Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 232130 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 330 PM CST Mon Jan 23 2017 .SHORT TERM...
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(tonight through Thursday) Issued at 330 PM CST Mon Jan 23 2017 ...Significant Winter Storm Set to Impact the Area Tuesday into Wednesday... The 12Z subjective upper air analysis indicated a a seasonably strong 150 kt H25 jet from southern CA into the central Plains. This was associated with a potent mid and upper level shortwave trough, which had 100-150 m H5 height falls this morning over the southwestern US. Downstream there were steep H7 to H5 lapse analyzed over the high Plains with delta-t values of 20+ C. Models still have a fair amount of uncertainty with regards to the synoptic/mesoscale evolution as this system emerges onto the Plains on Tuesday. The GFS continues to be slow to develop a closed mid-level circulation, slower to deepen the system, and farther north. Although the track of the system appears in the realm of possibility given the ensemble guidance, given the weak static stability it appears that the GFS model is to slow to deepen the circulation. Thus we continue to prefer a consensus of the UK/EC/CMC/NAM. This evening should start off quiet, but low-level WAA will increase after midnight and eventually lead to showers developing along the H85-H7 warm front. This area of precipitation will increase in coverage as it lifts to the north toward the SD border on Tuesday morning. We should also see a marked increase in precipitation intensity as stability decreases on Tuesday morning. Exactly where this strong frontogenetic band becomes nearly stationary is likely where the heaviest of the snow will fall, and currently this appears to be over the highway 20 corridor and north into SD. During the afternoon we should see additional development farther south as the strong CDPVA in the H7 to H4 layer increases. This will likely be rain south of I80, but maybe a mix of rain and possibly some sleet showers north of I80. As we get into Tuesday evening we will see the rain and snow line start to collapse south toward I80 as cooler air works into the region, while the deformation snow band continues in the northern CWA. We will also see winds increase later on Tuesday afternoon, and especially into the evening as the surface low tracks into southern IA. Winds of 15 to 25 MPH with gusts to near 30 MPH likely. Again, given the small differences in the track of the system and how weakly stable the atmosphere is there remains considerable uncertainty to the forecast. The CMC would develop another frontogenetic band within the highly unstable air near the I80 corridor on Tuesday evening with saturation that appears to start lower and work vertically. Although given the static stability this is possible, we are discounting this for now with the lack of baroclinicity in the area of this band in the CMC. Also decreasing forecaster confidence is some of the higher resolution guidance would lift the initial frontogenetic band farther north into SD/MN (similar to the GFS), which is also possible as models tend to concentrate the lift in these bands to low in the atmosphere. That said we are less than 18 hours from the start of the event, and thus will make some adjustments to the headlines. We will upgrade the watch to a warning where we have our highest confidence of 6+ in of snow as well as some blowing and drifting. We will issue a buffer advisory south of the warning for 2-5 in and some blowing and drifting. But some adjustments to these are possible or even likely with time. .LONG TERM...(Thursday night through Monday) Issued at 330 PM CST Mon Jan 23 2017 This system in the short term will lead to a pattern shift across the CONUS with the flow pattern become northwest for the central and northern Plains. This will likely lead to a drier pattern, but also quiet variable with temperatures. Current extended will have a dry forecast with near seasonable temperatures.
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&& .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1105 AM CST Mon Jan 23 2017 It appears that MVFR to IFR ceilings will dominate most of the TAF period with some breaks in the clouds possible at KLNK and KOFK this afternoon. Breaks also possible at KOMA later tonight. Snow chances will increase at KOFK after 12Z with LIFR conditions possible 12z-18z. Pcpn likely more a mix for KOMA and KLNK after 12Z, but lighter. && .OAX WATCHES/WARNINGS/ADVISORIES...
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NE...Winter Weather Advisory from 3 AM Tuesday to 9 AM CST Wednesday for NEZ030>034-042>044-050. Winter Storm Warning from 3 AM Tuesday to 9 AM CST Wednesday for NEZ011-012-015>018. IA...Winter Weather Advisory from 3 AM Tuesday to 9 AM CST Wednesday for IAZ043.
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&& $$ SHORT TERM...Boustead LONG TERM...Boustead AVIATION...Miller is the U.S. government's official web portal to all federal, state and local government web resources and services.