Marine Weather and Tide Forecast for Skaneateles, NY

KEY MESSAGES
1) There remains a threat for strong to severe thunderstorms this evening and again tomorrow afternoon and evening, with strong wind gusts, isolated hail and locally heavy rainfall.

2) The warm pattern through the week will break down late in the weekend. Much colder air arrives Sunday evening into early next week, with a chance for mixed snow and rain showers.

DISCUSSION
KEY MESSAGE 1...

The next couple of days will be warm and humid for this time of the year with 30+ knots of shear so there will be chances for some strong to isolated severe thunderstorms today and tomorrow. The synoptic forcing today is very week with just a subtle 500 mb shortwave passing through so that likely will not be the main driver of the convection but will help supply the shear (35-45 knots) and steeper mid level lapse rates of around 7 C/km are moving into the area from the west late this afternoon. Instability is beginning to build as surface temperatures rise into the mid-70s to lower 80s and surface dew points hover in the mid to upper 50s. Surface based CAPE early this afternoon is already reaching 500-1000 J/kg, but 100mb mixed layer CAPE is much lower thus far only 250 to 500 J/kg. Bulk 0- 6km shear is increasing, as expected, now between 35-45 kts, with effective layer shear in that same range. Latest visible satellite loop shower some cumulus build up beginning to occur, along with broken mid to high cloud layer over the region. There is a weak shortwave pushing into western NY at this time, that will likely be the main trigger for scattered thunderstorms to develop late this afternoon and evening. SPC maintains the Slight Risk over the eastern half of the forecast area, where the main threat will continue to be isolated severe storms that could produce damaging winds. SPC has also introduced a 2% chance for an isolated tornado or large hail up across Oneida County along a weak warm frontal feature. The main timeframe for storm potential looks to be from about 4-8 PM across our Central NY areas...and a little later, from about 6-10 PM in NE PA...this is based off the latest CAMs such as the 17z HRRR run. Overnight it should quiet down, under partly cloudy skies and very mild temperatures in the mid-50s to lower 60s.
Late at night into early Wednesday morning a remnant MCS looks to approach bringing renewed chances for showers and embedded thunderstorms.

Wednesday is unfortunately a similar story as today in regards to how the storms may evolve. The synoptic forcing is once again weak with the primary driver of the mid level shortwave is going to be the development of MCS's in the plains this afternoon and overnight.
Still, models are in better agreement that there will be more CAPE tomorrow (>1000J/kg of surface cape) and better shear (>40 knots of 0-6 km shear) so if the timing of the mid level wave that triggers the storms is like the current model guidance is showing (in the late afternoon to evening), strong to severe thunderstorms are likely and isolated supercells are possible. SPC maintains a Marginal risk across most of Central NY and NE PA for this potential, with a Slight Risk nearby in Central PA. The main potential threats with Wednesday's Storms will be isolated damaging winds,large hail and training of heavy downpours. WPC has introduced a Marginal Risk for excessive rain, and isolated flash flooding across most of the forecast area Wednesday into Wednesday night.

We will still be in this warm SW flow pattern with frequent shortwaves on Thursday. Models are showing scattered showers in the morning, but better forcing arrives late in the day along an incoming cold front. There is uncertainty in the amount of CAPE that ultimately materializes, but with temperatures back in the mid-70s to low 80s and dew points in the low 60s instability could again reach moderate levels (1000 J/kg +). This time period will need to be watched closely as 0-6km shear remains elevated between 40-50 kts once again over the region. The highest parameters look to be across the Twin Tiers down into Northeast PA at this time, so this may be the area to watch for more organized and stronger convection.

After the cold front pushes through Thursday night into Friday morning there will be some lingering showers and a chance for a few thunderstorms through the day on Friday. However, overall instability and shear are forecast to be much lower on Friday.
Temperatures will also come down some, with highs in the mid-60s to mid-70s expected.

KEY MESSAGE 2...

While this warm, early summer like pattern persist through the first half of the weekend, Sunday into early next week has continued to trend cooler. High latitude blocking in Greenland will help a deep late season trough to dig into the Northeast US. The GFS and AIGFS both are bringing 516 to 520 dm 500 mb heights on Monday which is well below climatology for mid to late April. 850 mb temperatures also have a high probability of reaching -12C Monday morning and only gradually moderating back toward 0C by Tuesday. With the Great Lakes likely warming up some over the rest of this week, it is possible they would be warm enough to generate lake effect snow shower activity with this pattern, as temperature differentials exceed 15C from the lake surface up to the 850mb level.

With the anomalously cold air mass in place it appears daytime highs may stay in the 30s to low 40s on Monday. Very cold overnight lows in the 20s are then expected Monday night into Tuesday morning. It then appears a gradual moderating trend will take hold Tuesday into the middle of next week.

As of now, the pattern with the cold is looking dry (outside of lake effect) so despite the cold, a widespread snow event is unlikely at this time. There is still time for the pattern to change as the evolution of the Greenland blocking pattern is all over the place but a cooler stretch of weather is likely, just how cold will it get is uncertain.

AVIATION /18Z TUESDAY THROUGH SUNDAY/
Scattered showers and thunderstorms are expected to develop this afternoon and move west to east across central NY. Timing looks to be in the 19-00Z range. Included TEMPOS to account for the scattered nature and slight timing uncertainity with any thunderstorms. Any potential for thunderstorms decreases sharply after 00Z. High confidence at KRME and KSYR for the formation of MVFR/IFR ceilings overnight with a lower potential at KITH and KBGM. Any ceiling restrictions should lift out between 12-16Z Wednesday.

Outlook:

Wednesday afternoon through Friday...Restrictions possible from showers and isolated to scattered thunderstorms.

Saturday...Additional restrictions look to arrive along with showers and storms late in the day Saturday.

Sunday... Restrictions possible from showers.

BGM WATCHES/WARNINGS/ADVISORIES
PA...None.
NY...None.