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Central PA Late January Thread Part III


Rick G

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SREFS a little colder again. Anyone want to take bets that the only reason they are still a little warm is cause the RSM's?

Yea def a shade cooler. For the main event we now have a lot more probs for sleet in the ptype maps. Esp along a line from near or just south of State College over to Allentown and north of that line. Basically what JMister was saying about UNV maybe being more sleet than zr is getting some SREF support now. High freezing rain probs are now evident the whole duration of the main wave along the southern tier or two of counties even in the Philly region.

To me, as long as the high pressure is there in a good position to provide the cold, this will be a classic snow to ice storm scenario with not very much of the plain rain to speak of until the very end of the event possibly. Folks north of I-80 a bit should stay mainly snow/sleet with the entire system, with perhaps a bit of a glaze of freezing rain. Along/just north of I-80 and the region between that and the turnpike and then I-78 should see the first snow wave, and then possibly start the second wave as snow or sleet..transitioning to a sleet/freezing rain mix, with the ridges of the Central PA ridge and valley/upper sus valley/Poconos seeing the highest freezing rain totals and all in that region possibly seeing some accumulation of sleet. The Laurel Highlands, and the region along/under the PA turnpike/I-78 east should see the second wave as primarily freezing rain/rain with the highest chance of seeing the worst ice totals. Especially in the Laurels. Far southwest PA underneath Pittsburgh should transition to rain after a couple inches from the first wave and advisory level freezing rain accretion. That's my initial take on rough p-type placement.

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Harrisburg does not even get to freezing looking at the 2m 0z NAM 6hr plots. It could get nasty around here.

Yes, MDT is f'd too. I'm in the city, which might save me a bit since our utilities are all underground and based in the capitol's grid system. I pray you, though, have a generator or fireplace.

We don't have a fireplace ... which probably will be very bad.

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NAM's not pretty, but it isn't necessarily a dire situation. Gonna bust out the Accupro maps for the two worst frames of the storm

Hour 60

post-1507-0-51526200-1296442854.png

Hour 63

post-1507-0-33954100-1296443125.png

As you can see, MDT is actually sleet through hour 60 (hour 57 too) and then ZR for 63.. this run actually ended up being a pretty good illustration of what i was writing about the last 15 minutes in the previous post.

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So here is the KUNV sounding for hour 60, right at the peak of the storm. I have been trying to read up on what the boundaries of a sleet vs. freezing rain profile looks like. It seems like if the freezing layer is deeper than 1km, and its cooler than a few degees C below 0, it becomes sleet. Does anyone know more on the subject, or have any examples of sleet/freezing rain profiles? I would really like to be able to determine IP vs ZR on skew-ts. Thanks!

To me, this is a sleet profile:

SFC 961 402 -3.8 -5.1 91 1.3 -4.3 116 14 272.4 272.9 271.0 279.8 2.71

2 950 491 -4.7 -5.6 93 0.9 -5.1 117 18 272.4 272.8 270.9 279.6 2.64

3 900 914 -6.3 -6.4 99 0.1 -6.4 129 35 275.0 275.4 272.5 282.3 2.62

4 850 1365 -1.5 -1.5 100 0.0 -1.6 169 44 284.5 285.2 279.5 295.9 4.01

5 800 1851 1.8 1.8 100 0.0 1.8 198 70 293.1 294.0 284.9 308.9 5.45

6 750 2375 3.0 2.9 100 0.0 2.9 216 85 299.8 301.0 288.3 318.5 6.31

7 700 2932 0.6 0.6 99 0.1 0.6 231 85 303.2 304.2 288.9 320.4 5.70

8 650 3524 -2.7 -2.7 100 0.0 -2.7 243 77 305.9 306.8 288.9 320.7 4.82

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NAM's not pretty, but it isn't necessarily a dire situation. Gonna bust out the Accupro maps for the two worst frames of the storm

Hour 60

post-1507-0-51526200-1296442854.png

Hour 63

post-1507-0-33954100-1296443125.png

As you can see, MDT is actually sleet through hour 60 (hour 57 too) and then ZR for 63.. this run actually ended up being a pretty good illustration of what i was writing about the last 15 minutes in the previous post.

Wow, those maps are textbook of your post earlier. Great job.

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So here is the KUNV sounding for hour 60, right at the peak of the storm. I have been trying to read up on what the boundaries of a sleet vs. freezing rain profile looks like. It seems like if the freezing layer is deeper than 1km, and its cooler than a few degees C below 0, it becomes sleet. Does anyone know more on the subject, or have any examples of sleet/freezing rain profiles? I would really like to be able to determine IP vs ZR on skew-ts. Thanks!

