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Central PA & Fringes - December-January 2014-15


djr5001

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HERE WE GO!

 

Winter Weather Advisory WIN.gif

Statement as of 3:58 AM EST on January 23, 2015


... Winter Weather Advisory in effect from 7 PM this evening to
1 PM EST Saturday...

The National Weather Service in State College has issued a Winter
Weather Advisory for snow... which is in effect from 7 PM this
evening to 1 PM EST Saturday.

* Locations... the southeast half of Pennsylvania.

* Hazard types... snow.

* Accumulations... 2 to 4 inches.

* Timing... snow will overspread the region late this evening. The
snow will taper off late Saturday morning. The snow could
potentially change to rain or freezing rain early Saturday
morning from around Harrisburg south and eastward.

* Impacts... roads will become snow covered and slippery tonight
into early Saturday.


Precautionary/preparedness actions...

Hazardous winter weather conditions are expected or occurring.
Use caution if traveling. For the latest weather information... go
to weather.Gov/statecollege or monitor NOAA Weather Radio.

Report snow or ice accumulation to the National Weather Service
State College by sending an email to [email protected]...
posting to the NWS State College facebook Page... or tweet
@nwsstatecollege with the hashtag c... T... p... W... x.
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Some thoughts I have to watch for today...

 

Looking at some local 12z soundings it appears as if there is a warm layer just above the surface that is warmer than what the 0z NAM/GFS had for 12z this morning.  While at the moment it could mean absolutely nothing later on, I am curious to see if this warm layer will factor into more mixing occurring than we would like to see.  With that layer also currently on the drier side, we could also have it wet bulb back below freezing and eliminate this concern or with the direction the moisture will be pulled in from the south and east the far south east could have much more mixing and a bust where there are some higher forecast totals currently.  Glad I don't have to make any official forecasts for the York/Lancaster and east areas on this one (11z RAP even showing rain for onset of storm).

 

While we do have some concern regarding mixing... there is a ridiculous amount of moisture being pulled in off of the Gulf that if this system can tap into a little more than what models have I would imagine the precip shield being a little larger and quite possibly over performing in some areas.

post-285-0-78589600-1422020050_thumb.gif

post-285-0-36894900-1422020102_thumb.gif

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If this warm layer can get the hell out of here, Cashtown's likely looking at warning criteria overnight.

Yeah, I might be in a good spot for this one. Between this event, the clipper sun night into Monday, and the cold to follow I'm rather excited. Add a big event in February for everyone and I'd call this winter successful.

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Low of 19. Dew went down to 16 which was lower than I expected

Mag-- Id love to see a snowmap from you and I always appreciate your thoughts and knowledge you bring to this forum.

 

Thank you very much, I'll see if I can get one together later this afternoon (might be hitting the slopes this evening).

 

We're getting close to HRRR/RAP time with getting a good gauge on this precip shield and how it's going to handle. The early looks on both are pretty solid so far... they kinda look like the RGEM placement wise and don't seem too fringy for our north central folks. One thing i'll be concerned about in your neck of the woods and especially down in I-83Blizzard's area is the potential for mixing. CTP mentions mixing or changeover likely from MDT southward. I suspect the damage will be done by the point it does much mixing anyways, the main event for us is going to be the initial big shield of precip that will lift up over the area. This storm doesn't look to loiter around and hang any deform over us... and thus will hold the top end down probably to a 4-6" maybe scattered 7" kind of event. If I get a map made I will be probably be applying low snow ratios (8 or 10:1) in the Lower Sus Valley and 12:1 elsewhere. 

 

18 hr RAP

post-1507-0-10898100-1422022454_thumb.pn

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Thank you very much, I'll see if I can get one together later this afternoon (might be hitting the slopes this evening).

 

We're getting close to HRRR/RAP time with getting a good gauge on this precip shield and how it's going to handle. The early looks on both are pretty solid so far... they kinda look like the RGEM placement wise and don't seem too fringy for our north central folks. One thing i'll be concerned about in your neck of the woods and especially down in I-83Blizzard's area is the potential for mixing. CTP mentions mixing or changeover likely from MDT southward. I suspect the damage will be done by the point it does much mixing anyways, the main event for us is going to be the initial big shield of precip that will lift up over the area. This storm doesn't look to loiter around and hang any deform over us... and thus will hold the top end down probably to a 4-6" maybe scattered 7" kind of event. If I get a map made I will be probably be applying low snow ratios (8 or 10:1) in the Lower Sus Valley and 12:1 elsewhere. 

 

18 hr RAP

attachicon.gifcref_sfc_f18.png

not sure how reliable and how much we can believe it right now at the end of its range but both RAP/HRRR showing profiles above freezing right now but both are quite wet for what is moving into PApost-285-0-02195700-1422023158_thumb.png

 

so fun to track but so frustrating that a difference of 1-2C around here tonight may be what separates 4-6" and <1"... Hope I am wrong but I have this strange feeling that you and the state college folks could wind up with more snow than some of us further south and east! :-)

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1-2" seems like a decent forecast for UNV. There will likely be an area of weak 700 mb frontogenesis over north central PA which,] coupled with the enhanced moisture, should produce some light precip. Snow growth looks less than ideal as the best lift associated with the frontogenetic circulation (when the profile is mostly saturated; after 06z) will be around the -8C level.

 

Farther south and east, the mesoscale lift will be stronger but precipitation type will become more of an issue. The 00z Euro is colder, keeping MDT all snow while the 06z GFS warms temperatures around 850mb to just above freezing by 06z Saturday.

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1-2" seems like a decent forecast for UNV. There will likely be an area of weak 700 mb frontogenesis over north central PA which,] coupled with the enhanced moisture, should produce some light precip. Snow growth looks less than ideal as the best lift associated with the frontogenetic circulation (when the profile is mostly saturated; after 06z) will be around the -8C level.

 

Farther south and east, the mesoscale lift will be stronger but precipitation type will become more of an issue. The 00z Euro is colder, keeping MDT all snow while the 06z GFS warms temperatures around 850mb to just above freezing by 06z Saturday.

 

I'm thinking favorable banding will push us to 2-4" here in State College. Based on the storms I've seen like this in the past (my admittedly limited experience), decent banding usually sets up near, but not at, the northern edge of the precipitation shield. Pretty much right where UNV is projected to be.

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I'm thinking favorable banding will push us to 2-4" here in State College. Based on the storms I've seen like this in the past (my admittedly limited experience), decent banding usually sets up near, but not at, the northern edge of the precipitation shield. Pretty much right where UNV is projected to be.

Well the 12z NAM prolongs the 700 mb frontogenesis over northern PA, probably a result of the better ageos. circulation in the jet exit region. The hires 4 km nest gives us close to .5" here. We'll have to see if the rest of the guidance follows.
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