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Posted at 11:00 AM ET, 12/11/2009

Sunday storm: Not a good snow setup

By Dan Stillman

* Sunny but cold: Full Forecast | Climate change photos on exhibit *

Next Chance of Accumulating Snow: Sunday morning
Probability of Accumulating Snow (1" or more): 35%
Most Likely Potential Impact:

A storm on course to affect the D.C. area on Sunday leaves a lot to be desired for snow fans. The storm itself looks pretty weak, its counterclockwise circulation likely not strong enough to pull cold air down from the north as it tracks up from our south.


Output from the Global Forecast System (GFS) model for 7 a.m. Sunday shows precipitation moving in from the south. Blue line represents approximate position of the surface freezing line (above 32° to the south and below 32° to the north). Though models sometimes estimate this line too far north/northwest.

Meanwhile, there will be no high pressure parked to the north to pump cold air southward, or even keep in the semi-cold air that will be in place Saturday night. Instead, high pressure will be positioned offshore to our east. The clockwise circulation around the high will only serve to push warmer marine air into the area.

The end result? A possible period of snow or a mix, especially from around D.C. and northward, as the precipitation begins, which will probably be within a couple hours of sunrise Sunday morning. Those that see snow or a mix are likely to see precipitation change to all rain (generally from south to north) by mid-to-late morning or early afternoon as highs reach the upper 30s to low 40s, if not a bit higher.

If anything, the odds of getting an inch of snow may be slightly down from yesterday, but for now we'll keep the probabilities the same, as things can sometimes trend colder as wet get closer to the event...

No snow: 35%
Dusting to coating (mainly on grass): 30%
1-3": 25%
3"+: 10%

The Snow Lover's Crystal Ball appears when the potential exists for accumulating snow beyond 24 to 36 hours.

By Dan Stillman  | December 11, 2009; 11:00 AM ET
Categories:  Snow Lover's Crystal Ball  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   Del.icio.us   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Cold & sunny 'til Sunday snow chance
Next: PM Update: Still cold with waning winds

Comments

Any chance we can break this pattern of cold rain every 3-4 days? I'll even take some 7 days of cold sunshine.

Posted by: jojo2008 | December 11, 2009 12:37 PM | Report abuse

This is the problem with El Nino. You finally get a good sunny Arctic outbreak like today...and it all erodes into a cruddy old RAINSTORM by the time the moisture arrives [Sunday]! Can't keep the cold air IN PLACE!!!

At least the rain isn't hitting my dance dates...it's hitting the Buddhist meetings instead! I've got one of THOSE Sunday...My big dance tonight is safe but cold at the bus stops. This is the last VIP Dances event of 2009...next one will be after the New Years festivities.

Posted by: Bombo47jea | December 11, 2009 12:50 PM | Report abuse

Bombo- are you saying that because of El Nino, we may be in for a pattern similiar to last year where we get cold breaks that end just in time for the rain, and then back again? That was SO frustrating. I hope that is not in store.....I have my heart set on a snowy winter!

Posted by: Snowlover2 | December 11, 2009 1:15 PM | Report abuse

I have some time here for a national & worldwide lightning summary.

Nationally, there's not much to report, only an area of thunderstorms in a rather unusual area...in the Pacific a number of miles offshore central California; the Monterey Bay/Point Conception area...though winter is the "thunderstorm season" in much of California...one reason they are rather rare in the Golden State. El Nino winters have more California thunderstorms than other years.

Worldwide we're seeing plenty of lightning in the usual hot spots for this time of year...South America north of Argentina, Africa south of the Equator and Indonesia. Some of the rather unusual areas with frequent lightning right now include a possible cold front approaching the Iberian Peninsula and Morocco, a Southern Hemisphere cold front between Australia and New Zealand, and the eastern Mediterranean between Greece and Syria/Palestine. The Pacific storm approaching California mentioned above is also seeing some activity. Otherwise the isthmus of Panama is still seeing some storms and there are two probable tropical systems in the Indian Ocean with a few strikes: one between the Indian subcontinent and Thailand and another south of the Equator and east of Madagascar. Principal activity in the North Atlantic is along the frontal boundary well offshore the Atlantic seaboard. This system is so far offshore the strikes are no longer being recorded on the national Vaisala map.

Posted by: Bombo47jea | December 11, 2009 1:29 PM | Report abuse

10% chance for 3"+ woohoo!

ok, this this weekend is a bust, but how's that mid-next-week storm shaping up?

Posted by: walter-in-fallschurch | December 11, 2009 1:53 PM | Report abuse

@snowlover2:

The problem with El Nino is that cold air tends to get bottled up by the strong Pacific zonal jet and stays near the Arctic Circle or gets flushed out over the North Atlantic. Strong zonal jets are no good for cold air advection. You need a good meridional pattern to get the cold air down here & keep it in place. This is where the blocking negative NAO high over Greenland comes in.

Last winter we had the exact opposite setup...plenty of cold air but it was too dry and strong to generate any big coastal storms. Moisture last winter stayed well to our south. The lack of a subtropical jet ensured little or no coastal or Gulf cyclogenesis. The jet was also very fast last winter, moving any storms which did form well out to sea.

As a rule whenever high pressure passes over us or to our south it advects too much mild air with the return flow as it retreats. High pressure to our north tends to feed in a northeasterly flow of cold Arctic air, particularly later in the winter when land [and ocean] is colder than at the beginning of the season.

We can still hope for a winter like that of 1986/87 when it gets cold late in the season & we get a lot of snowstorms after mid-January. Unfortunately, there are some signs the El Nino may be going "strong" as it did during the "busted" winter of 1997/98. That year we got the storms but all that we got was blustery cold rain, though we got a couple of exciting winter thunderstorms that year.


Posted by: Bombo47jea | December 11, 2009 2:00 PM | Report abuse

Thanks for the explanation! Very informative!

Posted by: Snowlover2 | December 11, 2009 6:01 PM | Report abuse

I agree, this is looking more & more like another snow starved winter. I predicted that this EL Nino would b stronger than predicted, & I'm still expecting a rather snowless winter. Seems like every El Nino is stronger than org. predicted.

Posted by: VaTechBob | December 11, 2009 7:23 PM | Report abuse

The comments to this entry are closed.

 
 
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