Marine Weather and Tide Forecast for Rochester, VT

KEY MESSAGES
As of 238 PM EDT Thursday...

1. Quiet before the storm today, and then rain and gusty winds tomorrow.

2. Cool, breezy weather with some mountain snow on Saturday will turn drier for the new week.

3. The long term continues to be very quiet with temperatures at or above normal and high confidence of an extended dry period of weather likely.

DISCUSSION
As of 238 PM EDT Thursday...

KEY MESSAGE 1: It's a beautiful fall day out there with chilly temperatures running about 5 degrees below normal. Winds are light, and the Sun is shining. Today will probably be the last day for optimal foliage, because it's going to get breezy and wet for Friday.

Overnight, a warm front will approach the area. Rain chances will quickly ramp up as strong ascent from moist air overrunning stable, dry high pressure produces a solid precipitation shield northwards.
After the warm front crosses, conditions will become increasingly favorable for gusty winds, particularly in the Champlain Valley.
Conditions are only marginally favorable for mixing, but the orientation of the winds, and channeled flow between low pressure reaching Montreal and retreating Atlantic high pressure will favor gusty winds in and around Lake Champlain. High res guidance also seems to favor northern slopes near Enosburg and Montgomery Center in eastern Franklin, as well as East Charleston and Derby Center.
Climatologically speaking, one cannot rule out areas like Malone and Ellenburg in New York either. Within the aforementioned areas, 35 to 45 mph are most likely from about 7am-1pm. Outside of these, still plenty of breezy winds 25-35 mph. Combined with the rain, this will almost certainly take away plenty of foliage, and it may be strong enough that some localized reports of large branches down and some power outages are possible. However, south winds are usually not as impactful given how common strong southerly gusts are in the Champlain Valley.

By mid-afternoon, the surface low will begin to reach Montreal and then shift eastwards. The attendant cold front will push southeast.
There could be some convective elements and some type of shear line that shows up on radar, but instability is marginal and any winds within precipitation will likely be lower than the ongoing synoptic scale winds. Still, between the strong warm front and some moderate rainfall rates likely in the cold front with higher PWATs around 250- 275 percent of normal, we should eke out at least 0.50", even for most terrain shadowed locations. Totals are most likely to range about 0.75-1.25", especially across higher terrain. No flood concerns are expected with the progressive nature of the feature.

KEY MESSAGE 2: Increasingly cool weather returns under northwest flow Friday night through the rest of the weekend. The backside of the upper trough doesn't shift southeast until later Saturday morning.
So with lingering moisture, upslope showers are expected. As temperatures cool, snow levels will gradually descend as temperatures fall into the mid 20s to mid 30s. Some snowflakes may manage to even make it to the valley floor if there are any.
Unblocked flow will generally favor most orographically enhanced showers near the summits and along their eastern slopes. Approaching noon, snow showers will taper off as moisture flows out of the region due to the unblocked flow and upper trough pulling away. Due to antecedent warmth, most accumulations will be on grassy surfaces for areas between 1000-2500 ft elevation. Above 2500 ft, snowfall amounts could approach 1-2".

Temperatures aren't going to warm a whole lot Saturday as brisk northwest wind gusts of 25 to 35 mph will remain much of the day.
Max temperatures will be in the mid 30s to mid 40s. So as winds slacken on Saturday night, we should see most all locations fall at or below freezing, except for perhaps a handful of spots in Grand Isle, Vermont and around the immediate shores of Lake Champlain.
South to southwest flow will resume on Sunday, and we will moderate closer to seasonal norms. The high pressure set up overhead will be very strong, and appears unlikely to budge anytime soon. Signals are quite good for a dry spell.

KEY MESSAGE 3: Little change was noted in the 12z guidance suite, which support expanding mid/upper lvl ridge acrs most of the Great Lakes and NE CONUS. Did note a weak moisture-starved backdoor cold front on Weds, which may knock our temps back below normal, depending upon magnitude of caa. Guidance shows building 1035mb ridge from Maine to VA by early next week, while closed cyclonic circulation lingers well east of Hatteras. This high pres is replaced by another 1034mb high pres over central Canada by mid-week, helping to advect slightly cooler temps into our cwa for mid to late week. However with very dry moisture profiles only a few sprinkles acrs the trrn wl be possible. Temps mostly in the mid 50s to l/m 60s with lows upper 20s to lower 40s thru most of the extended with dry conditions prevails. Fire weather concerns will increase next week, due to the long duration of dry weather anticipated, but winds will remain mostly light and terrain driven, with high pres.

AVIATION /18Z THURSDAY THROUGH TUESDAY/
Through 18Z Friday...VFR conditions will persist through 06Z with ceilings steadily dropping to 2500 feet between 6Z and 9Z.
Further reduction of ceilings into the 800-1200 ft range is expected by 12Z at most, if not all, terminals as rainfall overspread the region at the same time. Visibilities will drop to 3-5 SM for many sites with periodic decreases below 3 SM possible. Winds will continue from the north this afternoon with a switch to the south after 06Z. Winds will be in the 35 to 35 knot range from the south throughout the day on Friday with some KBTV possibly exceeding 40 knots during the afternoon. Wind shear will be a major concern tomorrow with winds in the 50 to 60 knot range at 2000 ft so wind shear has been included in all terminals. This wind shear will develop between 9Z and 12Z and likely linger well past 18Z on Friday.

Outlook...

Friday Night: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance SHSN.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.

MARINE
A new Lake Wind Advisory has been posted for early Friday morning as south winds increase sharply after midnight toward sunrise on Friday, especially across the central and northern portion of Lake Champlain. Light winds this evening will become south-southeast winds at 10 to 20 knots with gusts 20 to 30 knots toward sunrise on Friday, with waves building 1 to 3 feet. Very gusty southerly winds are expected to continue on Friday.

CLIMATE
Daily low maximum temperatures will likely be broken on Saturday.
Current records are indicated below at some climate sites in our region:

Record Low Maximum Temperatures:

October 17: KBTV: 42/1970 KPBG: 44/2015 KSLK: 36/1970

BTV WATCHES/WARNINGS/ADVISORIES
VT...None.
NY...None.