Grammar
N1AI-drafted〜んばかりに／〜んばかりだ
as if about to ~; almost ~ing
Formation
V-ない形(ない を取る) + んばかりに／んばかりの + N／んばかりだ（する → せんばかりに）
Usage
A literary, written-style expression describing something that looks as if it is just about to happen, though it does not actually happen. It is used for vivid description in novels, essays and news writing, and often exaggerates an appearance or attitude (泣き出さんばかり, あふれんばかり). Note the irregular form せんばかり for する, and remember it describes a third party's appearance, not the speaker's own plan.
Examples
彼女は泣き出さんばかりの顔で私を見た。
かのじょはなきださんばかりのかおでわたしをみた。
She looked at me with a face as if she were about to burst into tears.
店は客であふれんばかりだった。
みせはきゃくであふれんばかりだった。
The shop was practically overflowing with customers.
社長は「出て行け」と言わんばかりに机をたたいた。
しゃちょうは「でていけ」といわんばかりにつくえをたたいた。
The president banged the desk as if to say, "Get out!"