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Thread for 12/14 potential dusting, arctic air, and 12/17 potential slop

North Balti Zen

By North Balti Zen,
in Mid Atlantic

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feloniousq

feloniousq

Posted
Posted
4 minutes ago, mattie g said:

I imagine this is what winter "threat" threads are like in the southern Mississippi forum.

Southern Alabama and Mississippi got moderate to heavy snow the week before Christmas twenty years ago, so probably we're even worse.

 

https://web.archive.org/web/20070820002956/http://www.srh.noaa.gov/mob/121896Snow/18Dec96main.html

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BTRWx

BTRWx

Posted
Posted
1 minute ago, NorthArlington101 said:

Yeah that's also very true. The NAM's 3k counterpart dry-slots us completely. I doubt that's likely, but I guess it a dry-slot would be better then a soaking rain.

The Low is headed for the upper Great Lakes, so that scenario is not that unlikely imo.

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high risk

high risk

Posted
Posted
1 minute ago, BTRWx said:

Then what's the 12k?  I haven't seen data from it elsewhere.

     The parent NAM is run at 12 km.   The 32 km NAM is just the 12 km native grid interpolated to a 32 km grid.   

     The 12 km grid just covers an area slightly larger than CONUS - you'll see that if you try to display all of North America in TT, it can't do it for the 12 km grid.    Most users don't have the bandwidth to download a full-domain 12 km grid, but they want high resolution, so NCEP has a 12 km NAM CONUS display grid.   We make the 32 km grid, which covers the entire domain, so that users who want the full domain can have smaller files.

 

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BTRWx

BTRWx

Posted
Posted
12 minutes ago, high risk said:

     The parent NAM is run at 12 km.   The 32 km NAM is just the 12 km native grid interpolated to a 32 km grid.   

     The 12 km grid just covers an area slightly larger than CONUS - you'll see that if you try to display all of North America in TT, it can't do it for the 12 km grid.    Most users don't have the bandwidth to download a full-domain 12 km grid, but they want high resolution, so NCEP has a 12 km NAM CONUS display grid.   We make the 32 km grid, which covers the entire domain, so that users who want the full domain can have smaller files.

 

Thank you!  I thought the two outputs looked similar.

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Bob Chill

Bob Chill

Posted
Posted

Rgem is really icy. Decent precip through 15z before the flip to rain. Considering tomorrow may not even get above freezing, ice accretion could be higher than normal with heavier rain if the rgem has the right idea. I trust it more than the nam but I've seen it jump around and miss plenty. 

Hopefully yoda posts the text output 

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eurojosh

eurojosh

Posted
Posted
27 minutes ago, high risk said:

     The parent NAM is run at 12 km.   The 32 km NAM is just the 12 km native grid interpolated to a 32 km grid.   

     The 12 km grid just covers an area slightly larger than CONUS - you'll see that if you try to display all of North America in TT, it can't do it for the 12 km grid.    Most users don't have the bandwidth to download a full-domain 12 km grid, but they want high resolution, so NCEP has a 12 km NAM CONUS display grid.   We make the 32 km grid, which covers the entire domain, so that users who want the full domain can have smaller files.

 

I stand strongly corrected (and informed!)

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yoda

yoda

Posted
Posted
1 hour ago, Bob Chill said:

Rgem is really icy. Decent precip through 15z before the flip to rain. Considering tomorrow may not even get above freezing, ice accretion could be higher than normal with heavier rain if the rgem has the right idea. I trust it more than the nam but I've seen it jump around and miss plenty. 

Hopefully yoda posts the text output 

00z RGEM says we skate

1 inch of snow followed up by 0.3 tenths of an inch of ice before we break freezing at around 15z at DCA... definitely gives us a chance to see an unfamiliar winter storm warning issued

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showmethesnow

showmethesnow

Posted
Posted

Euro is a little drier and a little warmer. Hard to tell what falls as frozen because of the 10+ temp increase on the surface from hours 36 to 42. Best questimate would be .1-.2 through the metro areas and that may be generous especially for DC. Regions around the MD/PA line would do slightly better but not by much. Any hopes for snow, besides some initial pity flakes are all but shot. As far as back end snow, that is not looking good on the Euro either. Even the 00Z ensembles have lost what 1/3 of the members had on the 12Z with minor snow accumulations through the central portions of the region.

