It won't be much. But forecasters at Sterling NOW are warning that this rain could turn to snow just before rush hour Friday morning around Baltimore. It's not likely to accumulate much on the roads. But a burst of heavy snow showers here and there could stick just long enough to slick the roads as commuters are heading out.

I'm betting that will spook some school systems - especially north and west of I-95 - just enough to delay openings. We'll see.

But it's a tough call. Forecasters have been struggling all week with this complex and powerful storm system. And pinning down the rain/sleet/snow line in central Maryland has always been a winter challenge.

Earlier forecasts today seemed to downplay the risk of wintry precipitation to Baltimore and Washington. The tone seems to have changed tonight.

Here's part of this evening's discussion from Sterling:

"FRIDAY MORNING FORECAST IS EXTREMELY CHALLENGING. WESTERN EDGE OF
THE RAIN SHIELD WILL HAVE MOVED EAST...BUT THE UPPER LOW OVER THE
DEEP SOUTH NOW /WHICH PRODUCED SNOW OVER LOUISIANA AND MISSISSIPPI
TODAY/ WILL MOVE NORTHEAST ACROSS THE REGION.

"UPPER LOW WILL LIKELY WEAKEN ... BUT WILL LIKELY BRING SOME
PRECIPITATION RIGHT AROUND THE MORNING RUSH HOUR ... ALTHOUGH SURFACE TEMPERATURES ARE STILL FORECAST TO BE ABOVE FREEZING EAST OF THE MTNS. SNOW IS THE PREFERRED P-TYPE NORTH AND WEST OF INTERSTATE 95...WITH A RAIN/SNOW MIX IN BALTIMORE AND WASHINGTON AND AREAS SOUTHEAST OF THERE /EXCEPT FOR ALL RAIN IN
LOWER SOUTHERN MARYLAND/.

"AM MOST CONCERNED ABOUT LIGHT SNOWFALL
NORTH AND WEST OF BALTIMORE WASHINGTON...WHERE THERE IS THE
POTENTIAL FOR AN INCH OR SO OF SNOW. RECALL THAT [Sterling] NOW ISSUES
WINTER WEATHER ADVISORIES DURING HIGH IMPACT TIMES /IE RUSH HOUR
TIMES/ WHEN AN INCH OF SNOW IS EXPECTED.

"AN INCH OF SNOW IS NOW FORECAST ACROSS THE NORTHWEST SUBURBS OF BALTIMORE AND
WASHINGTON ... ACCUMULATIONS WOULD MAINLY BE ON NON-PAVED SURFACES /GRASS...CARS...ETC/ WITH
TEMPERATURES MAINLY IN THE MID 30S...BUT IF THE SNOW COMES DOWN HARD
ENOUGH IN A BURST THEN ITS NOT OUT OF THE QUESTION FOR A SLOPPY
ACCUMULATION ON SOME ROADS."

However it falls, it is plenty of water. Here are the storm's total accumulation estimates, based on radar returns.