Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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798 FXUS63 KOAX 250437 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1137 PM CDT WED AUG 24 2016 .SHORT TERM...(tonight through Saturday) Issued at 338 PM CDT WED AUG 24 2016 Chance for precipitation into the weekend is the primary forecast concern. Surface cold front had slipped into far southeast Nebraska and southwest Iowa this afternoon where calm winds and dew points were near 70. Upper level jet segment of 75kt at 300mb was knifing northeast through northeast Nebraska, placing tendency for upward motion over frontal zone in southeast Nebraska and southwest Iowa. As such, thunderstorms have developed in the 18Z to 1930Z time frame in our area, more along 850mb wind shift line. As upper/mid level jet segments lift northeast, so to will area of convection along 850 front. Shorter range hi-res model output has become relatively consistent this afternoon from run to run and between various models in suggesting this scenario. Those models also agree with ending largest threat of rainfall during the evening as forcing shifts east. So, a few things. One, will continue with fairly high precipitation chance in southeast Nebraska and southwest Iowa. Two, northern fringe of precipitation should hold to or just north of Interstate 80, but again stronger storms should remain farther south. Three, with forcing shifting east this evening, do not have high confidence in Flash Flood Watch currently in effect for five of our far southeast counties. Elevated instability now and into this evening is not expected to be high enough to support continued redevelopment of cells along convergence lines, especially with aforementioned forcing moving away. Precipitable water values remain very high, however, and any storms could dump a fair amount of water in a short time. Thus will continue the Flash Flood Watch thinking biggest threat is during the evening. Severe threat is also limited by only modest instability and shear parameters in Nebraska and Iowa. But again, areas just south of here have better numbers, and a slight northward shift is likely. Freezing levels remain relatively high, near 14kft, so large hail looks unlikely given modest instability. But there is still a small threat in our south nearer higher moisture/instability. Beyond this evening, eastern Nebraska and southwest Iowa remain in a relatively unsettled pattern into at least Saturday, with rain chances just about every day/night. Cold front just to our south should be pushed a little farther into Kansas with passing convection this evening. However given southwest flow aloft, front will not move very far south, and will tend to drift back north later tonight and Thursday. Overrunning precipitation will be possible north of this front late tonight and Thursday over the southern parts of Nebraska and Iowa. Better chances come Thursday night into Friday when shortwave ejects from the Rockies and drags front and higher dew points back into our area. Strongest storms with this system come Friday night when surface reflection rolls through eastern Nebraska providing focused convergence. Though we will continue with a small chance for precipitation on Saturday, chances are lowest of the 3-day period as subsidence suppresses most convection through much of the day. Temperatures through Saturday should hold in the 70s Thursday and Friday before return flow helps boost high back into the 80s on Saturday. .LONG TERM...(Saturday night through Wednesday) Issued at 338 PM CDT WED AUG 24 2016 Our unsettled weather pattern appears to hang around into the middle of next week. The strongest mid level westerlies will lift into the Northern Plains, however both GFS and ECMWF suggest a slow-moving shortwave will drift east through the Plains Monday through Wednesday. Persistent southerly low level flow will maintain moisture profile in lower layers of the atmosphere under slightly divergent mid level flow associated with shortwave. Will maintain at least small precipitation chances each day Sunday through Wednesday. Chances will likely diminish Wednesday afternoon as shortwave shifts east. Persistent high temperatures are expected with highs in the low to mid 80s, but lows should gain a few degrees given dew points in the 60s to near 70. && .AVIATION...
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(06Z TAFS for KOFK...KLNK and KOMA.) Issued at 1134 PM CDT WED AUG 24 2016 VFR conditions are expected to prevail through the period with widespread high level cigs across the region.
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&& .OAX Watches/Warnings/Advisories...
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NE...None. IA...None.
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&& $$ SHORT TERM...Dergan LONG TERM...Dergan AVIATION...Fobert

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