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Central PA - Winter 2020/2021 Part 2


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Boy I bet the DC metro folks are loving seeing the 0z NAM and some of the differences between other models this close to game time (||GFS vs GFS and Euro). 3k gives them almost nothing snowy and 12k NAM isn't much better and the 0z HRRR hits them good. My only worry for this region is some sleet mixing in at some point for a little bit in the southern counties. At least none of us are riding THAT edge for this event. 

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4 minutes ago, MAG5035 said:

Boy I bet the DC metro folks are loving seeing the 0z NAM and some of the differences between other models this close to game time (||GFS vs GFS and Euro). 3k gives them almost nothing snowy and 12k NAM isn't much better and the 0z HRRR hits them good. My only worry for this region is some sleet mixing in at some point for a little bit in the southern counties. At least none of us are riding THAT edge for this event. 

To clarify a bit, holy crap the NAM is sleeting on DC. 2.5-3"+ on both the NAMs lol. 

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5 minutes ago, MAG5035 said:

Boy I bet the DC metro folks are loving seeing the 0z NAM and some of the differences between other models this close to game time (||GFS vs GFS and Euro). 3k gives them almost nothing snowy and 12k NAM isn't much better and the 0z HRRR hits them good. My only worry for this region is some sleet mixing in at some point for a little bit in the southern counties. At least none of us are riding THAT edge for this event. 

LWX 9pm update

00Z IAD sounding showed a warm nose of 1.8C at the 809 mb
level. This is around 1C warmer than what most of the 18Z models
initialized. The 18Z Canadian Regional had the best
initialization of the 18Z guidance with a warm nose around 1C
with the 00Z NAM now having caught up to the warmer air aloft.
Although, there is a lot of dry air at that level which would
result in wet-bulb cooling once precip arrives, the trend in the
models has been for a faster changeover to mixed precip Thu
morning. Will be incorporating more of the 00Z NAM and 18Z
Canadian Regional in our update tonight. These two models have
verified the best with temps aloft this winter, especially with
the mid December 2020 and Feb 10 mixed precip events.

There has also been a trend toward a faster exit of the
precipitation late Thu night across the region with precip only
lingering across southern MD and in the upslope areas.
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6 minutes ago, Cashtown_Coop said:

LWX 9pm update

00Z IAD sounding showed a warm nose of 1.8C at the 809 mb
level. This is around 1C warmer than what most of the 18Z models
initialized. The 18Z Canadian Regional had the best
initialization of the 18Z guidance with a warm nose around 1C
with the 00Z NAM now having caught up to the warmer air aloft.
Although, there is a lot of dry air at that level which would
result in wet-bulb cooling once precip arrives, the trend in the
models has been for a faster changeover to mixed precip Thu
morning. Will be incorporating more of the 00Z NAM and 18Z
Canadian Regional in our update tonight. These two models have
verified the best with temps aloft this winter, especially with
the mid December 2020 and Feb 10 mixed precip events.

There has also been a trend toward a faster exit of the
precipitation late Thu night across the region with precip only
lingering across southern MD and in the upslope areas.

That is some good nowcasting.

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11 minutes ago, Cashtown_Coop said:

LWX 9pm update

00Z IAD sounding showed a warm nose of 1.8C at the 809 mb
level. This is around 1C warmer than what most of the 18Z models
initialized. The 18Z Canadian Regional had the best
initialization of the 18Z guidance with a warm nose around 1C
with the 00Z NAM now having caught up to the warmer air aloft.
Although, there is a lot of dry air at that level which would
result in wet-bulb cooling once precip arrives, the trend in the
models has been for a faster changeover to mixed precip Thu
morning. Will be incorporating more of the 00Z NAM and 18Z
Canadian Regional in our update tonight. These two models have
verified the best with temps aloft this winter, especially with
the mid December 2020 and Feb 10 mixed precip events.

There has also been a trend toward a faster exit of the
precipitation late Thu night across the region with precip only
lingering across southern MD and in the upslope areas.

Great catch. And the 0z sounding (weather balloon) is hard data too. This was my worry about the southern tier in terms of a getting a warm layer somewhere in between 850-700mb. Yea it will wet bulb down, but more robust WAA there is already being noted. Fortunately for our region I think this has been trending towards minimizing the threat for sleet/mixed (0z NAM didn't have it getting very far across the mason-dixon). But there's still a decent possibility of pingers at some point to consider in likely the bottom tier of LSV counties.

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Good night gents and good luck to everyone in the morning.  Latest from Horst.......

(1/2) This is one of those winter systems where just 25 - 50 miles will make a big difference in what accumulates. As I see things this evening, the system is stringing out under a rocking upper-level jet w/ less-than-expected right entrance region support. The result may be...

(2/2) ...a slight southward shift, perhaps less icy mix (here in Lanco), and a slight reduction in max snowfall amounts. Need to wait & see where the best (narrow) snow band sets up in the AM...but for now no reason to change my earlier idea of 4-8" (Rt 30 north) and 2-5" south.

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Just now, Mount Joy Snowman said:

Good night gents and good luck to everyone in the morning.  Latest from Horst.......

(1/2) This is one of those winter systems where just 25 - 50 miles will make a big difference in what accumulates. As I see things this evening, the system is stringing out under a rocking upper-level jet w/ less-than-expected right entrance region support. The result may be...

(2/2) ...a slight southward shift, perhaps less icy mix (here in Lanco), and a slight reduction in max snowfall amounts. Need to wait & see where the best (narrow) snow band sets up in the AM...but for now no reason to change my earlier idea of 4-8" (Rt 30 north) and 2-5" south.

Great writeup. I think this is so a game time decision and really not a forecast. 

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2 minutes ago, Mount Joy Snowman said:

Good night gents and good luck to everyone in the morning.  Latest from Horst.......

(1/2) This is one of those winter systems where just 25 - 50 miles will make a big difference in what accumulates. As I see things this evening, the system is stringing out under a rocking upper-level jet w/ less-than-expected right entrance region support. The result may be...

(2/2) ...a slight southward shift, perhaps less icy mix (here in Lanco), and a slight reduction in max snowfall amounts. Need to wait & see where the best (narrow) snow band sets up in the AM...but for now no reason to change my earlier idea of 4-8" (Rt 30 north) and 2-5" south.

i've been thinking the harrisburg area gets way less since that's just how the patterns been the past few weeks. we've ended up with way less snow/ice/sleet than modeled or forecast each time lol so wouldnt surprise me if this happens again and we get way less than the 6-9 inches called for. really sucks that none of these storms have been overachievers here

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