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February

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: 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.

Winter Storm Threat: February 26-27 (Only/Final Call)

It’s time for the southern folks to finally cash in this season. Some spots in North Carolina and southeastern Virginia are expected to get as much snow as they typically get in a year, so this should be a fun storm for them. I battled a bit in the placement of the 1″ and 2″ contours on the north edge of things, as there is a wide range of solutions in that department still. The rain/snow line across North Carolina is another big hurdle, but it seems the warm nose will be around 850mb, which made sorting it out on the models easier.

20150226-27_MAsnow_final

I expect a couple of 12+” reports out of this in North Carolina and southeastern Virginia. The northern edge of the 1-2+” has equal risks of busting high/low.

Winter Storm Threat: February 21-22 (Only/Final Call)

Lots of uncertainty with this system. How much precip. falls as snow before the changeover, timing of the changeover, rates during the daytime hours, etc. The only thing that’s not really in question will be the surface temperatures at the start of the storm. Cold, cold, cold.

20150221-22_MAsnow_final

Models overall show a little more potential to get higher totals than lower totals east of the Appalachians.

My brain is done. k bye.

Winter Storm Threat: February 16-17 (Final Call)

Cut back on totals in central and eastern Pennsylvania a little bit, and tweaked 8-12″ contour ever so slightly. On the south end of things, I lowered the snow+sleet totals in North Carolina east of the Appalachians and into far southeastern Virginia. Still a solid 5-10″ event around the greater D.C. region.

20150216-17_MAsnow_final

Would have been interesting if people didn’t have Monday off… onset around D.C. is during the afternoon rush hour. At least we get to avoid that fiasco this time around. Should end near or slightly before daybreak for most. Enjoy your fresh pow pow.

Winter Storm Threat: February 16-17 (Initial Call)

Holy crap, a decent storm around D.C. where the rain/snow/mix line won’t be a concern! It’s a miracle.

So the biggest question at this point is QPF. There are some really juiced-up forecast models, and some not so much. Either way, snow ratios start getting good around D.C. and points north… talking 15:1 or better (20:1 along/north of the Mason-Dixon?).

20150216-17_MAsnow_initial

Other questions include how far north the 1+” totals get, and how much snow/sleet occurs in North Carolina and southeastern Virginia before they change over to rain/freezing rain (yes, sleet is included in the snow totals in that region).

The 8-12″ band is a little ambitious, but I feel like the more aggressive play is the correct one at this point. I think a 50/50 blend between the wetter models and drier models results in something close to this, with ratios taken into consideration.

I’ll issue a quick final update tomorrow morning.