textproduct: Binghamton

WHAT HAS CHANGED

Forecast rainfall totals for Monday were lowered a bit, though it will still be wet day. Severe risk Monday, albeit rather limited, has also edged a bit farther north to include more of Northeast PA and Catskills counties of NY.

KEY MESSAGES

1) Isolated showers and thunderstorms will quickly dissipate with loss of daytime heating late this afternoon.

2) A passing low pressure system will make Monday cooler and wet. Though most of the area will be able to handle the rain, localized flooding and isolated strong to severe thunderstorms cannot be ruled out for parts of Northeast Pennsylvania to the Catskills and Eastern Southern Tier of New York.

3) Our next main chance of rain will arrive Thursday into Friday, as multiple waves move through the region to yield occasional showers and a chance of thunderstorms.

DISCUSSION

KEY MESSAGE 1... Isolated diurnally-driven showers and non-severe thunderstorms popped up during midday, though will also quickly fall apart in late afternoon with loss of heating.

An elongated weakening shortwave aloft, along with diurnal heating, resulted in the expected few showers and thunderstorms during late morning to early afternoon. However, there is very little forcing as ridging is working into the region, and mixed- layer Convective Available Potential Energy is topping out only around or slightly above 500 J/kg. Precipitable water values are under an inch, reflective of the significant amount of dry air in the column which is immediately entraining into any convective columns. Shear is also weak. Thus other than brief stronger gusts directly underneath pulses as they mix down, and spotty lightning, little impact is anticipated from these cells. They will succumb to the dry air and loss of heating in late afternoon.

KEY MESSAGE 2... Rain moves in quickly Monday morning. Models continue to favor our region generally being on the north side of the surface low track, which also makes sense with evolution of convection well upstream in the Mississippi Valley/Midwest. This supports the continued lowering of overall rain amounts, as our activity will be elevated and mainly stratiform. Average forecast totals range from about three-quarters of an inch northwest to an inch- and-a-quarter southeast. The main stem rivers will have no problem handling this rain, but under embedded thunder/heavier shower cells in afternoon-evening, rainfall rates could still lead to localized water issues especially in poorer drainage urban areas from Northeast PA into Eastern Southern Tier- Catskills NY; smaller creeks and rocky steeper-terrain areas will also need to be monitored.

However, there is a still a chance that the warm sector of the system could briefly sneak into the Wyoming Valley-Poconos area, and thus effectively a shallow warm frontal zone in Northeast PA-Catskills NY until the low passes. A ribbon of elevated Precipitable Water Values will sneak into that region via a southwesterly low level jet, along with some shear. The Storm Prediction Center has thus pulled the Marginal Severe Risk up a bit more to include most of Northeast PA and the Catskills counties, as there could be isolated gusty storms. The limited probabilities for any isolated tornadoes will be focused farther southeast where storms will tend to be more surface- based, though it is a non-zero chance.

KEY MESSAGE 3... After benign weather Tuesday through Wednesday night, a wetter period is likely Thursday into Friday. We will be within southwest flow on the front end of a general trough pattern evolving over the Great Lakes region, which will send multiple disturbances through our area. This will increase available moisture, yet models suggest that individual waves will also be on the weak side.

We can anticipate occasional showers and a chance of thunderstorms. However, the National Blend of Models has only a 10-30 percent probability for more than an inch of rain total in 48 hours, so we are not too concerned for an impactful amount of rain. Severe parameters are also rather limited; only modest amounts of instability and a little bit of shear in the 3-6 km layer. We will continue to monitor trends as it gets closer, but for now potential appears quite low for either severe thunderstorms or excessive rain.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Conditions will be VFR through at least the overnight hours. Ceilings will fall to MVFR Monday morning as rain moves into the region. Guidance quickly takes ceilings down to IFR at BGM, ELM, and ITH. If ceilings do not bring IFR conditions, there is a good chance that moderate rainfall will reduce visibilities to IFR. At SYR, RME, and AVP, guidance favors hanging onto MVFR restrictions through the end of this TAF period.

Northwesterly winds may be gusty at times this afternoon. Then winds become calm overnight. With the next system moving in, winds then become easterly to southeasterly with speeds around 5 kts.

Outlook:

Monday afternoon into Monday night...Restrictions due to rain showers with isolated embedded thunderstorms.

Tuesday through Wednesday...Mainly VFR.

Thursday through Friday...Additional restrictions possible as a short wave moves through the region with showers.

BGM WATCHES/WARNINGS/ADVISORIES

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