in a flash

instantly

Without any pause

• immediatelyWithout any pause
• swiftlyAt great speed
• rapidlyAt high velocity

quickly · speedily · promptly · hastily · briskly · expeditiously · lightning-fast · split-second · in no time · before you know it

abruptly

Without gradual transition

• suddenlyWithout prior indication
• unexpectedlyWithout prior indication
• without warningUnexpectedly, lacking prior notice

out of nowhere · all at once · in a snap · precipitately · impromptu · spontaneously · on the spot · just like that · bang · whoosh

momentarily

For a very short time

• brieflyIn few words
• fleetinglyFor a very short time
• transientlyFor a short time

ephemerally · short-lived · passing · temporary · evanescent · impermanent · for a moment · fleeting moment · brief spell · momentary

metamorphosis

Profound biological restructuring

• prestoVery fast tempo
• abracadabraSpell-casting utterance
• poofSound of vanishing

voilà · magic trick · sleight of hand · vanish · appear · conjure · transmutation · flip · switch · turnaround

startlingly

In surprising manner

• shockinglyIn a startling manner
• astonishinglyIn a stunning manner
• bolt from the blueSudden unforeseen event

thunderclap · bombshell · revelation · epiphany · eureka · breakthrough · realization · awakening · eye-opener · jaw-dropping

• Speed Expressionsin no time, lickety-split, lickety split, like lightning, quick as lightning
• Quick wordsinstant, swift, rapid, fast, speedy
• brief momentsjiffy, moment, instant, second, tick
• instantlysuddenly, instantly, immediately, at once, abruptly
• sudden thingssuddenly, abruptly, unexpectedly, instantly, spontaneous
• suddennesssudden, suddenly, abrupt, abruptly, instant