00Z Mon Model Discussion – Live Blogging

If you haven’t seen my first call forecast you can view that here. Lots go into the forecast, I only touched on a few things in that blog post, and in sharing these model discussions with you – but it’s a tricky forecast. The rain/snow line is crucial to the forecast, and we haven’t had a perfectly clear indication yet of how far west it pushes. Let’s hope this new set of guidance helps solidify the forecast… The order of the posts will be newest to oldest.


Like the GFS model, the we are now outside the time range where the Euro is useful, so I’m not including it. Lots to think about with this, and I may make a few changes before the final call map early Monday afternoon.


12:00 AM – GFS Model

At this time range the GFS model isn’t all that great. This is because the GFS is a global model and, as such, has too low of a resolution to properly discern specifics. However, it’s track remains almost unchanged, but the solution is warmer than past runs. It pushes the rain/snow line to I-95 by 3AM, then pushes back east after 7AM. Per the algorithm on the site I’m getting these maps from, it doesn’t show any sleet/freezing rain/mixing. However, looking at the temperature profiles, sleet and/or freezing rain and/or mixing  is possible in the I-95 corridor and just east, including Charles, PG, and Anne Arundel Counties. Something to watch…

Precipitation Type Map 8PM Mon to 8PM Tue, stepped 3 hours.

Snowfall map from GFS:


1130PM Update – RGEM Model

The RGEM is a short range model from the Canadians. It’s a very good model, and one of my favorites for winter storms as it generally handles things fairly well – not always, but more often than not.

The RGEM tracks the low along the coast and is incredibly warm. The rain/sleet line goes to the Blue Ridge, and the sleet/rain line pushes well into SoMD. It moves in as snow 6  – 9 PM, and the sleet/rain pushes into I-95 after midnight. The I-95 corridor sees a significant period of sleet and/or freezing rain during much of the overnight – this includes Charles, PG and Anne Arundel Counties. There is no return to snow on this model either, it keeps sleet and freezing rain all of Tuesday morning, and tapers early afternoon. This does present a significant ice storm for the I-95 corridor, which is even more concerning than snowfall. I’m hoping this is wrong, because a quarter inch of ice is not a good scenario.
This model is so warm, Salisbury, MD sees it’s temp jump to 50° before crashing as the low pulls away.

This does concern me considering it’s a great model, but I still am unsure of a track this close to the coast, or this warm. It’s got me thinking though… The RGEM, however, is not a high resolution model, so it may miss things that the high res models can pick up. It bears watching, nonetheless

Precip type from 8PM Mon to 8PM Tue, stepped every three hours.

Snow forecast:

Ice Forecast from RGEM:


1040PM Update – NAM Models

First up tonight is the NAM model. As I’ve mentioned, I don’t particularly like the NAM, but it does still have its purposes, and were now in the time range where the NAM does a little better. The NAM has two versions, a high resolution and low resolution model. I’ve been burned by the NAM for both ignoring it and following it and it’s you never know if it’s doing well until the event. I’m left uneasy by it because it’s been consistent – but it’s track record speaks for itself – it does not change my forecast. The NAM is crap, and I don’t think its right, but its more a yellow light that says use caution…

The High resolution model, is similar to it’s parent low res. version in bringing the low along the coast. This is a warm solution. Rain pushes to I-95, then from just east of I-95 almost to I-81 sleet and freezing rain are an issue most of the night. The model doesn’t wrap the cold air back around until after 7AM, when everyone turns over to snow. It snow most of the rest of the day, tapering during the evening. The heaviest snow exits during the morning.

Precip type map from 8PM Mon to 8PM Tue, stepped every 3 hours

And here is the snowfall

The new low res 00Z NAM has the low on the coast once again, and is the warmest it’s been yet. Rain pushes so far inland everyone east of the Blue Ridge sees rain before changing back to snow Tuesday morning as colder air wraps back around. Sleet pushes all the way to I-81. The NAM does hold heavy snow Tuesday morning over the area, and it snows almost all day too (something new), which may help all the areas that saw rain see some good snows. I still think the NAM is wrong with this, and is entirely too warm and too close to the coast.

Precip type forecast from the NAM from 8PM Monday to 8PM Tuesday, stepped every 3 hours.  (note: in the last few frames it may snow green indicating rain, that will be snow, it’s just the precip is light enough that the model algorithm classifies it as rain because the surface temp might be above freezing)

And here’s the snow map



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