Potential flooding rains next week?

[PoconoSnow]

18z gfs really pounds areas to the west.

[mike2010]

wow... you weren't kiddin.

With PW values high, amounts could be even higher than indicated.

A lot is dependant on Lee as well.. A little more of a track to the east, and it's Irene all over again for Jersey. (flooding wise)

[Sunny and Warm]

looks like HPC does not agree with the GFS. Either that or the precip will extend beyond 8pm Friday, which seems implausible.

[Voyager]

That was probably based off the 12z GFS which I posted earlier and said it showed a lack of heavy qpf northeast of Harrisburg.

looks like HPC does not agree with the GFS. Either that or the precip will extend beyond 8pm Friday, which seems implausible.

[Voyager]

Anyone see the 18z GFS 120 hr total qpf on Allan's site? 13.39" near State College!

[PoconoSnow]

Oz Nam, big time rain Nepa,Central Pa. That would be horrible for my area.

[ptb127]

Oz Nam, big time rain Nepa,Central Pa. That would be horrible for my area.

Big time rain.. but the 0z NAM is notorious for over predicting rainfall(QPF)

Irene for example had predicted 5-7" of rain while we received 3.5" which is what the GFS was really locked in on.

If it does occur, historic flooding in Wilkes Barre and other areas in NE PA.

[PoconoSnow]

Big time rain.. but the 0z NAM is notorious for over predicting rainfall(QPF)

Irene for example had predicted 5-7" of rain while we received 3.5" which is what the GFS was really locked in on.

If it does occur, historic flooding in Wilkes Barre and other areas in NE PA.

I agree and the nam has always been like that, but alot of models are coming around to a Central Pa soaker, doesn't look good. Models have been all over the place the last several days, but I have a feeling someone from Central P.a through Nepa is going to see some real serious rains this week.

Irene dumped 6.5 here in Pike County.

[Voyager]

0z GFS is even wetter than the NAM.

[stormspotterlive]

Some heavy rain fall dynamics already starting top spread into east pa this could result in some bonus rain fall for some tonight as precipitation is breaking out as a result. as to the event as a whole. models tend to under do how far west or east theses type bands spread. given the soundings on the models I could see places from the Delaware river on west picking up even higher then expected on the east side of this resulting in major river flooding.

Just how far east the best Dynamics and PWAT Values spread will be determined as the event occurs. one thing is for certain who ever is under then will see high rain fall rates with this event. additionally another aspect not mentioned to much with Lee is that the threat for isolated tornadoes will persist as it comes up the coast. weather or not in spreads in to the northern Atlantic remains to be seen but I defiantly think the Baltimore and dc area is fair game for isolated rotating cells within the bands and training.

My final concern as to flooding is that due to how much rain could fall in southeast New York and NE pa we could see a 1955 like situation for the Delaware river not saying it is set in stone yet but if the heaviest rain fall was to be more wide spread given all the rain fall we had in August it come likely that we see a near historic river flooding event. will certainly be very interesting to watch this situation unfold. Would expect to see river forecast for the Susquehanna river and flood watch forecast go up soon based on new data.

[LVblizzard]

0z GGEM is literally the worst case scenario, it gives what's probably 8+" of rain to parts of central/eastern PA before slinging Katia into NYC and causing even more major flooding. Luckily it's an outlier right now.

[r-ville]

Of course, one of the big questions here is where the EC frontal boundry decides to set up shop. As the energy associated with the related trough will be a better known variable within the next 24-36 hours (as it enters better data regions), we'll get a much better idea. I believe we've seen, in recent history, that the models this far out try to push said frontal boundries more off the EC than ends up happening. Thus the pattern would tend to repeat itself and there's a better than even chance that the front sets up up shop nearer the EC than farther from it.

06z GFS nothwithstanding (timing seems very suspect), the 0z GEFS appear to be in decent agreement to that notion. http://mag.ncep.noaa...el=&imageSize=M

3z SREFS paint a 30-50% of over .25" http://mag.ncep.noaa...el=&imageSize=M with a deep tap root to tropical moisture at 700mb.

