Answer:
On the West Coast, say, on the Outer Point of Point Reyes in N. CA, the most typical East Coast vagrants to see in the fall include Palm, Blackburnian and Blackpoll. Other species that often appear annually: Black-throated Blue, Black-and-white, Magnolia, and Chestnut-sided Warbler.
(Blackpoll Warbler, shown above.)
One reason relates to the orientation error displayed by migrating warblers. For many vagrants seen on the West Coast, the cause is due to first-year individual having an innate faulty brain, causing them to navigate south, then west — instead of south and, then, east toward Latin American expanses.
In traveling west by mistake, these newborn warblers continue as far as the land will take them — such as to the far western extreme of Point Reyes National Seashore. Unfortunately, these vagrants meet an unfortunate fate as they eventually continue moving west over the ocean.
In regard to West Coast vagrant warbler species, ongoing discussion is whether Blackpoll is truly a vagrant? -- given it's annually seen on the West Coast after the breeding season. It's possible these observed individuals nested in Alaska and, hence, migrated directly south after breeding.
In turn, the question then is whether these few sightings of Blackpoll should be termed vagrants, given many birders believe the term denotes disoriented individuals who have an in-born abnormality in their navigational abilities.
Consequently, the term vagrant remains an open question for birders wishing to debate the answer.
Perhaps the best solution is to simply use a different status identification as to whether a warbler sighting for one area deemed, for example, uncommon, unexpected and/or rare — and, thus, avoid the using the term "vagrant."
Meanwhile, consider rare sightings of warbler species on the East Coast and in the Midwest.
In these regions, it's not as common during the non-breeding season to have West Coast warbler species show up, but it does occur.
For example, in my home state of Wisconsin, it's a "big deal" for birders to see a Townsend's Warbler — which is one of the most common non-breeding season warbler species in the SF Bay Area (where I primarily live now).
A good site to check for vagrant warbler sightings throughout the USA: ebird.org
A 2006 sighting of Townsend's at Sheridan Park in the Milwaukee area coaxed oodles of birders to view this vagrant. Go to the following ebird link:
http://ebird.org/ebird/map/towwar?neg=true&env.minX=&env.minY=&env.maxX=&env.maxY=&zh=false&gp=false&ev=Z&mr=1-12&bmo=1&emo=12&yr=all&byr=1900&eyr=2017
to see evidence of this Townsend's surprise visit to Wisconsin.
