Midweek storm update - Tuesday noon
There's a lot of disagreement on this storm - some have us getting slammed with 8-12 inches of snow, some have us getting a coating to a couple of inches. Potential complicating factors like timing, mixing, borderliine surface temperatures, sun angle, and the formation of a "dry slot" (an precipitation-free area that forms inside a precipitation field) have made meteorologists reluctant to make a definitive forecast.
(Some in the meteorological community even speak of this as a "nowcasting" event - one for which all meteorologists can do is watch the storm as it happens and project what will happen next. What this really means is that they can't commit to a forecast, so they invented an oxymoronic term to deflect attention from this fact.)
So here is my best semi-educated guess:
Light snow develops around 7-9am Wednesday for our area, becoming steadier toward late morning. We will see the snow mixing with rain between 10 and 1, then becoming all rain for a time in the afternoon before changing back to all snow by 5 or 6pm Wednesday. The snow will continue through the evening, will taper a bit overnight, and will end just prior to the Thursday morning rush.
School closing meter:
Chance of cancellation Wednesday: 60%
Chance of delay Wednesday: 15%
Chance of early dismissal Wednesday: 35%
Chance of cancellation Thursday: 70%
Chance of delay Thursday: 80%
Accumulations:
Philadelphia and points south and east, 1-3 inches, lots of mixing
Northern and western suburbs of Philadelphia (much of Bucks, Montgomery, and Chester Counties), Reading, Allentown, 4-6 inches, a bit of early mixing; locally higher amounts
Lancaster, York, northern Maryland, moderate mixing, heavy snow, 6-10 inches
So that's my call as of noon. I will send out updates this afternoon and/or evening if my thinking changes...