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winter

Winter Storm Threat: March 13-14 (Final Call)

The wintry mix of snow, sleet, and rain appears to be creeping closer to I-95 on the models, so I tightened up the gradient a bit to reflect lower totals from D.C. to Baltimore. The same is true for Long Island, and could be true for eastern New Jersey and New York City as well.

On the flip side, higher QPF across most of Pennsylvania into northern New Jersey and eastern Upstate New York increased the snow total forecast for these areas. Some small increases also occurred along the Appalachians.

Highest risk is still how far north and west the sleet/rain mixing line gets tonight, which could cut deeply into totals along I-95. Once you get far enough north and west and enter the “safe zone” where no mixing is expected, locally higher snow totals are possible.

Oh yeah, and don’t forget about those winds, especially along the coast. Gonna be fun.

Winter Storm Threat: March 13-14 (Initial Call)

As has been the pattern of recent Marches, we in the Mid-Atlantic find ourselves with a late-season snow storm that contains significant snowfall. While the storm evolution may not be classic, it seems that we will see a fairly common snowfall distribution, with the highest snow totals hitting mostly north and west of I-95 while areas south and east see more of a rain and a wintry mix.

The two main questions are where the rain/snow line ends up, and how warm will the surface temperatures be when the snow is falling. For the D.C. to Philadelphia corridor, this will mean a lot. The models differ on just how cold it is along the I-95 corridor as the precipitation is falling, which is where most of the uncertainty with this forecast lies.

The QPF is also a bit of an issue, but taking a model blend seems to be the best way to go at this point. I wouldn’t count hugely on anomalous pockets of minimal QPF, and I’m sure there will be some area that gets sweet deformation banding and ends up with more snow than expected.

Winter Storm Threat: February 8-9 (Final Call)

I ended up going more bullish with the southern fringe of the different snow contours east of the mountains and across south-central Pennsylvania, otherwise my thoughts are pretty similar to yesterday.

20170208-09_final

Still looking at a fair amount of uncertainty regarding snow accumulation east of the mountains due to the very warm temperatures leading into this event. A good pasting of snow is expected once temperatures cool down early Thursday morning, but a 1-2 hour shift in either direction with the introduction of colder air could add or remove some 1-4″ of snow. That being said, once the changeover to snow is made, it will be snowing quite hard, and heavy snow can overcome marginal surface temperatures.

Winter Storm Threat: February 8-9 (Initial Call)

This time it’s the 40N crew that will cash in with this upcoming snow storm. After a very mild Wednesday along the East Coast, temperatures will come crashing down overnight as a disturbance develops over Virginia and tracks just south of Long Island.

20170208-09_initial

Ultimately, the strengthening and position of the surface low will have a large impact on how far north/south the 1″+ snow amounts end up. The snow will also be battling against a very warm antecedent air mass that will keep most spots as rain for at least the onset of precipitation. This means places like D.C. and Baltimore will struggle to change over to snow overnight. Heck, D.C. stands a risk of never changing over to snow at all Thursday morning if the more northern model solutions are correct.

As the initial storm system moves out Thursday morning and early afternoon, a second upper-level vort. max will slide through the Mid-Atlantic. This could trigger snow showers across more of the Mid-Atlantic Thursday afternoon and evening. Most places around/south of D.C. will still be too warm to see this light snow stick, but a little “snow TV” is better than nothing… I think?

Winter Storm Threat: January 6-7 (Final Call)

As the event is unfolding, time for a final update. A slight shift north and west, but overall similar thinking to yesterday’s forecast.

20170106-07_final

I think that there is a little more room for this to shift a bit further north and west compared to moving it south and east. The area of significant snowfall seems pretty locked in at this point, with concerns about mixing on the southern edge of the snow accumulation in the Carolinas.

Winter Storm Threat: January 6-7 (Initial Call)

A legit winter storm is finally coming to the southern Mid-Atlantic, but it probably won’t be a huge hit for D.C. residents as this suppressed storm system aims for areas south and east of I-95, instead of the usual jackpot areas.

20170106-07_initial

There is still a chance for this system to drift a bit more north and west, but for the past few days, forecast guidance has been pretty consistent in keeping any notable snowfall in the Southeast and in areas east of I-95 from Richmond, VA northward. Another concern is how much snow ends up falling over North Carolina, where some places will be battling with rain and a wintry mix before changing over to snow on the back end of the system. All-in-all, it looks like a solid hit for the more southern folks that get included in my snow forecast maps.

Winter Storm Threat: February 8-10 (Only/Final Call)

This storm has a complicated setup. You have multiple surface lows within a broader upper-level trough, marginal surface temperatures, and large discrepancies in QPF placement between the models.

Temperatures along and east of I-95 are the most uncertain, which are expected to be in the low-to-mid 30s through most of the event. Areas north and west of I-95 will start above freezing, and will cool to at or below freezing depending on how strong the snowfall rates are tonight.

Snowfall rates will be one of the most important factors in determining which areas see 4-8 inches, and which areas get 1-4 inches. The best rates are likely to be along the Maryland/Pennsylvania border into southern New Jersey.

20160208-09_MAsnow_final

The intensity of the initial coastal low, the secondary coastal low development, the strength of the low over the Great Lakes, and the timing of the strengthening and weakening of these lows are wreaking havoc on the QPF output on the various models.

I tried my best to offer a realistic compromise between the differences in QPF, while also accounting for the surface temperature and snowfall rate issues. I could definitely see a tighter gradient between accumulation amounts than what I have on the map.