textproduct: Binghamton

WHAT HAS CHANGED

Confidence continues to increase that Tuesday-Wednesday may be quite active for thunderstorm activity, and perhaps into Thursday.

KEY MESSAGES

1) Weak waves of scattered showers, and perhaps isolated embedded thunder at times, are expected through Monday night.

2) An active pattern of warm and humid conditions is anticipated Tuesday through at least Wednesday, with potential batches of strong to severe thunderstorms. This could linger into Thursday for parts of the area.

DISCUSSION

KEY MESSAGE 1...

Increased cloud cover has occurred from forced ascent in the right entrance region to the south of an upper jet, as a stronger wave swings through Quebec en route to New England. The west-northest flow aloft itself contains additional weak waves, yet there is also surface high pressure. So while there are attempted scattered showers, initial ones have had to battle a lot of dry air in the boundary layer. As the surface high shifts to our east, a light return flow and pooling moisture within a developing frontal zone will generate waves of scattered light showers tonight into Monday morning. This will squeeze more towards the western Twin Tiers to Wyoming Valley PA tonight-early Monday as high pressure gets a temporary hold over Central NY-Catskills, but that zone will then drift across the rest of the region Monday afternoon.

Any rain through Monday morning will be scattered and of little consequence. While that will remain mostly the case Monday afternoon through night, there will be more caveats. The developing frontal zone will see pooling moisture with precipitable water values reaching between 1.75-2.00 inches. Also, small amounts of instability aloft could result in isolated non-severe embedded thunder and thus more enhanced rates but that will be the exception not the rule. Most of the area will be just fine with a mostly cloudy seasonal day wand highs in the 70s to near 80 for the last day of August, with average rain amounts of only around a tenth of an inch or less. However, with the atmospheric profile trending more moist-adiabatic Monday afternoon through night, a narrow stripe or two of locally heavier rain cannot be totally ruled out if heavier showers can train over the same area. Meanwhile, there will be enough moisture around for typical areas of fog where breaks in clouds occur tonight-early Monday morning or Monday night.

KEY MESSAGE 2...

A ring-of-fire scenario is appearing to take shape for Tuesday through Wednesday, and perhaps into Thursday for at least part of the area. That is a setup when there is a hot dome located to our southwest, with a belt of westerlies over the top of the dome, sending potential multiple waves of strong convection dropping through our region. The Storm Prediction Center continues to highlight Slight Risk of Severe Thunderstorms/15 percent chance within 25 miles of a point for at least portions of our area Tuesday- Wednesday, and pressing south Thursday yet still possibly encroaching Northeast PA.

Warm and humid conditions at the surface will be coupled with brisk flow aloft and steepening midlevel lapse rates as any waves pass. Though the details have yet to shake out, convective parameters are favorable for there to be passing batches of strong to severe thunderstorms in our region, especially when and if waves coincide with peak diurnal heating each afternoon-evening. Convective Available Potential Energy (CAPE) probabilities have trended to 60-80 percent change of exceeding 1500 J/Kg for Tuesday afternoon and still 50-60 percent by Wednesday, especially west of I- 81. Top-heavy appearance of CAPE profiles in model soundings point to a large hail and wet microburst potential, with significant speed shear of 30-50 knots in the in 3-6km layer allowing for storm organization. This setup could even linger into Thursday for Northeast PA, though the primary belt of potential will be shifting south in response to more pronounced upper troughing across the northeast.

As with any setup that features multiple batches of storms in a warm and humid environment, each passing wave will pose an increase risk for excessive rainfall. Localized flash flooding thus cannot be ruled out through the midweek period, but details for where will not be apparent until we see where the initial zones of heavier batches of rain occur. As for the warmth, heat index values are likely to peak around 90 degrees Tuesday-Wednesday at lower elevations; not high enough for an Advisory but still very noticeable and perhaps impactful for anyone spending long periods outdoors without keeping up on hydration. Wyoming Valley PA could even push into lower-mid 90s for heat index both afternoons. That should trend a bit lower by Thursday.

A broad upper trough pattern should lead to milder more seasonal early September temperatures Friday onward, with limited moisture and thus probably dry most of the time. National Blend of Models has daily Probability of Precipitation peaking only in the 15-30 percent range each day through next weekend.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Mostly VFR flight conditions expected through this evening. Shower coverage will slowly fill in through the afternoon and evening from northwest to southeast. Lowering cloud bases with incoming moisture will bring CIGs down to MVFR by the late evening for the western terminals. Showers may have brief reductions to VSBY at times this afternoon/evening, mostly to MVFR. A few embedded thunderstorms will also be possible with this afternoons showers.

Tonight, conditions will deteriorate through the overnight as increased moisture and mid level pulses of energy track southeast out of the Great Lakes. This will bring the potential for fog and low stratus. Scattered showers will also be possible tonight, with the greatest potential for showers expected for the western and southern terminals. Conditions are expected to drop to IFR for both CIGs & VSBYs for most of the area, with lower cats possible in the more fog prone areas.

Monday, morning fog and low stratus will improve starting around 13/14Z, but CIGs are expected to remain at least at lower level MVFR, possibly IFR at times through the day. VSBYs will improve in the morning, but incoming showers/thunderstorms with localized downpours will bring the potential for lowered flight conditions. A few showers will be possible in the morning for the southern terminals, with additional showers/storms later in the day for most of the area. The afternoon showers/storms will have the best potential for reductions to VSBYs.

Outlook...

Monday night through Thursday... Scattered showers and thunderstorms possible with associated restrictions, especially each afternoon/evening.

Friday...VFR conditions expected with a few isolated showers possible.

BGM WATCHES/WARNINGS/ADVISORIES

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