Area Forecast Discussion

WHAT HAS CHANGED

Minor changes to the forecast with this update.

KEY MESSAGES

1) Scattered strong to severe thunderstorms continue through this evening with strong winds as the main hazard.

2) Cool Wednesday, with a chance of lingering showers ahead of a gradual warm up through the remainder of the week.

DISCUSSION

Key Message 1...Scattered strong to severe thunderstorms continue through this evening with strong winds as the main hazard.

Scattered showers and thunderstorms early this afternoon have spread across the Lake Ontario region on both sides of the international border associated with a compact shortwave noted on GOES WV imagery lifting just north of Toronto. This is all while earlier storms across the Southern Tier outran the axis of strongest instability leading to a swath of stratiform precipitation lingering. Regardless, severe thunderstorms were still observed this morning with gusty winds leading to downed trees and small hail reported. Clearing skies moving into western NY early this afternoon per GOES satellite imagery will help potentially refuel the atmosphere for the next round of strong to severe thunderstorms.

Ongoing development in eastern MI and southwestern ON within an area of 2000 J/kg of MLCAPE and 40 kt of bulk shear closer to the cold front will be worth monitoring as it moves east towards western NY later this afternoon into early this evening. Additionally, southwestward expansion of the ongoing convection near Toronto along the prefrontal trough associated with the aforementioned shortwave will also need close monitoring as atmospheric destabilization continues. These storms will progress eastward across western and north-central NY through the afternoon and evening.

Strong winds and heavy rainfall will continue to be the primary hazard with these storms. PWAT value reported from the KBUF 12z sounding was 1.50" and warm cloud depths exceed 10 kft. However, fast storm motions and line normal motions, as observed with earlier storms, would limit heavy rainfall durations. Additionally, the highest DCAPE values remain in southwestern ON and will be less than what was analyzed earlier across the Niagara Frontier around the time of severe wind damage reported.

Headed into late this evening, lingering showers and a few rumbles of thunder may continue until the cold front passes through western NY around midnight and early Wednesday morning for north-central NY.

Key Message 2...Cool Wednesday, with a chance of lingering showers ahead of a gradual warm up through the remainder of the week.

Cooler weather is expected Wednesday as the upper level low begins to exit to the northeast. With 850mb temps dropping around 6-8 degC, afternoon highs will struggle to reach 70 degF as most locations will be around 10 degF below normal for late July. Additionally, a secondary shortwave will round the backside of the departing low, supporting scattered showers along with the cooler air aloft and steep low-level lapse rates extending inland from the lakes under west-northwest flow. High pressure will begin to build into the lower Great Lakes late Wednesday through the remainder of the week leading to drier weather and gradually warming temperatures back towards slightly above normal this weekend.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Multiple rounds of showers and thunderstorms will continue this afternoon and into this evening with the passage of both a warm front lifting north, followed by a cold front sliding east. This being said, a conglomeration of flight conditions will continue through this evening, with an improving trend overnight into Wednesday. From the round of showers that just impacted the western 3 terminals (KIAG, KBUF and KJHW), expect these showers and embedded thunderstorms continue east into KROC within the hour, and reach KART a couple of hours later. Another line of showers is on our western doorstep as of 17Z, which will bring more showers and thunder early this afternoon. Additional, showers are then expected late this afternoon and into the evening with the arrival of the cold front.

This all being said, there is a Slight Risk for Severe Thunderstorms through this evening, where some of the thunderstorms will be capable of producing damaging winds, large hail, and torrential rain. Both visibilities and ceilings restrictions can be possible at times.

Otherwise, ahead of the cold frontal passage's arrival it will be breezy, with a 20-30 knot south-southwest wind gusts, especially for KIAG and KBUF this afternoon.

Outlook...

Wednesday...Restrictions likely with lingering showers/isolated thunderstorms.

Thursday through Saturday...Mainly VFR.

Sunday...VFR/MVFR with a chance for showers/thunderstorms in the afternoon.

MARINE

Southwest winds gusting around 30 kt over Lake Erie and western Lake Ontario will continue through this afternoon while winds over eastern Lake Ontario will veer to the southwest. Showers and thunderstorms will continue throughout the day with multiple rounds ahead of a cold frontal passage late tonight. Behind the front, winds will turn to be out of the west-northwest and increase once again, especially across Lake Ontario, headed into Wednesday. Small Craft Advisory continues for Lake Erie through tonight and for portions of Lake Ontario through Wednesday evening. Calmer waters are expected late this week into early this weekend as high pressure builds into the lower Great Lakes.

BUF WATCHES / WARNINGS / ADVISORIES

NY...None. MARINE...Small Craft Advisory until 9 PM EDT this evening for LEZ020. Small Craft Advisory until midnight EDT tonight for LEZ040- 041. Small Craft Advisory until 6 AM EDT Thursday for LOZ042. Small Craft Advisory until 10 AM EDT Thursday for LOZ045.