Be prepared for an ugly retail sales report on Tuesday

Wall Street is bracing for a disappointing June retail sales report on Tuesday.

Consensus expectations currently peg retail sales rising only 0.2% month on month in June and 0.5% when excluding auto sales.

These estimates come after a strong May report, in which retail sales rose 1.2%, and 1% when excluding auto sales.

But Michelle Meyer, US economist at Bank of America Merrill Lynch, thinks retail sales in June may have actually fallen.

Using internal credit and debit card data from the company, BAML estimates that June retail sales ex-autos dropped 0.1% month on month.

"This offset some of the gains over the prior two months, pushing the three-month moving average down to 0.2%," Meyer and her colleagues wrote in a note to clients on Friday.

"Growth also slowed on a [year-over-year] basis to 0.8% as the trend continues to suffer from the decline in gasoline spending at the start of the year... The softness in [our] spending data suggest caution heading into the June Census Bureau advance retail sales report given that the two measures trend together," they added.

The trend between BAML's internal data and the Census Bureau's numbers can be see in the chart below:

A decline in retail sales would likely be problematic because it is a significant part of the US economy. Personal consumption accounts for about two-thirds of US GDP, of which a large chunk is retail spending.

Overall, however, Fed Chair Janet Yellen doesn't seem to concerned about retail sales.

"Indeed, recent encouraging data about retail sales and light motor vehicle purchases in the beginning of the second quarter could be an indication that the pace of consumer spending is picking up," Yellen said in a speech Friday.

In that same speech, Yellen added that she expects it will be "appropriate" for the Fed to raise rates later this year.