This weekend across the Northeast and Mid-Atlantic could see a strong rain-generating scenario on Sunday thanks to a number of components that will facilitate heavy rain, showers and thunderstorms. We start by looking at a 500mb high setup to determine what our thrust on the ascent is to generate precipitation. We see the circle, a remarkable short wave circling the bottom of a long wave trough through Sunday, verbatim advance of the differential eddy – a key ingredient in whether we move. upward motion or not. We see that we actually have this, so a divergence is expected at the bottom of this bottom. Combined, at 300mb, what would add to the divergence even further would be a jet trail propagating into southeastern Canada as circled in black. Northeast will be adjacent within the right rear entrance of this jet trail – a vantage point that will experience an elevated divergence that helps “pull” mass away from the surface.
It is important to have a forcing mechanism, but we also cannot have increased motion and therefore precipitation without humidity. In fact, according to the Hurricane Forecast Center, areas along I-95 in the Mid-Atlantic and into the Northeast will see record-high PWAT values (above 2″) spike before a cold snap. , when a heatwave hit the commons on Sunday morning.
So we have the overhead divergence, the humidity and now let’s analyze the snapshot of the surface. Annotated verbatim here, we see a cold front moving slowly and becoming nearly stationary along the Appalachian Mountains. While we see that at 500mb we have a favorable divergence setup overhead, that doesn’t always mean rainfall is a guarantee; therefore, we need to see what could be the main coercive trigger in the boundary layer. We know we’re going to have a boundary ahead, which means we’re going to see rainfall.
We have what is needed for a given amount of precipitation: 1. Overhead divergence through the ray trail 2. Shortwave trough 3. Forced “activation” on the surface 4. Humidity. All together, this creates vertical movement from the required lifts, and when combined, we see an interesting scenario in favor of heavy rainfall with a high likelihood of urbanizing flooding. where most of these two areas have had a moderate amount of rain over the past few weeks.
Taking it all together, we should see a heavy rain axis above 1.5″ somewhere along the Appalachian from west of MD, up to PA and into NY in the east. While we have some variation between models determining where the heaviest rain axis is located, we do know that 1”+ will drop across the board.
At the same time, severe weather on Sunday looks likely, especially south of the Maxon-Dixon line, where instability and shear are favorable to create clusters that could generate rain. rock and gusty winds while thunderstorms are also possible north into the Northeast.
Finally, to add “insult to injury”, Weather Center has placed areas of the Mid-Atlantic and the Northeast at risk of “SMALL” excessive rainfall due to the atmosphere being extremely strong for the heavy rainfall that would result in the aforementioned flooding.
A rainy day is likely Sunday through Monday with areas of slow moving lows along the near-permanent boundary along with thunderstorms for these areas which have enjoyed a fairly active summer for now.
About the author
Hello! My name is Armando Salvadore and I am a Mississippi State graduate with a Bachelor of Professional Meteorology and an Activity Meteorologist working in the Private Sector. Stay tuned if you like technical, exotic, and general weather tweets! Also big on long-range forecasting as well! Twitter: @KaptMands