The computer forecast models agree on one thing: When the wave of energy in the upper air hits the coastal front, a storm will explode off the coast of the mid-atltantic states.
The coastal front is lined up along the southeast coast, where large areas of freezing rain and strong winds extend inland and are making travel impossible with over ten thousand already without power. Next the wave from the upper midwest collides with the front along the coast and ignites the fuse that blows up the storm off the NJ coast early Thursday.
The story for most areas is where the coastal front establishes itself after the storm winds up. Inland of the coastal front, lots of snow; on the coastal side, ice pellets and, perhaps rain.
For maps of the forecast snow and ice amounts, see>>>>>>
http://www.erh.noaa.gov/okx/
Scroll down and click on the “Storm Total Forecast” to see their take on the bottom line for snow amounts.
Here’s the technical stuff from the NWS 5am forecast discussion….Updates at:
http://forecast.weather.gov/product.php?site=NWS&issuedby=OKX&product=AFD&format=CI&version=1&glossary=1&highlight=off
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/…
ALTHOUGH THE 00Z AND BEYOND MODEL RUNS HAVE NOT CONVERGED ON AN
EXACT TRACK AND TIMING…THE SIGNAL IS THAT THE LOW WILL
ESSENTIALLY BOMB OUT S AND E OF THE AREA THU NGT. THIS IS IN THE
ENSEMBLES…GFS…ECMWF…GEM…NAM…WITH JUST ABOUT EVERYTHING
IN THE 970S INVOF CAPE COD. CONSENSUS TRACK IS JUST W OF THE
BENCHMARK.
FCST IS BANKING ON A STRONG CSTL FRONT DEVELOPING…KEEPING AREAS
NW OF THE FEATURE IN THE SNOW PERHAPS WITH SOME SLEET MIX AS
WARMING OCCURS ALOFT…AND AREAS ALONG THE ERN COASTS GOING TO
RAIN.
ALL AREAS WILL START AS SNOW LATE TNGT INTO THU MRNG. MAIN
CHALLENGE IS EXACTLY HOW MUCH FALLS BEFORE ANY CHANGEOVER ALONG
THE COASTS. IT IS ENTIRELY POSSIBLE THAT WRNG LVL SNOW OCCURS IN
THIS INITIAL BURST RIGHT DOWN TO THE BEACHES OF SERN LI BEFORE
CHANGING TO RAIN. FOR THIS REASON HAVE MAINTAINED THE WINTER STORM
WATCH FOR LI AND SERN CT.
Snow will start soon in North Carolina, by 7pm or so in DC and just after midnight for NYC.
For example, here’s a typical forecast for a northern suburb of NYC>>>>>>>
Tonight Snow likely, mainly after 3am. The snow could be heavy at times. Cloudy, with a low around 23. Northeast wind 5 to 8 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible.
Thursday Snow before noon, then snow and sleet. The snow could be heavy at times. High near 32. Northeast wind 10 to 17 mph. Chance of precipitation is 100%. New snow and sleet accumulation of 5 to 9 inches possible.
Thursday Night Periods of snow, mainly before 3am. Low around 23. Blustery, with a north wind 20 to 22 mph becoming northwest after midnight. Chance of precipitation is 100%. New snow accumulation of 2 to 4 inches possible.
The uncertainty is that different paths give us different amounts of rain vs. snow, so the snow total is totally different if the path is different.
My take: it’s all about how far the warm air gets pumped inland. How much is rain and how much is snow, not whether we get the storm. Either way, we don’t need it and Thursday will be dangerous in the northeast. For NYC Wednesday is ok and on Friday, it will go back to all snow, on and off as the storm departs.
Heads UP! 