The atmosphere will really be cranking up Monday evening and into Tuesday with the approaching trough of low pressure out of the NW United States. Currently this trough is merging the polar and subtropical jet streams in the Four Corners region and has already induced cyclogenesis over the central Great Plains. This storm system will continue to evolve and propagate eastward toward the Ohio Valley today and tonight. Tomorrow, more upper-level wind energy and difluent flow will kick off precipitation across the the State of Kentucky.
Below are a series of graphics generated from the latest NAM run (12 Z) illustrating the dynamics of this system at varying layers of the troposphere. These are valid for 00 Z tomorrow evening (6 p.m. CST):
- 300 hPa winds and heights – notice the large trough axis and jet streak to our SW as winds approach ~165 kts (~190 mph), as well as the difluent flow helping to aid large scale ascent.
- 500 hPa relative vorticity and heights: – Here you can see the vort max (curvature vorticity) over North Dakota associated with the closed low, as well as vorticity maxima (shear vorticity) associated with wind shear due to the jet streak mentioned earlier. Positive vorticity advection (PVA) will also aid lift with this system.
- 700 hPa heights and vertical velocity – The dynamics of this system will certainly favor synoptic scale lift, as well as localized convection to the south. Lift = clouds and precipitation for the area.
- 850 hPa winds and heights – In response to the upper-level jet streak, a strong low-level jet (LLJ) will develop across the area. Here, winds are forecast (by this NAM run) to be ~80 kts! The LLJ serves as a pipeline for low-level advection of warmer air and higher moisture content, necessary for storms and rainfall, which we desperately need.
- Surface MSLP, 1000-500 thickness, simulated precipitation: – Now you can see how the dynamics in the low, mid, and upper-levels of the atmosphere come together to create weather in our world. Here you can see the low over the Dakotas and trailing frontal boundary down into the Ohio Valley. The warm air and moisture advections ahead of the front are lifted via the warm conveyor belt and eventually result in the formation of rainfall.
In short, we have a dynamic system coming our way tomorrow. We will certainly see some much needed rainfall for the area, as well as some pretty gusty winds. With the LLJ parked over Bowling Green in the evening, surface wind gusts could easily approach the 40 mph range.
We should expect ~1″ of rain up to ~2″ in some places with temperatures getting up and around the 60 degrees. However, the cooler air won’t make its way into the region until Wednesday evening as the trough axis takes its time moving eastward. This is partly due to the upper-level ridge of the SE Florida coast and the digging nature of the trough out west. Hopefully this system puts a good dent in the drought conditions for the area and puts and end to the wildfires across the Appalachians.
Bring your rain jackets to work and school on Monday, and be prepared for additional rainfall on Wednesday as another round of PVA & other upper-level dynamics attempt to make their exit.
