textproduct: Binghamton

WHAT HAS CHANGED

Focusing a little more on potential for heavy rainfall and flash flooding Wednesday night into early Thursday. Still concerned about severe weather risk later Tuesday afternoon/evening and again on Wednesday afternoon.

KEY MESSAGES

1) Severe thunderstorm chances increase Tuesday through Wednesday.

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 general setup indicates a warm frontal boundary moving into the region and then stalling somewhere over CNY and NEPA for the first half of this week. Aloft...multiple waves will move through NW flow triggering several rounds of showers and thunderstorms. Timing the precision of these waves is proving to be difficult with a wide spread of solutions showing up in the guidance. Tonight...showers will continue into this evening before easing up a bit in coverage over night and early Tuesday as an initial wave departs the area however there is considerable uncertainty with the CAMS models where some do develop more convection during the wee hours.

One thing that is becoming more clear is that instability will return along and south of the warm frontal position setting the area up for stronger, more organized storms. Tuesday afternoon looks to be the warmer day, with ensemble probabilities eclipsing 70% for >1500 J/kg of CAPE along with around 40 knots of shear. One of the things working against Tuesday is the lack of a definitive trigger coinciding with the instability and shear parameters, but even if storms occur early or after dark, severe storms would be likely due to the prime atmospheric setup. It is difficult to pin down any one location at this time, however, the instability axis favors our western and southern zones.

Wednesday has a stronger shortwave passing through with the dominant model cluster showing a later day/night timing if correct. More moisture aloft will likely mean more clouds, less heating and overall CAPE development during the day. Still somewhere between 800 and 1500 J/kg is looking likely. Shear will be stronger, hovering around 50 knots and with the shortwave passing through, a trigger is present to get storms going even without a whole lot of CAPE.

KEY MESSAGE 2...

The warm front will still be stalled and could be a focal point for training storms mainly on Wednesday and Wednesday night which will be the primary focus for a higher potential for flooding. PWATs near 2 inches and a strong (~40 to 50 knot) low level jet forming in the evening on Wednesday feeding persistent, training storms could lead to significant flash flooding where they line up. The current thinking points to a cumulative spread of QPF between 2-3" of rain over the next 72 hours across CNY and a little less for NEPA. Locally higher amounts from persistent thunderstorm activity also can't be ruled out within this setup as deep layer moisture and high warm cloud depths will be present. National Water Model guidance and HREF ensemble guidance suggests that main stem rivers should be able to handle runoff from projected rainfall, however, smaller order streams and tributaries are showing low-medium probability signals for rapid onset flooding which will need close monitoring over the next few days.

With low level moisture remaining in place Thursday with more sun, instability develops again with high shear once again though the lack of a trigger may keep storms from developing but could have another day with a hail and wet microburst threat.

KEY MESSAGE 3...

For Friday into the weekend, 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 is looking mostly dry.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Highly variable flight conditions expected over the next 24 hours with passing upper level waves in the vicinity of a warm-stationary front. This will result in periods of showers and restrictions primarily wavering within the MVFR-IFR categories...with some VFR fluctuation possible and potentially also down to alternate minimums. Airport mins don't seem a high probability at this time. TSRA risk looks too low and further out in time to be included with this package...but overall instability will be increasing with time.

Outlook...

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

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

BGM WATCHES/WARNINGS/ADVISORIES

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