It almost goes without saying that by Sunday eve. we'll have a better idea of whether we need to think nuisance or problem. (then why did I mention it, right? - LOL)

Sunny and Warm, on 03 September 2011 - 08:09 AM, said:

If the front sets up closer to the coast, where is the axis of heaviest rain in your opinion?

Well - I would imagine inland areas along and E of the Apps from the lower MidAtl up to NY state where the GEFS suggest the highest PWAT values.

Time to see how my earlier thoughts stack up to current thinking now that we're past Sunday Eve.

http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?page=Image&prevPage=Paramℑ=..%2FGemPakTier%2FMagGemPakImages%2Fgfs%2F20110905%2F06%2Fgfs_namer_174_precip_ptot.gif&fcast=174&imagesurls=&model=GFS&area=NAMER&storm=&areaDesc=North+America+-+US+Canada+and+northern+Mexico&cat=MODEL+GUIDANCE&rname=PRECIP+PARMS&pname=precip_ptot&cycle=09%2F05%

2F2011+06UTC&imageSize=M&currKey=model&scrollx=0&scrolly=0&prevArea=NAMER&prevImage=yes

http://weather.unisy...t=cur&region=ea

How'd I do?

BTW - 4" overnight rain and lightning train.

http://radar.weather.gov/radar_lite.php?product=NTP&rid=CCX&loop=no

[Sunny and Warm]

Sunny and Warm, on 03 September 2011 - 08:09 AM, said:

If the front sets up closer to the coast, where is the axis of heaviest rain in your opinion?

Well - I would imagine inland areas along and E of the Apps from the lower MidAtl up to NY state where the GEFS suggest the highest PWAT values.

Time to see how my earlier thoughts stack up to current thinking now that we're past Sunday Eve.

http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?page=Image&prevPage=Paramℑ=..%2FGemPakTier%2FMagGemPakImages%2Fgfs%2F20110905%2F06%2Fgfs_namer_174_precip_ptot.gif&fcast=174&imagesurls=&model=GFS&area=NAMER&storm=&areaDesc=North+America+-+US+Canada+and+northern+Mexico&cat=MODEL+GUIDANCE&rname=PRECIP+PARMS&pname=precip_ptot&cycle=09%2F05%

2F2011+06UTC&imageSize=M&currKey=model&scrollx=0&scrolly=0&prevArea=NAMER&prevImage=yes

http://weather.unisy...t=cur&region=ea

How'd I do?

BTW - 4" overnight rain and lightning train.

http://radar.weather...rid=CCX&loop=no

Not bad so far. You're 1 for 1, and the models seem to agree with you on the future axis as well. However, Walt Drag has this to say in the morning AFD from Mt Holly:

TUESDAY NIGHT-WEDNESDAY...THE FRONT TO OUR SOUTH ATTEMPTS TO RETURN

NORTH WITH HIGH PWAT AIR OF 2 INCHES...AND MORE CONVECTIVELY

UNSTABLE. THE RRQ OF THE UPPER LVL JET ALONG THE ST LAWRENCE RVR

COMBINED WITH DEEP SOUTHERLY FLOW LIFTED BY THE SHALLOW FRONT

SHOULD UNLEASH BANDS OF HEAVY SHOWERS.

THE QUESTION IS WHERE THE PRIMARY FOCUS. FOR NOW AM NOT REAL SURE.

ONCE THESE FRONTS DEVELOP SOME STATIONARITY ...SOMETIMES THEY

DONT MOVE TOO FAR NORTH AND SO THE FOCUS OF HEAVIEST RAIN MAY END

UP SOUTHEAST OF MODELED... CLOSER TO TO THE HIGH PWAT/UNSTABLE AIR

AND SOURCE OF LIFT. WE NOTE THE MODELS ARE TRYING TO DEVELOP AN

INVERTED TROUGH OVER E OR CENTRAL PA AND ATTEMPTING TO FOCUS THE

HEAVIEST QPF THERE. UNKNOWN IF THATS THE WAY IT WILL GO AND HAVE

SOME DOUBTS. AM CONCERNED ABOUT FURTHER SE...CLOSER TO THE SFC

BOUNDARY AND DIFFLUENT THICKNESS IN THE NW 1/2 OF OUR FCST AREA.

