textproduct: Binghamton

WHAT HAS CHANGED

Overall little change to previous forecast. Small tweaks to the QPF with some shifts in where the front may stall.

KEY MESSAGES

1) Severe thunderstorm chances today and Tomorrow for most of the area, and the far south for Thursday.

2) Risks for locally heavy rainfall and potential flooding increases Wednesday into Thursday morning.

3) A cooler pattern with drier Northwest flow returns late week into next weekend.

DISCUSSION

KEY MESSAGE 1...

The next few days will be active for thunderstorms, especially Southwest of a line from Syracuse down to the Catskills. That is where many of the models have the warm front stalling so along and north of the front, more stable air will lower the severe risk but increase the heavy rain threat. Early this morning, water vapor imagery is showing an initial shortwave passing through leading to some rain showers. This has been well depicted in the models and helps lead so some uncertainty with storm chances this afternoon around peak heating when the severe ingredients are in place. Many of the models do not have a shortwave passage this afternoon and water vapor imagery does not show anything of note upstream for a ways. Even though we may see between 2000 and 3000 J/kg of SBCAPE and 30 to 40 knots of bulk shear this afternoon, we may not have a trigger to develop the deep convection. Still plenty of CAMs have some precipitation developing with a speckling of 40 dbz cores in the HREF. The front that is near by may be enough to get some initial convection near it and outflow boundaries are able to be the needed trigger for storms.

If storms do develop today, the large cape and dry air aloft will predominantly have a hail and wet microburst threat. There is a little bit of curvature in the forecast hodographs for this afternoon as well so an isolated tornado cannot be ruled out, especially closer to where the warm front is stalled.

Tomorrow is another difficult day to pin down as a marine layer is trying to push in from the west that could help at least stabilize the boundary layer. The more stable air is likely east of I-81 but farther west, it does look like there will be enough sun to become unstable. Along the edge of this marine layer will need to be watched closely as there will be enhanced environmental helicity. Any storms with supercell characteristics that form in the afternoon and cross from the unstable air into the marine layer may briefly pose a tornado risk. Shear tomorrow is also looking better today with most models showing 50 to 55 knots of Bulk Shear. More clouds may limit the overall CAPE to around 1000 to 1500 west of I-81 but that is still plenty to see organized convection. The timing of a subtle shortwave also looks better for storms to fire in the afternoon around or just after peak heating so if the stable marine layer does not push west through the entire region in the morning, there is higher confidence in more widespread severe Wednesday.

Thursday is not quite out of the woods yet for severe thunderstorms as low level moisture remains in place for part of the day with shear still in place. It is uncertain if dry air slowly advecting in will erode away at the instability prior to reaching the convective temperature in the afternoon.

KEY MESSAGE 2...

With a stalled front and high precipitable water values tomorrow into Thursday morning of around 2 inches, heavy rain and flash flooding is a concern. Now that more of the CAMs are within range, the HREF's probability matched mean which helps show some reasonable worst case scenarios does highlight an area from CNY down into the Catskills/southern Hudson River Valley where a strip of 2 to 3 inches of rain could fall in 12 hours. A low level jet feeding into the front Wendesday night into Thursday morning will help feed training storms if the front remains stalled all night so pockets of 3+ inches is expected. Flash flooding is likely where the front ends up stalling with potential for isolated significant flash flooding.

KEY MESSAGE 3...

For Friday into early next week, the large ridge in the central US retrogrades west with the trough in the northeast nudging into the mid Atlantic. This will help the flow become more northerly with cooler and drier air advecting in. Depending on how cool the 850 mb temperatures are, there could be some lake effect rain showers to deal with but for the most part the weekend into early next week is looking mostly dry.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Scattered showers are moving across much of CNY this morning, with a few isolated thunderstorms developing. A mix of restrictions are across the region, with LIFR restrictions due to fog and rain at ELM/SYR/BGM that should last into the mid morning hours. MVFR ceilings will remain at all terminals into the afternoon before scattering out at AVP/BGM/ELM/ITH by early afternoon. SYR and RME are forecast to remain mostly cloudy today with persistent MVFR ceilings.

The clearing across the Southern Tier into NEPA will allow for a chance of scattered thunderstorms to develop. AVP and BGM look to have the best chance for thunderstorms, but confidence is only moderate as timing and location of the storms remains uncertain. Prob30 groups were included in these TAFs for thunderstorms. ELM will have enough instability present but may be too influenced by high pressure which would limit storm potential.

A marine layer will work its way into the area after 00z, which could bring IFR ceilings to AVP and BGM. Fog could develop again for ELM/ITH/RME with IFR restrictions possible.

Outlook...

Wednesday through Thursday...Periods of showers and thunderstorms with associated restrictions, especially each afternoon/evening.

Friday and Saturday...Mainly VFR. Chance of early AM fog each day.

BGM WATCHES/WARNINGS/ADVISORIES

PA...None. NY...None.