Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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212 FXUS63 KOAX 271720 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1120 AM CST Mon Feb 27 2017 .UPDATE...
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Issued at 1120 AM CST Mon Feb 27 2017 Current forecast is in good shape, with just a few minor changes made for this afternoon. Did introduce a slight chance of showers for the southeast part of the forecast area as moisture and steeper lapse rates move in.
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&& .SHORT TERM...
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(Today through Wednesday night) Issued at 316 AM CST Mon Feb 27 2017 Weather will continue to trend milder, along with a somewhat more active weather pattern in the short term. Subjective 00Z upper-air analysis indicates largely zonal flow across the CONUS, with an upper-level trough coming ashore in the Pacific Northwest and a departing upper-level trough exiting New England. Strongest upper- level jet extended across the Ohio Valley at up to 150kt, with weaker upper-level jet in the western half of the CONUS. 850mb pattern was fairly nondescript, with a north-to-south temperature gradient that doesn`t seem tight enough to call a true baroclinic zone and with only weak ridges and troughs in the central US. At 08Z, a lee trough was noted in eastern CO to central WY. Main forecast concern is potential for fog and drizzle tonight, then rain and snow in the southern half of the CWA on Tuesday night. Temperatures today will continue to trend milder under mid-level warm air advection and low-level southerly winds. By 00Z, a lee surface low should take shape in northeast CO, sliding across NE on Monday night. In the warm sector ahead of the low, should be enough low-level moisture advecting in for stratus, fog, and drizzle. The drizzle area should focus mainly in the eastern half of the CWA and in northeast NE, while the highest risk of fog is more likely to be in areas with some snow left to melt today and particularly where snowpack lingers tonight. Temperatures tonight should remain above freezing in most places, with the exception being in northeast NE. Thus, a bit of light freezing drizzle is possible in the far northwestern CWA tonight, but confidence is low on duration and amounts (i.e. trace to a couple hundredths). Cold front will move through the CWA on Tuesday, bringing some reduction in temperatures and probably early-afternoon highs as temperatures fall off in the late afternoon through evening. The main upper-level shortwave should slide across SD/NE on Tuesday evening/night, with a lingering mid-level baroclinic zone extending from southern IA through northwest MO/southeast NE and into KS. GFS/NAM/ECMWF have slightly different placement on the baroclinic zone but do agree that it should be fairly potent, with strong mid- level frontogenesis on Tuesday evening that slides south of the CWA through Tuesday night. Should see precipitation develop in that area of frontogenetic lift on Tuesday evening, with precipitation changing from rain to snow as colder temperatures advect in behind the front and as dynamical cooling occurs. GFS/NAM are quite a bit farther north than ECMWF, but both of those solutions do pull the band southward shortly after precipitation likely would change to all snow. For that reason, have little accumulating snowfall in the CWA, though did bump up QPF as blended solution looked underdone where the band does end up developing. .LONG TERM...(Thursday through Monday) Issued at 316 AM CST Mon Feb 27 2017 Temperatures on Thursday will take a brief return to near-normal readings, with a reinforcing cooler air push during the day. By Thursday night, return flow should begin the warm air advection process as mid-level winds become southwesterly and low-level winds gain a westerly to southerly component. With virtually zonal upper-level flow and favorable downsloping and mixing winds, temperatures should rise quickly this weekend. Have added a couple of degrees to maximum temperatures on both Saturday and Sunday. An upper-level trough/low moving across the northern Plains to upper Midwest should drag a cold front through the region on Sunday night and Monday, bringing temperatures back down to normal. For now, the trough and frontal passage look to be more dry than wet, with gusty northwest winds.
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&& .AVIATION...
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(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1120 AM CST Mon Feb 27 2017 Expect at least temporary MVFR to IFR conditions tonight as low level moisture increases. Precipitation chances are not zero but seemed too low to mention in the TAFs at this time. Southerly winds will continue until we get on the backside of the low pressure system on Tuesday.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ UPDATE...Miller SHORT TERM...Mayes LONG TERM...Mayes AVIATION...Miller

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