Sunday, December 16, 2007

GUESS WHO'S COMING FOR DINNER?

Good thing I kept my expectations low for this morning, as I saw outside what some of you weren't expecting to see...windswept rain in the 40's. But scroll down to the set of 3 maps to see who I think may be coming to dinner.

I see that many location east of the Blue Ridge that were icing last night changed over to rain. While I expected that too (remember the "frozen-liquid-frozen" bit from yesterday), I can still hear the collective sigh from across the lands. It does just seem wrong and sacreligious to have a nice pretty coating of ice get washed away so quickly. So what happened? To put it in simple terms, strong southerly flow ahead of the primary low sent warm air intruding aloft, which overnight worked down to the surface, scouring out the marginal cold air east of the mountains. But from Hagerstown on west along the PA-MD line, surface cold air remained locked in, providing a constant supply of freezing rain. Secondly, Influence of subtropical moisture really revved up the secondary low as some of you observed with the heavy rain overnight.

What looks apparent to me on the national radar is proof of my long standing rule.. the primary low always seems to stay stronger longer. The benefit of that is areas east of the blue ridge are caught in this warm "occluded zone" keeping temps in the upper 30's to around 40. While that's depressing for those of you wanting ice (odd bunch they are) this setup also prevents surface moisture from evaporating. Theoretically, once the primary low decays, cold air will rush in to fill the gap left by it and the departing secondary low. For those in school systems (or elsewhere) wishing to have a delay or closing, we'll have to see rapid refreezing in the overnight hours.

First map is known as Surface Streamlines. Note the position of 2 lows and the counter-clockwise flow. What's interesting is the pull of air from New England and New York into PA on backside of the coastal low... now go on to the next map.

Surface Streamlines..note the 2 Lows

Surface Map for this morning, or view a current animation. Observe how the warmer air is being held to the coast and not intruding across PA, as evidenced by the precip type seen by the radar. Those of you along I-95 or in a blue zone here might say, "Well it's raining at my house but your map shows it's snowing." That rain may have been snow above for a brief time before melting on the way down. For the cold air to arrive, either the secondary low has to pull it in from the north, or the front to our west has to sweep through.

Surface Map as of 7:30 AM 12/16

The most interesting observations come from this map. See how the 30's are entrenched across PA, and the 40's are being held to the coastal plain. In fact, look at the contrast between northern and central NJ.. 29 vs. 41. Also note the lobe of 20's nosing down through eastern PA and the depth of near-freezing temps extending through central VA. This tells me there's a slow gravy train of cold air being setup by the developing secondary Low that's taking over air flow as the primary Low decays slowly. Will also be interesting to see how that large area of 40+ is dealt with as cold invades from the west and north during the day.

Is the cold air trying to sneak back in?

So who's coming to dinner? For areas east of I-81 in PA, MD and VA...whatever precip you have will changeover to snow showers with strong north winds late, followed by temps in the upper teens in central and eastern PA, and the 20's in MD west of the Bay, 30's east of the Bay. Too early to tell how temps and precip will impact schools, that may not become apparent until very late tonight. Until then, please consider posting your observations IF YOU NOTICE A SHARP CHANGE OVER A SHORT TIME, I think you'll start to see it soon...

19 comments:

playastyle said...

MAN! I WANTED SNOW!!!
lol

anywho, do you know when the next time were supposed to get a REAL snow storm? im talking massive. "The big daddy", "the snowzilla" "the snow'keel o niel..."(that last one may have been a stretch). I really want a blizzard!

Julee said...

Here is how I have learned to interpret Maryland winter weather predictions ...

PREDICTION: Big storm coming! Possible blizzard conditions! Bring in the dog! Check the milk supply!
ACTION: Plan picnic.

PREDICTION: Light dusting, to an inch ...
ACTION: Go to Lowe's. Buy snow blower.

Follow these instructions and you won't be disappointed.

Mr. Foot said...

Yes Julee, you are exactly right. PePop, one of the grandfathers to my girls, has a rule about these kinds of storms:

"The amount of precipitation that falls is inversely porportional to the amount of hype before the storm."

And that is exactly what happened.
While I did initially call for 12"+ as a possibility west of the mountains, I never did say it'd be an all-out snowstorm for I-95.

