Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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615 FXUS63 KOAX 180858 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 358 AM CDT Tue Jun 18 2024 .KEY MESSAGES... - Strong thunderstorms are expected Tuesday into Wednesday with severe weather possible. Locally heavy rains and flooding accompany the convection. - Rain chances continue every day Tuesday through Saturday. && .DISCUSSION... Issued at 400 AM CDT Tue Jun 18 2024 Quick southerly winds are gusting 20 to 30 mph at times and are helping to prop up overnight temperatures. Most locations are still holding upper 70s with plenty of lower-80s mixed in. Lincoln and Omaha have lost 1-2 degrees over the past five hours (11p to 4a). A non- diurnal temperature curve has been forecast with high temps in northeast Nebraska happening before noon as the meridional flow pushes a cold front through the CWA. Numbers will slip after frontal passage. The front should arrive at Lincoln and Omaha by 6pm as it`s equatorward push begins to slow. Believe convection will wait til the afternoon when convective temperatures will be met with 2000-3000 J/kg of CAPE available just ahead of the front. Temperatures at 850/700 hPa will slip through the morning as surface temps warm and dewpoints hold near 70. Low-level lapse rates will quickly grow as a result. Kinematics are best behind the front, despite the slower northerly surface winds behind the sinking front. Still expecting a line of convection with some supercells possible along the front, especially in the afternoon and evening with maximum buoyancy and broad forcing for ascent with the area under the 500 hPa jet`s right rear quadrant. Widespread severe weather seems less likely than the need for a few warnings for a couple of the strongest cells. Maybe flood warnings will outnumber convective warnings. Flash flooding will be a legitimate concern. Forecast PWAT values of 2" are in the 99th percentile for mid- June (NAEFS) and storm motion should be slow, especially prior to the cold pool development. QPF of 1.5-2" will be common with the HREF`s LPMM product producing some 4-5" values (currently a bullseye near Omaha and two others near Fairbury, NE and Falls City, NE). With mean winds of 850-250 hPa nearly parallel to the front, expect to see training storms and little front propagation. QPF accumulation should slow overnight and into Wednesday morning, though flooding concerns will linger as the totals add up. .WEDNESDAY and THURSDAY... With the front still draped across the area busy southwesterly flow with weak disturbances will set the stage for additional PoPs. Best chances will be with the day`s maximum heat. Severe weather isn`t anticipated. Wednesday`s QPF has slipped as has WPC`s category for the day (Slight excessive rainfall outlook is now a "marginal"). .THE WEEKEND... The surface ridge on the East Coast becomes less amplified and grows elongated from west to east. Still expect to see some moisture return through TX and KS and the ridge`s western edge and with continued southwesterly flow from SoCal through the OAX CWA, chance PoPs are warranted for Friday and Saturday with best forcing in the northern half of the area. Sunday`s pattern change brings a weak and transitive ridge through the central CONUS and a break in the chances for precip. June`s temperatures are already above 1991-2020 norms. Highs near 90 from Friday through next week will help drive the month`s averages even higher. (They`ll eventually influence 2001-2030 norms, too!) && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1031 PM CDT Mon Jun 17 2024 VFR conditions overnight with low-level wind shear as the low- level jet brings 50 to 55 kt winds just 1500 ft AGL out of the south. These winds will weaken around 12-13Z right around the time we see MVFR cigs start to spread across portions of eastern Nebraska. it may not be a solid deck with a mix of cigs around 2500-3500 feet, so confidence is around 70% that terminals will see a period of MVFR cigs. These cigs should lift to VFR by 18Z. A front will bring storms to the area Tuesday evening starting around 22-00Z, with lingering showers and storms possible through the remainder of the TAF period. Winds will be shifting to the north or northwest behind the front and weakening to around 10 kt. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Nicolaisen AVIATION...McCoy