Category Archives: Weather Updates


Updated Sun 7:25 AM highlighted below:

This update is really a cut and paste from my original forecast from Friday.

A weak warm front will move in before daybreak on Sunday. Some scattered showers before daybreak. Clouds early will break for sunshine by afternoon. 

As a result of this warm front, Sunday will have noticeably higher humidity (dew points) than Saturday. Dew points will move back into the uncomfortable 70º range.

Today’s models have the weak front moving through earlier on Sunday afternoon than previously forecast. Latest models have scattered showers and thunderstorms developing in western suburbs as early as 2 PM. High temp tomorrow 89.4º 88.3º± 1.2º Dew points uncomfortable, near 70º

Most models have the activity diminishing as it moves into NJ.

More rain later Sunday night, after midnight.

Meteogram timing still on-track

NBM precip forecast for Sunday, Blue Bell, PA (The peak probability is 2-6 PM and is not that impressive. ) Click on image for a larger view.
Canadian GEM regional model forecast 2 PM Sunday (Click on image for a larger view.)

Water Vapor Imagery and Advancing Warm front

I love looking at the clouds and seeing what they tell about the model weather forecasts. Today’s approaching warm front is visible on water vapor imagery. Latest water vapor imagery is can be seen at this link.

Unlike visible satellite imagery, the colors of water vapor imagery indicates the water vapor temperature and height. Here we see upper air disturbances spilling out ahead of the warm front just west of central PA about 2 PM Saturday.
The advancing upper air disturbances visible on water vapor to the north and west caused the development of some mixed clouds and cumulus clouds with vertical growth on the Pennsylvania side of the Delaware River at about 3 PM Saturday.


Update Sun 11:59 AM highlighted below

Friday’s Weekend Weather Forecast had so many updates, it’s difficult to comb through. So here’s an updated Sunday forecast:

High pressure will build back in on Sunday, A flow of increasingly hot and very humid air, typical for the end of June and beginning of July, will begin to affect us on Sunday and beyond. 

Mostly sunny, hot and increasingly humid. (Dew points in the uncomfortable upper 60s to above 70º!) High temp 90.3.º sd 1.3º (NBM Blue Bell)

There’s a chance of early to mid afternoon widely scattered showers northwest (Reading) and in central NJ.

Update Sun 11:59 AM— This morning’s models continue to show the chance of early to mid afternoon showers in central NJ and areas north. The HIRESW models seem to be overstating the rain. But Satellite Water Vapor shows a disturbance moving south that may interact and create some showers.

Temperatures on Monday, Tuesday and Wednesday will be even hotter, with temps 91º-94º with high dew points.


The original forecast for Sunday can be found here.

I’m trying to decide if I’m going out on that bike ride today. The forecast for periods of clouds with light, scattered showers early afternoon still holds. The latest HRRR has the axis of showers more into NJ, while the RAP maintains the track through Philadelphia.

Current Radar, Water Vapor, and superimposed RAP model Wind Streams (at 250 and 500 mb heights) at 9:30 AM Saturday. Shows moisture moving north and upper disturbance moving down over a ridge from the northwest. The forecast for periods of clouds with showers early afternoon still holds.

Latest RAP (RApid Refresh) model simulated radar forecast with accumulated rain (white contours), 2PM

RAP forecast 2 PM