Browse Month

January 2011

Heavy snow, sleet and thunderstorms innundate the region

As heavy snow (+SN) is falling outside my window, I can only imagine how crazy it is for anyone to be out at this time. I-95 city rush hours from DC to NYC are getting rocked by this storm, as seen on the map below (from 4:45pm EST):


(click for full res.)

It’s starting to look really bad in some areas… here’s I-81 at exit 313:

 
This is just the beginning as the system strengthens and heads up I-95. This will probably be the highest impact storm (in regards to total population affected) for this season.

Here’s a still of the composite radar for the area:

I got my one flash of lightning and clap of thunder, which is all I needed to go to bed happy tonight. Thunderstorms, thundersnow and thundersleet will continue to press north and east up the coast this evening.

Snow Threat: Jan 26-27 (final call)

My idea of a higher snowfall band has come to fruition on the models, though not at quite the angle (or with the somewhat lower snow amounts) that I expected. After some considerable brain-wracking, this is what I’ve come up with:

 
The map calls for a somewhat more northerly solution than what is currently shown on the models, with some heavy influence from the GFS/ECMWF solutions. This season’s trend of fully developing the coastal low and SN/+SN zone slower than expected has led me to think that the greatest snowfall totals in the coastal area will be further north and east than the 12z NAM shows. This area will also likely have better snowfall ratios than areas to the south, which will help towards breaking into the 8-12″ totals.

Along the mountains, there is the potential for some good upslope along the eastern Apps in northern VA. The position may end up being off, but I’m fairly sure some part of the eastern slopes will get into the higher totals of 8-12″ as the onshore mid-level flow of moisture starts to push into the area and is aided by higher snowfall ratios.

EDIT to add that thundersnow is possible along the I-95 corridor!

What to Watch Fore(cast) – Jan 24-31

Highlights:

Another coastal storm – There is yet another coastal storm in the works for the first half of this week as the Mid-Atlantic tries to get it’s first good snowfall of the season, and southern New England could be looking at a foot or more.

Great Lakes/Northeast snow late – Another snow-laden system will work into the Great Lakes and Northeast from western Canada at the end of this week, which could produce widespread snowfall on the order of 2-4″ with locally higher amounts.

The Southwest remains dry – An upper-level ridge continues to dominate the weather in the West as below normal precipitation continues in the Southwest.

—–
Discussion:

While my map will need some improvements (especially to add higher snowfall totals to the Apps), my general thoughts remain the same with the “stripe” of higher snowfall totals, which will likely be adjusted a bit for orientation purposes. A final call will come out tomorrow afternoon. This storm is expected to continue to track northeast just offshore, which will bring some significant snow to the New England coast as guidance consistently hints at totals approaching 1-2 feet in southern New England as the storm moves by Wednesday into Thursday. Most of the snow should come from the back edge (NW/W part) of the system as it moves through and gives some areas a dose of rain and warmer temperatures before it changes over to snow late.

At the end of the work week, a low pressure system diving in from western Canada could bring widespread snowfall to the Great Lakes and Northeast, which is currently forecast to drop a widespread area of 2-4 inches of snow in these areas. Locally higher amounts of 4-8+ inches will be possible, especially in areas with lake-enhanced snowfall. The actual track of the storm has plenty of time to move a little further north or south, and could prove to be a near-miss for many areas or it could surprise some folks in the northern Mid-Atlantic states with some snow (or rain).

A ridge of high pressure in the East Pacific continues to drive a warm, dry pattern over the Southwest, and the pattern shows little signs of changing this in the upcoming weeks. If this pattern continues, the Southwest could start to see drought issues not too long from now. This is in stark contrast to the heavy precipitation the Southwest was seeing a month ago.

Phew! It has been a long day. More on the coastal storm tomorrow!

Snow Threat: Jan 26-27 (first call)

Before I begin, I’d like to state that this forecast has fairly low confidence as we sit in the 3-4 day window with the coming coastal storm. There is still a lot of room for changes to the storm track and snow totals, so this forecast is to be taken with a grain of salt.

With a whole mess of rain and wintry weather from a wet inland solution via the 12z ECMWF, a rain/snow mix and precipitation cut-off closer to the coast on the 12z NAM, and a mostly out to sea but snowy coastal areas 12z GFS solution, which one are we supposed to pick? Using the last 1.5 months as a guideline of which way to lean, I have gone with what is basically the GFS solution with a more inland track and a more amplified cut-off of the eastern (above freezing) side of the storm that more closely resembles the NAM solution.

Rain and mixed precipitation is a huge concern for the coastal and southern parts of the region, which is the main reason why my confidence in this forecast is low. There is a very narrow area of opportunity for higher amounts of snowfall, and while I have more confidence that there will be a narrow strip of higher totals, where that ends up being remains a mystery.

 
EDIT to add that yes I do think this is a rather bullish/ambitious forecast, but it is still a first call and there’s plenty of room for change.

Mid-Atlantic – The Week Ahead (Jan 23-30)

It’s a cold start to this week as we enter another period of highly uncertain weather. We started this morning with lows in the teens, and we could be just as cold (if not colder!) tonight. Clouds will start to move in on Monday well ahead of our next potential storm system, which could still be a number of different things. Everything from a big snowstorm to lots of rain to an out-to-sea miss is possible with this system. The general consensus has been a mess of wintry precipitation and rain for the southern and eastern parts of the region as it moves through the Southeast/Gulf of Mexico and into the Mid-Atlantic coastal region. Precipitation is expected to move into the southern parts of the region Tuesday night as the precipitation spreads to the northern parts of the region late Wednesday morning.

Temperatures will run below normal after this storm moves out of the region on Thursday, but a brief warm up to near normal to above normal temperatures is in the forecast for Friday and Saturday as a weak storm system moves through the Great Lakes and Northeast, which will help draw warmer air up from the south/southwest. Some light rain and snow showers will be possible this weekend as the system’s cold front moves into the region, with lake-effect and upslope precipitation along the western side of the Appalachians.

Snowfall Verification for Jan 20-21

I found a link on NCDC that can help me do snowfall verifications. I haven’t found an archive of the data yet, but at least I found a way to easily verify my forecasts.

Here is the 3-day snowfall total map, ending at 15z today:

 
Here is the comparison, using my contouring (with some smoothing to the actuals):

 
The mixing in the southern parts of the contours proved to be further north than I had originally anticipated, which was due to better-than-expected daytime heating and a slower development of the coastal low. The western side of the Appalachians got a bit more snowfall than I expected as lake-effect and residual moisture was able to have more of an impact.

Overall, not a bad forecast, but certainly one that needed improvements in some areas. Overall, I would give it about a C grade.

Snow Threat: Jan 20-21 (final call)

Final map… probably 90% the same, with some tweaks to the snowfall gradient in West Virginia, extent of 4-8″ in the west, small adjustment north in northern Virginia and small adjustment south along the coast.

Added a HHMM timestamp (GMT/UTC time) on the issuance time because it seemed warranted. Hopefully this is the final version for awhile, but I might consider adding one more contour for the mixing/under an inch area.