Sunday, January 20, 2013

January 24-27 Potential Significant Winter Storm (Updated 1/20)

There is potential for a winter storm from January 24th to January 27th across much of the nation east of the Rockies. Let's do a model analysis and see what the latest forecasts hold.

Shown above is the GFS forecast, valid for the morning of January 25th. We can see the storm system is centered in eastern Tennessee, with precipitation also shown. Snow is shown in blue, and rain is forecasted in the traditional green colors. We see the system is moving relatively eastward towards the Mid-Atlantic, dropping some accumulating snow as it goes. This snow would most likely accumulate in the northern Mid-Atlantic, with cold air still in place following this weekend's cold outbreak and additional cold air following in the wake of this system.

It should be noted that the GFS model has been swaying from a north track (snow hits the Midwest and northern Ohio Valley) to a south track (snow impacts the areas shown above), reducing my trust in its credibility. Now that we have seen the southern track, let's take a glance at the north track.

ECMWF Model Hour 120

ECMWF Ensembles Hour 120
The highly-respected ECMWF model and its ensemble system (commonly called the EPS) are supporters of the northern track at this time. The ECMWF takes the system a bit north of its ensembles, putting the storm system in south central Indiana. Enough cold air would be in place to theoretically give snow to many of the areas described in the small paragraph above these images, like the Midwest, Ohio Valley and into the Lower Great Lakes. The EPS takes the storm system just a few hairs south of the operational ECMWF model, but nonetheless would keep accumulating snow within the same relative realm of the ECMWF model itself. A quick glance at ECMWF snow accumulations on a pay-to-view site agrees with my above thoughts in a swath of accumulating snow in Illinois, Indiana, Michigan and Ohio, to name a few states.

The Canadian GGEM model, usually not one to be in sync with other models, appears to be lining up relatively well with the ECMWF model, The low pressure system is a bit further north on the GGEM model, and temperatures are warmer than the ECMWF model, but the Canadian model can still theoretically be defined as in the north track. Although I don't really care for the GGEM on account of its messy track record, it's in one of the tracks at this time, and thus deserves to be noticed.

At the moment, looking at various teleconnections, I am seeing the Pacific-North American index go negative during this timeframe. This means negative pressure anomalies (low pressure) on the West Coast (hence negative PNA), which causes high pressure to build in the East. This would most likely prevent suppression of this storm, giving some strength to the North Camp. The Madden-Julian Oscillation (MJO) will be in a phase favorable for making storms stay away from the Deep South and instead taking a more northern route like the ECMWF/EPS are suggesting. The North Atlantic Oscillation (NAO), which, in its negative phase can cause Nor'easters, will be too weak to help this situation out.

My preferred forecast: ECMWF/EPS solution. Snow accumulates in Midwest, Ohio Valley and Great Lakes. Heaviest totals hit Illinois, Indiana, Ohio and Michigan, among others. Accumulations range from 2 inches to 6 inches. Confidence: 60%



Wally Gullang said...

Andrew Illinois is a big state. We talking South, Central or North ? Right now both Central and South have received some moisture but her in the North we can't seen to buy a snow flake let alone receive one free from Mother Nature.

Anonymous said...

U said michigan. R u talking about detroit mich getting snow

ERN WX said...

Be cautious with this one. Mdls are EVERYWHERE. The NAO may encourage a sthrly soln, but the PNA says no. The cold air is very strong, and that will have an impact on the track/pcpn. You mentioned this one a while back, I believe. Great work!!! Fcstrs are currently watching an inverted trough which could dump good snow for Cape Cod. 3-8 inches. Monday/Tues. The pattern has changed. The back-loaded winter we are looking at. The 24-27 storm has ptnl to impact a vast area with winter wx. Including snow, sleet, and freezing rain.

Andrew said...

ERN WX: Great analysis as always!