Waves of torrential rainfall will move northward out of central Virginia impacting the entire Washington Region through the day on Thursday. With the ground being so hard from a lack of rain, water will easily run off into streams, creeks, low-lying areas, poor drainage areas (underpasses) etc.
Here is a look at the latest full suite of short-range high-resolution models.Keep in mind that it is very hard to pinpoint exactly who receives the jackpot, but if you live in a flood prone area please make preparations for facing rapidly rising water overnight into the evening hours on Thursday.
Tornado and Hail Threat:
A low-level jet stream will provide enough spin that some storms may become severe with hail and isolated tornadoes being the primary threat. I say isolated because we have not had any sunshine to really destabilize the atmosphere, however wind shear values (helicity) are running marginal so an isolated spin up tornado is not out of the question this evening, hence the Storm Prediction Center has issued a Severe Thunderstorm Watch for our region this evening.
When analyzing the current high-resolution models one thing is clear: A widespread 3 to 5″ of rain is likely for all with the locations receiving “training thunderstorms” possibly picking up 5 to 12″ of rain!
Please monitor the latest forecasts from the National Weather Service and if a Flash Flood Warning is issued for your area have a plan to move to higher ground.
Scattered Strong Thunderstorms have already begun to break out across our Southern suburbs and exurban areas like Stafford county early this morning. Lightning is already showing up as instability is increasing with tropical air beginning to over-ride the relatively cooler air mass at the surface. Humidity will increase rapidly today as thunderstorms become numerous this afternoon. For those of you commuting, please pay close attention to the radar as torrential rain will make what is normally a horrible rush hour (in sunshine) even worse.
Here is the latest HRRR (High Resolution Rapid Refresh) model showing what the Future-Cast radar for today through 8PM:
Notice how this model shows explosive thunderstorm development starting early this afternoon across the Shenandoah Valley then developing rapidly across the Metro Region during the middle to tail end of the this afternoon’s rush hour. The damage will have been done by the start of rush hour with torrential rainfall (rainfall rates of 2″ per hour) coming down across portions of our area.
This next image is from the North American Model and shows torrential rainfall and thunderstorms continuing through late Thursday night.Again, this evening through Thursday is going to feature some of the worst of the widespread heavy rainfall, with additional heavy rain expected on Friday.Flash flooding is a huge concern not only for poor drainage areas in the metro region but I am extremely concerned about the eastern facing slopes of the Blue Ridge.
Latest North American Model raises eyebrows with up to 10″?! of rain possible in areas that are receiving training thunderstorms:
This amount of rainfall coming down the mountains will easily cause area rivers to swell and despite the recent dry conditions, rainfall rates of 2″ per hour over several hours could mean that folks who are not paying attention to the situation could face water rescues (this is why the National Weather Service service reminds people to “turn around, don’t drown” when you approach standing or moving water across area roadways).
The latest Operational runs of the American Global Forecast System (GFS) and Canadian models:
GFS: This model is not a “high-resolution” model but still shows the idea of at least expecting a widespread 3 to 5″ of rain, again areas that get hit by repeated (we call that training) thunderstorms could easily see higher totals!
The latest Canadian is more bullish showing 6 to 9″ of rain across parts of our area through Saturday morning!
Plan accordingly, watch the radars today and pay close attention to flash flood warnings. We have a very interesting afternoon and evening in store across the DC Region.
Again, three months worth of rain could fall in the next 36 hours… some locations will experience flooding (everyone remembers what happened in Howard county Maryland over the Summer)… this is the type of torrential rain that will be falling and unfortunately “training” across the area.