Heyer, M.Di Teodoro, E.Loinard, L.Lockman, F. J.Mcclure-Griffiths, N. M.Wang, Q. D.2025-05-232025-05-230004-6361ORCID:/0000-0003-2730-957X/work/184099463http://www.scopus.com/inward/record.url?scp=86000630365&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733752920Using the Large Millimeter Telescope and the SEQUOIA 3 mm focal plane array, we have searched for molecular line emission from two atomic clouds associated with the Fermi Bubble of the Milky Way. Neither 12CO nor 13CO J=1a- 0 emission is detected from the H I cloud, MW-C20. 12CO J=1a- 0 emission is detected from MW-C21 that is distributed within 11 clumps with most of the CO luminosity coming from a single clump. However, we find no 13CO emission to a 3I σ brightness temperature limit of 0.3 K. Using this limit and RADEX non-local thermodynamic equilibrium (non-LTE) excitation models, we derive H2 column density upper limits of (0.4a- 3)×1021 cm- 2 for a set of physical conditions and a H2 to 12CO abundance ratio of 104. Model CO-to-H2 conversion factors are derived for each set of physical conditions. We find the maximum value is 1.6×1020 cm- 2/(K km s- 1). Increasing [H2/12CO] to 105 to account for photodissociation and cosmic ray ionization increases the column density and X(CO) upper limits by a factor of 10. Applying these X(CO) limits to the CO luminosities, the upper limit on the total molecular mass in MW-C21 is 132±2 M⊙, corresponding to <27% of the neutral gas mass. For the three clumps that are fully resolved, lower limits to the virial ratios are 288±32, 68±28, and 157±39, which suggest that these structures are bound by external pressure to remain dynamically stable over the entrainment time of 2×106 years or are being disrupted by shear and expansion over the clump crossing times of 3- 8×105 years. The observations presented in this study add to the growing census of cold gas entrained within the Galactic Center wind.This work would not have been possible without the longterm financial support from the Mexican Humanities, Science and Technology Funding Agency, CONAHCYT (Consejo Nacional de Humanidades, Ciencias y Tecnolog\u00EDas), and the US National Science Foundation (NSF), as well as the Instituto Nacional de Astrof\u00EDsica, \u00D3ptica y Electr\u00F3nica (INAOE) and the University of Massachusetts, Amherst (UMass). The operation of the LMT is currently funded by CONAHCYT grant #297324 and NSF grant #2034318. The data described in this paper include LMT observations conducted under the scientific programs, 2023-S1-UM-16 and 2024-S1-MX-2. The LMT welcomes acknowledgement of the scientific and technical support offered by the LMT staff during the observations and generation of data products provided to the authors. This work made use of Astropy ( http://www.astropy.org ): a community-developed core Python package and an ecosystem of tools and resources for astronomy (Astropy Collaboration 2013, 2018, 2022). LL acknowledges the support of UNAM-DGAPA PAPIIT grants IN108324 and IN112820 and CONACYT-CF grant 263356. E.D.T was supported by the European Research Council (ERC) under grant agreement #10104075. This research was partially funded by the Australian Government through an Australian Research Council Australian Laureate Fellowship (project number FL210100039 awarded to NM-G). The NRAO is a facility of the National Science Foundation operated by Associated Universities, Inc.7en© The Authors 2025.Galaxy: centerGalaxy: kinematics and dynamicsISM: cloudsISM: moleculesISM: structure2025-03-0110.1051/0004-6361/20245287586000630365