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Jan

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).

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″.

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!

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.

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.

 

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