When were these pictures taken? Summer or just recently?

Overseed it in early spring - it'll fill in. One of the regular chores when you have a fescue lawn.

Pictures were taken the day I posted. I do let it grow tall but mow often so as not to cut off more than half.

When would be a good time to overseed? Our weather is crazy right now and it already feels like spring. Any info on where to get Seed and how much to apply would be appreciated :)

The tan spots/area looks like someone walked on the grass or even mowed it during a frost. The horseshoe shaped areas devoid of grass is probably were a mower is turning around and tearing up the turf. As for the fist sized spots, tall fescue sod is usually 25 to 50 percent or more kentucky bluegrass and that kentucky bluegrass is going to get taken out by either disease or drought (usually summer patch) and that leaves just the clumpy tall fescue. In the early fall, probably late september for you, aerify and seed tall fescue at a rate of 10 pounds per thousand. Prime Time is very good tall fescue blend and you can buy it on Ebay.

gsweater said, Overseed it in early spring - it'll fill in. One of the regular chores when you have a fescue lawn.

Noooooooooooooo! Well, sort of yes. One of the regular chores of a fescue lawn is reseeding, BUT you do it in the fall, not in the spring. Spring seeding leads to crabgrass in July. Fall seeding should give you sturdy and dense sod by April that resists weeds and will withstand the summer heat.

Anything I can do now to avoid a lawnful of weeds by the time fall comes around? My fear is that those empty patches will just fill with crabgrass or some other weed.

Any other recommendations on seed type and where to buy? Is Prime Time a good choice?

Use a preemergent herbicide with active ingredients Prodiamine or Dithiopyr. Apply the preemergent herbicide at a rate that will lose efficacy around the time you wish to seed. You can look at NTEP tall fescue trials and decide for yourself, however you won't find Primetime on the list. You have to look up each cultivar that is in the Primetime blend.

You could seed it, sigh. Just seed the holes and hope for the best. The problem with seeding in the spring is the daily watering is exactly what the crabgrass needs. If you just seed it and not go through the daily watering, maybe enough of your grass seed will sprout and help to fill in. It is still going to take a hit in the summer heat, so don't get too upset when you see grassy weeds come July.

I'm fairly certain the patchyness is due to the sod webworm infestation (and possibly other grubs) that we had last year. Only some areas of the lawn look like that, and other areas are lush and thick. The worst areas seems to be where there were bunches of moths flying up last year as we walked through them.

Also, is tall fescue okay for partial shade? It seems thinner in the more shady areas...

I'm wondering if I should lay down some sort of preventative against grubs/webworms? I was looking at the Guardian and Lawn Patrol products (beneficial nematodes). Any advice on grub treatment is much appreciated! When to apply, what rate, what product?

Tall fescue should be good in the shady areas.

Watch your porch lights in May and June for huge masses of beetles. If you don't have swarms of bugs, then you likely won't have a grub problem. If you do, then apply the nematodes. There is no huge hurry but get them down within the month.

Apply beneficial nematodes to a saturated soil. Run the sprinkler first to get an inch of water down. Then apply the nematodes and continue to water them in. They must have moisture in the soil to move around. I usually suggest applying them on the 3rd day of a 4-day rain event. For a lawn under 2,000 square feet you should get away with the small sponge of nematodes.