Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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986 FXUS63 KOAX 181748 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1248 PM 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 /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1246 PM CDT Tue Jun 18 2024 Primary focus this TAF issuance is on timing and intensity of thunderstorms. Have attempted to focus the greatest potential into a 2 hour window. It appears that the window for stronger storms, while around 2 hours long, may come in off-and-on greater intensity so maintained a tempo for the lowest conditions. After storms, there are questions about if/when/how long MVFR ceilings may persist. Especially at LNK/OMA, could have some MVFR or briefly IFR ceilings over the course of several hours, but feel that VFR is more likely for a majority of the time so have been a bit conservative with ceiling heights at this time. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Nicolaisen AVIATION...Barjenbruch