FWIW...00Z/5 GEFS NOW IS FCST WIDESPREAD ~4 INCHES RAINS IN ERN

PA WITH THIS WEEK SINGLE MEMBER TOTALS OF 7 TO 13 INCHES. 06Z GFS OP

HAS 48 HR TOTALS OF 2.5 AT KABE AND 4.5 AT KMPO...SELECTING

CENTRAL PA FOR ITS MAX AXIS.

THE 00Z GEFS NOW HAS A 30 TO 50 PCT PROB OF 4 INCHES IN THE 48 HR

PERIOD ENDING 18Z THURSDAY OVER ALMOST ALL OF THE SE HALF OF PA

EXCEPTING THE SE SLIVER OF THE STATE FROM NEAR KABE TO KPHL.

AM CONCERNED ABOUT THIS POTENTIAL FORCING RIVERS TO STAGES AOA

THOSE OF LAST WEEK. IF THE CURRENT HPC AND ENSEMBLE FCSTS ARE

CORRECT...THE MAIN ACTION IS FURTHER W THAN LAST WEEK AND BEGINS

NEW WIDESPREAD PROBLEMS IN E PA. THE FURTHER EAST SCENARIO IS NOT

ONE WE WANT TO DISCUSS RIGHT NOW...PRIMARILY BECAUSE ITS A MUCH

LESSER PROBABILITY.

What say you to that??

[phlwx]

0z GGEM is literally the worst case scenario, it gives what's probably 8+" of rain to parts of central/eastern PA before slinging Katia into NYC and causing even more major flooding. Luckily it's an outlier right now.

Major outlier...thankfully. Feel a lot better that the EC has nudged Katia eastward to about 70W.

[Sunny and Warm]

New HPC map supports the notion that the spine of the apps continues to see the focus of Lee's remnants. General 3-4" amounts over SE PA, with the majority coming in a 24+ hour period. If that is the case, I do not see anything more than minor flooding in the Mt Holly area. To me, 24+ hours is a long duration rain event and allows some of what falls at the beginning to be downstream by the time the last falls, so it isn't as bad a flooding than if you got 4" in six hours.

[r-ville]

Not bad so far. You're 1 for 1, and the models seem to agree with you on the future axis as well. However, Walt Drag has this to say in the morning AFD from Mt Holly:

TUESDAY NIGHT-WEDNESDAY...THE FRONT TO OUR SOUTH ATTEMPTS TO RETURN

NORTH WITH HIGH PWAT AIR OF 2 INCHES...AND MORE CONVECTIVELY

UNSTABLE. THE RRQ OF THE UPPER LVL JET ALONG THE ST LAWRENCE RVR

COMBINED WITH DEEP SOUTHERLY FLOW LIFTED BY THE SHALLOW FRONT

SHOULD UNLEASH BANDS OF HEAVY SHOWERS.

THE QUESTION IS WHERE THE PRIMARY FOCUS. FOR NOW AM NOT REAL SURE.

ONCE THESE FRONTS DEVELOP SOME STATIONARITY ...SOMETIMES THEY

DONT MOVE TOO FAR NORTH AND SO THE FOCUS OF HEAVIEST RAIN MAY END

UP SOUTHEAST OF MODELED... CLOSER TO TO THE HIGH PWAT/UNSTABLE AIR

AND SOURCE OF LIFT. WE NOTE THE MODELS ARE TRYING TO DEVELOP AN

INVERTED TROUGH OVER E OR CENTRAL PA AND ATTEMPTING TO FOCUS THE

HEAVIEST QPF THERE. UNKNOWN IF THATS THE WAY IT WILL GO AND HAVE

SOME DOUBTS. AM CONCERNED ABOUT FURTHER SE...CLOSER TO THE SFC

BOUNDARY AND DIFFLUENT THICKNESS IN THE NW 1/2 OF OUR FCST AREA.

FWIW...00Z/5 GEFS NOW IS FCST WIDESPREAD ~4 INCHES RAINS IN ERN

PA WITH THIS WEEK SINGLE MEMBER TOTALS OF 7 TO 13 INCHES. 06Z GFS OP

HAS 48 HR TOTALS OF 2.5 AT KABE AND 4.5 AT KMPO...SELECTING

CENTRAL PA FOR ITS MAX AXIS.