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Snowman.

Snowman.

Posted
Posted 
SOUTHERN BALTIMORE-NORTHWEST MONTGOMERY-
CENTRAL AND SOUTHEAST MONTGOMERY-NORTHWEST HOWARD-
CENTRAL AND SOUTHEAST HOWARD-SOUTHEAST HARFORD-WARREN-CLARKE-
PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-NORTHERN FAUQUIER-
WESTERN LOUDOUN-EASTERN LOUDOUN-
348 AM EST FRI DEC 16 2016

...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO
NOON EST SATURDAY...

THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
ISSUED A WINTER WEATHER ADVISORY FOR SNOW, SLEET AND FREEZING
RAIN... WHICH IS IN EFFECT FROM MIDNIGHT TONIGHT TO NOON EST
SATURDAY.

* PRECIPITATION TYPE...SNOW, SLEET AND FREEZING RAIN.

* ACCUMULATIONS...SNOW AND SLEET ACCUMULATION OF LESS THAN 1
  INCH...ALONG WITH AROUND A TENTH OF AN INCH OF GLAZE ICE.

* TIMING...SNOW AND SLEET WILL OVERSPREAD THE REGION AFTER
  MIDNIGHT TONIGHT, THEN CHANGE TO FREEZING RAIN BEFORE DAWN
  SATURDAY MORNING. THE FREEZING RAIN WILL CHANGE TO RAIN BY NOON
  SATURDAY.

* IMPACTS...HAZARDOUS TRAVEL IS EXPECTED DUE TO ICY ROADS AND
  WALKWAYS.

* WINDS...SOUTH 5 TO 10 MPH.

* TEMPERATURES...IN THE MID TO UPPER 20S LATER TONIGHT, RISING
  INTO THE LOWER 30S SATURDAY MORNING, AND ABOVE FREEZING SATURDAY
  AFTERNOON.

 

 

  

DISTRICT OF COLUMBIA-PRINCE GEORGES-ANNE ARUNDEL-SHENANDOAH-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-HARDY-EASTERN GRANT-
348 AM EST FRI DEC 16 2016

...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO
9 AM EST SATURDAY...

THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
ISSUED A WINTER WEATHER ADVISORY FOR SNOW, SLEET AND FREEZING
RAIN... WHICH IS IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM EST
SATURDAY.

* PRECIPITATION TYPE...SNOW, SLEET AND FREEZING RAIN.

* ACCUMULATIONS...SNOW AND SLEET ACCUMULATIONS OF LESS THAN 1
  INCH...ALONG WITH AROUND A TENTH OF AN INCH OF GLAZE ICE.

* TIMING...SNOW AND SLEET WILL OVERSPREAD THE REGION AFTER
  MIDNIGHT TONIGHT, THEN CHANGE TO FREEZING RAIN BEFORE DAWN
  SATURDAY MORNING. THE FREEZING RAIN WILL CHANGE TO RAIN AROUND
  MID-MORNING SATURDAY.

* IMPACTS...HAZARDOUS TRAVEL IS EXPECTED DUE TO ICY ROADS AND
  WALKWAYS.

* WINDS...SOUTH 10 TO 15 MPH WITH GUSTS UP TO 20 MPH.

* TEMPERATURES...IN THE UPPER 20S LATER TONIGHT, RISING INTO THE
  30S ON SATURDAY MORNING.
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showmethesnow

showmethesnow

Posted
Posted

06Z 12 k Nam has a more promising look then the Euro. Holds the surface in metro regions until most of the precip has already fallen. Total precip at DC sits at roughly .2 and those amounts increase north and west to where we see roughly .5+ on the MD/PA line and in NE MD. NAM also still likes the idea of some back-end snow but that is at range so needs to be taken with caution. If its snowfall maps are to be believed it is showing 2+ inches north and west of the cities. But in more likelihood most of that is probably sleet and/or freezing rain. 

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showmethesnow

showmethesnow

Posted
Posted

Would take the 06z RGEM in a heartbeat. Shows roughly .5-.9 precip area wide with 3/4+ falling as frozen. Just a quick glance suggests we would see an inch, maybe 2 of snow topped by a decent amount of sleet and crusted over by a glaze of ice. Nothing says welcome to the mid-atlantic until you have lived through a slopfest that the RGEM suggests. 

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