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Central PA Fall 2018

pasnownut

By pasnownut,
in Upstate New York/Pennsylvania

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MAG5035

MAG5035

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The Euro op has been easily the worst scenario the last few runs for central PA. Today's 12z run having a 2-4+" swath of rainfall through most of C-PA and LSV with the highest totals concentrating on the area that was affected the most from the flooding at the beginning of the week. It seems that the Euro maintains the core of what's left of Florence more than other guidance.. making for what would look to be a 6-12 hour timeframe of intense rainfall traversing the region Monday night. With how low the flash flood and headwater guidance is right now, that type of scenario would make for major issues. Esp in the JST/AOO/UNV corridor where headwater guidance shows that 2-3" or so in a 6 or 12 hr timeframe would send several of those smaller rivers into major flood stage pretty easily. Sus Valley is a bit better but still quite vulnerable to this type of a precipitation event as well.

Those FFG numbers could improve a bit the next couple days but it will remain pretty saturated throughout the region. Other guidance currently doesn't show such excessive rainfall, but even half of what the Euro has would still cause issues. One must also note the source region of this potential precip event (tropics), as even scattered activity associated with the remnants could yield intense downpours.

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sauss06

sauss06

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12 hours ago, canderson said:

I’m so f’n done with heat. Today sucked. Where is fall?

No chit, i agree. I said the same thing to my wife. Looks like Wednesday is going to be in the 80s and then we drop into the 70s for a little bit anyhow. And much better sleeping weather to go along with it. 

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pasnownut

pasnownut

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33 minutes ago, Wmsptwx said:

Seems wpc is concerned but nws is oddly mehhhhh.

alot of the local ponding that was largely evident last week, seems to have subsided around here.  I'm sure we still are at high saturation levels, but think it fair to say that the dry weekend and sun yesterday has lessened the potential impacts to the Susky valley.  i'd still be nervous if i lived in low lying areas, but my guess is 1-2" wouldnt do anything close to what we've seen.  Beyond that we get what appears a much less dreary pattern with an early fall preview.

 

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pasnownut

pasnownut

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10 minutes ago, Wmsptwx said:

WPC has us in moderate, last few we were in the slight category...just wondering if they were looking at different stuff. We had river flooding up until Wed and coming off 7 inches last Monday Tues so guessing FFGs are low. 

Area Forecast Discussion
National Weather Service State College PA
655 AM EDT Mon Sep 17 2018

.SYNOPSIS...
The remnants of Florence will track northeast across
Pennsylvania later today into early Tuesday. High pressure will
build into the region Wednesday and Thursday. A dying cold
front is likely to push south across Pennsylvania late Friday,
then stall out just south of the state next weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Regional radar loop at 09Z shows the shield of rain associated
with the remnants of Florence approaching southwest Pa. Deep
southerly flow of tropical air will overrun high pressure and
pool of relatively stable air over central Pa, causing rain to
spread northeast across the area, reaching even the northern
tier by afternoon. As surface warm front lifts north, expect
stratiform rain to transition to convective activity across
southern Pa this afternoon. A low cape/high shear scenario appears
to be setting up late today along the southern tier counties,
where the threat of low-topped supercells and eve an isolated
tornado exists.

Main threat remains the possibility of flooding, due in part to
the extremely wet antecedent conditions. Have issued a flash
flood watch for nearly the entire forecast area, with a later
begin time over the eastern counties based on latest HREFV2,
which indicates a low probability of excessive rain until at
least 00Z.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
CAMS indicate steadiest stratiform rainfall will shift toward
the NY border tonight, while scattered heavy downpours and
possible tsra appear more likely elsewhere. WPC storm total qpf
ranges from 1-2 inches over the forecast area, which runs close
to FFG/FFH guidance from the marfc. However, given anomalous
pwats and instability noted in the models, believe
significantly higher spots amounts are likely, similar to the
2-4 inch max amounts in the HREFV2.

