Convergence Zone Snow

As shown below, the convergence zone snow is continuing and strengthening in southern Snohomish County....some of the roads have gotten problematic.


You can watch this event unfold (and know what is going to happen to you during the next hour) by viewing the radar animation:

http://radar.weather.gov/radar.php?rid=ATX

http://www.atmos.washington.edu/weather/radar.shtml

Latest NWS Spotter Reports"

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
747 AM PST WED DEC 29 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0600 AM     SNOW             3 NE MILL CREEK         47.89N 122.16W
12/29/2010  M1.0 INCH        SNOHOMISH          WA   NWS EMPLOYEE   

            SNOWING. VISIBILITY BETWEEN A HALF AND THREE-QUARTERS OF
            A MILE. SNOW ACCUMULATING ON THE ROADS. ELEVATION ABOUT
            500 FEET.

0700 AM     SNOW             5 NNW EATONVILLE        46.94N 122.31W
12/29/2010  M2.5 INCH        PIERCE             WA   TRAINED SPOTTER

            SNOW HAD STOPPED. ELEVATION 740 FEET.

0729 AM     SNOW             EVERETT                 47.96N 122.20W
12/29/2010  E2.5 INCH        SNOHOMISH          WA   PUBLIC         

            SILVER LAKE AREA

0730 AM     HEAVY SNOW       NW DUVALL               47.73N 121.97W
12/29/2010  M2.0 INCH        KING               WA   TRAINED SPOTTER

            TWO INCHES IN 30 MINUTES. STILL SNOWING HEAVILY.

WSDOT is on top of this--here are some of their latest reports:

7:43 a.m., Wednesday, Dec. 29

Good morning,

Driver alerts:

• I-5 at 164th Street SW: Several disabled vehicles are blocking the northbound I-5 exit to 164th Street.
• I-405 near Alderwood: Multiple spinouts are blocking the two right lanes of southbound I-405.
• I-405 near Canyon Park: A disabled vehicle is blocking the northbound carpool lane just north of the interchange with SR 527.

Seattle is pretty much untouched by this at this point....

Its Snowing! (But not everywhere)

I5 in North Lynnwood

During the past few hours it has been snowing in Everett and at Sea Tac but RAINING at Boeing Field and Renton. In fact, the snow was relatively hard around Everett to Lynnwood and is accumulating on the roads (see above). Why? There is an intense band of precipitation...very narrow... extending over Everett and environs...take a look at the radar to see:


The models were hinting at such a feature yesterday and it appears to be associated with a Puget Sound Convergence Zone. Temperatures are marginal for snow over the lowlands right now. Where precipitation is light in such situation..you get rain near sea level. But at higher lowland stations and where precip is heavy you can get snow. What is the freezing level right now? You can find that out using the Seattle profiler, a device that gives us wind and temperature aloft in real time. Here is the temperature plot (actually something called virtual temperature so subtract one degree C for regular temp):Looking at this, the freezing level is about 400 meters (roughly 1300 ft) and the snow level can drop to around 1000 ft below the freezing level (takes about 1000 ft to melt completely). Paine Field and Sea Tac are also relatively high (roughly 500 ft). All our precipitation starts as snow higher up in the atmosphere, but usually melts in the warmer atmosphere near the surface. Intensity is important because precipitation evaporates and melts as it falls, causing the freezing levels and snow levels to drop. Heavier precipitation...the freezing level drops more.

So today will be a difficult challenge. Our temperatures are marginal for snow at sea level. On the higher hills (above 300 ft) the chances of snow are increased and where precipitation is heavy the snow level could descend to sea level. So watch the radar. If the convergence zone revs up perhaps we might see a few inches near sea level in the central Sound. If not, this could be a big bust for snow lovers in Seattle. Again, this is NOT November 22! The ground temps are above freezing and air temps are above freezing. The road surfaces are not going to freeze, although slushy snow can be a bit slippery. And daytime and warmer temps are coming.

This convergence zone will probably slip south during the morning and probably weaken later...but the details are everything now.

