Marine Weather and Tide Forecast for Rochester, NY

KEY MESSAGES
1) Summer-like heat Monday through Tuesday.

2) Spotty showers and thunderstorms possible late today through Monday, but dry most of the time.

3) A strong cold front will bring numerous showers and thunderstorms late Tuesday eve into Wednesday.

4) Drier and cooler conditions behind the front Wednesday through Friday, unsettle weather potentially returns for the weekend.

DISCUSSION
KEY MESSAGE 1...Summer-like heat Monday through Tuesday.

An early taste of mid-summer heat will build into the region Monday through Tuesday, with by far the warmest airmass of the spring to this point. 850MB temps will soar to near +17C Monday afternoon through Tuesday as a strong mid level ridge builds to the eastern seaboard and allows a thermal ridge to advect into the eastern Great Lakes. Highs will reach the 85-90 degree range both Monday and Tuesday afternoon away from lake influences. Overnight lows Monday night will also be very warm by May standards, in the mid to upper 60s.

Dewpoints will generally run in the upper 50s to lower 60s in most areas, possibly as high as the mid 60s on the lake plains. These values are not high enough to produce any appreciable heat index above the ambient air temperature.

KEY MESSAGE 2...Spotty showers and thunderstorms possible late today through Monday, but dry most of the time.

Dry weather will prevail most of the time this afternoon through Monday, with a few minor exceptions.

Visible satellite imagery shows an agitated cumulus field across the higher terrain of the western Southern Tier this afternoon. High-res CAMS guidance continues to suggest a few spotty showers and thunderstorms may develop across the western Southern Tier later this afternoon and evening. Coverage of this convection will be sparse, if it develops.

Tonight, a warm frontal segment will move quickly northeast across the Great Lakes, supported by a convectively augmented mid level shortwave. The most active portion of this warm front is forecast to move from near Lake Huron late this evening to the Ottawa Valley by Monday morning, where forcing and moisture is maximized. There is considerable uncertainty with the southern extent of showers and thunderstorms along the warm front, but some of the 12Z model guidance has trended wetter as far south as over and near Lake Ontario. With this in mind, increased POPS from the previous forecast down to near the NYS Thruway to account for the potential overnight warm frontal convection. The last of this activity will exit the North Country by mid morning Monday.

The rest of Monday will be mainly dry, although an isolated shower or thunderstorm cannot be ruled out late afternoon and early evening with peak heating and diurnal instability. If this occurs, it would be mainly across the Southern Tier, Finger Lakes, and/or southern Tug Hill region away from the stabilizing influence of southwest flow over and northeast of Lake Erie and Lake Ontario.

KEY MESSAGE 3...A strong cold front will bring numerous showers and thunderstorms late Tuesday eve into Wednesday.

The main challenge with this update will be timing of a strong cold front approaching the Lower Lakes for later Tuesday eve. That said...lets backing up a bit and talk about Monday night, Hi-res guidance continues to suggest a convectively enhanced shortwave ripping across Michigan on the fringes of the mid-level ridge. While it appears that most of the convection with this feature will weaken as it nears, a few showers or even an isolated storm could sneak into the region overnight into Tuesday morning. Have added 'low' end PoPs (< 25%) to account for this feature given so much uncertainty to how it will impact our area
Moving on
the next feature of concern is the incoming shortwave trough and arrival (timing) of a strong cold front for Tuesday eve and night. While there may be some storms that pop Tuesday afternoon given plenty of advertised CAPE (+2K j/kg), especially along lake breeze boundaries, more numerous showers and storms is anticipation with the front. SPC has place much of the area in a Marginal Risk (12Z Tuesday-12Z Wednesday)for the potential for severe storms with the main threat damaging wind gusts.

KEY MESSAGE 4...Drier and cooler conditions return behind the front Wednesday afternoon through Friday, unsettle weather potentially returns for the weekend.

Surface based ridging will begin to build into the Great Lakes region Wednesday behind the front with drier weather and cooler conditions. The coolest day of the week still looks to be Thursday where highs will be found in the 50s to low 60s in the warmest locales
After Thursday
a day to day warming trend begins which last into the weekend, we also could see increasing chances for showers.

AVIATION /18Z SUNDAY THROUGH FRIDAY/
The last of the MVFR stratus across the higher terrain of the Southern Tier and east of Lake Ontario will evolve into cumulus fields this afternoon with bases improving to VFR. Dry weather will prevail in most areas, although a few isolated showers and thunderstorms may briefly develop across the western Southern Tier later this afternoon and early evening.

Tonight, a warm front will move northeast across the area. The most active portion of the warm front is forecast to move from Lake Huron across southern Ontario overnight. The southern end of showers and scattered thunderstorms along and ahead of the warm front may clip areas near the Canadian border, supporting the chance of a brief period of showers and thunder across most of the terminals overnight. Otherwise, VFR will prevail outside of any showers.

A low level jet will move across the eastern Great Lakes late tonight through Monday morning, supporting a period of low level wind shear.

Monday, the last of the potential warm frontal showers and thunderstorms will exit the eastern Lake Ontario region early in the morning. This will leave mainly dry conditions and VFR for the rest of the day. There is a very low end chance of an isolated shower or thunderstorm late in the day from the Southern Tier through the Finger Lakes to the southern Tug Hill Plateau. Winds will gust in the 20-30 knot range across the Niagara Frontier from late morning through the afternoon.

Outlook...

Tuesday..Mainly VFR. A chance of a few showers and thunderstorms later in the afternoon.

Tuesday night through Wednesday...Areas of MVFR/local IFR with showers and thunderstorms, ending from west to east and improving to VFR Wednesday morning.

Thursday through Friday...VFR.

MARINE
The pressure gradient will gradually tighten across the lower Great Lakes Monday through Tuesday. Moderate southwesterlies will bring very choppy conditions to the west end of Lake Ontario by Monday afternoon, with lighter winds elsewhere.

Winds will increase further on Tuesday ahead of an approaching cold front. Winds and waves will likely support Small Craft Advisory conditions by afternoon on the western portion of Lake Ontario, with the stronger winds and greater wave action then spreading east to the east end of Lake Ontario later Tuesday night through Wednesday as the cold front crosses the lake. Winds on Lake Erie will be somewhat lighter, but still strong enough to produce a moderate chop Tuesday through Wednesday.

BUF WATCHES/WARNINGS/ADVISORIES
NY...None.
MARINE...None.