Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 061723 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1123 AM CST Wed Dec 6 2017 .UPDATE...
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Issued at 1118 AM CST Wed Dec 6 2017 Snow showers in northeast NE appear to have put down a quick dusting based on NEDOT webcams up by Wayne. This activity will continue move down the MO River valley into the afternoon, although as temps have warmed more than previously thought into the lower 40s, so this will have an impact initially. Temps will probably wetbulb down though resulting in a rain/snow mix. This narrow band will move across the Omaha metro area then into southwest IA. Temps behind the cold front have dropped into the the mid 20s near the NE/SD border, so have tried to account for falling temps where the front moves through.
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&& .SHORT TERM...(Today through Friday) Issued at 313 AM CST Wed Dec 6 2017 Northwesterly flow continues, with an attempt at precipitation today. Subjective 00Z upper-air analysis indicates a stacked low centered in northern ON, with the trough extending from the northern Rockies to the mid-Atlantic, and with a southwestern US weak upper low that was largely cut off from the main flow. An embedded shortwave in the northwesterly flow had moved from MT into western NE through the last few hours. An upper-level ridge was centered off the coast of OR/northern CA. A 130-150kt upper-level jet streak extended from the OH River valley through the eastern Great Lakes, with split jet flow in the western US. 850mb sub-0C temperatures extended across much of the central to northern Plains and eastward through the Great Lakes, as well as south to the OH-MS River confluence. Surface low at 08Z was well northeast in northern ON, with surface ridging in western MT/western WY, and still a rather distinct pressure gradient between across the central US. Pockets of sprinkles/flurries were sliding southeastward through the Dakotas into NE/IA/MN this morning associated with the embedded shortwave. Main forecast concern is the evolution of aforementioned sprinkles/flurries today and whether they will amount to measurable precipitation. A reinforcing shot of cold air will slide southward through the Dakotas/MN into NE/IA through the day, and the associated mid-level frontogenesis will provide some lift. Mid-level moisture is fairly meager, though, and there is considerable uncertainty whether any precipitation will measure. If it does, it is not likely to be very widespread, and have stuck with low-end POPs for that reason, with coverage mention for sprinkles/flurries. In wake of the cold air push today and tonight, 850mb temperatures will fall into the lower teens below zero into Thursday. Updated forecast continues to hold high temperatures below freezing for the first time this cold season. Climatologically, the average first day with a high below freezing is around November 15-20, and a December 7 occurrence would be around the 5th to 15th latest on record across the area. As mid-level temperatures rebound on Friday, so will surface temperatures, despite persistent (and dry) northwesterly flow. A surface to mid-level trough passage on Thursday night may bring increased clouds, but forcing and moisture both look too meager to wring out (measurable) precipitation. .LONG TERM...(Friday night through Tuesday) Issued at 313 AM CST Wed Dec 6 2017 Northwesterly flow will continue through the period, with a trough- east/ridge-west pattern locked in for some time. The central US will remain in the transition/gradient area, and thus temperatures are likely to fluctuate on either side of normal during this pattern. A consistent signal for warming on Sunday continues, with 850mb temperatures popping into the single digits above 0C, before colder air returns on Monday. With normal highs in the mid to upper 30s at this time of year, forecast temperatures are more above than below normal from Sunday through Tuesday. As long as the baroclinic zone remains near the area, weak and transient shortwaves could possibly generate enough lift for light precipitation (more in the sprinkles/flurries than rain/snow variety). There are low POPs in the grids on Monday and on Tuesday, but ultimately, confidence is very low in receiving measurable precipitation during the period && .AVIATION...
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(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1118 AM CST Wed Dec 6 2017 Showers in the vicinity of KOFK for another couple hours, but little accumulation there. Showers, initially rain, may mix with snow at KOMA by 19z, and linger through about 21z. A few rain showers may move into KLNK 20-23z. Otherwise, generally VFR conditions, although will have to watch for a brief period of MVFR at KOMA as the precipitation moves in.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ UPDATE...DeWald SHORT TERM...Mayes LONG TERM...Mayes AVIATION...DeWald

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