Marine Weather and Tide Forecast for Macedon, NY

KEY MESSAGES
1) Periods of rain tonight through Friday, along with gusty winds.

2) Much colder Friday night through Saturday night with a few wet snowflakes possible early Saturday morning.

DISCUSSION
KEY MESSAGE 1...Periods of rain tonight through Friday, along with gusty winds.

Sharp mid level trough will advance into the Great Lakes tonight through Friday. Surface low pressure will strengthen across the Great lakes tonight and move into southern Ontario by Friday morning, reaching the Saint Lawrence Valley by Friday afternoon.
The expected track of the surface low will allow the warm sector to build into the lower Great Lakes. A period of strong warm advection and moisture transport, enhanced by a 50+ knot low level jet, will arrive tonight and support an initial wave of rainfall.
This rain will arrive in western New York by around midnight, then spread quickly northeast overnight. Additional periods of rain will continue Friday through Friday evening as the trailing cold front moves southeast across the region, supported by mid level height falls and right entrance region jet dynamics.
Marginal instability in the warm sector may support a few embedded thunderstorms as well late tonight through Friday.

Rainfall amounts will vary widely across the area, generally ranging from 0.25" to 1.0". Terrain will play an important role given the strong boundary layer flow, with downslope areas of the Lake Erie shore and Genesee Valley likely on the low end of the range, while higher terrain is more likely to be on the higher end of the range from upslope enhancement. There may be a few small areas that exceed 1.0" if embedded convection develops.

It will become quite windy late tonight through Friday. A 50+ knot low level jet will propagate across the eastern Great Lakes late tonight through Friday morning. Gusts will increase into the 25-35 mph range areawide, with gusts possibly reaching or exceeding 40 mph in downslope areas along the Lake Erie shore and north of the Tug Hill Plateau briefly. Boundary layer flow will quickly swing around to the southwest Friday morning through mid afternoon, with gusts still in the 25-35 mph range in most areas, and up to 45 mph northeast of Lake Erie across the Niagara Frontier.

KEY MESSAGE 2...Much colder Friday night through Saturday night with a few wet snowflakes possible early Saturday morning.

Strong cold advection will develop Friday night in the wake of the departing low, with 850 mb temperatures dropping into the -5C to -8C range by Saturday morning. The cold air aloft will support increasing lake induced instability overnight with a brief lake response, but short NNW fetch and a rapidly drying synoptic scale airmass will keep lake effect muted and brief. Lake effect and upslope rain showers will develop southeast of the lakes Friday night, with a few wet snowflakes possibly mixing in very late Friday night through early Saturday morning before the lake effect showers quickly end by late morning. The best chance of a few snowflakes will be across higher terrain, but no accumulation is expected.

The coldest airmass of the fall season so far will arrive for Saturday, with highs only in the 40s areawide, and even upper 30s across the highest terrain despite some afternoon sunshine.
Temperatures will drop back into the low to mid 30s Saturday night on the lake plains, with some 20s likely across the Southern Tier valleys and North Country. The cold air will quickly depart, with temperatures back above average by early next week.

AVIATION /00Z FRIDAY THROUGH TUESDAY/
Aloft, W'erly flow backs gradually to SW'erly as a ridge exits E'ward and a trough axis approaches from the north-central U.S.
and eventually the central Great Lakes through 00Z/Sat. At the surface, a ridge continues to exit E'ward as a strengthening low wobbles NE'ward from near the southwestern Great Lakes to southern QC. This low track will allow a warm front to sweep NE'ward across Western and Central NY between ~04Z/Fri and ~13Z/Fri before a cold front sweeps E'ward through our region between ~17Z/Fri and ~22Z/Fri. Behind the front, troughing lingers over Western and Central NY through 00Z/Sat.

Ahead of the warm front, our regional surface winds veer from NE'erly to SE'erly around 5 to 10 knots. The warm front passage will cause surface winds to veer to S'erly to SW'erly and these winds will increase to around 10 to 20 knots in response to the strengthening surface low. Gusts up to 20 to 35 knots at times are expected. The cold front passage will cause surface winds to veer to W'erly to NW'erly around 10 to 20 knots with gusts up to 20 to 35 knots at times. Note: a SW'erly low-level jet of ~40 to ~50 knots at/near 925 mb should translate NE'ward across our region Friday morning and result in periodic low-level wind shear.

Widespread ceilings, primarily in the mid/upper-levels at first, will thicken and lower gradually to the MVFR to IFR range and generally from WSW to ENE the rest of this evening through ~08Z/Fri. Widespread MVFR to IFR ceilings are then expected through 00Z/Sat. Widespread rain, accompanied by VFR to MVFR visibility and associated with the low pressure system, should blossom over and overspread Western and Central NY generally from WSW to ENE between ~01Z/Fri and ~08Z/Fri. The widespread rain should then exit our region generally from west to east following the passage of the aforementioned surface cold front.
However, scattered rain showers associated with the upper-reaches of the front should linger through 00Z/Sat. Also, lake-effect rain showers should develop over and generally SE of the eastern Great Lakes between ~21Z/Fri and 00Z/Sat. Periodic MVFR visibility is possible with steadier showers behind the surface cold front.

Outlook...

Friday night...Mainly MVFR ceilings with scattered rain showers over and generally SSE of the eastern Great Lakes. Rain may mix with wet snow during the predawn hours of Saturday morning, especially inland from the lakes.

Saturday...Areas of MVFR ceilings and isolated rain and/or wet snow showers over and generally SSE of the eastern Great Lakes should end by late morning. Otherwise, dry weather and VFR expected.

Saturday night through Tuesday...VFR and dry weather likely.

MARINE
Northeast winds around 15 knots will continue to produce choppy conditions on both lakes this afternoon, but winds and waves will remain just below Small Craft Advisory criteria.

Low pressure will track across the southern Great Lakes tonight, reaching southern Ontario Friday morning. This low will continue to deepen as it moves northeast across the Saint Lawrence Valley Friday, reaching the Canadian Maritimes by Saturday.
Southerly winds will increase overnight tonight ahead of the system, then quickly veer to the southwest and west Friday as the low passes by just north of the lower Great Lakes, followed by gusty north-northwest winds Friday night through Saturday morning. Sustained winds during this timeframe will average 20-30 knots, producing high end Small Craft Advisory conditions on both lakes. Some periodic gusts to near gale force are possible.

BUF WATCHES/WARNINGS/ADVISORIES
NY...None.
MARINE...Small Craft Advisory from 2 AM Friday to 11 AM EDT Saturday for LEZ040-041.
Small Craft Advisory from 8 AM Friday to 11 AM EDT Saturday for LOZ042.
Small Craft Advisory from 8 AM Friday to 2 PM EDT Saturday for LOZ043-044.
Small Craft Advisory from 2 AM Friday to 2 PM EDT Saturday for LOZ045.