To me, this is a sleet profile:

SFC 961 402 -3.8 -5.1 91 1.3 -4.3 116 14 272.4 272.9 271.0 279.8 2.71

2 950 491 -4.7 -5.6 93 0.9 -5.1 117 18 272.4 272.8 270.9 279.6 2.64

3 900 914 -6.3 -6.4 99 0.1 -6.4 129 35 275.0 275.4 272.5 282.3 2.62

4 850 1365 -1.5 -1.5 100 0.0 -1.6 169 44 284.5 285.2 279.5 295.9 4.01

5 800 1851 1.8 1.8 100 0.0 1.8 198 70 293.1 294.0 284.9 308.9 5.45

6 750 2375 3.0 2.9 100 0.0 2.9 216 85 299.8 301.0 288.3 318.5 6.31

7 700 2932 0.6 0.6 99 0.1 0.6 231 85 303.2 304.2 288.9 320.4 5.70

8 650 3524 -2.7 -2.7 100 0.0 -2.7 243 77 305.9 306.8 288.9 320.7 4.82

Sleet profiles are usually when there is only a small piece of the atmosphere that is above freezing, and high enough so that the raindrop has time to refreeze before it reaches the surface.

Freezing rain profiles usually have a warmer (sometimes over 5 degrees C) and deeper layer of above freezing air, and it's closer to the ground which keeps the drop in liquid form until it contacts the surface.

I would agree, the sounding you have there looks like sleet.

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So here is the KUNV sounding for hour 60, right at the peak of the storm. I have been trying to read up on what the boundaries of a sleet vs. freezing rain profile looks like. It seems like if the freezing layer is deeper than 1km, and its cooler than a few degees C below 0, it becomes sleet. Does anyone know more on the subject, or have any examples of sleet/freezing rain profiles? I would really like to be able to determine IP vs ZR on skew-ts. Thanks!

To me, this is a sleet profile:

SFC 961 402 -3.8 -5.1 91 1.3 -4.3 116 14 272.4 272.9 271.0 279.8 2.71

2 950 491 -4.7 -5.6 93 0.9 -5.1 117 18 272.4 272.8 270.9 279.6 2.64

3 900 914 -6.3 -6.4 99 0.1 -6.4 129 35 275.0 275.4 272.5 282.3 2.62

4 850 1365 -1.5 -1.5 100 0.0 -1.6 169 44 284.5 285.2 279.5 295.9 4.01

5 800 1851 1.8 1.8 100 0.0 1.8 198 70 293.1 294.0 284.9 308.9 5.45

6 750 2375 3.0 2.9 100 0.0 2.9 216 85 299.8 301.0 288.3 318.5 6.31

7 700 2932 0.6 0.6 99 0.1 0.6 231 85 303.2 304.2 288.9 320.4 5.70

8 650 3524 -2.7 -2.7 100 0.0 -2.7 243 77 305.9 306.8 288.9 320.7 4.82

Yea, that profile would def support sleet considering the column is below zero from 850 down, and from 900 down it is well below freezing. And thats what the accupro maps print out on their p-type maps for the UNV area. If you click on skew-T east on Ewall it'll give you the skew-T diagram for each hour of the 0z and 12z NAM and GFS runs. And its got the more local stations like UNV. I'm still waiting for the new 0z NAM to see the skew T's on that.

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Sorry to ask again -- but would an elevation of 1,600' be more likely to have sleet or ZR in this situation?

it'd probably depend on the depth of the cold air. If it were something like the UNV sounding in your area..which it should be, then i'd think you'd have a good chance of seeing sleet or a sleet/zr combo. The highest elevations of the Pocono's probably will be where the threat of mainly freezing rain is for your area if the NAM is correct.

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it'd probably depend on the depth of the cold air. If it were something like the UNV sounding in your area..which it should be, then i'd think you'd have a good chance of seeing sleet or a sleet/zr combo. The highest elevations of the Pocono's probably will be where the threat of mainly freezing rain is for your area if the NAM is correct.

SLeet is pretty meh. I don't know what to think at this point though.

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The GFS has a 1032ish high over the top just above Maine, I really don't buy the all rain for 75% of PA solution.

Me neither. Think northern Pa will stay below freezing till the very end of the storm just as the precip is ending. Thinking .1-.2 of plain rain for northern Pa after a few inches of snow and a bunch of ice. Just my guess now.

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