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Central PA - Winter 2018-19


pasnownut

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2 minutes ago, paweather said:

Yeah frustrating this late in the game models don’t know what to do. This is 2019 not 1989.

In reality no matter what the LP does and when, I think we now need to look at thermal profiles and climo blend (like Horst does well) and try to figure in what happens and where. CAD and WAA will be our battle and as so many are so close, a subtle shift may make or break someone’s forecast.  Look at 700/ 850/925’s and you should be able to come to your own conclusions. Toggle thru prior runs to see trends. You can also get better profile view from soundings on pivotal for your area. They help to show depth of WAA or CAD. 

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3 minutes ago, pasnownut said:

In reality no matter what the LP does and when, I think we now need to look at thermal profiles and climo blend (like Horst does well) and try to figure in what happens and where. CAD and WAA will be our battle and as so many are so close, a subtle shift may make or break someone’s forecast.  Look at 700/ 850/925’s and you should be able to come to your own conclusions. Toggle thru prior runs to see trends. You can also get better profile view from soundings on pivotal for your area. They help to show depth of WAA or CAD. 

Your exactly right, Nut. 

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CTP at 9:56 pm is NOT backing down for the Harrisburg area with the Winter Storm Warning which they just updated.

National Weather Service State College PA
956 PM EST Fri Jan 18 2019

PAZ033>036-056>059-063-191200-
/O.CON.KCTP.WS.W.0001.190119T1800Z-190120T1800Z/
Somerset-Bedford-Fulton-Franklin-Perry-Dauphin-Schuylkill-Lebanon-
Cumberland-
Including the cities of Somerset, Bedford, McConnellsburg,
Chambersburg, Newport, Harrisburg, Hershey, Pottsville, Lebanon,
and Carlisle
956 PM EST Fri Jan 18 2019

...WINTER STORM WARNING REMAINS IN EFFECT FROM 1 PM SATURDAY TO
1 PM EST SUNDAY...

* WHAT...Heavy mixed precipitation expected. Total snow
  accumulations of 5 to 10 inches, with the lowest amounts south
  of the turnpike. Ice accumulations of one to two tenths of an
  inch are expected.

* WHERE...Portions of southern Pennsylvania.

* WHEN...Snow will develop Saturday afternoon and could become
  heavy at times by evening. The snow will change to mixed
  precipitation Saturday night, then taper off by dawn Sunday.

 

 

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9 minutes ago, Voyager said:

Still sitting at 35 degrees after a high of 37 this afternoon. Clouds and humidity (it's actually a little bit foggy/hazy here) are probably holding temps up. What implications that has for tomorrow, I don't know...

Likely not helping IMO. We want dews as low as possible to show cold air intrusion into column prior to onset of precipitation. Higher humidity only means we won’t “waste” Qpf when it arrives as column won’t need to moisten up. 

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I'm sure cloud cover is holding temps up a bit at the surface, but aloft the 925mb and 850mb temps are easily below 0ºC right now. The 850mb 0 line is running along southern VA right now per mesoanalysis. If surface temps are near or a tad above freezing at precip onset tomorrow they'll likely drop back some. In the far southern tier it may start as something else briefly until heavier precip cools the column all the way down. Onset of this isn't looking like it's till early afternoon in the Sus Valley. 

1550199744_ScreenShot2019-01-18at10_19_21PM.thumb.png.aa252ef5ee4dad86e5ee6ba3e8bcfe68.png

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22 minutes ago, bubbler86 said:

He is and that is the bad part...thermals up the column are important and heavy snow can bring down cold air but we are not getting a major snow or ice storm with DP's around 30 and a southerly wind.  Need something to import cold air in.  

Wet bulb will factor in to see how long it can snow in your area. Im not as versed on that as I’m more comfy in the big pic. Not the finer details. Soundings are a great way to get generalizations as to what the column supports. 

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1 hour ago, canderson said:

CTP has to be factoring in quite heavy rates tomorrow evening before the warm air hits. 

Which sounds awesome!

CTP & JB have both referenced the November storm for the the possibility of heavy snow for the front end thump tomorrow.

For that November storm in the Harrisburg area, the heavy snow started around 10 am & then lasted until around 4 pm when it then changed over to sleet.

The 8.8 inches of snow that MDT recorded basically took place 6 hours. 

Hopefully tomorrow we do that again!

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17 minutes ago, Blizzard of 93 said:

I would sign up for half of what this 0z NAM  Run shows for the Harrisburg area.

