Updated Sunday forecast, Sat 10:13 PM highlighted below

The weak front that moved through Friday evening will allow some drier air to move in for Saturday.

An mid-level disturbance may bring some clouds in the morning and even some sprinkles around noontime on Saturday, mostly far northwestern suburbs, but most of the day and the area will be partly sunny. High temp 84.7º ± 1.3º NBM Blue Bell.

For Sunday, the boundary that went through on Friday will return as a warm front. Considerable cloudiness in the morning with very some light showers possible, especially in far northern and western suburbs.

Clouds break for hazy sunshine Sunday afternoon with an increasing chance of showers and thunderstorms in the evening, especially western suburbs. The showers/thundershowers look less likely in Philadelphia and immediate suburbs.

Increasingly hot and humid. Dew points return to the uncomfortable upper 60s to near 70º. High 86.0º ± 2.6º NBM Blue Bell.

High 86.9º ± 1.7º NBM Blue Bell.

There is some uncertainty about the timing of showers on Sunday with the Canadian GEM having a somewhat different forecast than the GFS. Stay tuned.


Fri 08:18 PM Forecast Review — The storms developed and moved just south of Philadelphia as picked up by the afternoon HRRR.
NEXRAD radar at 6:55 PM

Updated Fri 4:25 PM, highlighted below, based on new HRRR
Updated Fri12:30 PM, highlighted below, based on new HIRESW

Strong thunderstorms expected early this evening. The latest HRRR shows all the ingredients coming together about 4:30 -8:30 PM 5:30 – 9 PM (peak 7-8 PM) in Philadelphia.

Update: The latest HRRR has the heaviest storms just to the south of Philadelphia

CAPE values in the 1600-2200 J/Kg range. Lifted Index moderately negative at -5. Very strong upward vertical motion is predicted to develop (blue shading/white arrow below) along with cyclonic upper air contour (blue arrows).

Heavy rain expected, especially from Philadelphia south and east.

HRRR 12z forecast for 8 PM showing very strong vertical velocity (blue shading/white arrow) right over Philadelphia and cyclonic upper air curvature. (blue arrows) (Click on image for a larger view.)