textproduct: Binghamton

WHAT HAS CHANGED

A flood watch watch for flash flooding has been issued for northeast Pennsylvania and Sullivan County, New York.

KEY MESSAGES

1) There is some potential for significant flash flooding somewhere across northeast Pennsylvania to Sullivan County, NY. However, where exactly the heaviest rain occurs is still uncertain at this time, but a flash flood watch has been issued where confidence is highest.

2) Low amplitude weak upper level trough remains in place Tuesday and Wednesday. This will bring partly sunny conditions, with chances for a few pop up showers or t'storms along with generally seasonable temperatures.

3) The next trough and front is progged to slowly move through the area Thursday into Friday. This will bring increasing chances of showers and thunderstorms along with more warm and humid conditions.

DISCUSSION

KEY MESSAGE 1...

Heavy rain is expected across portions of the region from this afternoon through early Tuesday morning. A flood watch for flash flooding is now in effect for all of NEPA and Sullivan County, NY through 8am Tuesday. There remains some uncertainty in how far north heavy rain will make it, but at this time, there just is not enough confidence to include the Southern Tier from Steuben to Delaware County in a watch, but it is possible that counties further north could be added in later updates.

Forecast sounding indicate a juicy atmosphere over the region, with PWATs near 2 inches and high warm cloud layer above 12K feet. The nearly saturated soundings show skinny CAPE throughout the column and weak 1000-700mb winds less than 10-15 kts that is parallel to a quasi-stationary boundary that will eventually edge northward and settle near or just north of the NY/PA border. Storm motions today will be slow and with the deep warm cloud depth and skinny CAPE, these storms will be efficient rainfall producers with intense rainfall rates near 2" per hour.

The atmosphere remains very well primed for heavy rain through tonight and Monday. An area of low pressure later this evening into the overnight hours will help to organize the rain and convection into a pivoting, rotating cluster, most likely over NEPA into SE NY, however, exactly where and how far north this feature makes it remains somewhat uncertain. This pivot point will be key on who will potentially receive significant rainfall, as this will increase the duration of intense rainfall rates over a particular area.

Widespread rainfall amounts of 1 to 2.5 inches will certainly be possible from the Twin Tiers on south and there is potential for localized stripes of 5 inches or more of rain across portions of NEPA and into the southern Catskills. If rainfall amounts this high or higher were to occur in any area it would likely cause major flash flooding, especially if it occurs across more susceptible flash flood prone areas such as the Poconos and Catskills, so the flood watch has been issued where this potential is most likely at this time.

The weak wave of low pressure should eventually pull out into the Atlantic late Monday night into Tuesday morning and this will bring an end to the heavy rain across the region.

KEY MESSAGE 2...

The upper level trough never really leaves the area entirely heading into Tuesday and this setup will keep at least a chance for at least isolated to scattered showers and t'storms in the forecast, along with mostly cloudy skies. With all the clouds and scattered showers around, it stays on the cooler side as highs only reach into the 70s once again. By Wednesday, the latest ensemble forecast guidance continues to show mainly dry conditions aside from a stray pop up shower or two. Skies are also expected to become partly to mostly sunny and high temperatures warm up into the upper 70s to mid-80s.

KEY MESSAGE 3...

Thursday is forecast to be the warmest day of the upcoming week and dry for the first half of the day. The area will be under a zonal flow pattern, however there is potential that a cold front pushes into western NY late in the day, bringing the chance for showers and thunderstorms. Depending on the exact timing, this front could bring strong to severe thunderstorms if it comes in during the peak heating hours of the afternoon, but some ensemble guidance has this front not passing until early Friday morning.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Spotty and slow moving rain showers are popping up this afternoon across the Southern Tier into NEPA. AVP has a chance that these showers will develop into thunderstorms so added a Prob30 through the evening. ELM, BGM and ITH dont have enough instability to have the confidence to add thunder and with the isolated nature of the showers so far, just kept vicinity showers for now unless one pops up right over a terminal.

Tonight, steadier and heavier rain will move in, mainly affecting the Southern Tier and Southward. Cigs will get to IFR at BGM, but lower confidence at AVP and ELM. There is a chance of persistent IFR vis in a narrow band of heavier rain though exactly where that sets up is unknown right now. BGM and AVP have the highest chances of seeing this band set up over or near the terminal.

SYR and RME look to remain north of most of the rain so VFR to intermittent MVFR tomorrow morning is expected.

Outlook:

Monday afternoon and night...Restrictions continue due to rain in the area.

Tuesday...Lingering rain showers in the morning with MVFR conditions, trending towards VFR.

Wednesday through Friday...Mainly VFR; High pressure building in, morning fog likely, mainly at ELM.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Flood Watch through Tuesday morning for PAZ038>040-043-044-047- 048-072. NY...Flood Watch through Tuesday morning for NYZ062.