Thursday, January 21, 2016

BLIZZARD WARNING: Baltimore/Washington Region to Experience High-Impact, Potentially Historic Snowstorm Late Friday to Early Sunday

The Sterling (LWX) county warning area (CWA) weather advisories as of 12:42PM EST January 21, 2016. The bright "international orange" represents a blizzard warning.

You will not often see the entire Baltimore / Washington area under a blizzard warning.

*******

The blizzard warning for at least D.C. stretches from 3PM EST tomorrow (Jan. 22, 2016) and running through 6AM EST Monday (Jan. 24, 2016).

The guidance has settled on approximately 24 inches of snow for the immediate Metro D.C. and Metro Baltimore areas, although the most recent (12Z) GFS again puts an improbable bull's eye of up to 36 inches almost directly over D.C. itself (the northern and western suburbs).

NWS generated "most likely" snowfall amounts (given as a range) for the Sterling (LWX) CWA encompassing the entire Metro D.C. and Metro Baltimore areas valid from 7AM EST January 22, 2016 to 7AM EST January 24, 2016.

This shows D.C. itself on the line of 18 to 24 inches and 24 to 30 inches.

Just for fun, here is the maximum amount (as a specific amount):

NWS generated maximum snowfall amounts for the Sterling (LWX) CWA encompassing the entire Metro D.C. and Metro Baltimore areas valid from 7AM EST January 22, 2016 to 7AM EST January 24, 2016.

These totals were break the Knickerbocker Storm record for D.C. That is not a sentence I ever thought I would write.

You can find the updated snow ranges here.

*******

This snowstorm will be on par with the biggies in the modern era: The 1979 Presidents' Day Storm, the February 1983 blizzard, the Blizzard of 1996, and 2003 Presidents' Day Storm II (or the "North American Blizzard), and the February 2010 double-whammy (Snowmageddon and the follow-on storm). While it did not hit this area, this storm could be on par with the Blizzard of 1978 that buried everywhere from New Jersey to Maine.

The 12Z 12/21/2016 GFS has the following liquid equivalents for the three main regional airports:

KDCA: 2.618 --> 26.2 inches
KBWI: 2.669 --> 26.7 inches
KIAD: 2.812 --> 28.1 inches

Were the deterministic guidance to be followed, this storm would potentially rival D.C.'s all-time record snowstorm, the legendary Knickerbocker Storm of January 1922. That the GFS has consistently pumped out -- except for the 0Z run last night, when it was "just" 17.7 inches -- "improbably" amounts of snow for KDCA itself has made this whole run-up to the storm especially vexing for meteorologists.

KDCA 180-hour cumulative snow total based upon the 12Z January 21, 2016 run.

*******

KBWI 180-hour cumulative snow total based upon the 12Z January 21, 2016 run.

*******

KIAD 180-hour cumulative snow total based upon the 12Z January 21, 2016 run.

*******

The snow depths are based on a 10-to-1 snow-to-liquid equivalent ratio, which in a blizzard probably is higher. The Sterling (LWX) discussion is talking about a 12-to-1 ratio, which would raise all those numbers to 31.4 to 33.7 inches, all all-time snowstorm records. From the Sterling (LWX) discussion at 3:58AM this morning:

THERE IS GOOD AGREEMENT THAT PROLONGED HEAVY SNOW IS EXPECTED ACROSS THE REGION FRIDAY NIGHT INTO SATURDAY. THE COASTAL LOW SHOULD BE LOCATED NEAR NORFOLK 12Z SATURDAY AND THE BEST FRONTOGENTICAL FORCING IS EXPECTED TO BISECT THE MID-ATLANTIC AT THIS TIME. DUE TO THE TOPOGRAPHY OF THE MID-ATLANTIC...ENHANCEMENT IS EXPECTED ACROSS THE HIGHER ELEVATIONS. MOISTURE FIELDS IN MODEL GUIDANCE SHOW 2-2.5 INCHES OF LIQUID PRECIPITATION THROUGH SATURDAY NIGHT AND THIS COUPLED WITH 12 TO 1 RATIOS GIVE 1.5-2 FEET ACROSS MUCH OF THE AREA. A WINTER STORM WATCH IS IN EFFECT FOR MUCH OF THE AREA.

The snowfall map for the northeastern quadrant of the Lower 48 U.S. based upon the 12Z 1/21/2015 GFS run.

*******

HOWEVER!

Any introduction of sleet into the precipitation -- a distinct possibility -- will significantly reduce these accumulations. This is one of the reasons that D.C. itself, especially its tidal Potomac-located National Airport climate station, has such a hard time reaching the tremendous amounts that fall in the northern and western suburbs.

