Memorial Day Weekend Weather Update

Forecast Updated Thu 9:16 AM in highlighted text below—

As indicated in this morning’s update, the position of the closed low has changed from yesterday’s models and yesterday’s outlook. There continues to be quite a bit of “spread” in the statistical models regarding the position of the closed low.

So there’s a lower confidence in the forecast than usual. (I expect this forecast to be revised again; upper closed lows are very difficult to forecast accurately.)

I wanted to post this update to indicate the major shift in the optimistic forecast I posted yesterday. Additionally, it does not look like a good NJ shore forecast in particular with windy/cloudy and chilly conditions.

The general trend is for more clouds and chances of showers over the weekend, and a reduction in the amount of rain Friday.


As the upper air flow transitions from a ridge to a trough, a surface low, originally to track over us will now track to our south. Unfortunately, this is translating into lower rain amounts for Friday. Instead of 1 inch, it looks more like 0.5 inches of rain. The latest ICON model has well over 1 inch of rain for Friday into Saturday. The NBM has 0.6 inches

Memorial Day Weekend

An upper air trough develops over our area on Saturday and lifts out by Monday. The upper trough will pinch off into a “closed low”.

The entire scenario has changed in a day. The position of the closed low is now south of us and the GFS is forecasting a coastal storm to form!

GFS model forecast for Sunday 5 PM with upper closed low (blue) and surface low (black) (Click on image for a larger view.)

(Average seasonal high temp is 77º-78º)


Saturday will be cloudy with scattered showers. High 61º sd 3.5º Chilly. (very high spread – high uncertainty!) The latest NBM has high temps 59º with an extremely high spread of 6º! The ICON has us in the mid 50s!


Cloudy. Dry according to the model blend (NBM). The GFS has some showers, especially in NJ. High 62.5º sd 5.2º High 60.0º sd 5.7º Chilly and windy.

Updated GFS forecast Sunday afternoon showing closed low (blue), surface low and showers. The forecast position of the 500 mb low keeps shifting. (Click on image for a larger view.)

Cloudy (GFS) or partly cloudy (NBM) High 70.0º sd 3.5º Partly to mostly sunny (GFS) and (NBM). High 71.0º sd 3.5º

Thu 09:20 AM Forecast Commentary —The aim of this blog is to demonstrate both how good the numerical weather models can be, but also to show how fluid and changeable  forecasts are, with model forecasts shifts  and changes clearly marked. 

In contrast, many of the TV forecasters seem to live in the moment and seem to hope that you don’t remember what they said the previous day (or previous program).   

5 thoughts on “Memorial Day Weekend Weather Update”

  1. If you have time to indulge, would you mind explaining the difference between the ICON and NBM models (the later I believe is a blend of models?), with an eye towards which rain forecast for tomorrow (modest or healthy) is the one you lean towards?

    Obviously it will be what it will be, but I would be interested in learning more if you have the time.

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