Vowel ə for Old Church Slavonic ѫ (yus), ь and ъ, as in Standard Bulgarian: мъж [ˈmɤʒ] (man), сън [ˈsɤn] (sleep).
Limited number of o [ɔ] reflexes of Old Church Slavonic ъ (back yer): in the suffix -ък [ɤk], the prefixes въз [vɤz] and съ [sɤ] and the prepositions във, въз and със: сос него [sɔs ˈnegɔ] vs. Standard Bulgarian със него [sɤs ˈnego] (with him), напредок [naˈpredɔk] vs. Standard Bulgarian напредък [nɐˈpredɐk] (progress)
щ/жд (ʃt~ʒd) for Proto-Slavic *tʲ~*dʲ (as in Standard Bulgarian) - леща, между [ˈlɛʃta], [mɛʒˈdu] (lentils, between). The future tense particle, however, is че: че че'теме [t͡ʃɛ ˈt͡ʃɛtɛme] vs. Standard Bulgarian ще четем [ʃtɛ t͡ʃɛˈtɛm] (we will read)
ръ (rə) and лъ (lə) for Old Church Slavonic groups ръ~рь and лъ~ль versus formal Bulgarian ръ~ър (rə~ər) and лъ~ъл (lə~əl): дръво, слъза [drɤˈvɔ], [slɤˈza] instead of formal Bulgarian дърво, сълза [dɐrˈvɔ], [sɐlˈza] (tree, tear).
Ending -м [m] in 1st person sg. present tense for verbs of all conjugations: четем [ˈt͡ʃɛtɛm] vs. formal Bulgarian чет'ъ [t͡ʃɛˈtɤ] (I read)
Lack of ending -т in the forms for 3rd person pl. present tense: яда [ˈjada] vs. formal Bulgarian ядът [jɐˈdɤt] (they eat)
Personal pronouns for 3rd person он [ɔn], она [ɔˈna], оно [ɔˈnɔ], они [ɔˈni], as in Old Bulgarian (той [tɔj], тя [tʲa], то [tɔ], те [tɛ] in Standard Bulgarian)
For other phonological and morphological characteristics typical for all Southwestern dialects, cf. the Northwestern Bulgarian dialects.
Sources
Стойков, Стойко: Българска диалектология, Акад. изд. "Проф. Марин Дринов", 2006