Saturday, March 1, 2014

Update on Impending Mid-Atlantic Region Major Winter Weather Event

**This entry was posted March 1, 2014.**

Let's hope past isn't prologue ...

Washington Post headline of January 29, 1922 announcing the Knickerbocker Theatre collapse in Adams Morgan due to the heavy, wet snow on the roof of the building.


The collapse killed 98 people and injured 155, an event that lent its name to that snowstorm, officially the largest ever in D.C. history at 28.0 inches. That was a pre-KDCA measurement -- and it is unlikely ever to be broken. (I'm unsure where the measurement was recorded, though possibly in West End around M and 24th Streets NW).

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OK, I'm back from the Anthony Bowen YMCA gym. I spent a full hour on the treadmill jogging a grand total of 5.80 miles (including 5-minute cool down) and then a bit over an hour weight-lifting, although it was a best a moderate workout. I skipped the pool as I just didn't feel like going into it. In addition, it was crowded (for it) with all the lanes taken. (The paramedics also showed up because a girl appeared to have hurt her arm, and she was taken out on a stretcher, though she was seated upright and still in her bathing suit.) I showered and dressed and walked home.

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Update on Impending Winter Weather Event / Snowstorm ...


Sterling NWS (LWX) county warning area (CWA) snowfall forecast valid through 7PM March 3, 2014 issued at 6:40PM March 1, 2014.

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Capital Weather Gang snowfall range and probability forecast map issued at 2:55PM March 1, 2014 for the extended D.C. region.

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The night is just cool -- not cold like last night. Temps. are around 42F. Tomorrow could potentially reach 60F but there will be a steep thermal gradient right across the region with highs not even reaching 40F on the Pennsylvania border and near 65F in central Virginia. Temps could vary even right across the Metro D.C. area significantly.

Current weather advisories in effect for a portion of the Lower 48 updated at 0500UTC (7:50PM EST) March 2 (March 1st), 2014.

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The precipitation moves in tomorrow evening initially as rain, and then the question is how fast the Arctic air returns even as the energized system moving along the quasi-stationary Arctic boundary approaches. The 12Z operational models were very snowy. The 18Z runs appear about the same, maybe a bit less on the GFS.

Today's 12Z 4-km NAM showing 2-meter temperatures valid at hour 32 / 20Z (3PM EST) March 2, 2014 over the mid-Atlantic region, as prettied up by WeatherBELL Analytics.

It shows temperatures in the 60s Fahrenheit across parts of Virginia and southern Maryland and near freezing on the Pennsylvania border. Compare this with the image directly below.

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Temps will plummet / crash by dawn Monday to and then below the 32F / 0C mark and the precipitation will transition from rain to sleet / maybe freezing rain to all snow by mid-morning.

Today's 12Z 4-km NAM showing 2-meter temperatures valid at hour 48 / 12Z (7AM EST) March 3, 2014 over the mid-Atlantic region, as prettied up by WeatherBELL Analytics. This is 16 hours later from the above forecast. Temps. are now in the lower 20s F across the District.

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The question then is how heavy is the precip., the exact track of the system, and the duration, not to mention the snow-to-liquid ratio. But temps should fall to near 20F by dusk, so the snow that does fall will stick everywhere despite the fact it is early March and despite the antecedent warm conditions (always a caution flag in D.C. when snow is in the forecast for the following day).

Of note, there is no significant coastal low with this event.


The regional temp. forecasts and snow amount probability map are taken from that entry.

The 430PM Winter Weather Forecast Discussion issued by NWS / NCEP / Weather Prediction Center contains a paragraph that is worth quoting in full (note the "terrible societal timing" line):

THEN ON MON... THE MORE UNIQUE PART OF THE SYSTEM... AS THE SHARP THERMAL ZONE AND ARCTIC AIR MASS SURGE ACROSS THE APPALACHIANS INTO THE MID-ATL REGION TO SET UP A MAJOR SNOWFALL ACROSS DC/BAL AND PERHAPS THE PHL METRO AREAS. THE LOW PRESSURE SYSTEM WILL TRACK ACROSS NRN MS/AL/GA TO THE SOUTHEAST...

A COPIOUS AMOUNT OF LL MOISTURE WILL ARRIVE INTO THE COLD SECTOR FOR YET ANOTHER SWATH OF HEAVY SNOW AND ICE. THE 12Z GUIDANCE HAS ALSO NARROWED THE FORECAST SPREAD... DEPICTING A NARROW BUT INTENSE DYNAMIC COOLING HEAVY SNOWFALL BAND SETTING UP NORTH OF THE FRONT...

ESPECIALLY INVOF OF THE NW QUAD OF THE SURFACE LOW. THUS HEAVY SNOW WILL BE POSSIBLE FROM SRN MO/NRN AR TO THE DELMARVA COAST WITH THE HEAVIEST AMOUNTS APPROACHING DOUBLE DIGITS OCCURRING FROM ERN KY/SRN WV THROUGH MD/NRN VA AND DE/SRN NJ AND TERRIBLE SOCIETAL TIMING AROUND THE DC/BAL AREA MON MORNING.

MEANWHILE ICE/SLEET WILL SETUP SOUTH AND EAST OF THE HEAVY SNOW WITH SIGNIFICANT ACCUMULATIONS POSSIBLE FROM SRN AR NORTH AND EAST TO WRN TN/SRN KY... WHICH COULD BE PARALYZING.

("LL" means "low level" and "INVOF" is "in the vicinity of".)

I will likely have a weather-themed entry tomorrow, especially if it appears that we are still on track for a major winter weather / snow event.

Lastly, I'm thinking of removing StatCounter outright from my blog. It really has been a source of much frustration for me for the past several months. I only check it now while on the treadmill at the gym (yes, you read that right -- I do so before one of my "regular" course runs). Today, I wasn't even able to do that because the site was "blocked by site administrator" with a weird message about "initiated in county: Europe."

As for tonight, I'm supposed to go to Nick's surprise birthday party at Bread Soda on Wisconsin Avenue in Glover Park here in D.C. This requires riding my bicycle over there since the place is not convenient to Metro. However, it's really not that far.

Thereafter, I plan to go to No. 9 and/or Nellie's tonight. Not sure if I'll do an Old Ebbitt Grill dinner, though.

In the meantime, I am going to post my jukebox Saturday night entry while watching that second part of that Wonder Woman two-part episode on Me-TV ("Judgment from Outer Space"). I discussed the first part in an entry last Saturday. It's on now.

--Regulus

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