 

F9A4AAF3-BBA1-4763-98D5-CA84CCD14A12.png

I have a physical geography degree in atmospheric sciences. (Did not have meteorology degrees back in the 70's at my college) This has been a serious hobby for me the last 40 years. I have seen this type of frontal setup for us in PA numerous times in the past 25 years. This model run as shown above IMHO is the most accurate of what I think will actually occur.  The snowfall amounts seem high but not impossible. The 850 above freezing warm layer will be held back at or near the Fall line. Yes there will be sleet mixed in the LV but that will occur in the heavier banding of snows. The 17" indicated at ABE seems high but it is possible. The record of snowing 5"  in an hour rates happened in 1983 at ABE in similar conditions.  At this time, many should be looking at the mesoscale models only for mid level temps and especially wind speed and their directions, banding snowfall rates and simply rely on weather history under similar conditions. Trying to figure out the snow/ice/rain transition lines in this type of storm is dam near impossible. The best way I relied on when I was in my 20's was wind direction and analogs of previous storm events. Once the winds changed direction to the SE, in the middle to end of the storm snow accumulations fell drastically as the mix set in - usually sleet and light freezing rain. Hope this helps. This storm has been a real challenge for me. My first call three days ago was 8-14 for the LV and I am sticking to it. I am leaning closer to 8 in if the mix sets up.

 

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Anyone know why Tropical Tidbits and Pivotal Weather are so different in their total snowfall maps for same model run and time? Does one include sleet while the other doesn't?

Basically, Pivotal has me at 3 inches @ hour45 and TT and even WxBell above have me at 20 inches.

 

 

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6 minutes ago, Albedoman said:

I have a physical geography degree in atmospheric sciences. (Did not have meteorology degrees back in the 70's at my college) This has been a serious hobby for me the last 40 years. I have seen this type of frontal setup for us in PA numerous times in the past 25 years. This model run as shown above IMHO is the most accurate of what I think will actually occur.  The snowfall amounts seem high but not impossible. The 850 above freezing warm layer will be held back at or near the Fall line. Yes there will be sleet mixed in the LV but that will occur in the heavier banding of snows. The 17" indicated at ABE seems high but it is possible. The record of snowing 5"  in an hour rates happened in 1983 at ABE in similar conditions.  At this time, many should be looking at the mesoscale models only for mid level temps and especially wind speed and their directions, banding snowfall rates and simply rely on weather history under similar conditions. Trying to figure out the snow/ice/rain transition lines in this type of storm is dam near impossible. The best way I relied on when I was in my 20's was wind direction and analogs of previous storm events. Once the winds changed direction to the SE, in the middle to end of the storm snow accumulations fell drastically as the mix set in - usually sleet and light freezing rain. Hope this helps. This storm has been a real challenge for me. My first call three days ago was 8-14 for the LV and I am sticking to it. I am leaning closer to 8 in if the mix sets up.

 

Thanks for commenting in this thread & please come back soon ! 

CTP & Mt. Holly both think that the Harrisburg to Allentown corridor get 5-10 inches of snow.

 

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12 minutes ago, Voyager said:

Anyone know why Tropical Tidbits and Pivotal Weather are so different in their total snowfall maps for same model run and time? Does one include sleet while the other doesn't?

Basically, Pivotal has me at 3 inches @ hour45 and TT and even WxBell above have me at 20 inches.

 

 

To your point here is the Pivotal map which seems to scream this is a non event for entire LSV.  Kuchera and straight 10:1 amounts at MDT are nearly the same.

 

snku_acc.us_ne.png

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8 minutes ago, canderson said:

Wasn’t there a storm here in the late 90s or something that had Mets predict8ng 2’ snow and it ended up a rainstorm with no frozen precip? I’ve heard that urban legend.

I believe it was Dec. 30th 2000 that we were under a WSW for a foot and not only did it not snow there were hardly any clouds.  Not rain though.  That storm equaled out the Jan 5th 2000 Miracle Blizzard where we got over a foot and had little to no snow forecast.  That one is an Eastern US WX Legend as weenies nowcasted their way into a blizzard. 

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1 minute ago, bubbler86 said:

I believe it was Dec. 30th 2000 that we were under a WSW for a foot and not only did it not snow there were hardly any clouds.  Not rain though.  

That’s brutallllll. 

I’m pretty certain on that date we still didn’t have power after a New Years Eve ice storm destroyed the grid in our rural east Texas town. 

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3 minutes ago, bubbler86 said:

I believe it was Dec. 30th 2000 that we were under a WSW for a foot and not only did it not snow there were hardly any clouds.  Not rain though.  That storm equaled out the Jan 5th 2000 Miracle Blizzard where we got over a foot and had little to no snow forecast.  That one is an Eastern US WX Legend as weenies nowcasted their way into a blizzard. 

Wright Weather....That was even Before Easterns time. 

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