textproduct: Binghamton

WHAT HAS CHANGED

Slightly increased chances for showers and potentially a weak thunderstorm Sunday afternoon and increased areal coverage of low PoPs on Sunday.

KEY MESSAGES

1) Seasonal temperatures the rest of this weekend with isolated to scattered showers and weak thunderstorms popping up across the region during the afternoon. Brief gusty winds are the main concern. Severe weather is not expected.

2) The next chance of widespread rain is expected to be Monday and Monday night before a brief break during the middle of the week and a return to a more active pattern later in the week.

DISCUSSION

KEY MESSAGE 1...

The synoptic pattern remains generally cyclonic through the weekend with slightly cooler air aloft being pulled southward from Canada while the surface conditions are allowed to warm through the afternoon. This setup is favorable for a few isolated showers to kick off during the 12-8 PM time frame today and showers and storms on Sunday.

Given the lack of sufficient forcing today and relatively dry air mass overall, confidence in any widespread, sustained threat of showers is low. Model forecast soundings reveal this very dry air mass, but do hint at a roughly 15 kft layer of saturation and a very high cloud base with an inverted-V sounding profile. This could also lead to some virga across the region. Very low confidence in gusty rain showers or dry downdrafts making it to the surface, but the threat is not zero. Any shallow convection that does develop will dissipate around sunset with the loss of solar heating to keep the updrafts going.

The addition of an upper short wave rotating through the region on Sunday will allow for a slightly higher chance of showers and a few weak thunderstorms Sunday afternoon. Model guidance is indicating around 100-200 J/kg of ML CAPE by the afternoon along with an overlapping corridor of deep layer shear around 40 kt extending NW to SE through central NY. With surface temperatures in the mid to upper 70s and dew points in the mid to upper 50s...combined with the short wave for forced ascent, believe there could be a slightly higher threat for thunderstorms in the afternoon than previously forecast. Main threat will likely be gusty winds and small hail.

KEY MESSAGE 2...

An embedded short wave within the broad cyclonic flow across the Great Lakes and Northeast will move through the area and combine with a gradually weakening surface low and very moist air mass to produce a swath of rain through the region on Monday. The surface low, with a warm front extending to the east is expected to lift north through the mid Atlantic as strong isentropic lift within the warm sector taps into a very moist air mass to produce a period of very efficient rain. Model PWs are generally around 1.5 to 1.75 inches, with close to 2 inches into the Poconos. These types of values are falling within the 75th to 90th Pctle for climatology for this time of year.

We will need to watch the track of the surface low, which will provide an answer to how unstable the area may get and how much moisture the atmosphere will be able to tap into. The latest NAM guidance is hinting at a more northerly track which will allow more moist/unstable air to be drawn north across ne PA and parts of central NY. This could lead to pushing more of the stable rainfall to the north, and more convective-type showers and storms to push into the southern forecast area. This type of pattern may be conducive to morning rain with a brief break and some clearing, then another round of showers and storms developing in the afternoon and evening moving SW to NE with the low track.

The potential addition of instability to the environment may also point toward an increased threat of heavy rainfall rates during the afternoon/evening hours. This would mainly impact the flash flood prone areas...steep terrain and urban regions mostly. A broad area of 1 inch of rain across the region is likely, with amounts greater than 1.5 inches and potentially closer to 2 inches is possible south of the NY/PA border.

A gradual warming trend sets in Tue and Wed with an increase in humidity too by the end of the week. The pattern turns active later in the week as well with afternoon/evening diurnal showers and storms scattered across the region.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Conditions will be VFR this TAF period. Some isolated showers are possible this afternoon. There is also a low chance for isolated showers and thunderstorms Sunday morning. For both rounds of showers, confidence was too low to include in the TAFs. Gusty winds finally become calm tonight. Winds gradually pick up again Sunday morning after 12z, though any gusts should stay below 15 kts.

Outlook:

Sunday afternoon...Mainly VFR, isolated showers and thunderstorms.

Late Sunday night through Monday...Wave of low pressure with rain, restrictions, and possible embedded thunder.

Tuesday through Wednesday...Mainly VFR.

Late Wednesday night through Thursday...Additional restrictions possible as a short wave approaches the region with showers.

BGM WATCHES/WARNINGS/ADVISORIES

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