THE 00Z GEFS NOW HAS A 30 TO 50 PCT PROB OF 4 INCHES IN THE 48 HR

PERIOD ENDING 18Z THURSDAY OVER ALMOST ALL OF THE SE HALF OF PA

EXCEPTING THE SE SLIVER OF THE STATE FROM NEAR KABE TO KPHL.

AM CONCERNED ABOUT THIS POTENTIAL FORCING RIVERS TO STAGES AOA

THOSE OF LAST WEEK. IF THE CURRENT HPC AND ENSEMBLE FCSTS ARE

CORRECT...THE MAIN ACTION IS FURTHER W THAN LAST WEEK AND BEGINS

NEW WIDESPREAD PROBLEMS IN E PA. THE FURTHER EAST SCENARIO IS NOT

ONE WE WANT TO DISCUSS RIGHT NOW...PRIMARILY BECAUSE ITS A MUCH

LESSER PROBABILITY.

What say you to that??

I say that's quite a bit for me on a holiday morning (one which by the way wakes to finding 4" from the overnight rain train)

Quickly though, after seeing the overnight suite of the modeling and taking a bleary eyed view of the current SPC Meso's, it looks to me that we're heading for some, at least moderate, trouble. PPP and 850 Moisture Transport extrapolated are additionally worrysome.

Seems as though the front lifts back after reaching a stationary status with a slightly positive tilt centering around VA (or so). Ridging is trying to build in to the north further enhancing the low level easterly flow - while the approaching vort (Lee or rem's) brings the rest of the soup. So when we get to Wed and I see things like this

http://www.meteo.psu.edu/~gadomski/compskwframe0z.html - I start to worry just a tad.

Then, as far as the inland impact - I ask myself if there doesn't have to be some orographic influenced lift. And that's not to mention the already aforementioned 4" from the localized events of last evening/overnight. Plus, unlike Irene - this event has substantial "lolipop" of ~15" falling in the West Branch Susq River Basin (going off GFS QPF), the East Branch already has a fair bit of water and it don't take much. There's been nor will be enough time fo hydrologic pressure relief.

Now, considering all that hazy thought process is quickly thought out on a rainy dreary Labor Day (Happy to you by the way) - I admit that my interest is only that of the hobbyist (but I do put out forecasts to a small but loyal group - sometimes, to my chagrin, they end up on FB)

[ptb127]

0z GGEM is literally the worst case scenario, it gives what's probably 8+" of rain to parts of central/eastern PA before slinging Katia into NYC and causing even more major flooding. Luckily it's an outlier right now.

What is causing Katia to turn like that?? If one model is showing it, even though it's main outlier, I would write it off completely, and would definitely be a scary solution..

How much rain would it take to push the susquehanna river over 30' in Wilkes barre. it's at 5' as of this writing.

[Sunny and Warm]

I say that's quite a bit for me on a holiday morning (one which by the way wakes to finding 4" from the overnight rain train)

Quickly though, after seeing the overnight suite of the modeling and taking a bleary eyed view of the current SPC Meso's, it looks to me that we're heading for some, at least moderate, trouble. PPP and 850 Moisture Transport extrapolated are additionally worrysome.

Seems as though the front lifts back after reaching a stationary status with a slightly positive tilt centering around VA (or so). Ridging is trying to build in to the north further enhancing the low level easterly flow - while the approaching vort (Lee or rem's) brings the rest of the soup. So when we get to Wed and I see things like this

http://www.meteo.psu...skwframe0z.html - I start to worry just a tad.

Then, as far as the inland impact - I ask myself if there doesn't have to be some orographic influenced lift. And that's not to mention the already aforementioned 4" from the localized events of last evening/overnight. Plus, unlike Irene - this event has substantial "lolipop" of ~15" falling in the West Branch Susq River Basin (going off GFS QPF), the East Branch already has a fair bit of water and it don't take much. There's been nor will be enough time fo hydrologic pressure relief.

