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Central PA - Winter 2020/2021


MAG5035
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1 hour ago, Jim Marusak said:

Upstream river forecast crest numbers are getting a bit scary.

  • Sunbury - mod flood - 27 ft
  • Danville - mod flood - 26.6 ft
  • Bloomsburg - mod - 26.4 ft
  • Wilkes Barre Courthouse - major - 33.7 ft
  • Meshoppen - moderate - 36.4 ft
  • Towanda - Moderate/Major 24ft
  • Waverly - major - 20ft

these types of numbers are looking an awful lot like January 1996 style numbers. And NWS-Binghamton is hinting there may be some chunks of ice in the Susquehanna as well, which may make things worse if they jam under a bridge. Let's hope this isn't the case on Christmas day.

I was just up to Towanda yesterday and there was very little to no ice in the river.  Ice dams should not be a concern.  Obviously they do have quite a snowpack up in that region however which is not good with these high dew points and mild temps!  

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It seems like the most significant flood potential focuses on the Susquehanna main-stem (and NE PA tributaries), especially in the Upper Sus Valley on into NE PA where that particular region has the trifecta of significant rainfall, the most significant existing snowpack, and a several hour period where warm temps via southerly flow punch up into eastern PA to further enhance a more rapid snow melt. Short range models like the NAM have been downright excessive with rain totals, and the next several hours this evening will reveal if that comes fully to fruition as radar trends look to be starting to focus the heavier rainfall rates into eastern PA along the Susquehanna. 

The other major tributaries coming from the central counties (West Branch and Juniata watersheds) look to have a significant rise but most point forecasts appear to stay below flood stage along those rivers. Temps in this part of C-PA are locked into the upper 30s-low 40s and as mentioned, heavier rainfall is starting to focus towards eastern PA. Appears that any surge in temps in the central probably comes close to/with the frontal passage as the stable b-layer gets mixed out. Lack of big time flooding coming from those two tributaries probably prevents the main stem from going full blown '96 repeat in lieu of a more minor-moderate flood event coming primarily from upstream in NE PA/southern NY. Definitely not ideal anyway you slice it, what an ugly Christmas Eve weather-wise. 

 

 

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14 minutes ago, MAG5035 said:

It seems like the most significant flood potential focuses on the Susquehanna main-stem (and NE PA tributaries), especially in the Upper Sus Valley on into NE PA where that particular region has the trifecta of significant rainfall, the most significant existing snowpack, and a several hour period where warm temps via southerly flow punch up into eastern PA to further enhance a more rapid snow melt. Short range models like the NAM have been downright excessive with rain totals, and the next several hours this evening will reveal if that comes fully to fruition as radar trends look to be starting to focus the heavier rainfall rates into eastern PA along the Susquehanna. 

The other major tributaries coming from the central counties (West Branch and Juniata watersheds) look to have a significant rise but most point forecasts appear to stay below flood stage along those rivers. Temps in this part of C-PA are locked into the upper 30s-low 40s and as mentioned, heavier rainfall is starting to focus towards eastern PA. Appears that any surge in temps in the central probably comes close to/with the frontal passage as the stable b-layer gets mixed out. Lack of big time flooding coming from those two tributaries probably prevents the main stem from going full blown '96 repeat in lieu of a more minor-moderate flood event coming primarily from upstream in NE PA/southern NY. Definitely not ideal anyway you slice it, what an ugly Christmas Eve weather-wise. 

 

 

I've picked up .33" of rain in the past 20 minutes. She's dumping...

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14 minutes ago, dcfox1 said:

Good there is little ice upstate.  96 had a lot of ice involved. I lived along the river in York Co (across from Marietta)  and watched boats coming down. House was on high ground so stopped short but had huge ice chunks till spring in 

I can remember doing a water rescue down around Cargill. Helicopter trying to get people off there roof, and huge ice chunks floating by. Not sure if you were on duty that day. 

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24 minutes ago, dcfox1 said:

Good there is little ice upstate.  96 had a lot of ice involved. I lived along the river in York Co (across from Marietta)  and watched boats coming down. House was on high ground so stopped short but had huge ice chunks till late spring in front. 

That it did. Even the Delaware  (which almost claimed my car) was bad. I parked in a parking lot on Larry Holmes Drive in Easton to check out the river, and the ice jammed up downstream, and I literally had to sprint to my car to get it moved. Fifteen minutes later, the lot was under 4-6 feet of water.

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25 minutes ago, daxx said:

I can remember doing a water rescue down around Cargill. Helicopter trying to get people off there roof, and huge ice chunks floating by. Not sure if you were on duty that day. 

Actually I was off that day but heard it on the scanner and heard about it the next shift. That guy should had have gotten out of there the day before. It Always floods there. He was a drunk. It was was at riverfront park and he rented it from the twp. It was torn down now and made part of the park. You were right the road to it is right at what was Cargill.

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14 minutes ago, dcfox1 said:

Actually I was off that day but heard it on the scanner and heard about it the next shift. That guy should had have gotten out of there the day before. It Always floods there. He was a drunk. It was was at riverfront park and he rented it from the twp. It was torn down now and made part of the park. You were right the road to it is right at what was Cargill.

We ran a lot of calls those couple of weeks from the blizzard to flooding.

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New Meso out for many of our areas (maybe cutting out I-81 corridor S of Harrisburg) WPC_MD0877

Quote
Rainfall coverage and intensity has increased over
the past few hours in response to strong warm air advection in
advance of a strong cold front approaching from the west.  The low
level jet is impressive with south to southeast flow of 60 to 80
mph at 850mb, and this is advecting copious deep moisture from the
western Atlantic and Gulf of Mexico over cold and snow covered
grounds for most of the outlook area.  Dewpoints are rising well
into the 50s south of the warm front, and this will accelerate
snow melt in addition to the rainfall.  Much of the existing
snowpack across northeast Pa and extending into east-central NY
has over two inches of liquid water content, and in combination
with 1 to 2 inches of forecast rainfall through 3 am, will likely
result in some aerial flooding and rising river levels.  If the
snow melting rate is quick enough, some flash flooding may also
occur near creeks and streams.

The latest suite of CAM guidance is suggesting the potential for
nearly two inches of additional rainfall over the Catskills and
Poconos, and this will tend to increase the threat of flooding for
those locations.  Another region of enhanced rainfall, with
amounts potentially reaching or exceeding one inch, will likely
extend between State College and Syracuse.  Although actual
rainfall rates are not expected to be impressive, mainly under
half an inch per hour, the combination of duration and snow melt
is the main concern.

 

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32 minutes ago, Blizzard of 93 said:

@MAG5035

How is the cold front doing in your Area now?

What are your thoughts on the prospects of seeing some snow from your area over to the Susquehanna Valley tomorrow?

I still don't think much makes it over to the Sus Valley but we'll have to see how much precip hangs on behind the cold front. Short range guidance like the HRRR and NAM haven't had much lingering by the time it's cold enough. There could perhaps be enough to witness a changeover period and perhaps a coating in spots in the region east of I-99 over to the Sus Valley. The big thing to watch first thing tomorrow morning is for untreated stuff to freeze up. 

 

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There's two boundaries that are noticeable on velocity images. One associated with the thin line of intense rainfall in the warm sector (impacting H-burg and LSV) and a secondary boundary further west, which i've noted with the blue dash.. that is the actual cold front boundary.

1531091924_ScreenShot2020-12-25at12_09_59AM.thumb.png.233f4aed8121e70671970a0cf0450f0f.png

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