So a coating to an inch is the forecast. The uncertainty is where.

Some models have the maximum precip from the city westward. Some have the maximum precip from the city eastward!

Temperature profiles run from a bit too warm to accumulate to cold enough to accumulate somewhat. Regardless of specifics the models are in agreement that much of it will be a rain or wet snow at the start, further reducing potential accumulations, then changing to snow.

The NAM has the highest accumulations (1.25″) and has the snow lasting into the afternoon. The GFS has the least, in some areas zero. The Canadian RGEM is forecasting about 1.2″ of snow.

Timing: The models have the snow/rain mix starting at 2-3 AM Sunday morning and ending either mid morning (ECMWF) or early afternoon (NAM).

I’ll update with my regular Weekend Weather Forecast later this afternoon/early evening.

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Update Thu @ 7:46 AM — Last night’s models have uniformly moved to a weak, unphased system with development occurring further from us. Totals of a coating to an inch are now forecast. With the strong model agreement last night, I think we can lower the focus on this ‘storm’. Unless there are dramatic changes (not expected), my next update will be my regular Weekend Weather Forecast, usually posted late Friday afternoon or evening.

BTW, I should mention that the storm now falls into the range of the NAM, which shows 1-2 inches of snow. While I’m a big fan of the NAM for snowfall, its forecasts for such things are often not credible until about 36 hours ahead of the event.

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Update Wed @ 8:28 PM — Another brief update. This afternoon’s ECMWF just became available as well as the ICON model. Both have moved towards a westward track and more snow for us. The ICON has 3″. Forecast is similar to this morning’s GFS which has subsequently moved in the other direction.

Here is the latest ECMWF 18z. (data available only until Sunday 7AM time frame)

We’re still in the 90+ hours time frame, requiring the global models. New updates tomorrow morning. The potential snow will then be in the forecast range of the RGEM, NAM and SREF models.

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Update Wed @ 6:11 PM — Significant lack of agreement with the model forecasts for Sunday. The GFS and ECMWF have the jet stream phasing late, with the storm to our east. Minimal accumulation (1″ or so).

The German ICON and the Canadian GEPS and GDPS have some phasing, enough to keep the storm near the coast, or in the case of the Canadian, inland!

In all cases, the amount of precipitation currently forecast would lead to 1, maybe 2 inches of snow. The Canadian’s western track would have a mix with rain.

Either way, no model is forecasting a major storm at this time. Things are likely to change. Stay tuned.

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Previously Posted Wed 10:02 AM —

Over the past three days, a seemly benign weather pattern with a warm up on Saturday now shows signs of what I like to call “interesting weather” for Sunday.

A broad upper air trough was long expected to form low pressure system in the southeast coast: this had been expected to just brush us.

The GEFS has been suggesting for two days that more precipitation might develop. Here’s the scenario: A cold front moves through Saturday night and stalls. Low pressure develops in the southeast coastal area. Some moisture over-running the stalled frontal boundary results in some snow possible here on Sunday. Track of the coastal storm depends upon degree of upper air phasing.

The latest GFS (06z) shows a northern-southern jet phased upper system with significant upper air energy—

The GFS is close to its ensemble version, the GEFS (suggesting increased confidence), but other models are not all on board with a phased upper flow.

Here’s a comparison of the GFS with the last night’s ECMWF (European). The ECMWF is not phased