Updated at 5 pm with information from the Portland Bureau of Transportation

Here we go again.

Snow is back in the Portland forecast. And it could mess up Tuesday morning’s commute.

How bad will it get? Once again, it’s hard to tell.

National Weather Service meteorologist Will Ahue said the heaviest precipitation is expected between midnight and 5 or 6 a.m. Tuesday. Some areas could get a dusting of snow, he said, while others could get a couple of inches.

Even if Portlanders don’t get snow, they’ll probably experience heavy rain.

Sounds like a blast.

A winter storm watch is in store for the Portland and Vancouver areas, as well as the western Columbia River Gorge, from late Monday through Tuesday afternoon. And the weather service says 1 to 2 inches of snow are possible Monday night in Portland.

One to 2 more inches could accumulate Tuesday.

Heavy precipitation expected tonight could allow snow levels to lower to the valley floor and POTENTIALLY bring low-elevation snow to portions of the N Valley and SW Washington. For the latest forecast visit https://t.co/3SFImIwQhQ or https://t.co/Mu5FYethCK. #ORwx #WAwx #pdxtst pic.twitter.com/INDvi6Xuut — NWS Portland (@NWSPortland) February 11, 2019

Ahue estimated there’s about a 30 percent chance — maybe a bit more — that downtown Portland is blanketed in white when residents awake Tuesday. But there’s also a chance most people crawl out of bed and see snowless streets.

Different parts of the Portland area could see drastically different amounts of snow, he said.

And if that’s not enough to make Portlanders’ heads spin, the area could also see some flooding.

It’s among the places under a flood watch from 7 p.m. Monday through late Tuesday night.

Ahue said metro area flooding is most likely along Johnson Creek in Clackamas and Multnomah counties.

Rain could cause overnight flooding that impacts traffic along Johnson Creek Boulevard and Foster Road, according to an advisory sent by the Portland Bureau of Transportation Monday afternoon.

“While we expect minor street flooding because of heavy rain in the area, we do not expect streets to be flooded by the creek,” the advisory states. “Flooding could affect some low-lying areas along the creek where homeless individuals camp and some private properties in the area.”

Portland park rangers and social service staff contacted people experiencing homelessness in areas near Johnson Creek to give them warnings about potential flooding, the advisory said.

The city is also providing free sand and sandbags to those who want to take extra precautions against flooding. Bring your own shovel to fill sandbags at the following locations:

SE 88th Avenue just south of Holgate Boulevard in the parking lot at Lents Park. Enter parking lot at the bottom of the hill, and follow one-way traffic to the sand pile at the exit on the east side of SE 88th;

SE 111th Avenue and Harold Street at the southeast corner of the intersection; and

SW 42nd Avenue and Vermont Street in the lower parking lot of Gabriel Park; enter Gabriel Park from Vermont.

A flood gauge near 152nd Avenue and Foster Road had reached 5.5. feet Monday afternoon and was expected to reach 10 to 11 feet Tuesday morning.

“When the gauge reaches 11 feet it is considered flood stage, when the creek overtops its banks in some places,” PBOT said. “As of Monday afternoon, the gauge is forecast to reach anywhere from 10 feet to more than 11 feet on Tuesday morning, and recede quickly. The flooding threat is expected to be reduced within a few hours.”

Residents can always expect a chance of ponding and urban flooding during heavy rains, as well. The Oregon Department of Geology and Mineral Industries also warned Monday that heavy rain can trigger landslides and debris flows in steep areas. That risk is heightened in areas burned by fires.

Yeesh.

Looking for a silver lining to Portland’s crazy weather picture? Temperatures are in the mid-40s Monday afternoon, and evening commuters won’t see any snowflakes.

We’ll save the snow for Tuesday … maybe.

-- Jim Ryan; jryan@oregonian.com; 503-221-8005; @Jimryan015

Visit subscription.oregonlive.com/newsletters to get Oregonian/OregonLive journalism delivered to your email inbox.