Saturday, February 8, 2014

February 13-15 Potential Snowstorm

It looks like we may see a winter storm along the East Coast in the February 13-15 timeframe.

The GFS model indicates we will see a negatively tilted trough work its way down into the Northeast and Mid-Atlantic around Valentine's Day, in the midst of an established northwest flow regime. We see this regime set up as a result of storminess over the Gulf of Alaska, and a suppressed ridge in the West US.

The GFS model wants to take what appears to be a strong clipper system eastward into the Northeast in association with the trough we saw in the image above. The clipper then transfers to the coast on the morning of Valentine's Day, resulting in snowfall for the interior Northeast. Rain looks to be the preferred precipitation type on this model solution for coastal regions. Since this is still in the long range GFS, none of this should be taken verbatim- we're trying to pick out the general pattern that could then yield a winter storm. In this case, the northwest flow with an Alberta Clipper transferring offshore seems like a rather likely scenario if the opportunity arises for a clipper to form around Valentine's Day.

The ECMWF has a similar situation, with the 500mb height anomaly forecast highly indicative of the northwest flow regime we discussed. The suppressed ridge and storminess over the Bering Sea is clearly evident, though the ridge in the Southwest is so suppressed the flow is borderline-zonal in that area. Nonetheless, we can still see the northwest flow alignment across the contiguous United States (CONUS).

The ECMWF model has the storm system impacting the Mid-Atlantic primarily, before heading off out to sea, only scraping coastal portions of the Northeast. This solution would lay down snowfall in the Mid-Atlantic states of North Carolina, South Carolina, West Virginia, and Virginia. This particular ECMWF model forecast lays down over 13" of snow in these areas, but these amounts would be better off cut in half for more accurate (but still slightly overdone) amounts.

So why will this storm hit the Mid-Atlantic and Northeast?

The answer lies in the jet stream and 500mb level. Here in the jet stream, we see the storm system well defined in the Central US on the 12th of February. If we look closely at the winds surrounding the jet stream, we see a jet streak (area of higher winds within the jet stream) positioned to the right of the trough. Typically, when a jet streak is to the right of the trough, the trough will lift north. This same principle applies here, as we then see the trough lift north and east, tilting negative as it does so to indicate the storm has reached maturity.

The 500mb level, shown two images above this jet stream graphic, also supports the storm lifting northward. We see a strong ridge of high pressure located well offshore of the East Coast of the US, which would nearly assure the storm lifting northward. Additionally, the trough beginning to tilt negatively in the East US would help out with the storm wanting to move north.

So what can we establish right now?

-The synoptic pattern looks favorable for a winter weather event in the East Coast, thanks to an evolving northwest flow pattern.

-A potential storm system is being modeled on forecast guidance that may impact the East Coast of the US.

-If a storm system does form in the United States, it looks like it will be favored to bring snow to inland portions of the East Coast, rather than coastal regions.



Unknown said...

Andrew you have made my day! I live in Danville, VA, right by the Dan River coal ash spill. Your forecast is just awesome, it puts us in the heart of the storm with about 8 inches of snow! I have monitered your blog, and the storm is set the hammer us here. Do you think the forecast will stay relatively the same for us here? Thanks,

Anonymous said...

Great blog Andrew!! So even with no ridging out west, we can still have the storm push up the coast with the help with the ridge out east? Oh and are you going to make a post about the pattern coming late feb into march? I'm seeing a brief break, but return of cold and storms into march. Maybe MJO enters E indian ocean and gets interesting??

Anonymous said...

so will this mean snow for philly

Unknown said...

Any chance that the Midwest will see atleast 1 more storm? :/