A mostly clear and chilly night is expected with most areas
away from Philadelphia and the Atlantic
Ocean dipping down into the twenties for low temperatures. In Philadelphia and along
the coast, temperatures will drop to around freezing.
We start off with some sunshine for Monday, followed by
increasing clouds. Precipitation should develop around or after 5 PM on
Christmas Eve ( a few models bring this in a bit earlier). This precipitation
will be in response to an area of low pressure moving into the Ohio Valley
and Central Appalachians . I am fairly
confident it will snow north of the Pennsylvania Turnpike and north of Route 1
at some point during this event. There is still some uncertainty as to where
the rain vs. snow line sets up and our current thinking is it will be north of
or around Interstate 95 and Interstate 195. The models have been waffling with
the location of this line run to run and have trended slightly cooler today.
Precipitation intensity has also come up a smidge introducing the chance of
evaporational cooling turning the rain to snow in the areas that are right on
the cusp of rain vs. wet snow during times of heavier precipitation (but this
appears to be short-lived with warmer air coming in aloft). I also think the
models might be underestimating the strength of the high to our north to an
extent and this would translate to the models being too warm at the surface
(but it still looks a tad too warm when taking this into account). It is going
to be hard to get it snow tomorrow outside of the northern areas; although it isn't impossible to get processes to work out perfectly in favor of snow as far
south as Cherry Hill, Philadelphia , and Toms River Southern
Delaware have a decent shot at receiving just rain. In-between
there, it could go either way…but the odds favor rain or a mix of rain and snow
(with most mix during the initial hour or two of precipitation) vs. all snow.
Also, the surface temperatures will probably be above freezing, meaning in this
questionable area, it would have to take steady snow for it to pile up. Don’t get
your hopes up for much. As this precipitation tapers off, drizzle is likely
going to occur. In the Poconos and perhaps the Lehigh
Valley into Central
Pennsylvania , surface temperatures could drop back to 32 degrees
allowing for patchy freezing drizzle. Again, at this time, temperatures appear
too mild a snowy solution with the exception of northern areas. Those northern
areas include Reading , Allentown ,
Quakertown, and Mount
Pocono Central Pennsylvania mountains,
you probably stand the best chances of getting accumulating snow out of this
with 1 to 3 inches possible. Some localized totals of around an inch is
possible immediately below Blue
Mountain Allentown might
pick up a coating to an inch of snow. By the way, the temperature profile could
favor some sleet mixing with the rain in the questionable area as well.
There could be some patchy fog as well in the evening hours of Monday into Tuesday Morning.
Next up is the Wednesday into Thursday storm that will spawn
the Boxing Day rain/snow/sleet/ and freezing rain event for the Mid-Atlantic. This
system is moving onshore to the West Coast as I write this post. This likely
means we aren't getting a good sampling just yet from our weather balloons and
it may take another 24 hours to ingest some decent data into the model outputs.
Also, I tend to favor letting the first system get through the system before
pinpointing the setup of the next as the exact track of the first system can
greatly influence what happens with the energy behind it. The models have also
been waffling with this system as well and we are not getting a complete
picture at this moment of the track and strength of the secondary low that may
form along the coast. Does this low hug the shoreline, move 50 miles offshore,
or move right over the Delaware
Valley Delaware
Valley Philadelphia
could see some brief sleet or freezing rain, followed by rain. Some models
indicate a drenching rain. This track would also introduce strong wind gusts to
the picture, especially along the coast and east of the low pressure center. How
warm we end up getting varies based on the outcome of the storm and its track.
The Poconos would see snow and sleet, transitioning over to freezing rain with
the potential there of an ice storm. Colder air does rush in as the system
departs on this consensus track, meaning that flurries and snow showers will
return for Thursday with a gusty wind. Of course, there is probably going to be
a tricky area in the Lehigh
Valley
Dare do I say there is a third system potentially in the
works to impact us next weekend! It is way too early to speculate, especially
given that some models don’t even have much of anything happening. Let us get
through the mid-week storm.
Merry Christmas and Happy Holidays!
