Area forecast discussion National Weather Service Omaha/valley NE 608 am CDT Friday Oct 24 2014 Short term...(today through sunday) issued at 310 am CDT Friday Oct 24 2014 Although temperatures remain primary focus in short term...fog and stratus this morning and possibly again Sunday morning remain secondary concerns. Early morning water vapor satellite imagery showed quite a bit of cirrus spilling southeast toward/across eastern nebr/western Iowa region. Although it had thinned as it moved over the forecast area through 07z...thickness of it upstream indicates at least some potential for high clouds impacting highs a bit...especially with weak mixing expected today and mainly northern zones where it could remain thickest. Although patchy fog also remains a threat early most areas...more widespread stratus/fog expected over western Iowa where it had moved into SW Iowa after 06z. This was supported by 05z hrrr...and to some degree the rap. However...the lower level relative humidity was forecast to shift/erode eastward through this morning per those models...probably limiting any impact to maximum temperatures. However...will issue a dense fog advisory far SW Iowa this morning and adjust according depending on whether or not it spreads or if conditions improve quickly. The pessimistic 00z NAM...regarding its widespread low cloud forecast for this morning much of the forecast area...was generally disregarded..although it was noted that stratus was developing west into southeastern nebr at 08z. Because of weak mixing and thicker cirrus threat...lowered maximum temperatures a bit central/northern zones. Wave tracking across southern Canada today still on track to push high pressure weakly into eastern nebr/western Iowa region tonight and model cross sections indicated less cirrus and much drier low level conditions Saturday. Although mixing potential not particularly strong given Erly component to winds...and lows likely to start out colder than this morning due to drier low level air...maximum temperatures possibly not that much cooler due to probably nearly full sunshine. However...kept highs a few degrees cooler than today because of the cooler start and absent strong mixing. 00z GFS/European model (ecmwf) continued to indicate the threat of fog/low clouds returning by Sunday morning as low level moisture returns ahead of next upper trough. Although did not mention fog yet...did increase sky cover Sunday morning central/northern zones where it could linger the longest. Airmass recovers any cooling through lower troposphere observed Saturday. However....besides the increased low cloud potential ..GFS indicated higher clouds returning as well and mixing due to winds could possibly be limited to far southern zones. Thus with the cloud and possibly weak mixing potential northern zones...kept maximum temperatures in lower 70s there with other readings close to those expected to today. Long term...(sunday night through thursday) issued at 310 am CDT Friday Oct 24 2014 Small precipitation chances were maintained in forecast Monday northern areas and all areas Monday night...partially to retain forecast continuity...as trough Cross Plains. However...model quantitative precipitation forecast per 00z GFS/European model (ecmwf) was limited Monday and mostly absent Monday night as strong middle level frontogenesis noted Monday afternoon behind front across the north shifts south/southeast of the forecast area Monday night. Also front appears to move a touch faster into southeastern zones so highs will be a few degrees cooler most areas than prior forecast. With 00z GFS/European model (ecmwf) now dry with little/no forcing...any precipitation mention for Tuesday was dropped...and a continued cool-down should persist. For several runs now a weak wave is forecast to cross the middle Missouri Valley on Wednesday providing area with modest warm advection. Although model/previous forecast blend allowed for a slight warm up over Tuesday...trends would indicate nudging upward more if warm advection clouds appear they will be limited. Earlier GFS lead the charge for a late week cool-down as trough sharpened to our east. European model (ecmwf) followed suit yesterday and continued the trend with 00z run. However...GFS has now flipped to a warmer pattern Thu/Fri. Forecast will continue to reflect a blend of the two to account for uncertainty. && Aviation...(12z tafs for kofk...klnk and koma.) Issued at 604 am CDT Friday Oct 24 2014 Vlifr ceilings/visby is just east of koma and most likely will not make it into the terminal this morning before pushing off to the east...but cannot rule out some MVFR visby through early this morning and will include a scattered vlifr deck in case the clouds do make it to koma. Some MVFR visby is also likely at klnk/kofk for a couple hours this morning. Otherwise will continue the mention of low level wind shear at koma/klnk through middle morning per koax vwp. Surface fnt will move through all 3 taf sites by middle afternoon switching winds to the west and northwest. VFR conditions are then expected from this afternoon through the end of the period. && Oax watches/warnings/advisories... NE...none. Iowa...dense fog advisory until 10 am CDT this morning for iaz080-090- 091. && $$ Short term...chermok long term...chermok aviation...
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