textproduct: Binghamton

WHAT HAS CHANGED

Expanded the Wind Advisory for 5PM this evening to 8AM Monday morning to also include Bradford and Wyoming counties in Northeast PA, as well as Chemung and Tioga counties in NY.

Also, confidence continues to increase regarding the potential for severe thunderstorms Monday afternoon into the early evening. The main threats with these thunderstorms will be damaging winds, heavy rainfall, and possibly an isolated tornado.

KEY MESSAGES

1) A round of light snow is expected this morning, followed by gusty winds late this afternoon through tonight.

2) Much warmer temperatures are expected on Monday, along with continued gusty winds. Showers and thunderstorms are also expected to develop on Monday, especially in the afternoon into the evening. Some of these thunderstorms may become severe with damaging winds, heavy rainfall, and possibly an isolated tornado.

3) Below normal temperatures will return for Tuesday and Wednesday behind the departing low pressure system, along with lake effect snow showers. This will be followed by seasonable temperatures to close out the week.

DISCUSSION

KEY MESSAGE 1...

A warm front aloft will produce a round of light snow this morning, before quickly exiting to the north by early this afternoon. Snow amounts will be light; mainly less than a half inch. That being said, a few of the higher elevations of Steuben County may get some terrain enhancement and perhaps around one inch of snow. Any snow that does fall and accumulate will quickly melt this afternoon with high temperatures expected to get into the 40s for most areas.

Otherwise, the main story for today and tonight will be the increasing winds. While winds will start off calm today, an increasing southerly flow combined with a tightening pressure gradient will allow for winds to quickly increase this afternoon and especially by this evening. These gusty winds are expected to be most widespread (40-50 mph gusts) across the Finger Lakes Region with downsloping from the Southern Tier of NY, but some of the gusty winds will also reach parts of the Southern Tier, as well as parts of Northeast PA (mainly the higher elevations of Bradford and Wyoming counties). The previously issued Wind Advisory for most of the Finger Lakes Region remains in effect from 5PM this evening to 8AM Monday morning, with Bradford and Wyoming counties in PA, as well as Chemung and Tioga counties in NY added to the advisory.

KEY MESSAGE 2...

A low pressure system moving over the Great Lakes region will continue to deepen on Monday. Meanwhile, our region will be firmly in the warm sector following the passage of a warm front and therefore temperatures are expected to surge into the 50s and 60s. An initial batch of rain showers associated with the warm front passage will move through the area late tonight/early Monday morning and should be largely through the area by 8AM Monday morning. Much of the morning after that should actually be mainly dry, except for possibly a few isolated showers. Skies are expected to be mostly cloudy, but there is a small chance that partial clearing could occur in the morning. Otherwise, southerly winds will remain gusty Monday morning into the afternoon, prior to the cold front passage, with occasional gusts of 30-40 mph possible at times.

Going into Monday afternoon, a strong cold front is expected to move through the area from west to east, clearing our eastern- most counties (Poconos-Catskills) by the early evening. Shear values are expected to be very high (60-80 kts of 0-6km shear, and perhaps as high as 90 kts). As is common this time of the year, instability will be on the lower side. That being said, even this will not be completely non-existent, with a pocket of 200-300 J/kg of CAPE modeled to be present across Northeast PA, extending northward into the Southern Tier of NY. There will also be some 0-1km helicity present, which combined with the abundant shear, could result in a few isolated tornadoes. If some discrete supercells were to develop ahead of the front, the tornado threat would be higher. This scenario is somewhat unlikely at this time with the best setup for discrete supercells being well to the south across the Mid-Atlantic Region. The severe weather setup for our region appears to be primarily from a QLCS, with a few embedded tornadoes within the line possible (otherwise mainly straight- line damaging winds).

With all of this in mind, SPC now has a "Slight Risk" (level 2 out of 5) for severe thunderstorms from Northeast PA, extending northward to just south of the NY Thruway corridor. The far southern portion of our forecast area (Luzerne County) is clipped by the "Enhanced Risk" (level 3 out of 5). Meanwhile, the northern third or so of our forecast area is in a "Marginal Risk" (level 1 out of 5).

Finally, while the line of thunderstorms is expected to be somewhat progressive, these thunderstorms will contain heavy rainfall, which will be also aided by PWATs around or just over one inch. This could result in localized flash flooding, especially in any urban or poor drainage areas. WPC has most of the region highlighted in a "Marginal Risk" for excessive rainfall in their Day 2 outlook.

KEY MESSAGE 3...

Following the passage of the above mentioned cold front and severe weather, much colder air will rapidly spill into the region with 850mb temperatures falling from around +10C to around -17C. This will set the stage for lake effect snow on Tuesday, but before that, a flash freeze is expected Monday night with any remaining moisture on roads expected to quickly freeze up. This could result in slippery road conditions for the Tuesday morning commute.

As far as the lake effect snow potential goes, an initially southwesterly flow should keep the initial band of lake effect snow north of the region/closer to Lake Ontario Tuesday morning. However, as winds shift to westerly, and eventually west- northwesterly, these lake effect snow showers will shift southward through Oneida County and eventually to the NY Thruway corridor Tuesday afternoon and Tuesday night. With the timing of the lake effect snow being mainly centered around Tuesday night, several inches of snow may fall around the NY Thruway corridor. Any remaining lake effect snow will dissipate during the day on Wednesday as high pressure builds back in.

Aside from the lake effect snow, temperatures will be quite cold for this time of the year, especially on Tuesday. Tuesdays highs are expected to be in the lower 20s to lower 30s, with lows Tuesday night in the single digits to mid teens. Then highs on Wednesday are expected to be mainly in the 30s. Milder air will return for Thursday and Friday with highs returning closer to normal (mainly in the 40s).

AVIATION /06Z SUNDAY THROUGH THURSDAY/

VFR conditions are currently present but a band of snow will develop around 9Z and lift northward through NY that could bring a period of IFR vis. AVP looks to miss out on the snow but all the NY terminals will likely experience the band for a little bit. With the band moving through fairly quickly, tempos were used for now but if timing becomes more exact once the snow forms, amendments will be made to make it more precise.

VFR conditions return once the snow band moves north with a strong low level jet forming later today. All terminals will develop strong LLWS from south to north so AVP could get it shortly after 18z and it wont reach RME until closer to 6Z. Even with the strong surface winds, there could still be near 5o knot wind difference between the surface and above the stable inversion a few thousand feet above the surface. Low stratus and potentially rain showers move in from the south after 0Z with conservative MVFR conditions for AVP for now, could fall to IFR by 6Z but was not confident on timing so did not introduce IFR yet. BGM may also get close to IFR being at higher elevation and flow is favorable for low stratus development on hill tops.

Outlook:

Rest of Sunday Night...Rain showers and associated restrictions. Low- level wind shear continues

Monday...Restrictions expected in rain and afternoon thunderstorms.

Monday Night through Tuesday Night...Rain changing to snow with restrictions possible. Widespread snow showers become more localized as lake effect snow over SYR and RME late on Tuesday.

Wednesday...Mainly VFR.

Thursday...Mainly VFR; a low chance for spotty rain/snow showers.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Wind Advisory from 5 PM this afternoon to 8 AM EDT Monday for PAZ038-043. NY...Wind Advisory from 5 PM this afternoon to 8 AM EDT Monday for NYZ015>018-022>025-036-044-055.