Thursday, December 7, 2017

Chilly Air in Place - Snow Lovers Keep Waiting

As promised, the colder weather has arrived. Chilly conditions will persist into next week with high temperatures ranging from the upper 30s to the mid 40s. This cold shot was well predicted by the model guidance. 

The next topic of discussion is snow chances. While there will be a relatively weak system off the coast this weekend, the most it will do for our area is some scattered/isolated rain or snow showers. Further, most of this activity will be to the south and east of the metro areas. Snow lovers will have to continue waiting for something significant. 

The trend of the last few runs of the GFS model for this weekends coastal system. You can see it has shifted a bit west again - but the area remains on the fringe regardless. Any impacts should be minor. 

The middle and longer range models continue to show an trough over the eastern portion of the country. This translates to continued chilly temperatures. There are numerous pieces of energy in the flow that *could* produce some lighter snow events. However, prospects of bigger snowstorms seem relatively bleak for the next period. This is not to say that a rogue system couldn't pop up and deliver a 1-3 inch event. 

A loop of the 06z GEFS model run from this morning. This particular view shows the 500mb height anomaly. Blue colors indicate a negative anomaly while the red colors indicate a positive anomaly. This ensemble GFS model shows good chances at continued cool temperatures. 
This is the ECMWF ensemble (EPS). This is the Euro equivalent to the GEFS. You can see it is in good agreement of negative height anomalies in the eastern part of the country. Whether this translates to snow remains to be seen. Safe to say the 60 degree weather is gone for the time being, though.
Many DC area snowstorms tend to come on the relaxation of the long wave pattern (as discussed in the last post). This could translate to a snowstorm threat down the line - but certainly not in the near range of the forecast. 

This period is a good example of the fact that cold weather does not always translate to increased snow chances. Often times what will happen is arctic air will flood so far south that storms become suppressed to the south and east (good example of what is happening this weekend). 

The TL;DR is that snow lovers will have to wait longer for the first shot at a good amount of snow. Conversational flakes still seem possible over the next week or so - not enough to close schools or workplaces, however. 

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