Marine Weather and Tide Forecast for Oswego, NY

NEAR TERM /THROUGH TUESDAY/
Two distinct areas of sfc high pressure, one retreating into the northwestern Atlantic and another quickly shifting east across Quebec, will continue to suppress more active weather across our region through tonight. A weak inverted trough lingering over the region between these features and a stalled frontal boundary over the Ohio Valley will lead to a wealth of stratus and patchy strato-cu through the rest of the day with a few scattered showers at times. Low to moderate confidence in overall coverage though best chances for any measurable precip will lie across the Niagara Frontier and Lewis/eastern Jefferson counties. Temps will top out in the mid/upper 70s for most areas, cooler across the interior Southern Tier.

A shortwave trough rippling across the stalled boundary will cause it to lift further northward as a warm front tonight. After some partial clearing, this will likely cause the thicker cloud cover to fill back in. A few showers may creep over the NY/PA border or up through the Finger Lakes overnight.

The warm front will further encroach on the region Tuesday as high pressure further loosens its stabilizing influence. This will bump daytime temps up a few degrees though main impact will be expanding chances for showers expanding across the region. Greatest chance for a few scattered thunderstorms will be across WNY in the afternoon, with minimal instability east of the Finger Lakes.

SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY NIGHT/
A shortwave trough responsible for pushing the stalled boundary northward and producing showers and thunderstorms Tuesday, will slide east of the area. The exiting shortwave trough combined with the loss of diurnal instability will support shower and thunderstorm coverage to begin to diminish Tuesday evening, however a secondary shortwave trough passing across northern Ontario/Quebec will edge a weakening cool front into our area from the northwest resulting in the possibility in a few showers throughout the night. Additionally, a few rumbles of thunder may be possible, though the instability will be on the tamer side.

The phasing of the aforementioned shortwaves will support a deeper longwave trough to carve out across the Great Lakes and result in a strengthening surface wave of low pressure. As this feature lifts northeast from the Upper Midwest to Quebec, a pair of fronts will slide across the area Wednesday through Thursday. Initially a warm front will lift north across the area Wednesday afternoon, supporting a warm humid airmass to advect across the area. The combination of strong diurnal heating and ample moisture will produce scattered showers and storms. Then, a strong southwesterly low level jet will move into the area, along with a prefrontal trough and eventual cold front late Wednesday night into Thursday morning, renewing the potential for showers and thunderstorms. The combination of PWAT values around 1.75 inches (amounts well over 90% of the daily mean) and a wind direction parallel to the front, would support heavy rainfall, as supported by WPC's Day 4 marginal risk for excessive rainfall. In regards for severe thunderstorms, the better low level lapse rates, and shear will lie across the northern Finer Lakes eastward, and therefore a few stronger storms can't be ruled out.

While convection will gradually diminish Thursday night a few showers may linger across the area through Friday as the longwave trough axis crosses the area. Additionally, cooler air will advect across the area in the wake of the trough axis Friday/Friday night.

LONG TERM /SATURDAY THROUGH MONDAY/
The next stout upper level ridge will slide across the Gulf States Saturday before amplifying northeastward Sunday and into the start of the next work week. This upper level feature will bring steady increasing heat and humidity into the region for the weekend and into the start of new work week. However, an ill-timed shortwave ridge-runner will support the possibility for a few rounds of showers and thunderstorms Saturday through Sunday before surface high pressure then dominates overhead for Monday. As alluded to previously, the combination of 500 mb heights building to near 600dm over the Ohio Valley and lower Great Lakes would support very hot and humid conditions with heat index values climbing well into the 90s by Monday.

AVIATION /18Z MONDAY THROUGH SATURDAY/
An inverted trough extending across the eastern Great Lakes region with lingering low-level moisture will maintain stratocu with low VFR to MVFR cigs. A few showers are possible across the Niagara Frontier through about 23z.

Partial clearing expected through the first half of tonight outside of the Southern Tier. After about 06z, lower cigs will begin to expand back northward as a warm front moves towards the region from the Ohio Valley. Variable cigs between low VFR (Niagara Frontier)
and LIFR (Southern Tier) expected by 12z. A few showers could move over the NY/PA border and into the Southern Tier overnight.

Tuesday, the warm front will move further into the region. Cigs will likely be mainly MVFR through the morning north of the Southern Tier, which may hold onto IFR into the early afternoon. Showers and thunderstorms are expected to develop in the afternoon, mainly across WNY though coverage will be greatest in the Southern Tier.
More notable improvement to VFR expected from KIAG to KROC after 18z.

Outlook...

Wednesday and Thursday...VFR/MVFR with showers and thunderstorms likely.

Friday...Mainly VFR. A chance of showers and thunderstorms, mainly east of KROC.

Saturday...Mainly VFR. Increasing chances for showers and thunderstorms.

MARINE
Minimal wave action and light to modest winds on the lakes through tonight as Canadian high pressure shifts into the northwestern Atlantic.

A more potent low pressure system will track from the Upper Great Lakes tonight to southern James Bay by Tuesday evening. This will cause winds to initially shift southeasterly before turning south/southwesterly through Wednesday, though SCA conditons are not expected. Choppier conditions will likely form Thursday as a more potent system and associated cold front move across the lakes.

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