Tuesday, February 4, 2014

Here comes the sun, here comes the rain

"Here comes the sun, here comes the rain..."
- Bridgit Mendler, Hurricane (VEVO video on Youtube)

7:00 PM 2/4 (Winter Stormcast Team) One look at the NWS watch/warning map, and you'll feel like "boarding up the windows and locking up (your) heart" like Bridgit Mendler says in her popular 2013 single. 

Though it may not be a hurricane, the number of people affected will be similar as Winter Storm Warnings plaster the country nearly 2,000 miles from end to end. 

NOTE: For preliminary details on the potential weekend event, please scroll to end of this post.

For the latest official statements on warnings in Maryland, visit the Baltimore/Washington NWS for the Western shore, and the Philadelphia/Mount Holly NJ NWS for the Eastern shore and southeastern PA. For central PA, visit the State College PA NWS office.

TONIGHT - Clouds increase toward sundown, and wet snow/sleet is expected before the overnight hours across most of the region. 
  • Ice amounts of 0.25" or greater are expected across a large area as indicated in the Winter Storm Warnings as denoted in DARK PINK on NWS maps.
  • Counties that border the PA/MD line should see freezing rain develop after midnight, continuing into Wednesday early to mid-morning. Areas in Pennsylvania under Winter Storm Warnings are likely to receive several inches of snow AND ice from freezing rain.
  • Southern counties of MD in a Freezing Rain Advisory (LIGHT PURPLE) may also see some snow linger into the early AM, before ice develops toward daybreak. 
WEDNESDAY - We know the trickiest situation of all, for everyone, is simply "When will temps rise above 32 F?"
  • Earlier computer models WERE showing that could begin between 7-8 AM, but later runs now depict much of the Maryland west of the Chesapeake Bay and northern Virginia may remain near 30 F until 10 AM. 
  • If precip is delayed or freezing rain starts later, the eventual warming Wed AM might also be delayed. The best plan is to be well-prepared and allow lots of extra time for your commute. 

THURSDAY - Cold conditions returns as High pressure builds in following this storm, refreezing and black ice are possible again tomorrow morning.

We have been tracking developments for a potentially significant to high impact storm this weekend.

It is too early to say with certainty if this storm will wallop Maryland and the Mid-Atlantic or miss the region entirely. We would like to point out the last time we saw a situation similar to this type of storm, it ended up swinging out to sea and missed the major cities entirely!

ABOUT THE LIQUID: It should also be noted that current liquid projections as developed by the spot-on meteorologists at the NOAA Weather Prediction Center are not as "robust" as one might think for the all the hype this hypothesized storm has received.

In the section below, we are outlining three possible scenarios for this event. The enclosed NOAA map shows the current NWS projection for 8 AM Sunday morning, based on information available at present. A scenario map will be posted tonight to accompany the text.

At this point, we believe all three of these scenarios have an equal chance of occurring, and we will assign confidence intervals and probability to the list on Wednesday.

  • SCENARIO A (WET THEN WHITE) Low pressure moving north out of the Gulf of Mexico on Saturday travels west of the Appalachians, producing a widespread wintry mix ahead of it. Some of this energy is transferred into a coastal storm which in Maryland would promote a "rain changing to snow" scenario from the major cities to the coastal communities. Lower liquid-to-snow ratios would yield lesser snow amounts by end of the storm, perhaps 6" or so due to the high water content of the storm.
  • SCENARIO B (SNOWBOOM) Low pressure developing on the heels of a residual frontal boundary in the Gulf of Mexico deepens rapidly as it moves from the Southeast to a position just off the VA/MD coast by Sunday afternoon. Some computer models, including the often touted European, suggest this outcome would produce 12 or more inches of snow for the I-95 corridor, if more liquid is incorporated into the storm with higher snow ratios in a colder environment.
  • SCENARIO C (CHRISTMAS 2010) In a setup similar to the Dec 25-26 near miss for the Mid-Atlantic, the upper level trough swings across the region faster than expected. While the storm develops in the southeast as expected, once it reaches the Virginia capes, the momentum of the trough pulls much of the energy out to sea. Heavy snow brushes the coastal communities from Virginia Beach, VA to Ocean City MD and Atlantic City, NJ but the remainder of the region experiences only flurries. 

We would prefer not to get your hopes up for any ONE of these scenarios regarding a storm that does not  yet exist, and is still 4-5 days away. By Wednesday afternoon we may have a more solid grasp on narrowing these scenarios down to two outcomes.

Best regards,
The Mid-Atlantic Winter Stormcast Team
(Collaborators: M/A Coordinator & Meteorologist Justin Barker, Forecasters Connor M., Jason M., Mike N., J. Baron, Mintong N., Dr. Pete W., Advisors R. Foot and B. Lear)