Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 212327 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 627 PM CDT Tue Mar 21 2017 .SHORT TERM...(tonight through Friday) Issued at 250 PM CDT Tue Mar 21 2017 Early after water vapor imagery indicated weak shortwave trough moving southeast through IA this afternoon. This was responsible for the strong frontogenetical band of snow over the northern CWA this morning. Upstream, height rises will start to advance east over the central and northern Plains tonight. This should lead to low- to mid-level WAA/isentropic ascent overnight. Short term models are in fair agreement in this leading to saturation after midnight and eventually light precipitation. The models though differ on the extent of this precipitation. The NAM appears to wet and we prefer a solution closer to the GFS/EC, which would generally just have some light amounts in the northwest CWA /NE NEb/. Thus have lowered/removed pops over the central and southern CWA. Point forecast soundings indicate that this precipitation would generally be in the form of light snow and we will include some half inch accumulations near the SD border. This band of clouds will likely lift to the northeast and we may see a few peaks of the sun on Wednesday afternoon. Clouds will again increase on Wednesday night though as a strong nocturnal LLJ develops ahead of the potent Great Basin trough. This will likely lead to deeper moisture into the area, but despite the better moisture and steeper lapse rates aloft increasing mid-level temperatures will likely limit overall precipitation threat. Will include some chance of showers, but it may end up being more drizzle than anything else. This is likely to continue into Thursday morning, but may tend to move east during the day. With the upper level trough slowly shifting east through the Rockies we will see a cold front move/develop into the northern CWA on Thursday night. Confluent flow into this zone will lead to increasing thermal gradient/frontogenesis with a band of rain likely on the cool side of the boundary. Closer to the surface and 850 mb boundary we may see a few rumbles of thunder as well, especially as the low-level jet develops and enhances mass convergence along this zone. This boundary will likely create a strong thermal gradient across the CWA on Friday. It is difficult to discern exactly where this boundary will setup with the GFS/GEM farther northwest, the EC in the middle, and the NAM much farther south. Given the early spring season we generally prefer a solution closer to the EC, but the NAM is certainly possible as well. Given the uncertainty though the current forecast will not reflect the likely strong temperature gradient /mid 40s north to potentially upper 60s south/ on Friday. Rain should continue during the day on Friday along and northern of the low-level boundary, with some chance of showers or a thunderstorm south of the boundary. .LONG TERM...(Friday night through Tuesday) Issued at 250 PM CDT Tue Mar 21 2017 With the expected slow movement of the trough we will likely see the chance of showers continue into the weekend as well along with the cool temperatures. Any break in the chance of precipitation will be short-lived however with another shortwave trough swinging into the Plains with additional chances of showers into early next week with continued below normal temperatures. && .AVIATION...
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(For the 00Z TAFS through 00Z Wednesday evening) Issued at 608 PM CDT Tue Mar 21 2017 VFR conditions expected thru the fcst pd.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Boustead LONG TERM...Boustead AVIATION...DEE

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