Forecasters add "rain" to snow chances Tues/Weds

The official BWI-Marshall forecast from Sterling calls for  "a chance of rain and snow" beginning sometime after 1 p.m. Tuesday. The afternoon high is predicted to reach 39 degrees. That' still a bit cold for this time of year, but would clearly seem to favor rain over snow. The surface temperatures would remain above freezing right through Tuesday night and Wednesday, if the forecast holds up.

The trend - at least in Sterling - seems to suggest they are siding with an analysis that would move the storm track more to the north and west, allowing more warm Gulf and Atlantic air into the region to erode the deep cold we've been dealing with this weekend.

On the other hand, the morning forecast discussion from Sterling suggests plenty of lingering doubt, and not just about the temperature: "... MY CONFIDENCE IS STILL NOT THAT HIGH THAT ANY PRECIPITATION WILL OCCUR DURING THE DAY TUES."

Sterling has acknowledged the uncertainties that remain in the various supercomputer forecast models about just where this storm will go:

"AS OF TONIGHT...NOTHING HAS CHANGED. LOOKING AT THE SURFACE LOW-PRESSURE POSITION OF THE 3 MAJOR MODELS AT 12Z [7 a.m.] WED - NAM [MODEL] SHOWS IT OVER RDU [RALEIGH-DURHAM] ...ECMWF NEAR HAT [HATTERAS]...AND GFS LAGGING SOUTHWARD TO ATL [ATLANTA]. TO ADD TO THE CONFUSION THE SREF HAS THE LOW EAST OF ACY [ATLANTIC CITY].

"FOR TUES NIGHT WE HAVE CHANCE OF SOUTH WESTERN 3/4 OF THE CWA [FORECAST AREA] W/ LIKELY RAIN/SNOW FROM I-95 EAST...THEN CHANCE RAIN/SNOW SOUTHEAST OF THE MOUNTAINS MAJORITY OF THE AREA DURING WED. GIVEN THE WIDE MODEL DISPARITY THAT SEEMS LIKE A REASONABLE PLAN OF ATTACK...

"BUT CONFIDENCE REMAINS *LOW* W/ THIS SYSTEM. MODELS HAVE HAD GREAT DIFFICULTY W/ COASTAL STORMS THIS SEASON...AND UNFORTUNATELY THIS ONE MAY HAVE THE GREATEST MODEL DIVERGENCE OF ALL.. SO WE`LL ALL WAIT AND SEE HOW THIS STORM DEVELOPS AND MAKE ACCORDING CHANGES TO THE FORECAST. STAY TUNED."

UPDATE 5:40 p.m.: Eric the Red has checked in with his assessment. The storm is slowing down, and that may move sigificant snow off the table. Here's Eric:

"The storm is slowing down, which in turn is allowing the high to our north time to slip offshore.  Not good.  As a result, we lose the mechanism to lock in the cold air... and really become totally at the mercy of the final storm track when it comes to getting any snow. 

"To make matters worse, the models are all over the place.  In short, we still have a shot at a signficant East Coast storm.  But the storm has slowed down, which ... which takes [our] snow chances down a notch.  The target period is now Weds into Weds night."

Like the nice man said, stay tuned. In the meantime, we have had another cold night, but not as cold as Friday/Saturday at 6 a.m. We did fall to a low of 5 degrees here at 6 a.m. on The WeatherDeck in Cockeysville. Between 9 and 10 a.m., the mercury jumped from 9 degrees to 21 degrees.

The overnight low of 13 degrees at BWI-Marshall was nowhere near the record of 0 degrees for a Jan. 23, set in 1936. The record for Jan. 22 was minus-7 degrees, set in 1984. The 6 a.m. readings elsewhere around the region (not necessarily the lows for the night) looked like this:

BWI-Marshall:  17 degrees

Maryland Science Center:  21 degrees

Baltimore Sun:  20 degrees

Martin State Airport:  18 degrees

Reagan National:  20 degrees

Dulles International:  15 degrees

Salisbury:  18 degrees

Easton:  19 degrees

Ocean City:  17 degrees

Annapolis:  20 degrees

College Park:  19 degrees

Oakland:  10 degrees

Cumberland:  23 degrees

Gaithersburg:  14 degrees