Area Forecast Discussion

WHAT HAS CHANGED

Forecast rain amounts have lowered across western NY Sunday.

KEY MESSAGES

1) Rain showers and isolated thunderstorms return to the region tonight through Sunday.

2) Below normal temperatures will continue into next week.

DISCUSSION

KEY MESSAGE 1...Rain showers and isolated thunderstorms return to the region tonight through Sunday.

Regional radar shows a swath of precipitation from the Mid-West to western NY this afternoon. An abundant amount of dry air across the region will result in continued dry weather through most of the afternoon. A few sprinkles can't be ruled out across far western NY late this afternoon.

Surface high pressure will move across New England this afternoon, before moving off the east coast tonight. Surface low pressure is expected to develop across the Mid-West today, then move east along a surface trough while approaching the region tonight. Strong low to mid-level isentropic lift will move across the eastern Great Lakes region through tonight. Deep moisture with PWATS over 1.5" (97th percentile) will enter western NY. Showers will expand in coverage from southwest to northeast across western NY tonight. Dry weather will continue across north-central NY through this evening, before showers enter late tonight into Sunday morning. Pockets of heavy rain are possible across the western Southern Tier late tonight as the column saturates. Models show little to no MUCAPE overnight, however horizontal wind shear in the mid-levels and deep moisture may result in a rumble of thunder.

The main region of isentropic lift will move east of western NY late tonight, while moving into central/north-central NY. This will bring a break in steady rain across western NY, however drizzle may persist especially across the higher terrain. Deep moisture with PWATS over 1.4" (90th percentile) will enter north-central NY. Light to moderate showers will spread across the Tug Hill region, with the heaviest rain staying south of the Saint Lawrence River through Sunday morning. Surface high pressure across Ontario/Quebec will build into the region Sunday. The surface trough will push south across western NY, while bending northward into the Adirondack region. Showers will taper off from north to south. A shortwave trough with available moisture will support additional showers across the western Southern Tier to north-central NY through Sunday afternoon. The building high will support dry weather across the region Sunday night through Monday.

Basin average rainfall amounts will range from less than 0.25" across the Saint Lawrence River to the Niagara Frontier to 0.50"- 0.75" near the NY/PA line and southern Tug Hill region. Rainfall amounts have trended down from previous forecasts.

KEY MESSAGE 2...Below normal temperatures will continue into next week.

Canadian high pressure will reside north of the border through a majority of next week. A cool, northeast flow will maintain below normal temperatures across the region. The coolest days will be Monday through Wednesday with highs in the low to mid 60s, upper 50s across the higher terrain. Low temperatures will fall to the 40s, however the upper 30s are possible across the Black River valley.

There remains uncertainty with the northward extent of precipitation and sky cover associated with low pressure across the Appalachians Monday night through Tuesday, and this may impact temperatures early in the week. Mean QPF and MSLP suggest that the high will build far enough south for showers to be possible across the western Southern Tier, however in scenarios where the high is weaker, measurable QPF could move as far north as I-90. Currently the forecast has low chances (20-30%) across far western NY.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Increasing cloud cover continues across western and north-central NY terminals through this afternoon. Portions of the western Southern Tier may see rain showers late this afternoon, while elsewhere will see scattered to numerous showers overnight and through the first half of Sunday. With the increasing moisture and rain showers, expecting at least MVFR conditions to develop tonight with IFR ceilings becoming widespread after 08z. Beforehand, brief periods of IFR will be possible with any heavier rain showers passing through. Low ceilings will likely continue into Sunday afternoon before gradually improving from north to south through the evening. Winds will primarily turn to be out of the north.

Outlook...

Sunday night...Lingering showers with MVFR or worse expected.

Monday...Dry weather and VFR likely.

Monday night through Thursday...Periodic showers with MVFR or worse possible. Isolated thunderstorms possible Tuesday night and Wednesday.

MARINE

Easterly flow and wave action will continue to come down on the lakes through this evening, with winds mainly 10 knots or less tonight through at least a portion of Sunday morning producing waves of generally a foot or less, however waves of 1 to 2 feet from Hamlin Beach westward.

Otherwise, periodic rain shower chances will be in the forecast through Sunday, with freshening northeasterlies developing later Sunday afternoon and especially Sunday night into Monday, likely leading to an extended period of small craft advisory conditions that may persist through midweek on portions of the lower lakes.

BUF WATCHES / WARNINGS / ADVISORIES

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