Quick peak at the system for tomorrow (Thursday 6/13)
Current 0z NAM shows trough dipping in down from the Plains. Ahead of it there is some shortwave energy in the southeast that has caused some thunderstorms earlier in the evening.
Below is the 500 mb vort/height map
And the 850mb map shows the counter-clockwise wind rotation in the southeast associated with weak low pressure area. Despite it being weak, it’ll interact more with the incoming trough, generating heavier precip in our area.
Fast forward to tonight, you can see the trough over the Plains swing over to the mid-west, there is a little tongue dipping into South Carolina. That is the interaction between the trough and mid-level low in the southeast.
850 mb temp and SLP shows low pressure over the Lakes and an unmarked low pressure area in South Carolina (note counter-clockwise winds)
And then as the cold front approaches from the west associated with the low pressure over the Great Lakes and warm air arriving from the southern low, we will have frontogenesis (warm air/cold air causing increased rising motion in the atmosphere). Purple shading shows the frontogenesis in our area early Thursday morning.
And then the radar according the NAM will look something like this. Heavy rain with embedded thunderstorm activity.
It’s possible flash flooding will be an issue depending on where the heavier bands set-up.
How the front interacts with the southern low will affect where the heaviest rain axis shows up. The sooner the interaction, the heavier and larger the heavy precip shield is and expanding westward. The later they interact, the more likely LI/SNE ends up with the heavier bands and rumbles of thunder.
Precip accumulations through rush hour Thursday according to the NAM shows 1-2″ of rain
Philadelphia Weather Authority 