Major winter storm likely Thursday into Friday after sun makes a rare appearance

» UPDATE: Read more here for the latest forecast on Thursday’s expected snow

After what is looking like a rough day for the surviving snowmen, forecasters say a significant snowfall and-or a wintry mess is likely later in the week, and if you get the feeling you read or heard something similar last week or the week before, that’s perfectly understandable.

The procession of storms in the East marches on, incited by historically cold air that has penetrated all the way to the U.S.-Mexican border and is interacting with the warm moist air of the Gulf of Mexico, forecasters say.

The sequence could climax with snow, perhaps several inches, on Thursday, with a hazardous topping of sleet and freezing rain perhaps into Friday, says the National Weather Service, which likely will post a winter-storm watch later Tuesday.

As for Tuesday, itself, it is expected to produce something completely different — abundant sunshine for the first time in eight days and run toward a high of 50, last seen on Feb. 5, which was several inches of snow ago.

Cold air is forecast to build back into the region after a front nudges through the region, and it will be place as the storm approaches form the Ohio Valley Thursday and spawns a coastal low. The weather service says snow, possibly 3 to 5 inches, could accumulate before warmer air moves in aloft at some point and the melting flakes mutate to sleet and freezing rain.

In short, the forecasts for the next 48 hours and even on Thursday are going to be moving targets and those snow maps will be drawn in pencil.

We should be used to this by now. We keep learning that a computer model’s capacity to foresee a snowstorm is rivaled only by its capacity to erase it.

» READ MORE: Why Philly storm forecasts have been conflicting and constantly changing this winter

For the last several days, snow threats have been popping on the models, only to mutate or disappear altogether, and then resurface.

The volatility took a benign turn on Monday night as a threatened ice storm failed to materialize as temperatures in most of the region never went below freezing. A “trace” of ice was reported in Willow Grove, Montgomery County, and that was pretty much the ballgame.

Meteorologists say the models have been having trouble keeping up with all the storm traffic racing across the country and more recently brewing in the shockingly frigid Gulf region.

“That’s crazy, crazy stuff,” said David Dombek, a meteorologist with AccuWeather Inc.

At lunchtime Monday, the temperature in Brownsville, Texas, right on the Mexican border, was 28 degrees, and a winter storm warning was in effect. The normal high for Feb. 15 would be 74. In McAllen, Texas, the low temperature of 21 broke the record for the date, 35, by a full 14 degrees.

The fact that so much cold air has invaded the central United States is related to the modest moderating trend around here, said Dombek: The planet has only so much cold air available at any given time.

For forecasters, “It’s a rough pattern,” said Nicholas Carr, a meteorologist at the National Weather Service office in Mount Holly.

We’ve noticed.