I would like to see the actual weed up close??? Please send another photo. However, just at first glance, and judging from the phone calls we've gotten at our Plant Clinic this month, it may very well be Poa annua, Annual Bluegrass. It's a tough one to eradicate. To help you decide if what you have is Poa annua, please take a look at these photos:
https://cdn.domyown.com/images/content/poa-annua-in-grass.jpg
Here's what to do:
Hoe and hand-pull the annual bluegrass to remove it, and of course, maintain healthy turf (proper mowing, irrigation, fertilization) to out-compete the weedy grasses.

See attached photos. It has a fern like appearance.

Ah--that's moss.  You're not alone. This is a very popular question this month. So much so that I wrote an article for our local paper in SW WA. This will tell you exactly what you need to do!

It’s a love/hate relationship for many of us. I love the verdant flocking of deciduous trees in deeps woods—looks like something from a Dr. Seuss book! But if you are trying to have a well-manicured lawn in the PNW, let's just tell it like it is: moss is a weed!

Moss grows so well over the winter in our lawns because the grass is dormant, exposing more bare earth to moss spores. And it's wet--hey, we live in the PNW--of course it's wet. Not to mention very little winter sunlight, the major enemy of moss. Moss also loves soil that's acidic, and we have that, too. So what can we do about it?

Have you noticed that moss usually appears in areas where grass struggles to grow, but where weeds invite themselves? That's an area where your lawn is "sick," for one reason or another. One of the best ways to deter moss is to have a healthy lawn so the grass can outcompete the moss and weeds. Always try the following cultural methods of controlling moss before escalating to chemical control. In a nutshell, to keep moss at bay: (1) let the sunshine in; (2) mow properly; (3) manage soil moisture properly; and (4) create good soil conditions for healthy grass.

Sunlight: Believe it or not, the best way to control moss in your lawn is to increase sunlight--prune trees to at least 6 feet from the ground, and perhaps thin the branches to allow more sunlight. If you don't create more light, the moss will come back regardless of what other steps you might take to eradicate it!

Mowing: Don't cut your grass too short. If you cut it shorter than 2 inches, you are inviting moss and other weeds into your lawn. Mow once a week to keep your lawn between 2-3 inches. Longer grass will put down deeper roots, and mowing it frequently will increase the density of the grass. Ultimately, it will be difficult for moss to invade and thrive.

Soil fertility: Moss loves acidic soil. You may need to add lime to maintain the pH around 6.0-6.5. Lime won't kill the moss, but it will help your soil to keep good nutrient values. Have your soil tested in a laboratory. It costs between $24 and $36, and the money you spend will save you money in the long run--you won't be buying products that you hope will take care of the problem--the report will tell you exactly what you need. Feed your lawn to keep it lush. For established lawns, buy a product that is high in nitrogen (N), low in phosphorus (P), and moderate in potassium (K); for example, NPK-3:1:2 or 4:1:2. Apply 1 pound of actual nitrogen at each application four to six times a year in spring and fall. Lush growth will overcome the mossy areas.

Irrigate properly: Moss loves wet conditions. There are some steps you can take to keep the wet affected areas less hospitable to moss--install French drains or a rain garden to divert rain runoff. When you water, plan on giving it ¼ inch each time you water, 4 to 6 times a week, totaling 1 to 1 ½ inches per week, especially during our dry summers. Measure the water with a rain gauge or a tuna can in the watered area.

If following the above guidelines doesn't work, there are other options. From mid-March through April when moss is actively growing, you can rake or dethatch your lawn in mossy areas to remove the dead grass stems and moss. You will probably need to overseed the dethatched area. First apply fertilizer as directed above, then spread lawn seed over the area. Plant a fine fescue like creeping red fescue in shady areas. If your lawn has shade and sun, plant a combination a perennial ryegrass and fine fescue. After seeding, mulch with a bit of straw, and water daily for at least two weeks.

Chemical products should be used only after using above recommendations. Please be sure to follow all directions on the label!

An environmentally friendly option is to apply products containing ferrous, iron, or ammonium sulfate from mid-March through April. Examples include Lilly Miller Moss-Out! for Lawns and Scotts Turf Builder with Moss Control 22-2-2. Ferrous sulfate will permanently stain concrete and other surfaces, so sweep any scatter from driveways and walkways. Complete fertilizers with iron sulfate will kill moss rapidly, and stimulate health grass growth at the same time. Wait until the moss is dead (usually around 2 weeks), rake it up, and then overseed.

Here’s to a lush, green lawn this year—and if you keep a healthy lawn, it won’t be moss green!

Resources:

Pacific Northwest Plant Disease Management Handbook Lawn and Turf-Moss

Oregon State University: Maintaining a Healthy Lawn ec1521

Oregon State University: Managing Moss in Lawns in Western Oregon EM 9175

Washington State University: Hortsense : Lawn and Turf Moss Factsheet

University of Alaska Fairbanks: Moss Control in Lawns HGA-00133

Thank you! Very helpful.