Wait for ground truth

This time in Baltimore, 
wait for "ground truth."

• EAST-WARD DIVING CLIPPER TO CROSS SOUTHERN OHIO VALLEY INTO MID-ATLANTIC LATE SUNDAY NIGHT INTO MONDAY

• COMPUTER MODELS SHOW HIGH MOISTURE SYSTEM SIMILAR TO JANUARY 6 - MODERATE PROBABILITY OF 4" OR MORE 

• WINTER STORM WATCHES POSTED FROM BALTIMORE METRO NORTH THROUGH NYC AND BOSTON TO CENTRAL MAINE.

Latest NOAA liquid projections show 0.50" or more for southern I-95 corridor, 
in excess of 1.00" for metro areas to New York City and into most of New England

6:30 AM 1/25 - UPDATED STATEMENT IN PROGRESS

With the NWS Advisory Map lighting up overnight straight to Maine, the "Boom" scenario is becoming more probable as a faster arrival of the clipper into the Mid-Atlantic with a faster development of the coastal Low puts the I-95 corridor under an increased risk of seeing 4 or more inches of snow. 

The projected surface map for 7 PM tonight displayed left shows the situation becoming a battle for control of the "Route 30" corridor between a southward pressing Arctic High and the Low developing underneath as it slides East.

A HYBRID CLIPPER AND A SCHEMING ARCTIC HIGH:

• Unlike traditional clippers that just swing through unimpeded by a High pressure system to the north, this one has to battle for control of the map as it moves East.
• This will enhance Easterly flow ahead of the system while the High delivers cold Arctic air, creating an ideal arrangement for snow,
• The outcome will be a tale of two different storms. The west to east clipper will eventually deliver it's energy to, and form a secondary coastal Low that should turn the corner and head north, bringing heavy snow to the northeast corridor.
• We think the cards are not yet all played, though. Southward pressing Highs like this can play a steady quiet hand through the round, then shoot the moon when you least expect it. Areas south of Baltimore and on the Eastern shore should stay alert for a changing forecast if this High tries to drop that Queen of Spades.

11:00 PM 1/24 - WSC TEAM ADVISOR'S STATEMENT 

Before everyone takes off into snowfall projection land for this next event, there is an important weather concern our Advisors and Senior Forecasters wish to bring forward. This message was also shared with our partners, clients and Powderhound Insider subscribers.

BOOM OR BUST? We believe there is both an increasing probability of a blockbuster event, AND an equally strong chance for a major bust. We have seen this kind of setup before, and we've seen the negative reaction from readers when a big forecast goes belly us. Here's the issue:

• "Clipper to Coastal" type energy transfer forecasts are fraught with peril. Sometimes they come together like a charm, other times you are expecting 6"+ of snow, and get clouds.
• A healthy and moisture laden clipper IS coming rapidly East from the northern Plains. A large coastal storm should develop on the heels of that clipper energy as it reaches the Atlantic.
• However, the scenario concerning us is that the Baltimore-DC region will be whipped into a frenzy just like this last dud (which we also expected to be a significant snow/ice event too....). Winter Storm Warnings will fly, then the snow will come down in sheets. Then some school districts may may pre-emptively announce closures Sunday night thinking that being proactive is always better.

Then--- at 3 AM, it shuts off-- and, crickets. The supposed energy transfer from the clipper to the coastal occurs too late. The front end snow turns out to be much less than we thought (when does that ever happen?) and there's a 12 hour window which was supposed to be all snow, and ends up as all nothing. Crews begin cleaning up, and viola! By 6 or 7 AM, many lots and roads are improving. 

But Monday would be beyond salvaging. Businesses and schools would be already closed, when they could have squeaked out a 2-hour delay or modified hours. It is true several models are showing 0.60" or more for BWI airport, and that translates to 6-8" easily, but we've seen the models overproject on snow several times this winter.

This system is not a traditional coastal, nor is it a customary clipper. It's a clipper-to -hybrid-to-coastal, and it MIGHT become an example of our old rule: "Storms from the West don't bring extra rest." (If you work in or attend a school system.)  For now, the one lesson we want to convey to all essential staff whose decisions impact their organizations:

This is one time we suggest you wait for ground truth to prove the forecast. 

Don't pre-emptively close Sunday night just because it looks like a blizzard, even if there's a Winter Storm Warning. Just wait and see what conditions look like at 5 AM Monday. Maybe this time ground truth, or lack of it, is all the observations you will need to make the call.