Area Forecast Discussion

WHAT HAS CHANGED

Minor changes to the forecast with this forecast update.

KEY MESSAGES

1) A few spotty showers and thunderstorms through this evening.

2) Greater coverage of showers and thunderstorms is expected from Monday through Tuesday night, some of these storms may produce gusty winds and heavy rainfall.

3) Chances for showers and thunderstorms are expected to linger into Thursday, with drier conditions for the end of the work week.

DISCUSSION

Key Message 1...A few spotty showers and thunderstorms through this evening.

An upper level trough deepens across the Northeast today. An embedded shortwave trough is expected to move from the Upper Great Lakes region to the Ohio Valley. Diurnal heating and modest dewpoints across the eastern Great Lakes region will support isolated to scattered showers and thunderstorms inland from lake breezes through early this evening. Further to the west, numerous showers and thunderstorms are expected to develop across southern Ontario into Ohio this afternoon, and this activity may reach the eastern Lake Erie shoreline and the Buffalo/Niagara Falls Metros by early evening. Hi-res guidance has trended drier in recent runs.

Key Message 2...Greater coverage of showers and thunderstorms is expected from Monday through Tuesday night, some of these storms may produce gusty winds and heavy rainfall.

An upper level ridge will build across the Northern Plains and Upper Great Lakes region through Monday. This will nudge the upper level trough over the Northeast while putting the eastern Great Lakes region within northwest flow aloft. Similar to previous days, diurnal heating and dewpoints in the 60s will support showers and thunderstorms inland from lake breezes Monday afternoon. Surface- based CAPE is expected to be higher Monday, leading to an increasing coverage of showers and thunderstorms. Winds aloft remain on the weaker side with mean 0-6km wind shear around 15-20 knots across far western NY, and less than 15 knots elsewhere. A shortwave trough and surface low are expected to dive across the Central Great Lakes to the Lake Erie region through Monday night. A corridor of increasing mid-level winds, steepening mid-level lapse rates, and high PWATS will move into the Ohio Valley and parts of western NY Monday night. Mean 0-6km wind shear will increase to 25-30 knots across far western NY, remaining less than 20 knots east of the Genesee Valley. The risk for an isolated strong thundertorm increases across far western NY overnight, especially if organized convection forms upstream Monday afternoon. If storms develop, the main hazards are damaging winds and locally heavy rainfall.

Upper level troughing will return across the eastern Great Lakes region Tuesday, and the surface low will become stacked and nearly stationary across western and central NY. Diurnal heating within a very moist environment will support numerous showers and thunderstorms Tuesday. While winds will be weak within the stacked low, a low level jet will wrap around the low and a few strong thunderstorms with heavy rainfall may lead to localized heavy rainfall across parts of western and central NY Tuesday afternoon through Tuesday evening. The low pivots into southern New England Tuesday night with a warm, moist conveyor belt moving into the eastern Lake Ontario region. The potential for showers and thunderstorms with heavy rainfall will continue into this region. Northerly flow and wrap-around moisture will move into western NY and chances for showers will remain overnight.

WPC has the entire region in a Marginal Risk for Excessive Rainfall Monday through Tuesday night.

Key Message 3...Chances for showers and thunderstorms are expected to linger into Thursday, with drier conditions for the end of the work week.

A cool season type set-up will persist Wednesday with a stacked low over the Northeast. Deep moisture will persist across the forecast area through Wednesday, before drier air builds into the region Wednesday night through Thursday. Diurnal heating will support another day of showers and thunderstorms across the region. Cooler weather is expected Wednesday and Thursday with highs in the 70s.

High pressure will move into the eastern Great Lakes region for the end of the week bringing dry and seasonal weather.

AVIATION /00Z MONDAY THROUGH FRIDAY/

While an isolated shower or thunderstorm will be possible early this evening, largely VFR conditions are expected to prevail tonight. Some Southern Tier patchy IFR/MVFR valley fog and/or lower stratus may develop overnight. Some light (MVFR) fog can also not be completely ruled out at KIAG overnight.

On Monday any early morning patchy fog/stratus across the Southern Tier should dissipate fairly quickly with the return of daytime heating/mixing. Continued diurnal destabilization will then allow for some widely scattered/scattered showers and thunderstorms (along with brief/localized restrictions) to develop mostly inland from the lakes Monday afternoon...with VFR conditions otherwise prevailing.

Outlook...

Monday night through Tuesday night...Showers and scattered thunderstorms pushing across the area from west to east...with initial VFR flight conditions lowering to MVFR/IFR.

Wednesday...Showers and a few leftover thunderstorms with initial MVFR/IFR possibly improving to VFR/MVFR.

Thursday...Mainly VFR with a chance of showers and slight chance of thunderstorms inland from the lakes.

Friday...Mainly VFR.

MARINE

Weak surface-based ridging will linger across our region through Monday...with a corresponding weak pressure gradient resulting in light to modest winds and minimal wave action...and localized lake breezes developing near the lakeshores both this afternoon and Monday afternoon.

Monday night through Tuesday a broad wave of low pressure will settle southeastward across the Great Lakes...with the low then slowly drifting to the mid-Atlantic coastline Tuesday night and Wednesday. Out ahead of the low a light to modest southerly flow will develop Monday night. Winds will then transition to northerly to northeasterly for Tuesday night/Wednesday once the low passes off to our southeast...though the finer details of this transition are not yet clear as these will be highly dependent upon the exact timing and track of the low...factors which remain rather uncertain at this time. Once we do get into the northerly/northeasterly flow behind the low though...this should at least turn moderately brisk and supportive of choppy conditions along the south shores of the lakes Tuesday night into Wednesday...with lower-end SCA-level conditions possible. Winds will then lighten and turn more westerly Thursday and Friday...allowing for a commensurate decrease in wave action.

Out ahead of the approaching low...some widely scattered to scattered showers and thunderstorms will also become possible Monday into Monday evening...with more widespread showers and scattered thunderstorms then expected later Monday night and Tuesday as the low crosses our region. Any storms could produce locally higher winds and waves...with this potential greatest across Lake Erie later Monday afternoon and Monday night.

BUF WATCHES / WARNINGS / ADVISORIES

NY...None. MARINE...None.