Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 272346 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 546 PM CST Mon Feb 27 2017 .SHORT TERM...(tonight through Thursday) Issued at 310 PM CST Mon Feb 27 2017 The main forecast concerns will be in the first 30hrs of the forecast related to temperatures...the extent and location of precipitation and precipitation type tonight into Tuesday evening. The 12Z upper air charts and water vapor satellite imagery highlight a broad trough that extends from Idaho through central California into the Pacific...with mid level moisture ahead of this trough. The h85 observations detailed h85 dewpoints across TX and OK and KOUN showed saturated conditions in the lowest 2500ft. the moist h85 dewpoints are forecast to spread northward into southeast Nebraska through 00z. H85 Warm Air advection/Theta-e advection has been ongoing through the afternoon and visible satellite imagery shows an increase in clouds. The forecast is a bit complex as there is a front over South Dakota with surface low pressure over eastern Colorado. Lead shortwave trough energy moves into the Plains tonight. During the evening...The low level jet strengthens to 45 or 50kts. the deeper moisture shifts quickly eastward into iowa...however does get pulled northward into northeast Nebraska...with the best forcing closer to the front across the Dakotas into Minnesota. There may be a few showers from eastern Nebraska into western Iowa. There is some elevated instability...cannot rule out some thunder. Confidence was low...thus did not mention at this time in our local forecast. Overnight...the surface low tracks from eastern Colorado into northeast Nebraska. Do have some fog and light precipitation mentioned in the vicinity of the low and the precipitation initially is liquid...however could see some mix due cooling. Low temperatures tonight will vary from 30 near the SD border to near 50 near the KS/MO border. Tuesday...the left exit region of the upper level jet combine with mid level omega/developing frontogenesis. There may be enough lift for rain or a rain/snow mix to develop in a band behind the front. The GFS is the most aggressive with this precip (1 to 2 inches)...while the other models show a signal...however the precip is lighter possibly 0.1" in our area along and south of I80 and into sw Iowa. The NAM tends to accumulate the snow south of the forecast area. Do mention rain and where it could switch to snow on the cool side of the precipitation band although kept any amounts light for now. Highs Tuesday should remain in the 30s to lower 40s in northeast Neb. and could warm into the lower 60s at Falls City. Northwest breezes and highs in the 40s are on tap for Wednesday. A weak front/clipper helps temperatures rise slightly...but still in the 40s for Thursday. .LONG TERM...(Thursday night through Monday) Issued at 310 PM CST Mon Feb 27 2017 Surface high pressure will be over the Missouri River Valley to start the extended with h85 temperatures lowering to -4 to -8deg C. South flow increases for Friday and Saturday as surface low pressure tracks across Manitoba into Ontario with a trailing front into the Plains. H5 flow is fairly zonal Saturday and begins to amplify a little more Sunday. Warm air appear to remain in place Sunday with 12-14deg C h85 temps...although there is some difference in the strength of the flow. The 12Z GFS has a ridge Sunday...with the 00Z EC showing a deepening trough with a front approaching the forecast area. These differences further continue into Monday. && .AVIATION...
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(For the 00Z TAFS through 00Z Tuesday evening) Issued at 541 PM CST Mon Feb 27 2017 Surface low pressure system in northeast Colorado will move into eastern Nebraska by 09Z, then east of the area shortly after 12Z. Areas of low level moisture streaming north ahead of the low will bring at least MVFR cigs to KOMA area after 06Z, with some chance cigs below FL010. Fog and maybe drizzle could also develop, dropping vsbys into the IFR range. KOFK and KLNK will be on the fringe of western extent of the low clouds and reduced visibilities, but expect at least MVFR conditions at those sites 06Z through 12Z. Behind the low pressure system, southwest then northwest winds will overspread eastern Nebraska, initially drying out low levels and improving conditions. However a trailing cold front will again bring MVFR cigs back into the TAF sites after 18Z, with a small chance for light rain before 00Z.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Dergan

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