Wednesday, February 18, 2015

Wednesday Morning Weather Discussion: Bitter Cold Followed by Weekend Storm

Lets dive right into it today, the bitter cold is relentless and will only get worse before it gets better. Check out the low temps Friday morning, yes that more sub zero..

Basically untill we get to our next storm system Saturday and Sunday expect more high in the Teens to low 20's with lows in single digits to negative values peaking on Friday.

So lets turn to our next storm system which looks like it can be a mixed bag for many areas with the exception of interior New England.

The period here will be later on Saturday into Sunday and frozen precipitation including snow can be expected in the beginning due to the cold air in place. However, this will change to ice then plain rain for some areas due to the upper air set up in place not being optimal for snow. I will watch this closely for an ice threat.

The image below explains this..

Few issues here. We have a western ridge too far off shore which causes the flow to flatten too much over the country. This flattening of the flow allows a ridge of high pressure to form downstream of the energy coming off the pacific and out of the sub tropics. Since we have no negative NAO, this storm will be allowed to cut more inland as opposed to running into blocking high pressure which would cause it to redevelop off the coast. 

Things can still change but based on all the model guidance I am looking at including the ensembles it does not look like this is a snow threat for many areas at this time (except for the start of the event). 

This next image proves my point even better. You can see the red ridge of high pressure over the east with the energy back over the plains. Notice no red over Greenland which would mean its a positive phase of the NAO. This helps support that southeast ridge. 

Moving on after we get our warmer air to filter in with this storm, cold returns next week as we get a continuation of the same bitterly cold weather pattern for eastern third..

As a refresher that massive ridge over AK allows air that is sourced from the north pole to flow down into our area. that is why it has been and will continue to be so cold. We can thank the very warm water off the west coast for this semi-permanent ridge. 

As long as it stays cold we will still have chances as more snow. I do not see any signs of this letting up until potentially after next week.

Thanks for checking in. 


  1. Willy, we could still get a snowy March, but barring that, looks like you're batting .500 on the overall winter forecast; you nailed the bitter temps, but missed on the above avg snow totals. As to the cold letting up, telecon forecasts today still calling for the 26th to be the flip day, PNA goes neg, and now the EPO even follows to + territory shortly thereafter. NAO mostly holds + and Arctic Osc still slated for a big + move. Since the 26th is roughly "after next week", I'll go along with you, but would say/guess that the signs for a change thereafter are pretty significant. As to Saturday and Sunday -- so we have a little ridge near the east coast that keeps the disturbance inland (consistent with + NAO ?), and invites some warmer air in for a few hours. What about that northern deviation that you've been talking about relative to the model runs since the Boston blizzard? I see the GFS and Canadian say that this coming storm could be rather wet, around an inch of liquid. Maybe in reality that will be less, if the north bias holds? Jim G

    1. Yes that is correct, my snow forecast (exception of Boston) is falling short right now. Def an active pattern in the future but we will have to see if those telcon forecasts verify. For a warm up the biggest thing to look at is the EPO going positive as the pacific has been dominating this pattern. As for Saturday and Sunday it is due to the positive NAO that the ridge is popping up since there is no high pressure held in place to resist it. I think this storm starts out as snow and quickly goes to freezing rain then rain but I do not think it destroys the snow pack. In terms of QPF maybe we are looking at an inch but I think it ends up being a little less. Temps should get into the upper 40's before crashing again in the storms wake. A flash freeze needs to be watched.