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Central PA Spring 2023


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Just now, Blizzard of 93 said:

Flood Watch

Flood Watch
National Weather Service State College PA
831 AM EDT Sun Apr 30 2023

PAZ028-041-042-046-049>053-056>059-063>066-302215-
/O.NEW.KCTP.FA.A.0001.230430T1231Z-230501T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Juniata-Northern Lycoming-Sullivan-Southern Lycoming-Union-Snyder-
Montour-Northumberland-Columbia-Perry-Dauphin-Schuylkill-Lebanon-
Cumberland-Adams-York-Lancaster-
Including the cities of Lebanon, Laporte, Lancaster, Bloomsburg,
Hershey, Harrisburg, Danville, Sunbury, Berwick, Carlisle,
Gettysburg, York, Lewisburg, Shamokin, Newport, Selinsgrove,
Williamsport, Pottsville, Mifflintown, and Trout Run
831 AM EDT Sun Apr 30 2023

...FLOOD WATCH IN EFFECT UNTIL 8 PM EDT THIS EVENING...

* WHAT...Flooding caused by excessive rainfall is possible.

* WHERE...A portion of central Pennsylvania, including the following
  areas, Adams, Columbia, Cumberland, Dauphin, Juniata, Lancaster,
  Lebanon, Montour, Northern Lycoming, Northumberland, Perry,
  Schuylkill, Snyder, Southern Lycoming, Sullivan, Union and York.

* WHEN...Until 8 PM EDT this evening.

* IMPACTS...Excessive runoff may result in flooding of rivers,
  creeks, streams, and other low-lying and flood-prone locations.
  Flooding may occur in poor drainage and urban areas.

* ADDITIONAL DETAILS...
  - Rain has been heavy overnight over much of the area, and
    additional rain of up to 2 inches is expected to fall through
    the daylight hours.
  - http://www.weather.gov/safety/flood

Lol…Epic drought to Flood….

Where is the drought monitor map?

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38 minutes ago, Mount Joy Snowman said:

Well the NWS still shows a high of 61 later. Who knows if that will actually happen but it’s what I was going off of. Even an average of 53 would only drop the monthly average .1 degree at this point. We are the only two people in the world haggling over whether a tenth of a degree difference puts us in 3rd or 4th place in the books haha. 

LOL, I am not haggling I just did not do that math and thought 53 would possibly take it down .2.   But yes, we are talking about something which will be solved in 13 1/2 hours.  

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More heavy rain and even some thunderstorms later. We have already picked up another 0.48" this morning bringing our last 5 day rain total to 2.52". Up to another 1" to 2" could fall across some areas by late tonight especially if any thunderstorms do develop.
Records for today: High 90 (1942) / Low 26 (1978) / Rain 5.77" (2014)
image.png.023bda73f8a8a1314da6dfd2291fc474.png
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Starting to see the best rain rates of the event finally (moderate) after it being mainly a light event most of the morning as the initial heavy rain bands went up east of here. Radar looks pretty solid and the frontal passage later on likely will mean totals will have a chance to catch up some. 

0.45” total for today, and 1.19” total since Friday morning. 

 

 

 

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Regarding the mountain snow chances, I’m definitely intrigued. CTP acknowledges to a point, noting potential of light accums on non-paved surfaces in the Alleghenies. Given the signal on the models, I think the potential is there for a more significant event but it’s going to be highly elevation dependent. The broad brushing of the globals (esp GFS) having the high totals over all of the Laurel’s is likely overdone. 

The 12z 3k NAM had a presentation of accums that looked a bit more realistic IMO. When I say highly elevation dependent I mean accums will be purely driven by it. Best timeframe appears to be Tuesday as a reinforcing shortwave pinwheels through driving upslope precip in western PA. During this time 925mb temps are marginal (a degree or so above zero. Since we’re under such a significant upper level low, 925mb heights are only around 570m, or about 1800 ft. 850 temps are below zero over all of PA during the duration of all this (mainly -2 to -4ºC).

Basically with all this in mind, I think accums will mainly reside at 2k feet and above. Headline worthy snow could fall in higher Cambria and Somerset areas but whether it’s widespread enough to warrant the actual headline is debatable. The best potential for more significant totals could be at an elevation above about 3k feet, though maybe down to 2,500’ish. That’ll be a key, as there’s only a couple places in the Laurels that top 3k feet. There are ridge lines that go into western MD and WV that are 2500’-2800’ or so in spots. Modeled accumulations really explode in WV because their ridge tops are much higher than that. Whatever happens, it’s certainly a cold, unsettled pattern especially the first half of the upcoming week to open up May of all months. 

 

 

 

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18 minutes ago, MAG5035 said:

Regarding the mountain snow chances, I’m definitely intrigued. CTP acknowledges to a point, noting potential of light accums on non-paved surfaces in the Alleghenies. Given the signal on the models, I think the potential is there for a more significant event but it’s going to be highly elevation dependent. The broad brushing of the globals (esp GFS) having the high totals over all of the Laurel’s is likely overdone. 

The 12z 3k NAM had a presentation of accums that looked a bit more realistic IMO. When I say highly elevation dependent I mean accums will be purely driven by it. Best timeframe appears to be Tuesday as a reinforcing shortwave pinwheels through driving upslope precip in western PA. During this time 925mb temps are marginal (a degree or so above zero. Since we’re under such a significant upper level low, 925mb heights are only around 570m, or about 1800 ft. 850 temps are below zero over all of PA during the duration of all this (mainly -2 to -4ºC).

Basically with all this in mind, I think accums will mainly reside at 2k feet and above. Headline worthy snow could fall in higher Cambria and Somerset areas but whether it’s widespread enough to warrant the actual headline is debatable. The best potential for more significant totals could be at an elevation above about 3k feet, though maybe down to 2,500’ish. That’ll be a key, as there’s only a couple places in the Laurels that top 3k feet. There are ridge lines that go into western MD and WV that are 2500’-2800’ or so in spots. Modeled accumulations really explode in WV because their ridge tops are much higher than that. Whatever happens, it’s certainly a cold, unsettled pattern especially the first half of the upcoming week to open up May of all months. 

 

 

 

Thanks for the great analysis!

Just 1 question…asking for a friend…

Does this mean no snow for Palmyra?

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It has rained much harder the last 30 minutes that what radar would indicate. Returns are very light but it’s almost moderate rain. 
Looking at radar estimate returns vs ground truth this thing seems to be a very efficient rain producer. Also I have a feeling the coastal low is really starting to get going with increasing low level easterly flow that's coming underneath the radar beam. Certainly is interesting

Sent from my SM-G970U using Tapatalk

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28 minutes ago, Jns2183 said:

The latest afd pretty much killed the threat for much more rain over our area for remainder of day.

Sent from my SM-G970U using Tapatalk
 

Models have been insistent that the heaviest rainfall would be early this evening in the LSV but the radar seems to be drying out. Looking like I'll end up with well under 1" for the day.

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