Heh, from now on Julee, we're going to send you down to check with the grocer before posting a call on a big coastal storm.

How's this for disappointed. Based on the glorious sunshine now permeating the region, I am watching our posssible 2 hour delay evaporate like candy canes in front of kindergarteners.

Mr. Foot said...

playastyle.. I am leaning on mid to late March for your big Kahuna.
Seriously.

We may blowtorch into the 70's come January, and even 80 one day in February. Then it will all come crashing down, oh, say 1-2 days AFTER the spring Equinox.

Dec 31, 1984 it was 75F at Ocean City. Then just weeks later Jan 20-22, 1985 one of the coldest periods in recent memory sent temps where I was in suburban Philly to -16 F one night.

I remember a surge into the 70's in January 1990, and also last year, on the 20th I was transplanting bushes at night in the backyard: 71 F.

The Saturday before Easter
(4/7/07): 1/2" snow.

The rule this winter might be that most of your accumulating snow occurs OUTSIDE astronomical winter.
And by this time next month, the media will be calling it "The Year Without A Winter!"

Just try telling that to the 1 million folks out west who lost power in the ice storms.

Anonymous said...

No... noooo.. nooo.... NOT MARCH!!Spring Sports will be a mess with a big Kahuna then! ::whining:: sorry...

Well.. I was hopin' to sleep in tomorrow too Mr. Foot... but with a Holiday Assembly looming and the students needing preparation time -guess this is acceptable!

E.H. Boston said...

Well, with my 8.5" of new snow, I'm not complaining.

Boston came in with 8.8" on top of Thursday's 10.1"...yeah...loving life here.

Prospero said...

Would have loved the 2-hour delay (at SPHS). Oh well, maybe the wind will knock out the power.

Not likely.

Grant said...

I would hope we would get a delay of some sort tomorrow or possibly off school but that look like that won't happen :( Ugh I hate being in of those states that is just in the Middle of everything :( You never know what would happen here in Baltimore.

Mr. B said...

So much ice last night. Hardly any damage here though.

Winds gusty now.

Peaked at 52mph. That should about do it.

Grant said...

Mr.B what do you mean "That should about do it"? As in what? Sorry for misunderstanding.

Mr. Foot said...

I think what Mr. B meant was that is the end of what this storm had to offer, some ice, lotsa wind and t-t-t-that's all folks.

I guess there's that outside chance of a delay given the strong winds..but highly unlikely.

Welcome to the Longest Week of the Year. No snow on the ground (at least south of MDL), no hope in sight of any this week, for Christmas or anytime after that.

Get ready to go tropical, after the 1st of the year. You won't have to head south for the holidays, the southlands are coming here. Just wait and see, January may end up feeling more like June!

Grant said...

Wow are you serious Mr.Foot? lol, that's CRAZY !

Mr. B said...

I meant that will mostly likely be my highest wind gust, but I hit 58mph.

I think the trees here are made of steel cause there was no ice storm damage and no wind damage. Looks like just north of DC is getting nailed with winds. Transformers blowing and trees on fire from what I hear. Anyways PSU mont alto where I go to school has trees down and no power. My finals tomorrow where canceled and moved to Friday. DOH!!

Grant said...

Your Lucky :( ! Wished that happened down here in Cool old Dumbdalk !

ANDY Southern York County, PA said...

I figured the models would not verify with the early prediction of 20-30 inches. Climatology does not favor such a large snow event around here this early in the season. There are a few more shots at snow before the 25th. It's something to watch, but not get excited about. Jan and Feb are our best chances for huge storms around here, so after the holiday rush and New Year libations all eyes to the sky.

E.H. Boston said...

Another 7.5" of snow here in Woburn today!

So...since last Thursday...10" Sunday...9.5"; Thursday 7.5"

Weekly Total Snowfall 27"

Snowpack to 20"!!!

Snowfall to Date 33"

ANDY Southern York County, PA said...

I think we need to move to Boston. Snow, Patriots, and Sox. I'm sold!

E.H. Boston said...

Andy...don't forget the Celts.

Merry Christmas everybody!

wvm said...

Merry Christmas. I hope you all have a very blessed and peaceful Christmas:)