Severe Thunderstorm Outlook: Thursday, August 27, 2020

finger lakes weather forecast thursday august 27 2020 severe weather analysis

Widespread thunderstorms are likely today and will produce numerous instances of severe weather, including isolated significant or widespread damaging winds or large hail.

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WHAT

A warm front is moving through the region this morning. Skies will, or already have, cleared for much of the region, but clouds will linger near I-90, especially in the east. A strong temperature gradient will set up, with 70s in the Syracuse area, but mid 80s as close as Ithaca and Geneva. Very humid air will also move in on strong west winds, which may gust to 40 mph outside of any thunderstorms.

Low pressure will ride along the front, causing it to come back south as a cold front. This will trigger thunderstorms during the early afternoon with multiple rounds of storms possible into the early evening.
Upper atmosphere dynamics, strong wind fields aloft, and favorable temperature-humidity profiles are all supportive of severe thunderstorms in our area. Significant severe weather, with winds over 70 mph and hail greater than 2” in diameter, will be possible.

ALERTS EXPECTED

The following severe weather alerts are *predicted* to be issued later today:

– A Severe Thunderstorm WATCH (very likely). A WATCH means that conditions are favorable for severe thunderstorms/tornadoes. Watches are issued over large areas for several hours at a time.

– Many Severe Thunderstorm WARNINGS (very likely). Severe Thunderstorm Warnings are issued over small areas for around an hour at a time to warn of ongoing damaging winds or large hail.

Tornado WARNINGS (0-4 total) and Flash Flood WARNINGS (0-4 total) are possible today, but not a guarantee.

WHEN

Thunderstorms will start to develop early this afternoon, likely between noon and 2 PM. The initial wave of storms should move southeast within two to three hours of development, but additional storms are possible behind the first wave. Most of the thunderstorms should weaken and move out of the area during the early evening hours, between 7-9 PM.

TEMPERATURES/DEWPOINTS

Temperatures will peak in the mid 80s early this afternoon for most of the region, but northeastern areas, such as Syracuse, will only see temperatures in the mid 70s.

The strongest storms are expected along and just south of this temperature gradient.

High dewpoints of 65-70 degrees will be widespread throughout the region.

finger lakes weather forecast thursday august 27 2020 severe thunderstorm risk map
The greatest threat for severe weather will be in the central and southeastern Finger Lakes, shaded here in the orange as a Level 3- Numerous threat. This area is also the most prone to flash flooding. Click to enlarge.

DAMAGING WINDS

Numerous reports of wind damage are expected. Localized areas could see widespread, significant damage.

Trees are likely to be uprooted and many large limbs will fall. Powerlines will be toppled. Weak outbuildings and barns could be knocked over. Roof damage from high winds will be possible. Prolonged power outages are possible.

Top gusts of 70-80 mph likely, with a small chance for localized microbursts with higher winds.

LARGE HAIL

Numerous hail reports are expected. Much of the hail will be between 1-2 inches in diameter.

Hail this size will be capable of breaking glass and causing crop and plant damage. A few hailstones at or above 2” in diameter are possible, which can destroy crops, shatter windshields, and cause damage to houses.

TORNADOES

A couple of storms may become capable of producing tornadoes today, but this is uncertain and will not necessarily happen.

The greatest chance for tornadoes will be during the first wave of the event, between 1-4 PM. It is important to remember that the wind potential today can cause damage equal to a tornado.

FLASH FLOODING

If multiple rounds of storms do form, flash flooding could become a serious concern locally. This remains uncertain and will most likely be on a small scale if it does occur.

Thunderstorms will be capable of very heavy rain, and while area streams and rivers are low, the hard, dry soil will increase runoff.

LIGHTNING

Frequent to continuous lightning is possible with the thunderstorms.

All lightning is dangerous. Seek shelter once thunder is heard. Lightning can and often does strike out ahead or behind the primary storm, sometimes even when it is not yet raining. Even if a storm is nearby, but not moving in your direction, seek shelter if you hear thunder.

FORECAST CONFIDENCE

High- There is little to nothing standing in the way of a significant severe weather event in the Finger Lakes region. I decided to keep the risk level at Level 3- Numerous due to the cellular nature of the storms, which will likely produce swaths of damage, but not quite at a scale worthy of a Level 4 designation. However, localized areas of Level 4 damage are very possible.

Thunderstorm events are never 100% certain though, and each event often has its own unique subtleties and surprises that will not become clear until the event unfolds. It remains impossible to pinpoint when, where, and with what intensity a thunderstorm will strike hours in advance.

FUTURE THUNDERSTORM OUTLOOK

– Thunderstorms with heavy rain are likely on Saturday. While the severe threat will be minimal, localized flooding could be a concern.

FUTURE UPDATES

  • A LIVE BLOG will be posted by the midday hours and will be updated constantly until the threat is over.

ADDITIONAL INFORMATION

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Follow Meteorologist Drew Montreuil:
Meteorologist Drew Montreuil has been forecasting the weather in the Finger Lakes region since 2006 and has degrees in meteorology from SUNY Oswego (B.S. with Honors) and Cornell (M.S.). Drew and his wife have four young boys. When not working or playing with the boys, he is probably out for a run through the countryside.