Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 170405 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1005 PM CST Sat Dec 16 2017 .UPDATE... Issued at 956 PM CST Sat Dec 16 2017 Mades some tweaks to the clouds...temps...and dewpoints based on latest trends and tight temperature gradient in parts of southwest Iowa near the front. The HRRR/RAP/SPC HRRR hinting at some light precip a little farther west initially toward 11Z, however the general trend is for the light precip to be confined southeast Nebraska and farth southwest Iowa. Still mention rain, however a mix is possible on the northwest edge of the precipitation area Sunday morning. && .SHORT TERM...(Tonight through Tuesday) Issued at 230 PM CST Sat Dec 16 2017 Potential for light precipitation late tonight into Sunday morning and temperatures through the period are the main forecast concerns through Tuesday. Closed low at 500 mb which was over Mexico at 12Z this morning continued to lift northeast across TX early this afternoon, while the kicker shortwave trough was digging toward northern Baja. Mid level height falls this morning were strongest over CA but also stretched up farther to the northeast with the wave in the northern stream across Canada. A fairly decent mid level temperature gradient was setting up from the central Rockies out in the Plains, while at 850 mb a warm airmass extended from the desert southwest into KS and NE. Cooler air was pushing southeast though behind a surface cold front that should extend from northern IL back to southeast CO by early this evening. Lift and moisture will be on the increase later tonight across the southern part of the forecast area. Some of the high resolution and other models (GFS and ECMWF) bring some light precipitation north from KS into our southern zones prior to 6 am Sunday. Will keep some low chances going there, and continue those through late Sunday morning. This looks like mainly a light rain event with a potential for a mix on the northern fringes of the precipitation shield. Of some concern is amount of low level moisture that could result in holding down temperatures for Sunday. At this time, have highs close to a blend of GFS and NAM. Longer range models are in fairly good agreement that the rest of the day Sunday and then into Tuesday should be mainly dry. Mild air will again spread east across the region for Monday, with highs in the lower and mid 50s. A weak cold front pushes through the area Monday night which will put highs in the 45 to 50 degree range in our northern zones but still in the lower 50s near the KS and MO borders. .LONG TERM...(Tuesday night through Saturday) Issued at 230 PM CST Sat Dec 16 2017 Precipitation chances starting late Wednesday night and continuing through Thursday night will be the main concern in the long term. At the start of this period there will be a weak closed low tracking east across the southern Plains and a pretty strong wave extending from southwest Canada to off the coasts of WA and OR. That feature then pushes southeast toward the northern Plains and central Rockies through Wednesday. Wednesday night the flow becomes more split, with some energy dropping south which forms a weak circulation that starts to close off over UT. To the north, a piece of energy will track across the northern Plains, helping force a cold front through the region. Mid level forcing and moisture should be adequate for some light rain and light snow initially, then as the column cools it will turn to all snow. There are hints of a coupled jet structure Thursday, with the main jetstreak over the Great Lakes region and a secondary max from southern AZ toward western KS. The 12Z model guidance was generally in better agreement than it was this time yesterday, in regards to snow amounts. The GFS, ECMWF and Canadian models all bring at least some light snow to the region. This will be accompanied by much colder air and north winds from 15 to 30 mph. Temperatures Thursday should be falling through the day, bottoming out in the 5 to 10 degree range in northeast NE and from about 9 to 15 degrees for southeast NE and southwest IA Friday morning. Then it looks like temperatures should remain below normal into Saturday and Sunday. There are signals for light precipitation next weekend, but those signals are weak and will not include anything at this time. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 530 PM CST Sat Dec 16 2017 VFR conditions are expected to deteriorate to MVFR/IFR between 07Z-12Z at all through sites. Reinforcing cool and moist air will settle in from the north, meanwhile...a storm system will track across Kansas. There is some uncertainty with a narrow area of subsidence between the systems that may hold clouds in the VFR category...thus this will need to be watched for KLNK and KOMA. The precipitation from the Kansas will approach KLNK and KOMA however is currently not forecast to reach them. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ UPDATE...Zapotocny SHORT TERM...Miller LONG TERM...Miller AVIATION...Zapotocny

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