056- 069-079-080-090-091. && $$ SHORT TERM...Pearson LONG TERM...Pearson AVIATION...DeWald is the U.S. government's official web portal to all federal, state and local government web resources and services.