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nj2va

President's Day Storm Obs & Nowcasting

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HRRR does get some of that front running stuff to the ground. Verbatim someone could get 1". I wonder about it though.. the main body is still well west. Radar looks like at least 10-12 hours or so to start time to me.

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RAP has that little finger develop over the area around midnight too. Kind of in the squeeze zone between departing high and arriving precip.

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Rgem gives dc and south a half inch of snow by 1am. It seems too early to me but other guidance has it too. I would think dry air would keep the brakes on early accums like that.

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There is some hint of a frontogenic zone trying to set up where the RAP/HRRR show that band around midnight.. sort of parallels the Potomac on them. SPC mesoanalysis shows it a bit. RAP has the band for 2-3 hours then a break before the main activity moves in around sunrise. HRRR seems to hint at the same thing but doesn't go as far.

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12z 5k HI-RES NMM is best case scenario if we want lots of snow and ice... keeps the area below freezing through 12z TUE

Don't really have time to check. Out in Bowie this afternoon. Map?

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Clear skies overhead here in Media Delaware County, PA but there are high clouds gathering in the skies to the west-southwest.  19f 21% humidity dew point -12f wind north at 15 mph pressure 30.51 steady.   That dew point -12f will be a killer here for snow but may bring more ice with that profile later in the game.

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   and the Hi-Res Window ARW is the worst case scenario with the morning snow basically hitting a brick wall at the Potomac

 

12z 5km HI-RES NMM is best case scenario if we want lots of snow and ice... keeps the area below freezing through 12z TUE

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There is some hint of a frontogenic zone trying to set up where the RAP/HRRR show that band around midnight.. sort of parallels the Potomac on them. SPC mesoanalysis shows it a bit. RAP has the band for 2-3 hours then a break before the main activity moves in around sunrise. HRRR seems to hint at the same thing but doesn't go as far.

 

21z RAP hints at it as well around 11pm-2am... so does 21z HRRR

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Didn't take much time for snow to make it to the surface once the more solid returns were overhead. Already have a coating on sidewalks/roads etc. Down to 19 degrees.

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