Blizzard of 93

Great discussion from CTP this evening, ”Clouds Wed evening steadily lower/thicken-up late Wed night. Precip may arrive in the Laurel Highlands as early as midnight Wed night, and push northeastward towards the I-99 and I-80 corridor by sunrise Thu. Nearly all model guidance has a nose of warm air (+5C) at about 4-5 kft during the onset of precip, maximized over Somerset county. This will likely result in freezing rain for Somerset and Cambria counties during the morning Thu. Our preliminary freezing rain totals call for up to 0.25 inch of ice in the higher terrain of Somerset and Cambria Counties. Freezing rain impacts could be exacerbated by strong southeasterly winds, sustained 15-20 mph with gusts 30-40 mph. Strong winds and freezing rain may result in tree and powerline damage. As precip continues to overspread central PA during the daylight hours Thu, it will push into colder air. Although max wetbulbs aloft may be above freezing at the onset of precip, evaporative and dynamic cooling should bring the temp and td below freezing as the heaviest precip develops. Model guidance suggests the period from about 15z Thu - 00z Fri Thu will feature deep isentropic ascent and a fully saturated troposphere, with substantial upward motion in the DGZ aided by frontogenesis between 700-500 hPa. Our preliminary snowfall forecast calls for 4-6 inches of snow accumulation from AOO northeastward towards Potter and Tioga counties during this period of time. Gusty winds could result in reduced visby during moderate or heavy snow. After 00z Thu, the forecast becomes more uncertain. Warm air will advect northward, likely bringing the rain-snow line towards or even north of I-80. A dry slot aloft will significantly reduce the depth of the saturated layer, potentially resulting in the loss of ice within the clouds for a portion of the CWA. This part of the forecast depends largely on how quickly a secondary coastal low can develop - a stronger coastal low developing more quickly along the Mid Atlantic coast can draw in colder air to and more moisture, resulting in more snow accumulation Thu night into Fri. Additional snow accumulations during this period are most likely in our northeastern zones. Precip type, storm track, and storm intensity are still complicating factors that contribute to uncertainty at this time. We will continue to provide updates over the next few days as the system approaches and the forecast becomes more certain.”

CTP is starting to ramp up the Thursday potential… A potentially significant winter storm will brew over the central CONUS and spread into Pennsylvania on Thursday, lasting into Friday.

The 18z Euro ensemble snow map also increased snow amounts for the LSV this run.

The 18z Euro ensemble also improved for the LSV & CTP in general. The mean low tracks from eastern NC/VA border to the DelMarVa coast near OCMD to near Atlantic City, NJ.

We are going to be doing a lot of tracking between now & the holidays…buckle up!

Great post! This will be a fascinating storm to track. The best part is that we should have a couple of more storm chances to track as we approach the holidays!

Here is the 18z Euro snow map.

The 18z Euro has also improved snow chances for the LSV & shows the thump potential as well. The Euro tracks the low from Central NC Thursday afternoon to near Cape May, NJ by early Friday am.

Here is the 18z GFS snow map through Friday.

Yes, the 18z run starts all of us off with a mix changing to snow for the eastern half of PA. If the precip rates are moderate to heavy, dynamics could help the snow potential with marginal temperatures. If the low jumps from the central Chesapeake out to well off of the NJ coast like this run shows, we could really be in business.

6z Euro also came in better for Front end snow & mix for the LSV, especially from Harrisburg north & west.

Here is another view of the 6z GFS snow map for Thursday/Friday

The 6z GFS shows yet another option that could benefit CTP for the Thursday storm. The low track this run goes from NC to the DelMarVa to off the coast of OCMD to off of the NJ coast. Harrisburg & North & West if I-81 again do well this run.

The 0z Euro starts many of us off as snow but the LSV then switches to rain due to t to the inland track of the low. The I-99 corridor & northern PA do well.

The 0z GFS has a better solution for snow chances for the Thursday/Friday storm. The Harrisburg area I-81 corridor to the north & west do well this run.

Tamaqua? Maybe that’s @Voyager station set to his preference!

Lol, Is that MDT?

The 18z Euro Control run keeps most of us in the game for this Thursday/Friday.

The 18z GFS that I just posted agreed!

Yes, Christmas Eve Eve & Christmas Eve….the pattern should support cold with storm chances chances. What a run!

The 18z GEFS still has several ensemble members that are on or just off of the coast of the DelMarVa by 12z Friday am Lots of time to go to see where the final lines will be drawn.

The 18z GFS says that Harrisburg area & to the north & west is still in the game for Winter weather on Thursday

Most of the GEFS ensemble members are on or just off of the coast. Only a few inland runners this run.

The 12z GFS & GEFS are too close for Thursday/Friday for many of us especially back near I-81.

The 6z EPS & GEFS both have low tracks that will work for Winter weather for the LSV for Thursday/Friday. We still have a couple of days until this is resolved