Winter Weather Advisory extended for some counties

PITTSBURGH — Patchy fog could impact your plans late Wednesday and into Thursday.

LIVE weather updates NOW in our streaming apps and we'll have Severe Weather Team 11 coverage on the conditions on Channel 11 News starting at 4:30 a.m.

UPDATE 11 p.m. Wednesday: Visibility could drop as low as 1-2 miles at times, creating quickly changing travel conditions. A few icy spots will also be possible, especially in valleys where colder temperatures are slower to  move out.

Highs will eventually climb into the 40s, melting snow and keeping roads wet. Sunshine returns Friday, but another system moves in for the weekend with more rain showers.

UPDATE 9 p.m. Wednesday:  A Winter Weather Advisory has been extended until 1 a.m. for Armstrong, Clarion, Mercer, Indiana and Venango County.

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UPDATE 6 p.m. Wednesday: A Winter Weather Advisory has been extended until 9 p.m. for Armstrong, Clarion, Indiana, Mercer and Venango counties.

UPDATE 4:05 p.m. Wednesday: Rain and fog will slow your travels tonight.  Drains clogged by snow and ice could lead to ponding on area roads, so watch for quickly changing travel conditions.

PHOTOS: Snow slowing morning commute

UPDATE 1:50 p.m. Wednesday: The Mon Wharf will be closed starting Thursday and until further notice, the Public Parking Authority of Pittsburgh announced Wednesday. The decision was made after a flood advisory was issued for the Ohio River for Thursday and Friday.

Additional parking is available at the First Avenue Garage and Second Avenue Plaza.

UPDATE 1:13 p.m. Wednesday: The crash in the outbound lanes of the Parkway East has been moved to the right hand side.

Traffic is getting by in two lanes with delays.

UPDATE 12:55 p.m. Wednesday: PennDOT has lifted the speed limit restrictions on all roads except for I-79 north of Allegheny County, where the speed limit remains 45 mph.

UPDATE 12:46 p.m. Wednesday: Parkway East outbound is closed near Greenfield Ridge due to a crash.

UPDATE 12:00 p.m. Wednesday: The winter weather advisory has expired for Southwestern Pennsylvania, but there are still many icy and snowy roads.

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UPDATE 11:13 a.m. Wednesday: Some areas saw around 5 inches of snow this morning.

UPDATE 10:44 a.m. Wednesday: A Port Authority bus slid on ice and jackknifed into row houses in Pittsburgh's Uptown neighborhood.

UPDATE 10:20 a.m. Wednesday: A salt truck overturned in Pittsburgh's Carrick neighborhood.

The driver was taken to a hospital.

UPDATE 10:05 a.m. Wednesday: McKnight Road has reopened in both directions.

UPDATE 10:25 a.m. Wednesday: Meteorologist Scott Harbaugh said there will be some area that will see more than 4 inches by the time everything is done falling.

UPDATE 9:45 a.m. Wednesday: McKnight Road inbound has reopened at Babcock Boulevard.

The outbound lanes remain closed.

UPDATE 9:45 a.m. Wednesday: Snow, sleet and freezing rain will ease up a bit and will allow crews an opportunity to start to catch up.

UPDATE 9:36 a.m. Wednesday: All on-street bus routes are now delayed about an hour due to traffic and weather conditions, according to a tweet from the Port Authority.

Bus routes Y46 and Y49 outbound are blocked at 51 at Brownsville Road due to a jackknifed tractor-trailer.

UPDATE 9:21 a.m. Wednesday: According to a tweet from Pittsburgh International Airport, there are about 20 flights canceled to D.C., Philadelphia, Boston and the East Coast as of 8 a.m.

UPDATE 9:04 a.m. Wednesday: Allegheny County tweeted that their crews will be out until at least 9 p.m. salting and plowing

UPDATE 8:55 a.m. Wednesday: McKnight Road is closed in both directions in the area of lower Babcock Boulevard in Ross Township.

Police are redirecting traffic until the road can be treated.

UPDATE 8:30 a.m. Wednesday: The I-279 HOV lanes are closed until further notice due to weather conditions, according to PennDOT.

UPDATE 8:45 a.m. Wednesday: Pittsburgh Public Schools released a statement on social media after they did not cancel classes today:

UPDATE 8:41 a.m. Wednesday: Meteorologist Scott Harbaugh says the mix line is heading north fast. There is now freezing rain in Washington.

UPDATE 8:39 a.m. Wednesday: Inbound rive times are close to or over an hour across the area.

UPDATE 8:30 a.m. Wednesday: A wintry mix is falling in Washington. What started as snow changed to sleet and then to freezing rain.

UPDATE 7:30 a.m. Wednesday: Road conditions are deteriorating as snow picks up and more cars head out for the morning commute.

UPDATE 6:35 a.m. Wednesday: Snow continues to push north, with a wintry mix south of Interstate 70.

UPDATE 6:15 a.m. Wednesday: Snow has reached Pittsburgh as it continues to spread north.

UPDATE 5:40 a.m. Wednesday: Sleet is overtaking areas south of Interstate 70.

UPDATE 5:30 a.m. Wednesday: The worst travel conditions because of the winter storm are expected between 7 a.m. and 11 a.m.

UPDATE 4:45 a.m. Wednesday: Snow has started falling in Washington County before it overspreads the entire area later this morning.

ORIGINAL STORY: Moderate to heavy snow is possible during the morning hours. Expect delays and cancellations to build heading into the day.

A Winter Weather Advisory will be in effect Wednesday for much of the area, and a Winter Storm Warning for the mountains.

Snow will start before sunrise south of Pittsburgh, then move north through the rest of the area during the morning.

Roads will quickly become snow covered, and snowfall rates could be as heavy as 1 inch per hour at times. The combination of steady snow and rush hour traffic will lead to major delays as road crews try to keep roads passable.

STORM TRACKER: Hour-by-hour look at snow, wintry mix for Wednesday

Several inches of snow will fall, then a mixture of sleet and freezing rain will move into the area by mid-morning. A layer of snow, then a layer of ice on top will make travel hazardous through at least noon for many locations.

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Temperatures will climb above freezing by the afternoon, with the wintry mix changing to rain.

Rain could be steady at times, and drains clogged by snow and ice could lead to ponding on roads.

This is a tricky storm as warm air moves in from the south and snow changes to freezing rain, sleet and rain. Check back for updates from Severe Weather Team 11.

Cox Media Group