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January 2011

What to Watch Fore(cast) – Jan 31 – Feb 7


Blockbuster snow storm – A wide swath of heavy snow extending from Oklahoma to Maine on the order of 6-12″+, along with crippling freezing rain, will rock the Midwest and Northeast tonight through Wednesday.

Weekend coastal storm – A storm that could once again “thread the needle” and produce significant snowfall (2-4″+) in the Mid-Atlantic is on the table for Saturday and/or Sunday.

Big cool down in the mid-country – A strong area of high pressure will dive in from Canada and introduce very (record-breaking?) cold into the Plains mid-week.

Even more rain in the Southeast – The weather pattern seems desperate to alleviate the Southeast drought conditions as yet another storm system is progged to develop in the Southeast next Monday.


So when I said that last Wednesday’s storm could be the biggest population-wise… I was wrong. Sources estimate that this week’s storm could impact 100 million people. Simply an incredible storm.

Winter Storm Threat: Jan 31 – Feb 2 UPDATE

I made some changes in the Wednesday forecast to account for warmer surface temperatures… not too much of a shift, but it could change the plans for a significant amount of Maryland workers.

We’re still looking at 0.1-0.2″ of freezing rain along the northern parts of the rain area before it switches over around the morning rush hour in areas. Hopefully there will be enough normal rain to keep the big freezing rain from causing too much fuss in the major metro and commuter areas.

Winter Storm Threat: Jan 31 – Feb 2

The strength of the cold air damming will be a big player in determining where the different areas set up. Based on recent guidance and trends, I’ve come up with the following maps depicting the first event (with light precip. totals over most of the region) and for the second event (which will have QPF in the 0.4-0.8″ range for the most part in MD/North VA and 1″+ QPF possible in PA):

Please note the word MOSTLY in the mixed precipitation and rain categories. This indicates that these areas will fluctuate a bit during the events. Some mixed precipitation is also possible in the snow areas (in the 1-2″ contour and maybe even in the southern parts of the 2-4″ contour).

Mid-Atlantic – The Week Ahead (Jan 30 – Feb 6)

We jump right into it this week as the complicated winter weather pattern continues to make forecasting rather difficult. The region will be a bit colder tomorrow as mostly cloudy skies and northerly winds kick in and cold air damming develops along the eastern slopes of the Appalachians. The strength of the CAD will be key on Monday night through Wednesday as precipitation starts to move into the region from the south and west. It should start off as light snow from central VA and southern MD northward, with mixed precipitation just south of that and rain even further south near the VA/NC border. The wintry weather will shift further north as we work into Tuesday, with areas from DC north changing over to freezing rain. There should not be that much precipitation on Tuesday south of PA as the main bulk of the storm moves into the area on Wednesday. Areas north of Montgomery County, MD could see significant icing from this storm as QPF amounts support around 0.5-0.75″+ of wintry precipitation on Wednesday. I’ll go into more detail on a map (coming very soon!) that will show the main bulk of the precipitation breakdown. Areas further north in PA will see nearly continuous mixed precip. and snow Monday night through Wednesday as a band of moisture sets up on the northern side of a stationary boundary.

We’ll get a small break after this storm exits the region Wednesday night and high pressure takes over. Right now the models are calling for a late Friday into Saturday snow and mixed precip. storm event for the region, but I suspect they could be kicking the upper-level energy out of the Southwest too quickly, and we could actually be talking about a Sunday/Monday event. Regardless of the timing, we are seeing similar model trends to last Wednesday’s snow storm, with some issues with timing and where the main band of snow sets up. I hate to use this terminology, but we’re looking at a “thread the needle” situation for this storm (much like we had with the last storm), in that the system will have to set up just right in order to produce big snowfall (6″+) over the region. There will be an update on this storm tomorrow and I’ll make a first call snowfall map around Wednesday/Thursday depending on the timing of the system.

So in summary, we’re looking at two more winter storms this week. The first one could produce significant/crippling ice from just north of DC up to the PA border, and the second one has the potential to do something similar to last Wednesday’s storm. No breaks for the East Coast this winter!

Potential for an epic winter storm in the Plains, Midwest, Northeast

Just giving the heads-up since the main discussion isn’t for another couple of days… the makings of an epic winter storm is coming up next week for the Southern/Central Plains, Midwest and Northeast. We’re talking 6-12 inches or more over a large area in a SW-NE oriented swath. The bulk of the storm is expected to be from the 1st to the 3rd, with lighter accumulations before and after this timeframe.

To the south and East of the big snowfall, sleet and freezing rain will be possible. The mixed precipitation could be just as crippling (or worse) as a foot of snow, so where that sets up will be a critical thing to track as well.

Here we’ve got the latest snowfall forecast from the GFS, showing the potential for big totals (image courtesy of MDA/EarthSat):

Of course, this is just a very rough depiction of what could happen. I’ll keep an eye on changes and bring it up on Monday’s What to Watch Fore(cast).

Snowfall Verification for Jan 26-27

Using another snowfall site from the NWS in addition to the site I linked in my previous verification post, I came up with this for the snowfall totals:

The most striking differences are the snowfall totals in WV and the snowfall totals from MD north of DC up through southeast PA and into central NJ. These areas were under-forecast by 2-4″, which was partly due to the better-than-expected snow totals from the first shot of precipitation (which was 1-4″ when I was expecting 0.5-2″) and partly due to the northern extent of the snowfall, which was about 50-100 miles further north than I (and the models) predicted for the 1-2″ contour. This snow also helped the second snowfall to start accumulating a bit faster since there was no loss due to melting (which would have been minor anyway). The higher totals in central NJ were due to better banding than I expected. Also, the conversion over to snow happened a little more quickly than forecast, which accounted for an additional 1-2″ of snow.

Overall, I’d give my forecast a B. The general contouring and cut-off areas were excellent, but higher snow totals brought down the grade.

Clipper system a bit better than expected

Areas in northern VA, MD, DC and Delmarva could see 1-2″ of light snow today as a clipper system moves over the region. I was thinking 0.5-1″ earlier, but with the radar filling in and areas of moderate snow forming, higher amounts are expected, with some areas possibly even going over 2″. The band setting up between Frederick and Hagerstown, MD is particularly concerning:


EDIT: Looks like 0.5-1″ was the way to go… the radar didn’t fill in nearly as nicely as it was looking originally. Add small flakes that easily melt and you got 0-1″.