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Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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048 FXUS63 KOAX 110845 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 345 AM CDT Thu Jul 11 2024 .KEY MESSAGES... - Dangerous heat is expected for much of the area this weekend into Monday, with heat index readings of 100 to 110 degrees likely. Sunday and Monday will be the hottest days. - Could see a few spotty showers and storms tonight and Friday night (10-20% chance, highest in northeast Nebraska). - More widespread storm chances (20-40%) arrive Monday night and linger through Wednesday. && .DISCUSSION... Issued at 345 AM CDT Thu Jul 11 2024 Early this morning a few spotty storms were ongoing along the NE/KS border on the nose of some moisture transport and along some low to mid-level frontogenesis. Not expecting these to amount to much, but one or two could produce some small hail. Farther north, some patchy fog was developing across portions of southwest IA. Expect more to develop across much of the area through sunrise, but it should dissipate rather quickly this morning. Today should be pretty quiet in the area with guidance trending away from spotty shower development and even less cumulus this afternoon. Really most of the "cloud cover" you`ll see today will be from wildfire smoke, most of which should remain well above the surface. Otherwise, expect temperatures to top out in the mid to upper 80s. For tonight into early Friday, low level moisture transport will ramp up and looks to point toward northeast NE and extreme southeast NE, leading to some shower and storm development. Instability and shear look to remain on the weak side, but there might be just enough for some elevated small hail producers. Some notable heat and humidity will start to build in Friday as the large scale upper level ridge over the western CONUS will just start to edge into the area. Expect highs in the lower 90s and dewpoints in the upper 60s to lower 70s to lead to heat indices near 100 for some locations. Like Thursday, guidance has trended toward less diurnal cumulus/showers for Friday with a very stout cap in place. Once again, will likely need to wait until the overnight/early morning hours on Saturday for any storm development when low level moisture transport increases and points into the area. Attention then turns to increasing potential for dangerous heat for the weekend as the aforementioned ridge continues eastward progress and southerly flow continues to usher in warm, humid air. In addition, area crops are reaching their annual max in evapotranspiration, further contributing to the humidity. As a result, expect widespread heat indices in the 100 to 105 range Saturday. We warm even further for Sunday with NAEFS suggesting 850 mb temperatures in the 90th to 99th percentile of climatology. While we may not mix quite that high, temperatures still look to top out in the mid 90s to near 100 with dewpoints climbing into lower to mid 70s resulting in 105-110 heat indices for many. A "cold" front will start to push south into the area Monday, but it won`t be fast enough for much of southeast NE and southwest IA, where similar heat is expected. Even north of the front, still expect highs in the lower 90s. With all that said, we`re firmly in Heat Advisory criteria Sunday and Monday, and possibly Saturday. Will need to keep an eye on potential need for an Excessive Heat Watch/Warning as there could be a few spots that reach a daytime heat index of 110 and stay above a 75 heat index for multiple nights. By Monday evening, chances increase for storm development along the aforementioned front. The boundary will move very slowly south, lingering in the area through Wednesday which will bring continued shower and storm chances, especially when the low level jet/moisture transport strengthens at night. By Wednesday, expect high temperatures to be back down in the lower to mid 80s. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1117 PM CDT Wed Jul 10 2024 Patchy fog is still expected to develop across eastern Nebraska and western Iowa tonight after 08Z. Any individual location will have a 30 to 40 percent chance of fog. As such, have opted to leave out of TAFs due to low confidence. Nonetheless, if fog is able to develop at a TAF site, visibilities may drop as low as 2 miles. Probability is highest at KOFK, so put in a couple hours of BR for the most likely time to see fog at this TAF site. Will monitor closely tonight for the low probability situation where TAFs need to be amended to include fog at a TAF site. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...CA AVIATION...Darrah