Flash Flood Watch for the area for tonight (Thurs)

9/22/21

The NWS has issued a Flash Flood Watch for the area for tomorrow night (Thurs)

A cold front will move through the area tomorrow evening and night. This, along with the moist air in the area now, means there is a chance that we get 1 - 2" of rain over a 3 - 6 hour window. In addition, there is a chance of slow-moving thunderstorms that would increase the likelihood of 1.5 - 2" rainfall. As always with this level of rainfall, there is a chance of road ponding and field flooding, so the NWS has issued a Flash Flood Watch. There is a marginal risk of severe thunderstorms ('marginal' means less than 'slight' in this context; for you stem majors slight is 10% and marginal is 5%).

Timing is still somewhat up in the air, but should be confined to the overnight hours.

Remember, even a few inches of water can sweep a car or SUV off the road. It is very hard to judge how deep the water is. Best to turn around.


9/23 Thurs morning update

Flash Flood Watch for this evening and tonight.

Forecast is trending towards the wetter side, 1 - 2 inches of rain with an upside if we get significant thunderstorm activity.

Timing looks a bit earlier, with rain starting around 4 or 5 (perhaps a few scattered showers earlier).

Regarding comparisons with Ida:

This system is a common cold front moving into a humid airmass. Ida was a tropical depression feeding off the ocean. This system has PWATS* of 2" and if it overperforms could reach 3". Ida had PWATS of 8". This system has the potential to drop a maximum of 3" over 6 hours. Ida dropped 3" over less than 1 hour, and over 8.25" total.

This system has the potential to be annoying, inconvenient, and might knock a tree over somewhere. There is even a nonzero but very very low chance of a tornado. Systems like this happen weekly this time of year, and most of our infrastructure is built to handle it. I don't want to minimize this system, and I appreciate how triggering storms are now after Ida, but this is not the same level of risk. Live your life, put a thundershirt on the dog, take transit instead of driving, don't walk in the rain when there's thunder or lightening, and don't drive through puddles. Be prudent. I hope over time the trauma will fade.

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*Precipitable Water = amount of water that could fall as rain or snow


Thanks, Max. Many of us are still cleaning up after Ida, and the thought of more rain pouring into our houses is at the forefront.


The air is full of moisture.  It feels like storm weather.


Alexa says humidity is 87%.


max_weisenfeld said:

This system has the potential to be annoying, inconvenient, and might knock a tree over somewhere. 

One of the trees you predicted might get knocked over was in front of my sister's house and took out their power. (Fortunately, didn't hit the house).



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