The chances for accumulating snow in Central Maryland late Monday and Tuesday have inched upward a bit, now set at 70 percent for Tuesday, according to forecasters at the National Weather Service.

But just how much snow is likely remains unclear. The problem is the difficulty of predicting whether, where and how two separate storm systems might come together in the region. If the timing is right, and the two systems "phase," we get more. If they straggle through separately, we get less. The tracks matter, too, as the more southerly storm could drift off the Southeast coast and out to sea before giving us much trouble.

The NWS forecasters out at Sterling say a 30 percent "chance" of snow late Monday will evolve to a 70 percent "likely" snowfall Tuesday and 60 percent Tuesday night.

For now, they don't think the more northern storm - riding the northern "polar" jet stream out of the Great Plains and crossing our region Tuesday - will phase with the storm spinning up over the Gulf until they've passed off the Atlantic coast:

UPDATE, 8 a.m. Sunday:

"IF THIS PHASING OCCURS PAST THE MID ATLANTIC...THIS WILL LIKELY PREVENT
A SIGNIFICANT SNOW EVENT ACROSS THE CWA [FORECAST AREA] AND THIS WOULD LIKELY BE
MAINLY AN ADVISORY SITUATION TUESDAY AND TUESDAY NIGHT.
HOWEVER...IF THE PHASING OCCURS SOONER...THEN PORTIONS OF THE CWA
COULD SEE A MORE SUBSTANTIAL SNOWFALL /ASSUMING NO MIXING...WHICH
COULD OCCUR ACROSS SOUTHERN MD/.

"RIGHT NOW WE ARE LEANING TOWARD
THE FORMER IDEA OF PHASING OCCURRING NORTHEAST OF THE MID ATLANTIC
COAST...BUT THIS IS CERTAINLY NOT WRITTEN IN STONE GIVEN THE
COMPLEXITY OF THE SYNOPTIC SITUATION SO PLEASE STAY TUNED."

Meanwhile, AccuWeather.com hasn't pushed its predictions past Monday for the mid-Atlantic (updated map). But their assessment through Monday shows some nasty weather ahead for the South. And we would seem to be next in line.

Saturday morning's snowfall didn't amount to much in Central Maryland, although McHenry, out in far western Garrett County saw 5 inches. Greensboro, in Caroline County reported 2.7 inches. A few spots saw 1 to 2 inches, but most of the rest of us had less than an inch.