Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 211138 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 538 AM CST Sat Jan 21 2017 .SHORT TERM...(today through Monday) Issued at 300 AM CST Sat Jan 21 2017 Manual 00z upper-air analysis and early-morning water vapor imagery indicate the presence of a high-amplitude wave pattern over the lower 48 states. An embedded short-wave trough over the mid MO Valley will continue northeast into the upper Great Lakes today, ahead of a potent sub-tropical-branch trough progressing into the southern Plains. In the low levels, a moist air mass which has contributed to areas of dense fog and drizzle/rain showers early this morning will become displaced by a drier boundary-layer advecting into the the mid MO Valley from the west and northwest. Decreasing clouds coupled with the downslope, low- level flow will yield seasonably warm temperatures by this afternoon with highs in the mid 40s to lower 50s. Sunday into Monday, a mid-level ridge will build east into the Great Plains in the wake of a strong synoptic system over the southeast U.S., and ahead of the next major trough moving onto the West Coast. A slightly cooler air mass will filter south into the mid MO Valley on Sunday before a deepening lee cyclone promotes a strengthening low-level warm advection pattern over the central Plains by Monday. High temperatures will remain above normal; in the 40-45-degree range. .LONG TERM...(Monday night through Friday) Issued at 300 AM CST Sat Jan 21 2017 The primary concern in the long term is the potential for accumulating snow Tuesday into Wednesday. Latest medium-range guidance remains in general agreement in suggesting that a strong synoptic cyclone will traverse the central U.S. early next week, with the potential for a swath of heavy snow to the immediate north of the surface low track. However, model differences do exist in the specific track and timing of this system. The GFS is now the most progressive solution with respect to the track of the surface low through the central Plains, and this is a significant departure from the previous model run. The Canadian/GEM is the slowest with the surface low track, while the ECMWF is a compromise between the two, exhibiting remarkable run-to-run consistency. Given the above considerations, we are motivated to most strongly consider the ECMWF solution which depicts a swath of potentially heavy snow developing from northeast Nebraska into west-central Iowa Tuesday into Tuesday night. Under this scenario, light snow would begin late Monday night over northeast Nebraska before becoming heavy during the day Tuesday. A mix of rain and snow or all rain would gradually transition to all snow across the remainder of the area Tuesday afternoon into Tuesday night with the snow ending on Wednesday. Again, the highest probability of significant snow accumulation appears to be over the northern part of the forecast area, with lesser amounts farther south. Strong north winds on the backside of the departing cyclone will be conducive for some blowing and drifting of snow Tuesday night into Wednesday. The north-central U.S. will remain in northwest or north flow aloft through the remainder of the extended range. This upper-air pattern should yield cooler conditions at the surface with highs in the 20s and 30s. && .AVIATION...
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(For the 12Z TAFS through 12Z Sunday morning) Issued at 533 AM CST Sat Jan 21 2017 LIFR to IFR stratus and fog will give way to improving visibilities and scattering ceilings this morning. VFR conditions are indicated through the rest of the TAF cycle, but confidence is low, as some guidance does hint at fog potential again late in the TAF cycle. Winds will remain light through the TAF cycle, with variable direction becoming westerly but speeds around 5-7kt or less.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...Dense Fog Advisory until 9 AM CST this morning for NEZ015- 030>034-042>045-050>053-065>068-078-088>093. IA...Dense Fog Advisory until 9 AM CST this morning for IAZ043-055- 056-069-079-080-090-091. && $$ SHORT TERM...Mead LONG TERM...Mead AVIATION...Mayes

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