NYC/BOS area Friday snow storm

[Ed Mahmoud]

GFS says NYC and Island probably turn to rain, maybe sleet away from immediate coast, as a spread develops between magic 540 and 284 thickness and 850 freezing lines. Onshore flow means rain on Coast.

WRF seems to suggest great happiness, although Friday snow doesn't cancel school, and the Sunday storm may be a tad warmer...
GFS

WRF



I imagine we can extend this thread after Friday's snow by looking at Sundays rain on the coast (maybe even to Boston) snow storm.

[Ed Mahmoud]

I think better than a foot for BOS. QPF indicated 1 to 1.25 inches, and with strong omega and 850 mb near perfect for dendrite growth, near -10ºC, and nearly saturated conditions through the 700 mb layer, the fluff factor, instead of the normal 8 to 1 or 10 to 1, may be closer to 15 to 1, or possibly in excess of 15 inches. Close to 40 cm!

A little more liquid equivalent in NYC, but warmer temps, and a possible mix with sleet and even liquid rain, probably means about 6 inches of slush. Maybe more. BOS snow will be almost broom sweep-able, NYC will have heart attack snow. of course, earlier GFS runs showed a change to rain NYC and environs. We shall see what we shall see.

The 540 dm thickness line North of NYC indicates warmer air moving in aloft...

The 284 dm thickness line is much closer to NYC.

The 850 mb freezing line is South of NYC. Usually, these will be close to each other, but here, we see warm air aloft moving in, which is why NYC may change to sleet. Warm air up about 3 km, but colder air from about 2 km down. Surface temps may rise a touch above freezing because of flow off the ocean, but the precip may stay sleet because the surface layer above freezing might be relatively thin.

I was going to show pictures, but it is from my PPV AccuWx model graphics. I can show this when the PSU page updates to the 0Z NAM, if that happens before bed time.

[srainhoutx]

Good luck with that Ed.

[Ed Mahmoud]

Good luck with that Ed.

People will just have to take my word for it on the thicknesses and 850 mb temps.

No, they won't, non PPV 4 panel courtesy of the good folks at Penn State. I hope Joe Pa and the Lions kick the semi-pro athletes of Southern Cals butts!




ETA 6 panels!

[Ed Mahmoud]

Northeast Radar Loop- Here It Comes!



New WRF still shows about 1.1 inches liquid equivalent, and with 850 mb temps near/below -10ºC, I expect better (in my unofficial opinion) than a foot of snow, maybe 15 inches for BOS.

[Ed Mahmoud]

The snow has started in NYC. It looks like the rain/sleet line will be very near the city. It doesn't look to stay all snow.


Obs did show temps drop slightly and dewpoint start to rise with onset of precip, and the dewpoint is still a few degrees below freezing. Bummer being so close to a big ocean that doesn't cool down quickly.


But there is always February.

[jinftl]

Hopefully most folks went home early today...not a night to be driving in the northeast...Boston reporting near blizzard conditions with sustained winds of 30 mph!

REGIONAL WEATHER ROUNDUP
NATIONAL WEATHER SERVICE TAUNTON MA
500 PM EST FRI DEC 19 2008

BOSTON SNOW 30 E30G35
WORCESTER HVY SNOW 21
NANTUCKET LGT SNOW 34
PROVIDENCE HVY SNOW 31
HARTFORD HVY SNOW 25
NEW HAVEN HVY SNOW 29
PORTLAND ME SNOW 13
CONCORD NH LGT SNOW 18
ALBANY SNOW 14
NEW YORK CITY LGT SNOW 31
TRENTON LGT RAIN 34
ATLANTIC CITY LGT RAIN 47
PHILADELPHIA RAIN 37
ALLENTOWN FRZ RAIN 32
SCRANTON MIX PCPN 30

[Stephanie]

Yep, we were way too warm for any frozen precipitation.

Actually, I'm glad that we've received all of the wet weather we've been getting since November. It's usually a dry season.