Area Forecast Discussion

WHAT HAS CHANGED

No significant changes with this forecast package.

KEY MESSAGES

1) Showers and thunderstorms today with localized heavy downpours and an isolated severe weather risk.

2) Mainly dry weather returns Sunday through early next week with warm temperatures.

DISCUSSION

KEY MESSAGE 1...Showers and thunderstorms today with localized heavy downpours and an isolated severe weather risk.

A mid level trough will move eastward into the lower Great Lakes today. A weak cold front will advance southeastward into the region, late this afternoon and this evening, although most of the showers and thunderstorms will focus on a pre-frontal trough and lake breeze boundaries rather than the cold front itself.

An initial round of showers will cross the area this morning as a weak shortwave crosses the eastern Great Lakes. The more organized area of rain with this feature will cross far northern portions of the area into southern Ontario. Most areas will see a return to dry weather following this early activity. Additional showers and thunderstorms will then develop as the mid level trough and cold front encounter increasing diurnal instability. A moderate southwest flow regime will be in place, supporting stable lake shadows over and northeast of Lake Erie and Lake Ontario. This will limit convective potential in these areas, with the better coverage of thunderstorms inland from the lake shadows from the Southern Tier to the Finger Lakes and southern Tug Hill region. Coverage of rain will be very uneven, with plenty of dry time through the day.

RAP forecast soundings later this afternoon showing favorable shear profiles for organized convection, with near 40 knots of deep layer shear and even some favorable hodograph curvature across the Southern Tier, which could support supercell development. The degree of instability is more uncertain, with morning clouds and showers possibly holding down surface temperatures in some areas. The greater severe weather risk will likely be across the Southern Tier and Finger Lakes where greater instability is expected away from the stable lake shadows. The main risk will be localized damaging wind gusts, with a lower but non-zero risk of large hail and an isolated tornado. The main severe weather risk will be roughly 2PM to 7PM when instability and forcing maximize. Thunderstorms will also produce brief heavy downpours, but fast storm motion and much drier antecedent conditions compared to a few weeks ago should keep the flooding risk very low.

KEY MESSAGE 2...Mainly dry weather returns Sunday through early next week with warm temperatures.

The mid level trough will move east across New England Sunday, taking the majority of the showers with it. A few showers may linger east of Lake Ontario in moist, cyclonic northerly flow behind the departing trough, with dry weather prevailing farther west. Morning clouds in northerly upslope flow will give way to some clearing in the afternoon across Western NY.

An Omega Block will develop by Sunday night over the Great Lakes, then drift slowly east to the east coast and flatten with time through the middle of next week. This will support dry weather and above average temperatures Sunday night through at least Tuesday. A mid level trough and plume of deeper moisture over the Ohio Valley may move far enough east to bring a chance of showers and thunderstorms again by mid week.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Initial shortwave trough riding northeast along the back side of a departing ridge bringing a round of showers and an isolated thunderstorm this morning. CIGS through 12z will gradually lower but should remain VFR. Any VSBY restrictions will be limited to localized heavier showers/isolated storms.

Flight conditions will deteriorate ahead of an approaching cold front with widespread MVFR CIGS developing through today, with some IFR CIGS possible across the western Southern Tier and North Country. An additional round of showers and thunderstorms is expected this afternoon ahead of the cold front. Some storms may produce strong gusty winds. However, a stout lake breeze will develop northeast of the lakes with a lake shadow setting up from midday on. This will limit convection for our KBUF/KIAG/KROC/KART sites through much of afternoon, however there is the chance for a secondary line of showers and storms to cross the area late in the day. If the lake shadow weakens enough, a few of these may be able to make it into these aforementioned terminals. Expect localized IFR conditons within any heavier showers and thunderstorms.

It will be breezy today with widespread SW to WSW winds gusting 20- 25 knots, with 30-35 knots possible northeast of Lake Erie from midday on.

Outlook...

Sunday...Mainly MVFR/VFR. Localized IFR in any showers and thunderstorms east of Lake Ontario.

Monday and Tuesday...VFR.

Wednesday...Mainly VFR with a chance of showers and thunderstorms. Localized lower flight CATs within any heavier showers or storms.

MARINE

Southwest winds will increase today ahead of an approaching cold front. Winds will initially be strongest on Lake Erie, where Small Craft Advisory conditions are expected. Winds will increase on Lake Ontario from west to east through the day today, with low end Small Craft Advisory conditions possible.

Scattered thunderstorms are expected this afternoon and early evening, with a few storms producing locally stronger winds and higher waves. The cold front will move south across the lower Great Lakes tonight, with post-frontal northwest winds still producing choppy conditions on Lake Ontario Sunday.

BUF WATCHES / WARNINGS / ADVISORIES

NY...None. MARINE...Small Craft Advisory from 8 AM this morning to 8 PM EDT this evening for LEZ020-040-041.