It's Sad That I Understand This Only In The Most Abstract Way

Having never watched either of the shows in question, I can only vaguely understand the joke. But I know some of you do, so it seemed worth sharing.

Empire Strikes Back Chosen Amongst Others For The National Film Registry

Since the NFR is about preserving films as part of the American cultural legacy, my question is: which version of The Empire Strikes Back are they seeking to preserve... the one we all saw as children, or the re-edited version Lucas came out with instead.

It is an interesting question, is it not?

Wednesday Lowland Snow??

Snow at the top of Seattle Hills and rain near sea level often occurs
during marginal snow situations

There has been talk for nearly a week for the potential for lowland snow on Wednesday. I will analyze the situation below, but let me make it very clear at the outset--this is a VERY, VERY different situation than November 22nd. You will not see a powerful arctic blast associated with strong high pressure in British Columbia and a major coastal low over SW Washington. Temperatures will be far more marginal. Far less icing potential. But there COULD be some interesting wrinkles....like a chance for Puget Sound Convergence Zone snow.

A frontal system is moving through now and moderate to heavy snow is falling in the mountains. Between today and tomorrow, perhaps 1-1.5 feet in the mountains (see graphic). Good for skiers, snowboarders, and anyone who likes to play in the snow.

Cascade Mountain snowpack is running close to normal now, while the Olympics are way above normal. But this is not what you are probably interested in.

Tuesday will actually be a fairly nice day over the the lowlands, but the "action" follows later on Tuesday night into Wednesday as cooler air invades the region. For the lowlands, this air has a marine origin and thus the temperatures will be marginal for snow near sea level. This is not the primo cold air from the interior of British Columbia. Furthermore, the ground surfaces are above freezing. Here is the surface chart for 10 AM on Wednesday. The shading indicates temperature at around 1 km above the surface and below freezing is shown by white and blue colors.

A weak trough of low pressure over western Washington, but no low center near the coast and no strong high pressure area and intense cold over southern BC. Where precipitation is heavy enough, some snow showers could reach the surface, but nothing substantial. Here is the forecast 24-h snowfall ending 4 PM on Wednesday:


Snow showers over SW Washington and over the eastern Puget Sound suburbs and western Cascade slopes. Some suggestion of a Puget Sound convergence zone, with enhanced snow showers over the central Sound...but only a few light showers over Seattle. In fact, the forecast winds at 10 AM do indicated a convergence zone...see below.

The Convergence Zone is only transient and doesn't do much. If the CZ is stronger than forecast then more snow could hit the Puget Sound lowlands. However, forecast temperatures are predicted to peak near 40F on Wednesday. This looks marginal to me...only heavy precipitation and the cooling associated with it...something that is not predicted... could bring several inches of snow to Seattle.

We will continue to monitor the evolution of this event, but right now it does not look serious event near sea level. Eastern suburbs could get few inches. Not an icing situation during the day...

Polish OoB PDF

Since the Polish OoB has been downloaded 1010 times by this point I wonder if anyone have tried out the rules in a regular battle?

I frequently use the Polish OoB for cavalry, tankettes and everything connected to the Armia Krajowa (Polish resistance platoon) for my SoTR games. Would be interesting to hear whether other people find these rules fun and worthwhile :-)  ?

Axis and Allies: Pacific

Played Axis & Allies: Pacific this evening with a friend, I really like this game - I have not played any other A&A games but think this one has great balance and lots of different ways of winning as both sides. There is actually a very well thought and well written review of this game over at BoardGameGeek where a fan really does an in depth analysis of this game and the full potential.

It's completely centered on the pacific region, and it is a 2-3 player game. One player controlling Japan, and 1-2 players controlling India/Australia (UK) and China/US. The only downside is the overwhelming "setup" phase where you have to place units on the board. It takes a loooong time, the first turn is also very long since you will grind through allied regions and armies as Japan creating a vacuum and winning some time before the allies start to pile in on Japan from 3 fronts.