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February 2012

March 2012 temperature forecast

Another warm month is on tap for the eastern two-thirds of the country as we enter the start of meteorological spring:

Risks are to the warm side throughout the country as the “torch” continues. Many indices point towards warmth in the eastern US as you have a +NAO, +AO, -PNA, +WPO, and +EPO going into the first couple of weeks in March.

Mid-Atlantic Discussion – Feb 29, 2012

We end the last day of meteorological winter not with snow, but with severe as storms threaten the region for the second time within a week.

Currently, there are two tornado watches active in the region… one that extends into most of WV, and another that encompasses extreme southeastern WV and most of western VA.

Both watches are set to expire during the first half of the evening. The main concern with these storms is damaging wind, with isolated tornadoes possible and a low risk of severe hail. The main cluster of storms is moving through WV/VA now, but another cluster of storms is expected in the same areas in the early evening. Both of these clusters are expected to weaken as they get east of the mountains in the northern areas, but a risk for severe will continue into the overnight hours in southern VA and NC.

Mid-Atlantic Discussion – Feb 24, 2012

I can’t believe I haven’t done one of these since August… been too long.

The first real chance for severe weather in the Mid-Atlantic this year has arrived! Tomorrow’s looking increasingly promising for at least some severe wind threat in addition to an isolated tornado or two and maybe some hail. Strong post-frontal winds and brush fires are also risks with this system.

The latest models have been pushing out CAPE values of 500-1000 J/kg in parts of the Mid-Atlantic from DC down to eastern NC tomorrow afternoon, which isn’t much, but for February it’s not too shabby. The low-level jet will also be roaring in southern VA and eastern NC, which strong thunderstorms could mix down to the surface. There is enough directional shear in the low-levels for a tornado threat in southeast VA and eastern NC, which is where I plan to storm chase.

Behind the front, dropping dewpoints and strong winds gusting to 50-60+ mph will bring a risk for brush fires to the region as well, especially in the areas that were north of the recent snowfall from last Sunday.

All of this will be going on during the afternoon and evening hours tomorrow, though winds will remain somewhat gusty going into Saturday.

Here’s the latest forecast from the SPC (click the image for their discussion):

Snowfall Verification for Feb 19

While my first two maps left much to be desired, I finally got the storm zoned in on my final forecast:

The southern edge of the system did a bit better than expected east of the mountains as the snowfall rates were able to overcome the above freezing surface temperatures. The northern edge of the 4-8 inch contour also did better than expected in central VA, with spotty 8-10 inch reports in the higher elevations. I also overdid some of the snow in the far southern Appalachians.

A solid B+ forecast overall.

Winter Storm Threat: Feb 19 (final call)

Following the latest model trends, it looks like another bust for the DC folks:

Finally a decent snow storm for the southern areas, but the DC region will miss out on the good totals once again. A coating to an inch seems like the best forecast for DCA at this time.

Winter Storm Threat: Feb 18-19 (second call)

Everything trended south in the last 24 hours…

So what happened? The main northern stream energy that was supposed to interact/guide the southern energy creating the snow storm has actually moved out ahead of the storm. This changes a few things…

1. The boundary layer will be able to get cooler and drier ahead of the system.

2. The storm itself (the southern stream energy) has slowed a bit and is allowed to stay further south.

3. Less phasing/interaction with the northern stream leads to a weaker, less amplified system.

There will still be some boundary layer issues along the southern line of the snowfall area, but the boundary layer impact on accumulation is significantly less than what we were looking at a day ago.

Many risks still plague this forecast, and they are

1. The storm could be even more suppressed, which would shift the snow further south.

2. Some models still show a more amplified solution, expanding the precipitation northward.

3. Convection in Alabama and Georgia cutting off some of the moisture feed from the Gulf, which would result in lower QPF and lower snow totals.

I will probably make my final snowfall forecast late tomorrow after the 18z models come out. There are still some big differences between the models, but the trends have been hard not to notice. The most likely change would be shifting the whole thing south.

Winter Storm Threat: Feb 18-19 (first call)

What a nightmare of a forecast…

If I didn’t already say I was going to put out a snow map today I would probably have waited until tomorrow for a first call. As it is, I might do a second update before my final call on Saturday if the forecast seems to converge well over the next 24 hours.

As has been the case all winter, the boundary layer temperatures are going to be a big issue with this event. Most (if not all) of the snow will be on the back end of the system, which doesn’t help matters, either. The latest models would suggest pulling the QPF further south and maybe some of the snow totals along with it, but it wouldn’t be much further south than what I currently have depicted. With high enough snow rates being depicted by the models on the back edge of the system, I think the snow will be able to stick eventually despite the surface temperatures being in the 33-36 range in the lower elevations. Localized 8-12 inch accumulations will be possible in the mountains that get the higher QPF totals.

I believe that the 4-8 inch snow contour could/should extend east of the mountains at some point, but with the discrepancies between the models at 12z and the inconsistency in the run-to-run storm evolution it would be difficult if not impossible to accurately place it east of the mountains.