Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 271154 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 654 AM CDT Thu Jul 27 2017 .SHORT TERM...(Today through Saturday) Issued at 330 AM CDT Thu Jul 27 2017 ...Cooler Weather for the Next Several Days... Forecast concerns will be early morning fog then cooler temperatures and spotty thunderstorm chances. Wednesday was a challenging forecast day with multiple rounds of precipitation and the clouds hanging on keeping the temperatures down for much of the area. Through 7am Wednesday...rainfall varied from 0.01 in the Ashland area to 1.06" at nearby Gretna. In general, the early morning rains were heaviest in northeast Nebraska where 2.35 inches was recorded near Lyons in Cuming Co., however a north to south line of efficient rain producing thunderstorms developed with 1.68 inches in Johnson Co. and other 1 inch amounts northward for parts of Sarpy and Douglas Co. Additional locally heavy rains occurred during the day and these amounts will be reported Thursday morning, however some early storm totals include 5 inches that fell near Columbus and 3.2 inches at North Bend. Lincoln had a third of an inch with the morning round, but picked up 2.5 inches more during the with a storm total of 2.83 inches. Other storm totals included 0.57 at Omaha Eppley, 1.23 inches at Norfolk, and 1.64 inches at Gretna. The flash flooding set up just south of our area in parts of Kansas and Missouri Overnight, patchy dense fog developed with the clearing skies...wet ground and residual high dewpoints. At 08Z...the drier dewpoints had made it to KOFK with 60...however dewpoints were still near 70 at KOMA. The h9 winds are forecast to increase through 12Z...so this should help keep the dense fog at bay save for perhaps in southwest Iowa were it may fill in. Will mention some patchy fog in southeast Nebraska and southwest Iowa along with some stratus. The PWAT on the 00Z OAX sounding was 1.97 inches and is forecast to drop to around 1.39 by 12Z and 1.10 by 00Z. After some variable morning stratus, patchy cu may develop and there may be some isolated showers try to develop toward Falls City. Due to low confidence, do not have a mention in the current forecast. Troughing deepens over the Great Lakes while the ridge builds to the west...however a shortwave does impact parts of the Plains Friday and Saturday. For now, the storms are expected to remain mainly west of the forecast area. Cooler high temperatures in the 80s can be expected with lows in the upper 50s to lower 60s. .LONG TERM...(Saturday night through Wednesday) Issued at 330 AM CDT Thu Jul 27 2017 Sunday...surface high pressure is forecast over the Great Lakes with the mid tropospheric ridge over the Rockies. In-between, we are in northwest flow aloft with a shortwave tracking through Plains. Thunderstorms are forecast to be ongoing at the start of the period...possibly holding together as they drop southeast across parts of the forecast area. The 00Z GFS is a bit stronger with this feature compared to the 12Z/00Z dry EC...thus some pops included in collaborative fcst. Monday -Tuesday are dry with the focus for storms just to are west, however pops may be added if these hold together longer than expected. The medium-range models handle the timing and strength of the shortwave traversing Canada a little differently. Both the GFS/EC increase the chance for thunderstorms Tuesday night-Wednesday night especially in northeast Nebraska and depending on the frontal position. Again, the EC is mostly dry. && .AVIATION...
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(For the 12Z TAFS through 12Z Friday morning) Issued at 654 AM CDT Thu Jul 27 2017 LIFR fog and ceilings dissipated shortly before TAF issuance as slight increase in H9 winds helped to mixing slightly drier to the surface. A few stratofractus could develop this morning, but should dissipate within an hour or two. Otherwise, VFR conditions will prevail the majority of the forecast period. Forecast models hinting at stratus and fog development at KOMA and possibly KLNK toward the end of the TAF period, as low level winds veer to an easterly direction and advect low level moisture back into the area.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Fortin

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