Will also have to continue to monitor the severe weather threat
tonight over the southern tier counties, where a combination of
instability and shear south of surface low track could support
supercells and even a possible tornado.

Improving conditions will overspread the region from west to
east Tuesday morning, as the surface low tracks passes east of
the state. By early afternoon, the bulk of model guidance have
pushed the low east of Pa. However, the back edge of the showers
will likely lag by a few hours, due to passage of mid level
shortwave. Brightening skies by afternoon should help push
temperatures well into the 70s to near 80F.
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daxx

daxx

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3 minutes ago, maytownpawx said:

With convective activity comes surprises, Horst alluded to that this morning. While he's calling for general .75" - 2" totals he also notes that some areas could receive more. If any one area gets under multiple bands...

Those high pwats over two inches working up from the south could lead to crazy rainfall rates if convection fires up!  Someone will get a lot of rain.

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pasnownut

pasnownut

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Looking like a nothin burger over this way.  Was suspicious of it this morning and i think so far it may just be the right suspicion.  Latest HRR 3k blend of total precip still looks like 2" for much of the susuqu valley but if the radar is any indication, i dont see that happening.

Man...I'm starting to sound like another poster from the land of Yuengling......

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MAG5035

MAG5035

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51 minutes ago, Wmsptwx said:

Lol...dude we honestly won't know ...it's where banding develops and storms form moreso not shield rain. HRRR has been awful all day.

I think we've recovered enough the last several days that a 1-2" general rainfall will cause some decent responses to waterways but likely not many flooding issues. As you mention, we will have to watch for bands that could train over the same areas wherever that may be this evening. Given we have a tropical system and  associated extremely moisture laden source region, any bands will have intense rainfall. Shorter term rainfall (1 and 3hr flash flood guidance) is still where we remain quite vulnerable while longer duration (6 and 12 hr guidance) had improved the most. This is starting to look more like an areawide event where most waterways reach caution or perhaps minor flood in places with these potential areas of banding providing scattered areas in our region with perhaps more significant flooding issues vs an overall widespread flooding event like we achieved a week ago. 

23 hours ago, canderson said:

I’m so f’n done with heat. Today sucked. Where is fall?

Me too, I'm over this summer. If it hasn't been raining 75% of the time.. it's been very warm and especially humid. Unfortunately I think we're going to be taking an above average temp regime into October as I don't see much changes (or major catalysts to flip the pattern) the next 6-10 days. We're already over halfway through September, temps cracking into the high 70s/low 80s would be considered above average for most everyone. There's a lot of low height's progged over Canada and Greenland, which drives up heights south of the border in the US (+NAO/AO). This persistent pattern of high heights in the east and displacement from the mean storm track (well to the north) has been why we've been in this exceptionally stagnant pattern. We've been long overdue for a major shift in things, so I would expect we may see that as we get into October. 

I'm not sure what to expect yet as we get towards winter. We've been running essentially ENSO neutral all summer with modeling developing El Nino conditions as we get into the winter months. I currently would anticipate weak El Nino or perhaps a + biased ENSO neutral, which may influence but not necessarily dictate our winter pattern. CPC just put out a new ENSO update today which can be looked at HERE. Another thing of note is significant positive SST anomalies off the eastern seaboard. If that were to persist into winter that could influence a more feisty regime of coastals and maybe drive some higher heights into the NAO region that has been so lacking in positive influence in our winter weather the last couple years. Other than that, I don't really see any glaring things that would tip me off to having to be concerned about anything either side of normal at the moment. It'll be interesting to see if we carry this amazing run of above average precip into winter. 

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Voyager

Voyager

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2 hours ago, pasnownut said:

Looking like a nothin burger over this way.  Was suspicious of it this morning and i think so far it may just be the right suspicion.  Latest HRR 3k blend of total precip still looks like 2" for much of the susuqu valley but if the radar is any indication, i dont see that happening.

Man...I'm starting to sound like another poster from the land of Yuengling......

:whistle:

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