textproduct: Binghamton

WHAT HAS CHANGED

The Wind Advisory that was previously issued for parts of the Finger Lakes Region to the western Twin Tiers has been extended to 2PM this afternoon. A separate Wind Advisory was issued for the Wyoming Valley and Poconos in Northeast PA, which will be in effect from 2PM this afternoon until midnight tonight. For the severe weather potential this afternoon into this early evening, very little has changed.

KEY MESSAGES

1) A strong cold front will bring the potential for scattered severe thunderstorms this afternoon into this evening with the main threats being damaging winds and possibly an isolated tornado. Brief heavy rain could also lead to localized flash flooding. Gusty southerly winds will also be present ahead of the cold front, followed by gusty westerly winds behind the front.

2) There will be a rapid drop in temperatures with the passage of the cold front tonight, which will increase the risk of a flash freeze.

3) Accumulating lake effect snow is possible north of the New York Thruway Corridor Tuesday afternoon through Tuesday night.

DISCUSSION

KEY MESSAGE 1...

Northeast PA and portions of Central NY continue to be under the threat for severe thunderstorms this afternoon and evening ahead of a strong cold front. Our region will be firmly in the warm sector following a warm front passage this morning, which will allow for temperatures to surge into the 60s for most of the area. The amount of warming that will occur will contrast significantly with the incoming air mass on the back side of the system, 850mb temps around -12C and surface temperatures in the upper 20s. This will create a very strong surface baroclinic zone that will help focus the convection on.

This event will be dominated by the intense amount of shear, with roughly 60-70kts of 0-6km bulk shear and 0-1 km shear values exceeding 40kts. ML CAPE values roughly 100-200 J/kg could be bumped up a little higher if the area can scour out the cloud cover in the late morning and early afternoon. If there is more clearing that anticipated at this time, some of the convection that initiates ahead of the cold front could allow for more cellular storm types. However, most of the focus will be on the linear convection that is expected to develop in west central PA late this morning and lift to the east/northeast through the afternoon across southern/central NY and Northeast PA. This could actually be a situation, if the instability does not increase, where the line of "thunderstorms" may not have much in the way of lightning and could be mostly low-topped. The primary threat will be damaging winds along the line, but embedded quick-spin up tornadoes cannot be ruled out given the extreme amount of shear. The threat for severe storms will move east of the eastern Catskills after 8-10 PM.

The additional threat with this storm system will be the centered around the potential for heavy rainfall rates that may lead to some instances of flash flooding, especially as PWATs will be around one inch. That being said, the convective line this afternoon/this evening is expected to be rather progressive, so that will likely limit the flash flood threat. The usual poor drainage and urban areas still could see some localized flash flooding issues.

Finally, separate from the convective line this afternoon, winds will remain gusty today. Pre-frontal southerly winds will continue to gust between 40 and 50 mph across some of the elevated areas of the Southern Tier of NY, Northern Tier of PA, and the downsloping areas of the Finger Lakes. These gusty southerly winds will be mainly this morning, before the briefly diminish somewhat by the late morning/early afternoon. Due to remaining gusty winds, the existing Wind Advisory has been extended to 2PM, although it is possible that some counties may be able to be dropped from the advisory before then.

Then post-frontal gusty westerly winds are expected to develop, especially across the Wyoming Valley and Poconos. It is across those areas that a separate Wind Advisory has been issued for 2PM this afternoon until midnight tonight.

KEY MESSAGE 2...

Behind the cold front, a very cold airmass for this time of year will move in quickly and cause surface temperatures to drop 20-25 degrees in a 3-5 hour window (between 8PM and midnight). There is some concern for a flash freeze in this situation given how quickly the air temperatures drop behind a rain-producing front. A limiting factor in this situation will be related to the fact that the ground temperatures overall are much warmer than even a couple weeks ago. Remaining gusty winds tonight into Tuesday morning may also help to dry out the wet roads before the cold air really settles in.

KEY MESSAGE 3...

Behind the cold front, 850mb temperatures will drop to -16 to -18C. The wind orientation will initially be westerly, or even west- southwesterly Tuesday morning, which will allow for most of the lake effect snow showers to initially be located north of Oneida County/closer to Lake Ontario. However as the primary upper trough shifts eastward, the flow will become more northwesterly, which will favor an upstream lake connection and allow for the lake effect snow to shift southward Tuesday afternoon, first into Oneida County, then towards the NY Thruway corridor Tuesday evening. With the band likely being present late in the day Tuesday and Tuesday night (rather than mid-day Tuesday during the strong mid-March sun angle), several inches of snow will be possible in the most persistent snow. Winter Weather Advisories will likely be needed as we get closer.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Widespread MVFR to Fuel Alternate restrictions are present this morning, with KBGM at IFR. Brief IFR restrictions also cannot be ruled out elsewhere this morning, but confidence is low.

A cold front moves through in the late afternoon and evening, between 20Z and 2Z with a strong wind shift as well as a squall line of showers and thunderstorms along it. There could be embedded gusts along the squall line near 60 knots but odds of a terminal being struck by these isolated gusts are low. Still over 40 knot gusts is a higher potential.

Temperatures drop rapidly behind the front with precipitation transitioning from rain to snow quickly. The snow wont last long as the precipitation begins to move out of the region by around 06Z for all terminals, but KSYR and KRME who may have lake effect snow developing as the precip moves out.

LLWS is expected today before diminishing this evening.

Outlook:

Tuesday through Tuesday Night...Widespread snow showers become more localized as lake effect snow over SYR and RME late on Tuesday. With winds staying gusty, blowing snow will also be possible.

Wednesday...Mainly VFR.

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

Friday...A chance for additional showers.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Wind Advisory until 2 PM EDT this afternoon for PAZ038. Wind Advisory from 2 PM this afternoon to midnight EDT tonight for PAZ043-044-047-048-072. NY...Wind Advisory until 2 PM EDT this afternoon for NYZ015>018- 022>025-036-044-055.