Now, considering all that hazy thought process is quickly thought out on a rainy dreary Labor Day (Happy to you by the way) - I admit that my interest is only that of the hobbyist (but I do put out forecasts to a small but loyal group - sometimes, to my chagrin, they end up on FB)

Thanks for the reply. For some reason, I couldn't find anything on your link. Probably my end, and I'm short of time to debug. I agree actually with you and HPC. In fact, the NAM and GFS are closing aligned as well at 6z. Seems everything is a GO for central PA extending east to the I81 corridor or thereabouts.

[LMolineuxLM1]

New HPC map supports the notion that the spine of the apps continues to see the focus of Lee's remnants. General 3-4" amounts over SE PA, with the majority coming in a 24+ hour period. If that is the case, I do not see anything more than minor flooding in the Mt Holly area. To me, 24+ hours is a long duration rain event and allows some of what falls at the beginning to be downstream by the time the last falls, so it isn't as bad a flooding than if you got 4" in six hours.

Not sure how this is going to work, its gonna take like the same setup as lastnight and overnight of training slow moving thunderstorms like the LV had and Central Parts of the State of Pa. Nothing so far is organized and is spotty. And with the in and out sun there isnt much for this to pop good storms out of it. We are only in See Text and the main focus is WIND. So this i doubt will occur. I think its just overdoing the precip east of central PA which already has had upwards to near 4 or more inches over yesterday and thats already counted into this isnt it?

[Mahantango]

Not sure how this is going to work, its gonna take like the same setup as lastnight and overnight of training slow moving thunderstorms like the LV had and Central Parts of the State of Pa. Nothing so far is organized and is spotty. And with the in and out sun there isnt much for this to pop good storms out of it. We are only in See Text and the main focus is WIND. So this i doubt will occur. I think its just overdoing the precip east of central PA which already has had upwards to near 4 or more inches over yesterday and thats already counted into this isnt it?

Where can I get a map that has the counties shown on the map?

[r-ville]

Where can I get a map that has the counties shown on the map?

http://water.weather.gov/ahps2/forecasts.php?wfo=ctp&view=1,1,1,1,1,1,1,1&toggles=10,7,8,2,9,15,6

[Harbourton]

Moisture feed goes all the way to the Bay of Campeche!

[phlwx]

http://water.weather...10,7,8,2,9,15,6

Probably a better map would be this: http://www.erh.noaa.gov/marfc/Maps/qpf/Northern_O48hr_Total.png

It's just 48 hours but it has the qpf broken down by county and ob site that the MARFC is looking at.

[Mahantango]

Where can I get this precipation map with the counties listed? thanks

New HPC map supports the notion that the spine of the apps continues to see the focus of Lee's remnants. General 3-4" amounts over SE PA, with the majority coming in a 24+ hour period. If that is the case, I do not see anything more than minor flooding in the Mt Holly area. To me, 24+ hours is a long duration rain event and allows some of what falls at the beginning to be downstream by the time the last falls, so it isn't as bad a flooding than if you got 4" in six hours.

[famartin]

Moisture feed goes all the way to the Bay of Campeche!

Actually it appears to go all the way to the eastern Pacific.

[phlwx]

Looking at the 12z guidance it looks like tomorrow will be cool/rainy before Lee's mid level feature pulls north and pulls warmth back north. Could be awfully humid/murky Wednesday/Thursday in Philly.

Heavy rain threat continues to set up in Central PA...generally conveyor belt type rain on Wednesday to the west of I-81 if the GFS is right.

[Sunny and Warm]

Looking at the 12z guidance it looks like tomorrow will be cool/rainy before Lee's mid level feature pulls north and pulls warmth back north. Could be awfully humid/murky Wednesday/Thursday in Philly.

Heavy rain threat continues to set up in Central PA...generally conveyor belt type rain on Wednesday to the west of I-81 if the GFS is right.

for our sakes, let's hope the GFS is right this time. Most guidance supports it.

[Rainshadow]

for our sakes, let's hope the GFS is right this time. Most guidance supports it.

I'm not looking forward to this week.

[Sunny and Warm]

I'm not looking forward to this week.

Without you getting into trouble with the PGA Tour, are you saying you believe the models may be too far west??

[phlwx]

I'm not looking forward to this week.

at least tomorrow will be cooler!