textproduct: Binghamton

WHAT HAS CHANGED

Rainfall totals and coverage have been increased. A Flash Flood Watch has been issued for Sullivan and Pike counties from 11am Tuesday to 8pm Wednesday.

KEY MESSAGES

1) Isolated showers and thunderstorms will develop this afternoon and evening. Showers may produce locally heavy rainfall, small hail and gusty winds.

2) A strong low pressure system will bring multiple rounds of showers and storms producing periods of moderate to heavy downpours Tuesday thru Wednesday.

3) Scattered light showers will be possible from Thursday into the weekend as the low slowly moves to the northeast. Rain showers will be possible in the weekend.

DISCUSSION

KEY MESSAGE 1...

Isolated showers and storms have developed along and just west of I-81 this afternoon. We have enough surface heating to break any low level cap that was in place, and with CAPE values around 1000-1500 j/kg, isolated thunderstorms are developing. Shear values are very low so storm organization is not really expected and these should be pulse type storms that develop and dissipated quickly, with additional cells building along outflow boundaries and areas of higher CAPE. A few of these storms have grown tall enough to warrant a severe thunderstorm warning, with the threat of a collapsing core pushing strong winds to the surface. Some small hail may be possible if an updraft gets tall enough, but chances for this are low.

Storm motion should be mostly from the NNW, but a few deviant motions may occur as cells develop along outflow boundaries. These motions will also be slow, which could produce isolated instances of flash flooding, especially across urban areas and/or those areas prone to flooding.

Storms should dissipate in the evening as we loose daytime heating.

KEY MESSAGE 2...

A very strong upper level trough will dig over the Northeast tonight into tomorrow. This trough is expected to cutoff by late Tuesday afternoon and it over much of the northeast through midweek. A strong surface low will develop as the upper levels cutoff, making the weather pattern look much more like we are in the fall instead of the end of July. Some uncertainty remains as to how the low will progress, with some solutions having a single center low meander from N to S through CNY on Tuesday then hang out over western New England on Wednesday. Other solutions have a double low forming, with energy transfered to a low off the NJ coast that moves NE into eastern New England. Current thinking is that the single low solution is more likely, which brings multiple rounds of moderate to heavy rain to the region, starting tonight through Wednesday.

A widespread 1.5 to 2.5 inches is expected across much of the area from tonight through Wednesday. Atmospheric dynamics kick it up a notch over the Catskills and into the Poconos where a strong LLJ is expected to develop on over the Hudson Valley that will tap into and pull enhanced moisture from the Atlantic into the region. Multiple models show signals that somewhere over this area east into southern New England could see large rainfall amounts in the 4-5 inch range, with isolated 6in+ possible. The majority of this heavy rain is expected Tuesday afternoon into Wednesday morning. This conveyor belt of moisture is progged to wrap around the center of the low, bringing a deformation bands on the NW side of the low as it moves into New England. This would bring chances for moderate rain showers across the area through Wednesday.

A Flash Flood Watch has been issued for Sullivan and Pike counties from 11am Tuesday to 8pm Wednesday. Upslope flow combined with the enhanced dynamics could bring impactful rainfall amounts to this area. A Slight Risk for Excessive Rainfall leading to Flash Flooding is present from Otsego county S to far eastern portions of Luzerne. A Moderate risk touches portions of Sullivan county, where upslope enhancement should provide the heaviest rainfall. The rest of the area is under a Marginal risk given the multiple periods of heavy rain could cause isolated flash flooding if an area is hit multiple times.

The Flash Flood risk should start to dissipate Wednesday afternoon as we loose a lot of the convective nature of the rainfall.

KEY MESSAGE 3...

The upper low and surface low will be pretty stacked and is forecast to hang out over southern New England into Thursday thru Friday, which will push scattered rain showers across the area from the north. The low will push east by Saturday. The weekend forecast is still uncertain as guidance handles a shortwave dropping into the Great Lakes differently. The shortwave could start moving eastward by Saturday morning, pushing a warm front into the area and generate showers along it, or it could dive farther south, get cutoff from the easterly flow and not impact us on Saturday. Either way, rain showers could develop on Sunday as another trough from Canada digs into the region.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Pop up showers and isolated thunderstorms are expected through this evening. Given the spotty nature of the convection, vicinity showers are in the forecast with TEMPO groups for thunder for all terminals except RME and SYR at this time where confidence was lowest. If need be, any thunderstorm will be amended in for those locations. Early tomorrow morning, a band of showers is expected to move through from west to east generally from 08Z-14Z that can produce at least MVFR restrictions. Confidence in thunder is too low at this time, but something that will be monitored. Additional scattered showers and isolated storms are expected throughout the rest of the TAF with lowering ceilings with MVFR/Fuel alt restrictions expected. IFR ceilings can't be ruled out, but confidence wasn't high enough to include this go around.

Outlook:

Tuesday afternoon through Thursday... Showers and isolated thunderstorms with restrictions through Wednesday then scattered showers Thursday with possible restrictions.

Friday and Saturday...Mainly VFR; low chance of a shower or thunderstorm.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Flood Watch from Tuesday morning through Wednesday evening for PAZ048. NY...Flood Watch from Tuesday morning through Wednesday evening for NYZ062.