awake
wide awake
alertly
erect
superalert
wide-awake
heads-up
on guard
open-eyed
keep one's head on a swivel
prenotification
nimble
sharpie
keep one's eyes peeled
bright-eyed
overalert
ping
notif
observant
foretokening
warningfully
on watch
ex professo
knowing
knowledgeable
wakeful
admonitorily
preadmonish
alerted
wake
alarm
waker
forefeelingly
signally
indicium
right now
bewake
look sharp
foremessage
unalarming
arrey
on one's guard
tempestively
yare
at a moment's notice
out of nothing
from nowhere
keep one's eyes open
out of thin air
forewarn