Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 182345 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 545 PM CST Sun Feb 18 2018 .SHORT TERM...(Tonight through Wednesday) Issued at 345 PM CST Sun Feb 18 2018 Forecast concerns continue to be the winds this afternoon, then drizzle and freezing drizzle developing late tonight and continuing Monday morning with a mix of sleet and snow in northeast Nebraska. The OAX 12Z sounding showed a strong 52kt h85 jet and this resulted in strong south winds gusts mostly in the 40 to 50mph range, however we did have some higher gusts at Norfolk and Lincoln with 53mph and Omaha had 58h mph. Water vapor satellite imagery and lightning/obs showed some lightning over Idaho overnight...and this was ahead of closed h5 low pressure system that have moved across Washington state. Farther south, there is a southern portion of the upper level trough and there is moisture streaming ahead of that across Mexico into the southern Plains. The mid-tropospheric pattern through Monday for the h5 trough to deepen from Montana through Nevada with southwest flow aloft across the southern Plains. At the surface...this progression is pushing a cold front into the region. At 21Z...the cold front had made it to ONL and with continue to push into northeast Nebraska through 00z. Through 12Z...the front will push across the forecast area. Updated the hourly temperatures overnight with a RAP/GFS blend as these had the best initial temperatures at midday. Temperatures are balmy now...some 10 to 20 degrees above normal in the 40s to nearly 60 degrees. By 10pm...we have temperatures dropping to below freezing at KOFk, however parts of southeast Nebraska and southwest Iowa are still in the 40s and 50s. Between 4am and 7am we have the temperatures falling to near or below freezing at KLNK/KOMA/CBF with temperatures in the mid to upper 40s still at FNB. Visible satellite imagery and observations show low clouds fl010-020 over southern Kansas into Oklahoma. This is where the deep moisture with 10+ deg C dewpoint temperatures were progged to be. h85 winds are forecast to increase from 45 to 55kts through 00z into southern Nebraska. Meanwhile, low level moisture increases with 4 to 6 deg. h85 dewpoints while the 10 to 12 deg C dewpoints remain in KS and MO. Some of these 10 deg dewpoints get close around 9Z then settle southward. The precipitation starts as drizzle then due to the lack of cold air/ice...freezing drizzle where temperatures are below freezing. There chance for light accumulations are slight before 06Z...with the precipitation area increasing between 06-09Z and through 12Z in sync with the surge of deeper moisture. The front then settles farther south between 12-18Z and the better precipitation begins to shift eastward with north winds 15 to 30 mph across the area and falling temperatures. Left the winter weather advisory in place from midnight to noon. Ice amount will vary from a trace to a tenth of an inch. Higher amounts...0.05 or more tend to be from Ft. Calhoun toward South and into west central Iowa... with a trace to 0.04 elsewhere. Light snow of an inch or less is possible in northeast Nebraska. Through Tuesday the large h5 high pressure system over the southeast U.S. and the Atlantic remains in place and the H5 trough tries to push eastward, however the northern stream does make some progress while the southern stream remains over the southwest U.S. For Monday night into Tuesday, there are some differences in the models, however, the general risk for another round of ice and some light snow is for 1 to 3 inches of light snow in northeast Nebraska...light icing amounts for east central Nebraska and some .1 to .2" icing possible in southeast Nebraska and southwest Iowa. The h85 flow of the NAM is very favorable for the icing. The GFS is less aggressive and the EC is more aggressive, however more in IA and MO compared to Nebraska and southwest Iowa. May need another advisory to cover this, however it may start Monday evening and did not want to blanket and advisory for a long period of time when we did not have freezing drizzle occurring. .LONG TERM...(Tuesday night through Sunday) Issued at 345 pM CST Sun Feb 18 2018 Highs Wednesday should top out in the 20s with 30s for Thursday. Thursday through Saturday we have chances of precipitation with a mix due to highs in the 30s and 40s Friday and Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 541 PM CST Sun Feb 18 2018 Deteriorating conditions are expected through the evening as MVFR cigs near FL015 develop by 06Z at all eastern Nebraska TAF sites. Then areas of drizzle are expected from 06Z through 18Z for parts of the area, with temperatures dropping below freezing causing Freezing Drizzle to be the primary precipitation type for several hours at all sites. Occasional IFR cigs could occur with areas of heavier drizzle. Also, north winds will increase into the 15 to 25kt range from 06Z to 18Z, but then diminish somewhat Monday afternoon. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Winter Weather Advisory from midnight tonight to noon CST Monday for NEZ012-015-017-018-030>034-042>045-050-051. Winter Weather Advisory from 3 AM to noon CST Monday for NEZ052- 053-065-066-078. Winter Weather Advisory from 6 AM to noon CST Monday for NEZ067- 068. IA...Winter Weather Advisory from midnight tonight to noon CST Monday for IAZ043-055. Winter Weather Advisory from 3 AM to noon CST Monday for IAZ056. Winter Weather Advisory from 6 AM to noon CST Monday for IAZ069- 079. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Dergan is the U.S. government's official web portal to all federal, state and local government web resources and services.