That same Sterling (LWX) discussion states:

A SCREAMING 70KT 850 JET IS EXPECTED ACROSS THE REGION AS WELL SATURDAY WHICH WILL LIKELY PRODUCE STRONG WINDS WITH THE HIGHEST CONFIDENCE ALONG AND EAST OF I-95. A BLIZZARD WATCH CONTINUES FOR THIS REGION DUE TO THE STRONG WINDS CLOSE TO THE COAST. THIS JET MAY ALSO ALLOW WARM AIR TO MOVE INTO THE MID-LEVELS AND SLEET IS POSSIBLE MAINLY ACROSS SOUTHERN MARYLAND BUT COULD STRETCH AS FAR NORTH AS BALTIMORE / HARFORD COUNTIES. THIS WOULD HAMPER SNOWFALL ACCUMULATIONS IN THIS AREA. THE HIGHER CONFIDENCE OF SLEET IS ACROSS SOUTHERN MD AND STORM TOTALS REPRESENT THAT.

*******

Point grid NWS forecast as icons and text for 3 miles NNW Washington, D.C., Jan. 21 - 23, 2016.

*******

Of note, a clipper system swept across the region last night bringing approximately 1 inch of snow that immediately froze on untreated roadways and caused significant traffic snarls (see this CWG entry). This was due, in part, to the event being overshadowed by the impending blizzard.

Snow totals were as follows:

KDCA: 0.7 inch (bringing its seasonal total to 1.0 inch)
KBWI: 0.7 inch (bringing its seasonal total to 0.8 inch)
KIAD: 0.1 inch (bringing its seasonal total to 0.5 inch)

The impending storm will raise these totals tremendously.

The following was taken from yesterday's Sterling (LWX) area forecast discussion:

A POTENTIALLY HISTORIC SNOWSTORM IS PROJECTED TO IMPACT THE AREA FRIDAY THROUGH SATURDAY. BELOW IS A LIST OF RECORD HIGHEST 1- 2-AND 3- DAY SNOWFALL TOTALS FOR OUR THREE MAIN CLIMATE SITES.

RECORD 1-DAY TOTALS
DCA...21.0 INCHES (JAN 28 1922)
BWI...23.3 INCHES (JAN 28 1922)
IAD...22.5 INCHES (FEB 11 1983)

RECORD 2-DAY TOTALS
DCA...26.0 INCHES (JAN 27-28 1922)
BWI...26.3 INCHES (JAN 27-28 1922)
IAD...32.4 INCHES (FEB 5-6 2010)

RECORD 3-DAY TOTALS
DCA...28.0 INCHES (JAN 27-29 1922)
BWI...26.8 INCHES (FEB 16-18 2003)
IAD...24.6 INCHES (JAN 6-8 1996)*
*THE HIGHEST 3-DAY TOTAL FOR IAD IS LESS THEN THE HIGHEST 2-DAY TOTAL BECAUSE THE STORM IN 2010 ONLY LASTED 2 DAYS.

*******

Here are some informative CWG entries to read:




16th St. and Vermont Ave. by McPherson Square, Washington, D.C., at snowy evening rush hour, 6:38PM January 20, 2016.

*******

As for last night, I went to Trade after work to meet Gary and talk weather. I walked there from McPherson Square Metro (hence the pictures). Later, I stopped at Floriana to talk briefly to Jamie and had a couple drinks at Dito's bar.

Snowy evening at the intersection of Rhode Island Ave and 14th St NW, Washington, D.C., 6:49PM January 20, 2016.

*******

Of note, the regular young bartender who served us at Trade last night started talking to another customer about his work representing "cloud forcing in a radiative model," and I was a bit taken a back.

I didn't expect that. Turns out that he is, or was, a graduate student in the very same Univ. of Md., College Park meteorology program that Gary and I attended, except that program has since been related the Department of Atmospheric and Oceanic Science to more accurately reflect what it does.

The triangular area between New Hampshire Ave and the 1900 block of 16th St NW, Washington, D.C., 9:39PM January 20, 2016.

*******

When I was there, it was the Department of Inscrutable Chinese Computer Scientists and Tenured Professors on Lifelong Academic Welfare, I mean, Meteorology. And with that, I will sign off now.

Snowy sidewalk in the 1600 block of R St NW, Washington, D.C., 11:00PM January 20, 2016.

*******

My intention is to update the blog tonight after the gym with the latest guidance, although I'm probably going to have to complete my co-worker's task late tonight from home as well.

--Regulus

No comments: