Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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942 FXUS63 KOAX 201807 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1207 PM CST Fri Jan 20 2017 .UPDATE... Issued at 1155 AM CST Fri Jan 20 2017 Did a mid-morning update to continue the dense fog advisory through Noon. STill a few sites around 1/4sm-1/2sm in dense fog, however the majority of locations are improving steadily. && .SHORT TERM...(today through Sunday) Issued at 338 AM CST Fri Jan 20 2017 Manual 00z upper-air analysis and early-morning water vapor imagery indicated a high-amplitude wave pattern present over the CONUS with the primary feature of interest being a short-wave trough presently near the Four Corners region. This disturbance will undergo amplification as it ejects northeast through the central Plains into mid MO Valley by tonight. In the low levels, an evolving area of low pressure over the central and southern High Plains today will develop into eastern NE/western IA late tonight/early Saturday, in tandem with the parent upper-air system. Surface observations indicate a saturated or near-saturated boundary layer this morning across the central Plains into Ozarks, to the north of the evolving surface low over the southern High Plains. Persistent low-level warm advection and moisture flux will maintain areas of fog and drizzle today with little diurnal temperature range. Tonight, large-scale forcing for ascent will strengthen through a deeper layer, yielding a transition from drizzle to rain. Highest PoPs will stretch from our central into northeast counties within a deformation band developing to the north of the migratory surface low. Forecast soundings indicate that the boundary layer will remain sufficiently warm to support an all-rain event. Saturday, we may see some breaks in the clouds by afternoon in the wake of the aforementioned weather system moving into the upper Midwest. West or northwest downslope flow in the low levels and the potential for slightly greater diabatic warming (compared to previous days) will yield afternoon highs in the mid to upper 40s. Sunday, an intense mid-level trough will progress from the south- central into southeast U.S. with any associated precipitation remaining to our south. This system, in concert with a weaker polar-branch cyclone over the upper Great Lakes, will contribute to the advance of a slightly cooler --but still above normal-- air mass into the mid MO Valley. .LONG TERM...(Sunday night through Thursday) Issued at 338 AM CST Fri Jan 20 2017 The main focus in the long term remains the potential for accumulating snowfall in the Tuesday-Tuesday night timeframe. The suite of 00z medium-range guidance indicates that a potent mid- level trough will traverse the Interior West on Monday prior to forming an upper low over the central Plains or mid MO Valley Tuesday into Tuesday night. While there are slight differences between the deterministic models in the track and intensity of this system, confidence in a strong synoptic-scale low over the central U.S. on Tuesday remains high at this juncture. Current indications are that the highest probability of accumulating snowfall will exist across the northern part of our CWA with a mixture of rain and snow or all rain farther south. A continental-polar air mass will be drawn south through the mid MO Valley on Wednesday in the wake of the departing synoptic cyclone, yielding cooler and drier weather through the remainder of the work week. && .AVIATION...(For the 18Z TAFS through 18Z Saturday morning) Issued at 1155 AM CST Fri Jan 20 2017 Variable conditions across the TAF sites with LIFR cigs and MVFR/VFR vsbys. Moisture remains in place through the TAF period with continued mid/upper level support as surface low pressure develops over the region and shifts east into Iowa Saturday morning. Have deteriorating conditions later this afternoon and overnight with LIFR/IFR vsbys and cigs with fog/drizzle/light rain. Between 12-15Z low level moisture/shows improvement through 18z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ UPDATE...Zapotocny SHORT TERM...Mead LONG TERM...Mead AVIATION...Zapotocny is the U.S. government's official web portal to all federal, state and local government web resources and services.