Memorial Day Weather Update [5/27] Peak Into Tomorrow


  • Remember those who have given the ultimate sacrifice
  • Tomorrow, temps in the low 80s
  • Chance of strong storms tomorrow, isolated tornado possible
  • Long Term outlook for June tomorrow


Taking a look at IR satellite, we see large deep trough out west and then another moving through the Ohio Valley. High pressure is sliding off the coast. We have a boundary moving in from the west (red line). This will create showers and perhaps a rumble of thunder for the morning. The orange circle is a deeper area of convection that will likely be the culprit for the storms. In lavender is another plume of clouds and precipitation. Between the orange circle and the lavender circle is another area of low pressure, which will head east into Upstate NY.

Taking at simulated IR and radar from the NAM. Roughly 10 AM.

After this area of showers and thunderstorms moves through. The evening looks comfortable regarding temperatures

But the main low pressure area itself will not have moved through just yet, the shower activity induced by mid-level action.

Here is the NAM for 3 PM, as you can see, the main area of low pressure is over NY State, still hanging back towards the Great Lakes. Note the surface winds from the south.

To the south of this low pressure, CAPE values will be on the increase through the afternoon, suggesting higher levels of instability. Any shading over 1000 is enough to sustain thunderstorm activity. Values over 2000 could support severe cells.

In this map we also have wind directions. The white barb is for the surface, green is at 850mb, and yellow is 700mb. If you look closely at the wind barbs, you can see significant change of wind direction the higher you go (from surface to 850 to 700), particularly in E PA, NJ, DE. There is a chance for isolated tornado because of this wind profile.

Soundings (below) in Philly show two main ideas SBCIN/MCLIN, which are indices used to describe inhibition, are low. Values <50 signify low inhibition. And the other is the CAPE will be >2500 J/kg, suggesting more than enough energy to create and sustain thunderstorms. Storm relative helicity (measure of updraft rotation in cells) is also relatively high >250 between 0-1km and >350 between 0-3km. All suggestive of possible thunderstorm activity and within that thunderstorm activity could be cells that rotate and produce tornadoes.

Here is another soundings map, this time with analogs (lots of numbers). Hopefully you are not too overwhelmed with this chart. I simply want to highlight the Soundings Analog box which shows increased tornado and hail probabilities (SARS-Soundings Analogs)

We will keep an eye on this as it evolves tomorrow. For those that are concerned, the good news is that the low pressure area will approach the Philly region later on in the evening, so some of the energy available will be gone from the sun. The other thing to keep an eye on is the morning precipitation, which has been known to be an inhibitor for thunderstorms later on. If those storms are stronger, it is possible the evening ones will be weaker.

It does not appear to be widespread, it’s unlikely a line of thunderstorms forms. Mostly isolated/scattered cells that may congeal and form a quasi-line, but I’m not expecting a full line of storms at the moment.

Another Update In The Morning

Long Range Outlook For June Tomorrow

Follow me on twitter @Philly_Weather1 Below

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