Thursday Aftn Technical Discussion

Synopsis: A very active pattern will plague the state over the next five days as pieces of energy ride along the jet stream and right through Pennsylvania. This pattern will keep the chilly weather in Pennsylvania, but even colder air should move in late in the period as a strong cold front pushes across the nation.

 

Short Term: High cirrus as well as some mid-level stratus clouds are pushing through Pennsylvania Thursday afternoon. Expect most areas in Pennsylvania to fall below freezing. This will set up some wintry precipitation Friday morning as a storm system moves west of Pennsylvania. At the moment it seems the GFS has a better handle on the storm than the NAM as far as precipitation coverage so am favoring the GFS solution. GFS sill is overdoing precipitation amounts at the moment so expect it to be high as well. Portions of central Pennsylvania will hold on to the cold air at the start of the rainfall leading to periods of freezing rain as the storm pushes west of Pennsylvania. The rain will be light at the onset and so rain will freeze to surfaces quickly. Most areas will see between a tenth to two tenths of an inch of ice at most. The freezing rain will switch to plain rain by mid-afternoon. All other portions outside of Pennsylvania should only see plain rain for the entire storm. All rainfall should end overnight on Friday leading to some dry conditions for at least part of the day Saturday.  

 

Long Term: Saturday should see some partial clearing before another piece of energy moves west of the state again. Since clouds will still be spread across the state, no areas will be able to fall to freezing and so am not expecting any wintry precipitation from the storm on Saturday. Periods of rain will move through Saturday before ending around midday Sunday. From here the forecast becomes tricky as all three of the major models have their own ideas on some large pattern changes for early next week. The GFS has the cold front much slower as it comes through Monday night with very cold air behind it. High pressure builds in behind the cold front leading to dry conditions for a least a few days. The NAM on the other hand brings it much quicker and occludes it into Ontario. It then brings a storm along the cold front as it pushes through which rides just off the coast. The EURO is the most interesting scenario as it is similar to the NAM and quickly occludes the low into Canada and then rides a storm up the front. The storm however stays on the coast and leads to a coastal storm with snow likely in western Pennsylvania and New York. Am favoring a NAM/EURO solution as the NAO should be around -2 to -3 during the time frame leading me to believe a coastal storm is likely. There are many things to watch over the next few days as many possibilities exist with this cold front. One thing is for sure, cold air will return after the cold front pushes through.