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Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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913 FXUS63 KOAX 122355 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 655 PM CDT Mon Aug 12 2024 .KEY MESSAGES... - Below average temperatures (highs in the 70s) are expected across the region through Tuesday, then back to near normal temperatures (widespread 80s) for Wednesday and beyond. - Periodic shower and storm chances continue through the work week, especially during the evening through early morning hours. Some severe weather and/or localized flooding appear possible on Tuesday night, and again Wednesday afternoon and evening. && .DISCUSSION... Issued at 308 PM CDT Mon Aug 12 2024 --Tonight and Tuesday-- Widespread clouds present across eastern NE and western IA as of early afternoon will diminish some through the remainder of the afternoon into evening before becoming widespread again tonight into Tuesday morning. Areas of fog appear likely as well. Showers and thunderstorms developing over the the central High Plains this evening are forecast to consolidate into at least one longer-lived complex which will track generally east across KS and perhaps southern NE tonight. The PoP forecast will indicate that notion with highest values (30-60%) late tonight into Tuesday morning across southeast NE. Widespread clouds are likely to linger into Tuesday afternoon, which will limit highs to the 70s. --Tuesday night through Wednesday night-- A low-amplitude shortwave trough is forecast to traverse the mid MO Valley Tuesday night ahead of a stronger mid-level system moving through the same area on Wednesday night. In the low levels, there is some model variability in the track of an associated surface low. The deterministic ECMWF depicts the northern-most and deepest low over eastern NE by 7 pm Wednesday, whereas the deterministic GFS and Canadian models indicate farther south and weaker solutions. Forcing for ascent attendant to lead disturbance coupled with warm advection and moisture flux along a nocturnal low-level jet (LLJ) are expected to foster a band of showers and thunderstorms across the area Tuesday night into Wednesday morning. The moisture advection along the LLJ will contribute to a destabilizing air mass overnight with some potential for isolated severe storms capable of large hail, damaging winds, and locally heavy rainfall. Severe weather potential on Wednesday afternoon and evening will be conditional on: 1) the eventual surface low track, and 2) the extent to which the morning precipitation and clouds clear during the afternoon, allowing the air mass to destabilize. The more northern, deeper surface low solution (ECMWF) would support the highest ceiling on severe-weather potential across our area Wednesday afternoon and evening with the GFS/Canadian model scenarios offering a lesser severe-weather threat. Regardless, the setup will be supportive a fairly widespread rainfall event with localized flooding possible. Highs on Wednesday will also be contingent on the surface low track and any lingering precipitation and cloud cover. This forecast update will indicate readings ranging from the 70s across portions of northeast NE and west-central IA to around 90 along the KS border. --Thursday and Thursday night-- Another shortwave trough is forecast progress southeast through the northern Plains and mid MO Valley, contributing to the amplification of a broader-scale trough from the Great Lakes to mid MS Valley by Friday morning. At the surface, a cool front is expected to move through the area sometime on Thursday with additional shower and thunderstorm chances along the front. Severe-weather potential will be conditional on an afternoon/ evening frontal passage. High temperatures will also be dictated by frontal timing. --Friday through the weekend-- There`s good model agreement that a mid/upper-level high centered over the southern High Plains will strengthen with associated ridging building north through the northern High Plains. Weak disturbances moving down the backside of the ridge axis will support minor precipitation chances with highs in the 80s. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 655 PM CDT Mon Aug 12 2024 MVFR ceilings continue at KOMA whereas ceilings of FL030-045 persist at KOFK and KLNK. Satellite denoting gradual clearing west to east, which should realize in sky conditions becoming scattered at KOMA between 00-02UTC. Weak isentropic descent will maintain scattered sky conditions through the evening hours, then as weak to neutral ascent returns aft 06z, all three TAF sites will experience deteriorating sky conditions, with MVFR ceilings FL015-025 developing by 07-09utc and LIFR ceilings FL003-005 by 10-11utc. In addition, visibilities are expected to diminish to between 1/2 to 3/4SM by 10z and persist through 13z before diurnal mixing allows visibilities to improve into MVFR range. As for ceilings, deterministic and ensembles keep LIFR ceilings ensconced at all three TAF sites through 15 utc. Improving ceilings expected by midday as a drier air 850-700mb may erode depth of cloud layer, and for now have improved ceilings into low VFR category between 19-20 utc. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Mead AVIATION...Fortin